Atmospheric Environment (v.79, #C)

The relationship between airborne small ions and particles in urban environments by Xuan Ling; Rohan Jayaratne; Lidia Morawska (1-6).
Ions play an important role in affecting climate and particle formation in the atmosphere. Small ions rapidly attach to particles in the air and, therefore, studies have shown that they are suppressed in polluted environments. Urban environments, in particular, are dominated by motor vehicle emissions and, since motor vehicles are a source of both particles and small ions, the relationship between these two parameters is not well known. In order to gain a better understanding of this relationship, an intensive campaign was undertaken where particles and small ions of both signs were monitored over two week periods at each of three sites A, B and C that were affected to varying degrees by vehicle emissions. Site A was close to a major road and reported the highest particle number and lowest small ion concentrations. Precursors from motor vehicle emissions gave rise to clear particle formation events on five days and, on each day this was accompanied by a suppression of small ions. Observations at Site B, which was located within the urban airshed, though not adjacent to motor traffic, showed particle enhancement but no formation events. Site C was a clean site, away from urban sources. This site reported the lowest particle number and highest small ion concentration. The positive small ion concentration was 10%–40% higher than the corresponding negative value at all sites. These results confirm previous findings that there is a clear inverse relationship between small ions and particles in urban environments dominated by motor vehicle emissions.
Keywords: Small ions; Aerosols; Particles; Urban pollution;

Aerosol properties and radiative forcing over Kanpur during severe aerosol loading conditions by D.G. Kaskaoutis; P.R. Sinha; V. Vinoj; P.G. Kosmopoulos; S.N. Tripathi; Amit Misra; M. Sharma; R.P. Singh (7-19).
The present work analyzes the aerosol episode (AE) days and examines the modification in aerosol properties and radiative forcing during the period 2001–2010 based on Kanpur-AERONET data. AEs are defined as the days having daily-mean aerosol optical depth (AOD) above the decadal mean + 1 STD (standard deviation); the threshold value is defined at 0.93. The analysis identifies 277 out of 2095 days (13.2%) of AEs over Kanpur, which are most frequently observed during post-monsoon (78 cases, 18.6%) and monsoon (76, 14.7%) seasons due to biomass-burning episodes and dust influence, respectively. On the other hand, the AEs during winter and pre-monsoon are lesser in both absolute and percentage values (65, 12.5% and 58, 9.1%, respectively). The modification in aerosol properties on the AE days is strongly dependent on season; during post-monsoon and winter, the AEs are associated with enhanced presence of fine-mode aerosols from anthropogenic emissions and/or biomass burning, while during pre-monsoon and monsoon seasons, they are mostly associated with dust. Aerosol radiative forcing (ARF) calculated using SBDART shows much more surface (∼−69 to −97 Wm−2) and Top of Atmosphere cooling (−20 to −30 Wm−2) as well as atmospheric heating (∼43 to 71 Wm−2) during the AE days as compared to seasonal means. These forcing values are mainly controlled by the higher AODs and the modified aerosol characteristics (Angstrom Exponent α, single scattering albedo SSA) during the AE days in each season. Furthermore, the vertical profiles of aerosols and atmospheric radiative heating exhibit significant increase in lower and mid troposphere during the AE days. This may cause serious climate implications over Ganges Basin and surrounding regions with further consequences on cloud microphysics, monsoon rainfall and melting of Himalayan glaciers.
Keywords: Severe aerosol; Optical properties; Radiative forcing; Kanpur AERONET;

Estimating farm-gate ammonia emissions from major animal production systems in China by Zhiling Gao; Wenqi Ma; Gaodi Zhu; Marco Roelcke (20-28).
Ammonia (NH3) emissions from livestock production in China are an important contributor to the global NH3 budget. In this study, by estimating total nitrogen (N) intake based on herd structures and excreted N, a mass balance model was used to estimate NH3 losses from animal housing and manure storage facilities of dairy cattle, beef cattle, pigs, broiler and layer productions within animal farm gate and their corresponding NH3 emission intensities on the basis of animal products, N and protein in animal products. In 2009, NH3 emissions from pigs, layers, beef and dairy cattle and broiler production systems in China were 1.23, 0.52, 0.24, 0.21 and 0.09 million tons, respectively. The NH3 emission intensities were 26.6 g NH3–N kg−1 of pork, 28.1 g NH3–N kg−1 of layer eggs, 39.4 g NH3–N kg−1 of beef meat, 6.0 g NH3–N kg−1 of dairy milk and 4.6 g NH3–N kg−1 of chicken meat, or 1260 (pigs), 1514 (layers), 1297 (beef), 1107 (dairy) and 123 g NH3–N (broilers) kg−1 N in animal products. Of the sectors of NH3 emission, manure storage facilities and farmyard manure (FYM) in animal housing were the major contributors to the total NH3 emissions except for layers; housing emissions from slurry were also major contributors for dairy and pig production.
Keywords: Ammonia; Emission intensity; Housing emissions; Manure storage; Mass balance model;

Influence of the diagnostic wind field model on the results of calculation of the microscale atmospheric dispersion in moderately complex terrain by Ivan V. Kovalets; Vladimir Y. Korolevych; Alexander V. Khalchenkov; Ievgen A. Ievdin; Mark J. Zheleznyak; Spyros Andronopoulos (29-35).
The impact of diagnostic wind field model on the results of calculation of microscale atmospheric dispersion in moderately complex terrain conditions was investigated. The extensive radiological and meteorological data set collected at the site of the research reactor of the Chalk River Laboratories (CRL) in Canada had been compared with the results of calculations of the Local Scale Model Chain of the EU nuclear emergency response system JRODOS. The diagnostic wind field model based on divergence minimizing procedure and the atmospheric dispersion model RIMPUFF were used in calculations. Taking into account complex topography features with the use of diagnostic wind field model improved the results of calculations. For certain months, the level of improvement of the normalized mean squared error reached the factor of 2. For the whole simulation period (January–July, 2007) the level of improvement by taking into account terrain features with the diagnostic wind field model was about 9%. The use of diagnostic wind field model also significantly improved the fractional bias of the calculated results. Physical analysis of the selected cases of atmospheric dispersion at the CRL site had been performed.
Keywords: Meteorological preprocessor; Diagnostic wind field model; Atmospheric dispersion;

Retrieval of multi-wavelength aerosol lidar ratio profiles using Raman scattering and Mie backscattering signals by Jia Su; Zhaoyan Liu; Yonghua Wu; M. Patrick McCormick; Liqiao Lei (36-40).
We advance a novel retrieval technique that combines a Raman and multi-wavelength elastic backscattered signals to retrieve multi-wavelength lidar ratio profiles of aerosol. With profile of backscatter coefficients at 355 nm retrieved from elastic backscatter signal at 355 nm and Raman scattering signal at 387 nm, lidar ratio profiles can be calculated at 532 nm and 1064 nm from the elastic backscatter signals at these wavelengths, taking advantage that the 532 nm/355 nm and 1064 nm/355 nm backscatter ratios are generally approximately equal for two neighboring range bins. This technique has been tested using numerical simulations and applied to lidar measurements at the Hampton University, Hampton, Virginia.
Keywords: Aerosol; Lidar ratio; Multi-wavelength;

Influence of ventilation and filtration on indoor particle concentrations in urban office buildings by Tran Ngoc Quang; Congrong He; Lidia Morawska; Luke D. Knibbs (41-52).
This study aimed to quantify the efficiency of deep bag and electrostatic filters, and assess the influence of ventilation systems using these filters on indoor fine (<2.5 μm) and ultrafine particle concentrations in commercial office buildings. Measurements and modelling were conducted for different indoor and outdoor particle source scenarios at three office buildings in Brisbane, Australia. Overall, the in-situ efficiency, measured for particles in size ranges 6–3000 nm, of the deep bag filters ranged from 26.3 to 46.9% for the three buildings, while the in-situ efficiency of the electrostatic filter in one building was 60.2%. The highest PN and PM2.5 concentrations in one of the office buildings (up to 131% and 31% higher than the other two buildings, respectively) were due to the proximity of the building's HVAC air intakes to a nearby bus-only roadway, as well as its higher outdoor ventilation rate. The lowest PN and PM2.5 concentrations (up to 57% and 24% lower than the other two buildings, respectively) were measured in a building that utilised both outdoor and mixing air filters in its HVAC system. Indoor PN concentrations were strongly influenced by outdoor levels and were significantly higher during rush-hours (up to 41%) and nucleation events (up to 57%), compared to working-hours, for all three buildings. This is the first time that the influence of new particle formation on indoor particle concentrations has been identified and quantified. A dynamic model for indoor PN concentration, which performed adequately in this study also revealed that using mixing/outdoor air filters can significantly reduce indoor particle concentration in buildings where indoor air was strongly influenced by outdoor particle levels. This work provides a scientific basis for the selection and location of appropriate filters and outdoor air intakes, during the design of new, or upgrade of existing, building HVAC systems. The results also serve to provide a better understanding of indoor particle dynamics and behaviours under different ventilation and particle source scenarios, and highlight effective methods to reduce exposure to particles in commercial office buildings.
Keywords: Ultrafine particles; Indoor; I/O ratio; Deep bag filter; Electrostatic filter; Dynamic model;

An accurate evaluation of the airborne particle dose–response relationship requires detailed measurements of the actual particle concentration levels that people are exposed to, in every microenvironment in which they reside.The aim of this work was to perform an exposure assessment of children in relation to two different aerosol species: ultrafine particles (UFPs) and black carbon (BC). To this purpose, personal exposure measurements, in terms of UFP and BC concentrations, were performed on 103 children aged 8–11 years (10.1 ± 1.1 years) using hand-held particle counters and aethalometers. Simultaneously, a time-activity diary and a portable GPS were used to determine the children's daily time-activity pattern and estimate their inhaled dose of UFPs and BC.The median concentration to which the study population was exposed was found to be comparable to the high levels typically detected in urban traffic microenvironments, in terms of both particle number (2.2 × 104 part. cm−3) and BC (3.8 μg m−3) concentrations. Daily inhaled doses were also found to be relatively high and were equal to 3.35 × 1011 part. day−1 and 3.92 × 101 μg day−1 for UFPs and BC, respectively.Cooking and using transportation were recognized as the main activities contributing to overall daily exposure, when normalized according to their corresponding time contribution for UFPs and BC, respectively. Therefore, UFPs and BC could represent tracers of children exposure to particulate pollution from indoor cooking activities and transportation microenvironments, respectively.
Keywords: Ultrafine particles; Black carbon; Children's exposure; Cooking; Personal monitoring; Dose;

Yields of methacrolein (MAC) and methyl vinyl ketone (MVK) from the OH-initiated oxidation of isoprene were measured under NO x -free conditions at 303, 323 and 343 K and 1 atm in a quartz reaction chamber coupled to a mass spectrometer. Measured yields of MAC and MVK were approximately 9–11% and 17−22%, respectively at temperatures between 303 and 343 K, in good agreement with previous studies. The measured yields of MAC and MVK, at 303 and 323 K as well as the measured yield of MAC at 343 K were reproduced reasonably well using an explicit model of isoprene oxidation. However, the experimental yields of MVK at 343 K were underestimated by the model, suggesting that a temperature dependent source of MVK was missing. Several recently proposed additions to the isoprene oxidation mechanism, including 1,6- and 1,5-H shift isomerization reactions of isoprene-based hydroxyalkyl peroxy radicals, were tested in order to determine if these mechanisms can explain the observed temperature dependence of the product yields.
Keywords: Isoprene; Methyl vinyl ketone; Methacrolein; Hydroxyl radical;

We conducted a source–receptor relationship (SRR) analysis of the total deposition of nitrate (TDN; dry + wet, gas + aerosol) in Northeast Asia using an aerosol chemical transport model. Six regions were included in the study: North China, Central China, South China, South Korea, Japan, and Ocean. More than 95% of the TDN across China consisted of contributions from Chinese emissions. The largest intra-regional contributions and the second largest contributions were attributed to the Central China region. The contribution of the three China regions accounted for approximately 50–60% of the TDN in South Korea and Japan and 75% of the TDN in the Ocean region, respectively. The spatial distributions of the SRR indicated that the sub-regional high was more than twice the regional averages of the TDN. We also investigated the effects of sea salt on the transport and deposition of nitrate. During the long-range transport from the Asian continent over the ocean, nitric acid gas condenses on sea-salt particles to form NaNO3. The presence of sea-salt particles increased the TDN over the downwind regions of the Asian continent by approximately 10–25% in South Korea and Japan and by up to 40% in the Ocean region. However, the sea-salt effects on the SRR of the TDN were small (the absolute differences were smaller than approximately 10%).
Keywords: Long-range transport; Nitrate formation; Dry deposition; Wet deposition; Sea-salt effects; LTP project;

Mass absorption efficiency of elemental carbon for source samples from residential biomass and coal combustions by Guofeng Shen; Yuanchen Chen; Siye Wei; Xiaofang Fu; Ying Zhu; Shu Tao (79-84).
Optical properties of particulate matter are of growing concern due to their complex effects on atmospheric visibility and local/regional climate change. In this study, mass absorption efficiency (MAE) of elemental carbon (EC) was measured for source emission samples obtained from the residential combustions of solid fuels using a thermal-optical carbon analyzer. For source samples from residential wood, crop straw, biomass pellet and coal combustions, MAE of EC measured at 650 nm, were 3.1 (2.4–3.7 as 95% Confidence Interval), 6.6 (5.5–7.6), 9.5 (6.7–12), and 7.9 (4.8–11) m2 g−1, respectively. MAE of EC for source sample from the wood combustion was significantly lower than those for the other fuels, and MAE of EC for coal briquette appeared to be different from that of raw chunk. MAE values of the investigated source emission samples were found to correlate with OC/EC ratio, and a significantly positive correlation was found between MAE and particle-bound polycyclic aromatic hydrocarbons (pPAHs), though pPAHs contributed a relatively small fraction of OC.
Keywords: Mass absorption efficiency; Residential combustion source; Solid fuel; Organic carbon; Polycyclic aromatic hydrocarbon;

The aim of the present work is to define top-down approaches to allocate atmospheric emissions from non-industrial combustion plants (residential, institutional and commercial sectors) to a detailed grid system of 100 × 100 m2. The conceptual model adopted permits the use of suitable proxy variables for the scaling down of atmospheric emissions from a provincial to a local scale. ‘Resident population’, ‘building volume’ and a statistical combination of both have been used as proxy variables for realizing three emission disaggregation models. The choice of the proxy variables was influenced by both data availability and relevance. The results of the emission disaggregation models have been compared with emission values resulting from a bottom-up approach starting from local data. The selected case study was located in the Emilia-Romagna Region (NE Italy), and NO x was the reference pollutant.Display Omitted
Keywords: Proxy variables; Spatial disaggregation; CORINAIR Atmospheric Emission Inventory;

Short time dissolution kinetics of refractory elements Fe, Al, and Ti in Asian outflow-impacted marine aerosols and implications by Shih-Chieh Hsu; Fei-Jan Lin; Tsun-Hsien Liu; Shuen-Hsin Lin; Shuh-Ji Kao; Chun-Mao Tseng; Chao-Hao Huang (93-100).
A six-step sequential extraction protocol was employed for marine aerosols with varying mixture of dust and pollution particles collected from the East China Sea to study the dissolution kinetics of refractory elements Fe, Al, and Ti (with a focus on Fe) in relation to acidic substances such as sulfate, nitrate, and water-soluble organic carbon. The three elements might be of a natural origin such as Asian dust and/or anthropogenic origins such as coal fly ash and biomass burning; however, this study focused on the dissolution kinetics, instead of their sources. We selected three samples with varying dust loading but close acid loadings for the experiment so that the acidic effect on the aerosol Fe dissolution could be explored as the direct contribution of water-soluble Fe from anthropogenic sources, if any, might be constrained at a relatively constant level among the samples. Extraction was stepwise performed with six steps for total 30 min, and the leaching duration was as short as ten seconds in the first five steps. No saturation was found for the analyzed elements. Two phases of dissolution curves were observed in all interested compositions, which could be explained by an aged aerosol particle model, with an intrinsically insoluble core and weathered surface. The first phase curve approximates the first-order reaction, with considerably high dissolution rates of 6.5–277 μmol g−1 min−1, indicating the likely existence of an “extremely fast iron pool” that may exist on the weathered surface of aged particles, along with other three pools proposed by Shi et al. (2011). Acid/dust ratio could be a crucial factor that facilitates parameterization of aerosol iron dissolution. Results of this study are useful in improving aerosol iron and other transition element dissolution schemes in atmospheric chemistry models.
Keywords: Asian dust; Solubility; Iron dissolution; Acid processing; East China Sea;

Efforts using the Community Multiscale Air Quality (CMAQ) model to investigate the impacts of aircraft emissions from the Hartsfield-Jackson Atlanta International Airport have previously shown aircraft emissions increased total daily PM2.5 concentrations by up to 9.4% (0.94 μg m−3) with overall impacts varying by modeled grid resolution. However, those results also indicated that secondary organic aerosol (SOA) concentrations in the airport grid cell were reduced due to aircraft emissions at coarser grid resolutions (36-km and 12-km) but not at a finer resolution (4-km). To investigate this anomaly, this study instruments the CMAQ model with process analysis, an advanced diagnostic modeling tool, and focuses on changes to SOA concentrations due to aircraft emissions in the grid cells containing the Atlanta airport at grid resolutions of 36-km, 12-km, and 4-km. Model results indicated aircraft emissions reduced hourly anthropogenic and biogenic SOA concentrations at the 36-km and 12-km grid resolutions by up to 6.2% (0.052 μg m−3) by removing nitrate, hydroxyl, and hydroperoxy radicals through chemistry. At the 4-km resolution, however, hourly modeled SOA concentrations increased (primarily due to changes in biogenic SOA) by up to 11.5% (0.081 μg m−3) due to primary organic aerosol emissions from aircraft, with the additional organic mass shifting partitioning of SOA semi-volatile gas phase species into the particle phase.Display Omitted
Keywords: Aircraft emissions; CMAQ; Secondary organic aerosols; Process analysis; Particulate matter; Grid resolution;

Species profiles and normalized reactivity of volatile organic compounds from gasoline evaporation in China by Yanli Zhang; Xinming Wang; Zhou Zhang; Sujun Lü; Min Shao; Frank S.C. Lee; Jianzhen Yu (110-118).
In China, fast increase in passenger cars and gasoline consumption with yet quite limited vapor recovery during gasoline distribution has procured growing concern about gasoline evaporation as an important emission source of volatile organic compounds (VOCs), particularly in megacities hard-hit by air quality problems. This study presents VOC species profiles related to major pathways of gasoline evaporative loss in China, including headspace displacement, refueling operations and spillage/leakage. Apart from liquid gasoline and headspace vapors, gasoline vapors emitted when refueling cars in service stations or tank trucks in oil marketing depots were also sampled in situ with vapor recovery units (VRUs) turning on/off. Alkanes, alkenes and aromatic hydrocarbons accounted for 55–66, 21–35 and 4–8% in refueling vapors, 59–72, 18–28 and 4–10% in headspace vapors and 33–51, 8–15 and 38–48% in liquid gasoline samples, respectively. During refueling with VRUs turning on, total VOCs in vapors were less than one fifth of that with VRUs turning off, and aromatic hydrocarbons had higher weight percentages of about 8% in contrast with that of about 4% during refueling with VRUs turning off. Refueling vapors, especially for that with VRUs turning off, showed a larger fraction of light hydrocarbons including C3–C5 light alkenes when compared to headspace vapors, probably due to splashing and disturbance during filling operation. In refueling or headspace vapors the ratios of i-pentane/benzene, i-pentane/toluene, and MTBE (methyl tert-butyl ether)/benzene ranged 8.7–57, 2.7–4.8, and 1.9–6.6, respectively; and they are distinctively much higher than those previously reported in vehicle exhausts. Calculated normalized reactivity or ozone formation potential of the gasoline vapors in China ranged 3.3–4.4 g O3 g−1 VOC, about twice that of gasoline headspace vapors reported in USA as a result of larger fractions of alkenes in China's gasoline vapors. The results suggested that reducing VOC emission from gasoline distribution sector would particularly benefit ground-level ozone control in China.
Keywords: Gasoline evaporation; Volatile organic compounds (VOCs); Source profiles; Ozone formation potential (OFP); Normalized reactivity; Vapor recovery units (VRU);

Epidemiological studies have reported that both ozone (O3) and temperature are associated with daily mortality. However, few studies have explored the interactive effect between O3 and temperature on mortality. Moreover, whether different O3 metrics influence this interaction is still unknown. This study used a Poisson generalized additive model to examine the interactive effects of daily average temperature and O3 on mortality in Suzhou between 2008 and 2009. The results showed that the O3 effects were stronger in cold season and low temperature days. On days with low temperatures (0th–25th percentile), an interquartile range increment in 1-h maximum O3 corresponded to a 15.96% (95% CI: 1.52, 32.45) increase in total mortality and an 18.77% (95% CI: 0.09, 40.95) increase in cardiovascular mortality. On days with normal temperatures (26th–75th percentile) or high temperatures (76th–100th percentile), the estimates were only 2.04% (95% CI: −5.94, 10.69) or 1.65% (95% CI: −3.21, 6.76) for total mortality, and 7.82% (95% CI: −15.21, 37.10) or 6.14% (95% CI: −17.35, 36.31) for cardiovascular mortality. Using an 8-h maximum metric yielded similar interactive effects between ozone and temperature. For total and cardiovascular mortality, evidence indicates that low temperature has a stronger modifying effect on the 1-h maximum and the maximum 8-h average O3 concentrations than the 24-h average O3 concentrations. The interaction pattern of O3 with temperature was less sensitive at different cut-offs for temperature levels and including co-pollutants in the models. Our findings provide evidence that low daily average temperature significantly modifies the acute effects of ozone on daily mortality for both the 1-h maximum metric and the maximum 8-h average metric in Suzhou, China.
Keywords: Ozone; Temperature; Morality;

Influence of semi-volatile species on particle hygroscopic growth by Paolo Villani; Karine Sellegri; Marie Monier; Paolo Laj (129-137).
In this study, we use a Tandem Differential Mobility Analyser (TDMA) system combining particle volatilization and humidification conditioning (VH-TDMA) to test the effect of the gentle volatilization of a small fraction of the atmospheric particles on the particle hygroscopic growth in several environments (urban to remote). We first give an overview of the Hygroscopic Growth Factors (HGF) in these various environments, showing that in most of them, aerosol particles are externally mixed. We then show that the particle hygroscopicity can either be increased or decreased after thermal conditioning of the particle at moderate temperatures (50–110 °C). The hygroscopic growth factor changes induced by volatilization indicate that some volatile compounds, although present at low concentrations, can significantly influence the hygroscopic growth of particles in a way that can most of time be theoretically explained if simplified assumptions are used. However, simplified assumptions occasionally fail over several hours to explain hygroscopic changes, kinetic/surface effects observed at remote environments are suspected to be important.
Keywords: Hygroscopicity; TDMA; Kohler theory; Volatility; Mixing state;

The influence of dust events on precipitation acidity in China by Dan Wu; Shigong Wang; Junrong Xia; Xiaoyan Meng; Kezheng Shang; Yueyu Xie; Ruibin Wang (138-146).
Acid rain and dust events are both serious environmental problems striking China nowadays. This study investigates the distribution and change of precipitation pH and discusses the influence of dust events on precipitation acidity qualitatively and quantitatively in China. Acid rain exhibits remarkable regionality with strong acidic in South China and the acidity gradually decreases from the South to the North. This distribution is decided not only by the concentration of SO2 in atmosphere but also has relationship to the occurrence of dust events. Comparing the monthly changes of precipitation pH in the semiarid region (which is influenced by dust events) with those in the humid region (which is acid rain areas), it is found that the variation trends are just opposite in the two regions and there is an obvious peak value of pH in spring in semiarid region which coincides with the increase of dust event days. Chemical analysis results of precipitation in Lanzhou (a semiarid city intruded by dust events frequently, especially in spring) indicate that the ratio of Ca2+ plus Mg2+ concentrations (indicators of soil dust) to the total cation concentrations is the highest in spring, and the Ca2+ and Mg2+ concentrations are 1.8 and 1.9 times higher in spring than in summer respectively. The acidity of precipitation can be restrained by dust events qualitatively by increasing alkaline materials in the atmosphere and precipitation. The analysis of daily dust events and precipitation data at 6 stations in Northwest China indicates that the pH of precipitation influenced by dust events is greater than the precipitation not influenced by dust events. The increase degrees are different between different stations and have lagging effects. The direct increases are from 0.03 to 0.91 for the precipitation pH. Dust events can promote the precipitation pH to a certain extent quantitatively.
Keywords: Precipitation pH; Dust events; SO2 concentration; Chemical components of precipitation;

Effect of OH radical scavengers on secondary organic aerosol formation from reactions of isoprene with ozone by Kei Sato; Satoshi Inomata; Jia-Hua Xing; Takashi Imamura; Risa Uchida; Sayaka Fukuda; Kazumichi Nakagawa; Jun Hirokawa; Motonori Okumura; Susumu Tohno (147-154).
In order to understand the effect of OH radical scavengers on secondary organic aerosol formation, aerosol yields from the isoprene ozonolysis were measured in the presence of sufficient amounts of OH radical scavengers. Cyclohexane, CO, n-hexane, and diethyl ether were used as the OH radical scavengers. The aerosol yield was determined to be 0.002–0.023 for experiments without OH radical scavengers in the aerosol mass range 2–120 μg m−3. Similar aerosol yields were observed in experiments using cyclohexane. The aerosol yield observed with n-hexane was close to that observed without scavengers at 120 μg m−3, but this aerosol yield was slightly lower than those observed in reactions without scavengers in the range 3–83 μg m−3. The offline aerosol samples obtained in experiments with cyclohexane or n-hexane contained oxygenated hydrocarbons with six or more carbon atoms. Aerosol formation in experiments that used cyclohexane or n-hexane as the scavenger was enhanced. This was caused by the oxidation products of the OH radical scavengers, although the increase in the yield could not be quantified. The aerosol yields were 0.002–0.014 for experiments with CO and diethyl ether in the aerosol mass range 4–120 μg m−3. The reaction of CO with OH radicals forms HO2 radicals, whereas the reactions of cyclohexane, n-hexane, and diethyl ether, respectively, with OH radicals form organic peroxy (RO2) radicals. Present results show that the aerosol yield is independent of the HO2/RO2 ratio or that it decreases with increasing HO2/RO2 ratio. Since the HO2 concentration is much higher than the RO2 concentration in the atmosphere, the results obtained using CO in this study will be a good approximation of the aerosol yield from the ozonolysis of isoprene in the atmosphere.
Keywords: Environmental chamber; Biogenic volatile organic compound; Ozone–alkene reaction; Stabilized Criegee intermediate; Radical chemistry;

Anthropogenic atmospheric emissions of cadmium in China by Xiao Shao; Hongguang Cheng; Qian Li; Chunye Lin (155-160).
In this study, we estimated atmospheric Cd emissions from anthropogenic sources in China from 1990 to 2010 on the basis of consumption or output data and emission factors. China emitted approximately 2186 t Cd to the atmosphere in 2010, with approximately 77% and 14% of the emissions arising from non-ferrous metal smelting and coal combustion, respectively. Temporal changes in the total Cd emissions were characterized by two periods of increase (1990–2000 and 2001–2010) and a short period of decrease (2000–2001) due to application of energy-saving and cleaner production technologies. Overall, atmospheric Cd emissions increased from 474 t in 1990 to 2186 t in 2010 due to rapid economic growth, whereas energy-saving and cleaner production technologies have been in use since 2000. Spatial distribution of the atmospheric Cd emissions was dominated primarily by non-ferrous metal smelting and coal combustion. Emissions are high in Hunan and Yunnan Provinces because of high production non-ferrous metal smelting and in Shandong Province because of high coal consumption and moderate non-ferrous metal production.
Keywords: Anthropogenic; Cadmium emission; Temporal change; Spatial change; China;

Rate coefficient for the reaction of β-pinene with OH radicals was determined at 298 K and 800 Torr of N2 using the relative rate technique. Isobutylene was used as a reference compound and the concentrations of the organics were followed by gas chromatographic analysis. The rate coefficient for the reaction of β-pinene with OH radical was measured to be (9.35 ± 2.79) × 10−11 cm3 molecule−1 s−1. Theoretical kinetic calculations were also performed for the title reaction using canonical variational transition state theory (CVT) with small-curvature tunneling (SCT). The kinetics data obtained over the temperature range of 200–400 K were used to derive the Arrhenius expression: k(T) = 8.24 × 10−23 T 3.41 exp[2421/T] cm3 molecule−1 s−1. The OH-driven atmospheric lifetime (τ) and global warming potential (GWP) for β-pinene were computed and concluded that β-pinene is very short lived (2.5 h) in the Earth's atmosphere with a GWP of 1.6 × 10−2 at 20 years horizon of time and which is negligible. The ozone formation potential of β-pinene was also calculated and reported in this present work.Display Omitted
Keywords: β-pinene; OH radicals; Rate coefficient; Atmospheric lifetime; Global warming potential; Ozone formation potential;

Interpreting aerosol lidar profiles to better estimate surface PM2.5 for columnar AOD measurements by D. Allen Chu; Tzu-Chin Tsai; Jen-Ping Chen; Shuenn-Chin Chang; Yung-Jyh Jeng; Wei-Li Chiang; Neng-Hui Lin (172-187).
Satellite aerosol optical depth (AOD) products have been used to estimate surface PM2.5 in different parts of the world. However, some revealed good but some relatively poorer relationship between AOD and PM2.5. The increasingly available lidar-based aerosol extinction profiles provide insights into the boundary layer as well as residual above it. Here we report a study in Taiwan using four-year (2006–2009) MPLNet data to characterize aerosol vertical distribution. We derived haze layer height (HLH) from MPLNet aerosol extinction profiles and classified profile differences by mean PBL extinction (MPE) and near-surface extinction (NSE). The former represents the mean extinction within boundary layer and the latter the closest extinction to surface. The comparison of MPE versus NSE leads to three distinct classifications of aerosol profiles to help interpret the relationship between AOD and PM2.5. The approximation of normalizing AODAERONET by HLH closely follows MPE in correlating with PM2.5 (≥0.8 with respect to season or ≥0.85 with respect to profile classification). The correlation resulted from AODMODIS/HLH is systematically lower than that derived by AODAERONET/HLH. PM2.5 values are overall better estimated by profile classification than those derived by season. Better performance of PM2.5 is obtained with the approximation (i.e., normalizing AOD by HLH) than that using AOD only. The performance metrics used in quantifying the relationship reveal improvements in uncertainty by 2.9 μg m−3 (or 20%) with AODAERONET/HLH and 2.3 μg m−3 (or 15%) with AODMODIS/HLH in comparison to using AOD only.
Keywords: Taiwan; MODIS; Aerosol optical depth; Planetary boundary layer height; Haze layer height; Particulate matter;

Emission characteristics and air–surface exchange of gaseous mercury at the largest active landfill in Asia by Wei Zhu; Zhonggen Li; Xiaoli Chai; Yongxia Hao; Che-Jen Lin; Jonas Sommar; Xinbin Feng (188-197).
The emission characteristics and air-surface exchange of gaseous elemental mercury (GEM) at Laogang landfill in Shanghai, China, the largest active landfill in Asia, has been investigated during two intensive field campaigns in 2011 and 2012. The mercury (Hg) content in municipal solid waste (MSW) varied widely from 0.19 to 1.68 mg kg−1. Over the closed cell in the landfill, the mean ambient air GEM concentration was virtually indistinguishable from the hemispherical background level (1.5–2.0 ng m−3) while the concentration downwind of ongoing landfill operation (e.g. dumping, burying and compacting of MSW) was clearly elevated. GEM emission through landfill gas (LFG) was identified as a significant source. GEM concentrations in LFGs collected from venting pipes installed in different landfill cells varied widely from 3.0 to 1127.8 ng m−3. The GEM concentrations were found negatively correlated to the age of LFG cells, suggesting GEM released through LFG declined readily with time. The GEM emission from this source alone was estimated to be 1.23–1.73 mg h−1. GEM emission from cover soil surfaces was considerably lower and at a scale comparable to that of background soil surfaces. This is in contrast to earlier reports showing enhanced GEM emissions from landfill surfaces in Southern China, probably due to the difference in soil Hg content and gas permeability characteristics of soils at different sites. Vertical concentration profiles of GEM in the interstitial gas of buried MSW were sampled, perhaps for the first time, which exhibited a wide spatial variability (4.9–713.1 ng m−3) in the 3-year-old landfill cell investigated. GEM emission from landfill operation was estimated to be 290–525 mg h−1 using a box model. This suggests that GEM degassing from Laogang landfill is quantitatively largely dominated by emissions from daily landfilling operations with a much smaller contribution from LFG venting and insignificant (bi-directional fluxes near zero) contribution from surfaces capped with a soil layer. This study reveals divergent GEM emission patterns among landfill cells of different ages, and provides essential emission estimates for formulating Hg emission reduction strategies for a large landfill.
Keywords: Landfill; GEM flux; Landfill gas; Interstitial gas GEM; Shanghai;

Air pollution and early deaths in the United States. Part I: Quantifying the impact of major sectors in 2005 by Fabio Caiazzo; Akshay Ashok; Ian A. Waitz; Steve H.L. Yim; Steven R.H. Barrett (198-208).
Combustion emissions adversely impact air quality and human health. A multiscale air quality model is applied to assess the health impacts of major emissions sectors in United States. Emissions are classified according to six different sources: electric power generation, industry, commercial and residential sources, road transportation, marine transportation and rail transportation. Epidemiological evidence is used to relate long-term population exposure to sector-induced changes in the concentrations of PM2.5 and ozone to incidences of premature death. Total combustion emissions in the U.S. account for about 200,000 (90% CI: 90,000–362,000) premature deaths per year in the U.S. due to changes in PM2.5 concentrations, and about 10,000 (90% CI: −1000 to 21,000) deaths due to changes in ozone concentrations. The largest contributors for both pollutant-related mortalities are road transportation, causing ∼53,000 (90% CI: 24,000–95,000) PM2.5-related deaths and ∼5000 (90% CI: −900 to 11,000) ozone-related early deaths per year, and power generation, causing ∼52,000 (90% CI: 23,000–94,000) PM2.5-related and ∼2000 (90% CI: −300 to 4000) ozone-related premature mortalities per year. Industrial emissions contribute to ∼41,000 (90% CI: 18,000–74,000) early deaths from PM2.5 and ∼2000 (90% CI: 0–4000) early deaths from ozone. The results are indicative of the extent to which policy measures could be undertaken in order to mitigate the impact of specific emissions from different sectors — in particular black carbon emissions from road transportation and sulfur dioxide emissions from power generation.
Keywords: Air pollution; Early death; Emissions; Particulate matter; Ozone; Sector;

Differences in ozone photochemical characteristics between the megacity Tianjin and its rural surroundings by Su-qin Han; Min Zhang; Chun-sheng Zhao; Xue-qiang Lu; Liang Ran; Meng Han; Pei-yan Li; Xiang-jin Li (209-216).
Ground level ozone and its precursors were measured from July 10 to September 30, 2009 within Tianjin. The data were used to analyze differences in ozone photochemical oxidant production in urban and rural areas. Results showed more pronounced risk of O3 exposure at the rural site, Wuqing. During the observation period, ozone varied monthly, peaking in Jul. and reaching a minimum in Sep. The daily maximum ozone concentration was found to exceed 80 ppb for 28 days 100 ppb for 12 days, 120 ppb for 7 days at Wuqing, while it exceeded 80 ppb for 10 days, 100 ppb for 2 days, and 120 ppb for 1 day at the urban site, Tieta. The daily maximum ozone concentrations at Wuqing and Tieta were 193.7 ppb and 130.4 ppb. The daily maximum ozone concentration occurred at noon in Tieta and at 14:00 in Wuqing. NO and NO x peaked in September and reached minimum values in Jul., CO showed little variation at both sites. NO x and CO showed similar double-peak diurnal cycles resulted from a combination of diurnal variation of emission and the Planetary Boundary Layer During the VOCs (volatile organic compounds) sampling period, the average total VOCs concentration showed considerable day to day variation, which was 87.91 ppb with a range of 27.2 ppb–437.3 ppb at Tieta, and the average total VOCs was 197.95 ppb with a range of 63.48 ppb–473.97 ppb at Wuqing. A sensitivity study performed with the NCAR-MM model showed alkenes to be the most numerous contributors to O3 production, accounting for 53.3% of the total. Aromatics and alkanes accounted for 35.1% and 9.2%, respectively.
Keywords: Difference between urban and rural; Ozone; NO x ; VOCs; Tianjin;

An inverse dispersion technique for the determination of ammonia emissions from urea-applied farmland by Wenliang Yang; Anning Zhu; Jiabao Zhang; Yujun Zhang; Xiaomin Chen; Ying He; Liming Wang (217-224).
A backward Lagrangian stochastic (BLS) model for estimating ammonia emission in the field, utilizing data from ammonia concentration measurements by the open-path tunable diode laser method, was assessed by comparing it with the benchmark provided by simultaneous monitoring by the micrometeorological mass balance (MMB) technique. The results indicated that after rejecting data with u* ≤ 0.15 m s−1 or |L| < 10 m, the ammonia emissions derived by the BLS model were very similar to those by MMB (regression gradient = 0.966, R 2 = 0.959). The BLS model was also compared with the static chamber (SC) method of monitoring changes in gas concentration (enrichment/depletion) over time; it was found that these methods yielded significantly different results for both diurnal ammonia fluctuations and total ammonia loss. The results also showed that the mean time had little effect on the accuracy of the BLS method, but a short averaging time was preferable when investigating diurnal change of ammonia emissions.
Keywords: Ammonia emission; Backward Lagrangian stochastic model; Open-path tunable diode laser; Micrometeorological mass balance method; Static chamber method;

Establishing multiple regression models for ozone sensitivity analysis to temperature variation in Taiwan by Pao-Wen Grace Liu; Jiun-Horng Tsai; Hsin-Chih Lai; Der-Min Tsai; Li-Wei Li (225-235).
Sensitivity of meteorological variation to air quality has attracted people's attention since climate change became a world issue. The goal of this study is to investigate the sensitivity of ground-level ozone concentrations to temperature variation in Taiwan. Several multivariate regression models were built based on historical data of ozone and meteorological variables at three cities located in northern, mid-western, and southern Taiwan. Results of descriptive statistics indicate that the severe pollution from the highest to the minor conditions following by the order of the southern (Pingtung), mid-western (Fengyuan), and the northern sites (Hsichih). Multiple regression models containing a principal component trigger variable effectively simulated the historical ozone exceedance during 2004–2009. Inclusion of the PC trigger were improved R 2 from the lowest 0.38 to the highest 0.58. High probability of detection and critical success index (mostly between 85% and 90%) and low false alarm rates (0–2.6%) were achieved for predicting the high ozone days (≧100 ppb). The results of sensitivity analysis indicated that (1) the ozone sensitivity was positively correlated with the temperature variation, (2) the sensitivity levels were opposite to that of the ozone problem severity, (3) the sensitivity was mostly apparent in ozone seasons, and (4) the sensitivity strongly depended on the seasonality in the urban cities Hischih and Fengyuan, but weakly depended on seasonality in the rural city Pingtung.
Keywords: Regression; Ozone; Principal component; Sensitivity analysis; Climate change;

Ambient air SO2 patterns in 6 European cities by Susann Henschel; Xavier Querol; Richard Atkinson; Marco Pandolfi; Ariana Zeka; Alain Le Tertre; Antonis Analitis; Klea Katsouyanni; Olivier Chanel; Mathilde Pascal; Catherine Bouland; Daniela Haluza; Sylvia Medina; Patrick G. Goodman (236-247).
An analysis of the hourly SO2 pollution patterns with time can be a useful tool for policy makers and stakeholders in developing more effective local policies in relation to air quality as it facilitates a deeper understanding of concentrations and potential source apportionment.A detailed analysis of hourly inter-annual, seasonal and weekday-specific SO2 concentration patterns using data obtained from 6 cities involved in the Aphekom project was conducted. This type of analysis has been done for other pollutants but less so for SO2, and not in a systematic fashion for a number of European cities.Individual diurnal SO2 profiles and working weekday versus weekend specific 24-hr plots were generated using hourly SO2 measurements from a roadside and an urban background monitoring sites for 1993, 2001 and 2009 for each of the 6 European cities (Athens, Barcelona, Brussels, London, Paris, and Vienna). This facilitated the assessment of city specific patterns and comparison of changes with time.SO2 concentrations varied throughout the day and tended to be lower on the weekends. A general decreasing trend for SO2 levels with time was observable at all stations.This study provides a useful European perspective on patterns of exposure. For the 6 EU cities examined, road traffic, heating, and shipping in port cities appeared to be important sources of SO2 emissions, and hence the driving components widely reflected in the diurnal profiles with lower levels on the weekend likely due to lower traffic volume and industry related emissions. Although ambient SO2 concentrations have fallen over the assessed study period at all measurement sites, the daily patterns remained relatively unchanged.
Keywords: Air pollution; Hourly SO2; Diurnal variation; Diurnal profile; Weekday vs. weekend;

The transport of atmospheric sulfur over Cape Town by Samantha L. Jenner; Babatunde J. Abiodun (248-260).
Cape Town, renowned for its natural beauty, is troubled by an unpleasant brown haze pollution, in which atmospheric sulfur plays a major role. This study investigates whether Cape Town is a net producer or recipient of anthropogenic sulfur pollution. In the study, two atmospheric chemistry-transport models (RegCM and WRF) are used to simulate atmospheric flow and chemistry transport over South Africa for two years (2001 and 2002). Both models reproduce the observed seasonal variability in the atmospheric flow and SO2 concentration over Cape Town. The models simulations agree on the seasonal pattern of SO2 over South Africa but disagree on that of SO4.The simulations show that ambient sulfur in Cape Town may be linked with pollutant emissions from the Mpumalanga Highveld, South Africa's most industrialized region. While part of atmospheric SO2 from the Highveld is transported at 700 hPa level toward the Indian Ocean (confirming previous studies), part is transported at low level from the Highveld toward Cape Town. In April, a band of high concentration SO2 extends between the Highveld and Cape Town, following the south coast. Extreme sulfur pollution events in Cape Town are associated with weak flow convergence or stagnant conditions over the city, both of which encourage the accumulation of pollution. However the study suggests that atmospheric sulfur is being advected from Mpumalanga Highveld to Cape Town and this may contribute to atmospheric pollution problems in Cape Town.
Keywords: Sulfur; Pollution meteorology; Atmospheric transport; Modeling; RegCM; WRF;

Spatially detailed estimation of exposure to air pollutants in the urban environment is needed for many air pollution epidemiological studies. To benefit studies of acute effects of air pollution such exposure maps are required at high temporal resolution. This study introduces nonlinear optimisation framework that produces high resolution spatiotemporal exposure maps. An extensive traffic model output, serving as proxy for traffic emissions, is fitted via a nonlinear model embodying basic dispersion properties, to high temporal resolution routine observations of traffic-related air pollutant. An optimisation problem is formulated and solved at each time point to recover the unknown model parameters. These parameters are then used to produce a detailed concentration map of the pollutant for the whole area covered by the traffic model. Repeating the process for multiple time points results in the spatiotemporal concentration field. The exposure at any location and for any span of time can then be computed by temporal integration of the concentration time series at selected receptor locations for the durations of desired periods. The methodology is demonstrated for NO2 exposure using the output of a traffic model for the greater Tel Aviv area, Israel, and the half-hourly monitoring and meteorological data from the local air quality network. A leave-one-out cross-validation resulted in simulated half-hourly concentrations that are almost unbiased compared to the observations, with a mean error (ME) of 5.2 ppb, normalised mean error (NME) of 32%, 78% of the simulated values are within a factor of two (FAC2) of the observations, and the coefficient of determination (R 2) is 0.6. The whole study period integrated exposure estimations are also unbiased compared with their corresponding observations, with ME of 2.5 ppb, NME of 18%, FAC2 of 100% and R 2 that equals 0.62.
Keywords: Air pollution monitoring; Exposure; Nonlinear optimisation; Traffic model output;

Polycyclic aromatic hydrocarbons (PAH) are currently generating a great deal of interest because of their recognised toxicity, including carcinogenicity. In this study, source apportionment (SA) has been carried out using Positive Matrix Factorisation (PMF) with a dataset of 29 individual PAH (sum of vapour and particulate forms) collected by the UK National Network between 2002 and 2006. Analysis of data from 14 urban sites revealed four major source categories corresponding to unburned petroleum, diesel combustion, wood combustion and coal combustion. When a separate set of sites known to be influenced by local industrial sources was analysed, three source categories were identified corresponding to the unburned petroleum, diesel combustion and coal combustion seen in the full data analysis. When SA data were applied to the individual sites, the estimated apportionment could be explained in terms of local emission characteristics. Unburned petroleum showed the highest contribution to the sum of PAH, averaging 51.9% across the network, but benzo(a)pyrene (BaP) was more influenced by the coal combustion source which contributed 59.5% across the entire network. At the subset of sites with local industrial influence, industry was both the main contributor to the sum of PAH (accounting for 48.4% of PAH mass) and of BaP (67.9% of mass). A spatial analysis was also conducted in which the traffic source was evaluated by the difference between a roadside and a nearby urban background site, the urban source by difference between urban background and a rural site, and the industrial source by difference between a site close to a major steelworks subtracting data from a local urban background site. This showed considerable similarity between the net urban contribution and the road traffic factor, and between the net industrial contribution and the PMF coal factor profile. In both cases the congener profiles corresponded fairly well to UK national emissions inventory data. When PMF was applied separately to a more recent dataset for particle-bound PAH (2008-10) in three site groupings, it was able to distinguish the domestic coal burning source from the industry-related coal combustion source. For the urban sites, vehicle exhausts contributed the largest amount of particulate PAH and BaP across the whole year, with significant attribution to domestic coal combustion seen in the cold season.Display Omitted
Keywords: Polycyclic aromatic hydrocarbons; Source apportionment; Receptor modelling; PMF;

Mercury and metals in South African precipitation by Susan W. Gichuki; Robert P. Mason (286-298).
Even though mercury (Hg) is a global pollutant there are few studies of its concentration in the Southern Hemisphere, either in the atmosphere or in atmospheric deposition, and this is particularly true for Africa and developing nations such as South Africa. Emission inventories suggest that there is the potential for anthropogenic impact through elevated deposition in South Africa to sensitive ecosystems. To begin examining such impact, measurements of Hg and other trace metals (Al, Fe, Mn, Co, Ni, Cu, Zn, Cd and Pb) were made of rain collected using a bulk deposition collector at Cape Point, at the tip of Africa, and in Pretoria, a city within the industrial and mining heartland of South Africa. As expected, concentrations and fluxes were elevated in Pretoria, the more urban location. However, there is also evidence that Cape Point site can be impacted by regional pollution during the winter. The volume weighted mean Hg concentration at Cape Point was 10.6 ng L−1 compared to 15.8 ng L−1 in Pretoria. Comparison of rain concentrations for Hg and other metals, and relative fluxes (normalized to Al), indicate the importance of regional sources of contamination to both sites. The importance of impacted air masses at Cape Point was further investigated using ancillary data (CO and Rn) and back trajectory analysis. Overall, these results suggest that Hg and trace metal concentrations and fluxes are comparable to other locations in the world that are impacted by regional anthropogenic sources.
Keywords: Mercury; Trace metals; Precipitation; South Africa; Deposition; Metal pollution;

The surface winds and backward trajectories were analyzed to investigate sources of sodium and potassium ions measured in rainwater in the metropolitan area of São Paulo (MASP), Brazil, from July-2002 to December-2005. In this study, we evaluated the chemical composition of 315 rainwater samples with focus on precipitation events with high concentrations of sodium and potassium, with cations concentrations, at least 1.5 times higher than the sulfate and nitrate concentrations. In the results from the total samples, the Na+ and K+ volume weighted mean (VWM) concentrations were 10.4 and 3.2 μmol L−1, respectively, while for the excess events, the concentrations were 32.4 and 11.1 μmol L−1. From the 31 sodium excess events, 45% showed an influence from ocean air masses by the wind direction evaluation while 57% of backward trajectories for 7 potassium excess events indicated a contribution of biomass burning air masses from the northwestern region of the São Paulo State. Although some excess events pointed the pattern of long-range transport, they represented less than 15% of total samples. The results suggest that the megacity itself is predominantly involved in the process of emission and removal of the compounds and the influence of external components are limited to circumstantial events.
Keywords: Rainwater; Sea-salt; Biomass burning; Backward trajectories; HYSPLIT; Long-range transport;

In this study, a new approach combining the environment monitoring, model simulation and source apportionment methods was proposed to investigate the impact of vehicular emissions on the PM2.5 pollution. The method can identify the contributions of various emission sources to both the primary and secondary particles. A case application was conducted in Beijing, China. An intensive monitoring covering the period of December 2010 to January 2012 was conducted to obtain the detailed chemical components proportions in the total PM2.5. The vehicular emission contributions (VECs) to primary organic aerosols (POA), element carbon (EC), SO2, NO X , NH3, elements and VOC were estimated based on the MM5-CMAQ simulation, factor analysis and references investigation. The VECs to different components and to the total PM2.5 were then calculated. Results showed that there was no clear difference in the total VECs of different seasons. The annual average contribution ratio was approximately 22.5 ± 3.5%. Among all the chemical species, nitrate and SOA accounted for the highest contribution percentages. In addition, the influence of road dust on the PM2.5 pollution was also simulated using the MM5-CMAQ modeling system. It is indicated that the road dust contributed approximately 4.9 ± 1.3% of the total PM2.5 on an annual average. Considering both the contributions from motor vehicles and road dust emissions, the annual average direct contributions from road transport to the PM2.5 in Beijing was approximately 27.4 ± 4.8%.
Keywords: Source apportionment; PM2.5 pollution; Vehicular emissions; Environment monitoring; MM5-CMAQ; Road dust;

Local emission of primary air pollutants and its contribution to wet deposition and concentrations of aerosols and gases in ambient air in Japan by Masahide Aikawa; Takatoshi Hiraki; Nobutaka Tomoyose; Tsuyoshi Ohizumi; Izumi Noguchi; Kentaro Murano; Hitoshi Mukai (317-323).
We studied wet deposition by precipitation and the concentrations of aerosols and gases in ambient air in relation to the primary air pollutants discharged from domestic areas. The concentrations of aerosols and gases were influenced by nearby emissions except for non-sea-salt SO 4 2 − , which is transported long distances. The area facing the Sea of Japan showed much larger wet deposition than other areas, although the domestic emissions of the primary air pollutants there were small and showed a peak in wet deposition from October to March, as distinct from April to September in other areas. We performed the correlation analyses between wet deposition of each component and the product of the concentrations of corresponding aerosols and gases in ambient air and the two-thirds power of the precipitation. From the results, following scavenging processes were suggested. • Sulfate and ammonium were scavenged in precipitation as particulate matter such as (NH4)2SO4 and NH4HSO4. • Nitrate was scavenged mainly in precipitation through gaseous HNO3. • Ammonium was complementarily scavenged in precipitation through aerosols such as (NH4)2SO4 and NH4HSO4 and through gaseous NH3.
Keywords: Emission; Wet deposition; Sulfate; Nitrate; Ammonium; Japan Environmental Laboratories Association (JELA);

Spatial–temporal variations of particle number concentrations between a busy street and the urban background by Vanessa Dos Santos-Juusela; Tuukka Petäjä; Anu Kousa; Kaarle Hämeri (324-333).
To estimate spatial–temporal variations of ultrafine particles (UFP) in Helsinki, we measured particle total number concentrations (PNC) continuously in a busy street and an urban background site for six months, using condensation particle counters (CPC). We also evaluated the effects of temperature, wind speed and wind direction on PNC, as well as the correlation between PNC and PM2.5, PM10 and black carbon (BC) at the street. We found that on weekdays, hourly median PNC were highly correlated with BC (r = 0.88), moderately correlated with PM2.5 (r = 0.59) and weakly correlated with PM10 (r = 0.22). Number concentrations at the street were inversely proportional to temperature and wind speed, and highly dependent on wind direction. The highest PNC occurred during northeastern winds while the lowest occurred during southwestern winds. As these wind directions are nearly perpendicular to the street axis, the formation of wind vortices may have influenced the dispersion of UFP in the site. Although the temporal correlation for PNC was moderately high between the sites (r = 0.71), the median concentration at the street was 3 times higher than the urban background levels. The results indicate that people living or passing by the busy street are exposed to UFP concentrations well above the urban background levels. Thus, the study suggests that urban microenvironments should be considered in epidemiological studies. In addition the results emphasize that regulations based solely on PM2.5 and PM10 concentrations may be insufficient for preventing the adverse health effects of airborne particles.
Keywords: Ultrafine particles; Particulate matter; Spatial variations; Street canyon; Particle number; Helsinki;

Ultrafine particle emissions from desktop 3D printers by Brent Stephens; Parham Azimi; Zeineb El Orch; Tiffanie Ramos (334-339).
The development of low-cost desktop versions of three-dimensional (3D) printers has made these devices widely accessible for rapid prototyping and small-scale manufacturing in home and office settings. Many desktop 3D printers rely on heated thermoplastic extrusion and deposition, which is a process that has been shown to have significant aerosol emissions in industrial environments. However, we are not aware of any data on particle emissions from commercially available desktop 3D printers. Therefore, we report on measurements of size-resolved and total ultrafine particle (UFP) concentrations resulting from the operation of two types of commercially available desktop 3D printers inside a commercial office space. We also estimate size-resolved (11.5 nm–116 nm) and total UFP (<100 nm) emission rates and compare them to emission rates from other desktop devices and indoor activities known to emit fine and ultrafine particles. Estimates of emission rates of total UFPs were large, ranging from ∼2.0 × 1010 # min−1 for a 3D printer utilizing a polylactic acid (PLA) feedstock to ∼1.9 × 1011 # min−1 for the same type of 3D printer utilizing a higher temperature acrylonitrile butadiene styrene (ABS) thermoplastic feedstock. Because most of these devices are currently sold as standalone devices without any exhaust ventilation or filtration accessories, results herein suggest caution should be used when operating in inadequately ventilated or unfiltered indoor environments. Additionally, these results suggest that more controlled experiments should be conducted to more fundamentally evaluate particle emissions from a wider arrange of desktop 3D printers.
Keywords: Indoor aerosols; Three-dimensional printers; Thermoplastic emission; Molten extrusion deposition;

Towards an improved inventory of N2O from agriculture: Model evaluation of N2O emission factors and N fraction leached from different sources in UK agriculture by L.M. Cardenas; R. Gooday; L. Brown; D. Scholefield; S. Cuttle; S. Gilhespy; R. Matthews; T. Misselbrook; J. Wang; C. Li; G. Hughes; E. Lord (340-348).
National and international requirements for greenhouse gas emissions demand the development of more accurate inventories and mitigation options that are effective in reducing emissions. The UK government set a target for the year 2050 of an 80% reduction in greenhouse gas emissions compared to the 1990 baseline. Estimate of UK national emissions is based on IPCC default methodology and as agriculture contributes about 7% of total GHG emissions of which 60% is N2O, efforts to improve the inventory and assess mitigation options are needed. Models can be used to derive N2O emission factors providing high spatial and temporal resolution. In this study, we used two models, the UK-DNDC, a mechanistic model to estimate N2O emissions from soils and the NITCAT model to estimate the fraction of N applied that is leached and causes indirect emissions, both at county level for the UK. Four mitigation options were assessed and the results showed there were differences in the emission factors according to location. Average emission factors for N2O from soils for inorganic fertiliser did not differ from the IPCC default value but for organic fertiliser the model gave much lower values. FracLEACH for arable land was higher than that for grassland (UK averages of 0.28 and 0.09 respectively) and the national average value was 0.18. For N2O, the most effective mitigation measure was adjusting fertiliser rates to account for crop available manure N. For N leaching, the most effective measure was implementation of a manure closed period.
Keywords: UK-DNDC; NITCAT; Model; Nitrous oxide; FracLEACH; Agriculture;

Direct radiative forcing and climate effects of anthropogenic aerosols with different mixing states over China by B.L. Zhuang; S. Li; T.J. Wang; J.J. Deng; M. Xie; C.Q. Yin; J.L. Zhu (349-361).
An online coupled regional climate and chemistry model was used to investigate the direct effects of anthropogenic aerosols (sulfate, nitrate, black carbon BC and organic carbon OC) with different mixing states over China. Three mixing assumptions were considered, including external (EM), internal (IM, BC-core surrounded by well mixed scattering-shells) and partially internal (PIM, 32.2% of sulfate and nitrate, 35.5% of BC and 48.5% of OC were internally mixed) mixtures. Results indicated that high levels of anthropogenic aerosols were found in Southwest and Central to East China. Regional mean surface loadings of sulfate, nitrate, BC, primary OC over China were 9.56, 3.64, 2.30, and 2.99 μg m−3, respectively. PIM-aerosol optical depth and single scattering albedo, which were consistent with AERONET and satellite observations, were 0.51 ± 0.37 and 0.95 ± 0.02 in Central to East China, implying that proportions of internally mixed aerosols in PIM were reasonable to some degrees. Both aerosol direct radiative forcing (DRF) and corresponding climate responses were sensitive to aerosol mixing states and BC/OC hygroscopicities. The more BC was internally mixed or hydrophilic, the more solar radiation was absorbed, thus leading to more decreases in cloud amount (CA) and subsequently less surface cooling. Combining with the uncertainties of BC/OC hygroscopicities, regional mean PIM-aerosol DRF at the top of atmosphere ranged from −0.78 to −0.61 W m−2 in all-sky and from −5.24 to −4.95 W m−2 in clear-sky. Additionally, responses of cloud amount and water path, total column absorbed solar radiation (TCASR), surface air temperature and precipitation (TP) to PIM-aerosol DRFs over China were about −0.45∼ −0.37%, −0.44 ∼ −0.32 g m−2, +0.69 ∼ +0.72 W m−2, −0.13 ∼ −0.11 K and −4.56 ∼ −4.29%, respectively. These responses were also sensitive to the lateral boundary condition perturbations especially for CA, TCASR and TP, while DRFs themselves were not.
Keywords: Anthropogenic aerosols; Direct effects; Radiative forcing; Externally mixing states; Internally mixing states; China;

Determining rate of refrigerant emissions from nonprofessional automotive service through a southern California field study by Tao Zhan; Denis Clodic; Lionel Palandre; Arnaud Trémoulet; Youssef Riachi (362-368).
Vehicle owners in the United States can recharge their vehicles' air conditioning systems with small containers of hydrofluorocarbon-134a (HFC-134a, CH2FCF3). This refrigerant, with a Global Warming Potential of 1430, may be emitted to the atmosphere during the recharging operation and from the residual heel in partially used containers, contributing to climate change. A field study was conducted in southern California to quantify the rate of refrigerant emissions from nonprofessional recharging practices and identify emission mitigation opportunities. Based on the results of the study, an average of 489 g of HFC-134a is used when recharging the sample vehicles with an average nominal charge of 858 g. An average 67% of the container content is effectively charged into the systems, 11% of the refrigerant is released during service, and the remaining 22% is left in the containers after operations are completed. A comparison with two other independent studies indicates that the findings of the current study may be applicable not only to southern California, but also to the entire U.S.
Keywords: HFC-134a; Greenhouse gas; Motor vehicle air conditioning; Nonprofessional service; Do-it-yourself recharge; Emission factor;

Biogenic isoprene in subtropical urban settings and implications for air quality by Jia-Lin Wang; Clock Chew; Chih-Yuan Chang; Wei-Cheng Liao; Shih-Chun Candice Lung; Wei-Nai Chen; Po-Ju Lee; Po-Hsiung Lin; Chih-Chung Chang (369-379).
Isoprene has potentially a large impact on secondary oxidant formation, particularly in the polluted urban atmospheres. The environmental conditions in tropical and subtropical cities with high temperatures and light flux are conducive to the production of large amounts of biogenic isoprene. Measurements of speciated volatile organic compounds (VOCs) were conducted in Taipei, a subtropical metropolis, to investigate the characteristics of biogenic and anthropogenic isoprene during the hot seasons (summer and autumn) and to assess their significance in secondary pollutant formation. The daily and daytime average concentrations of isoprene at the subtropical urban site in summer were 0.72 and 1.26 ppbv, respectively, which were considerably higher than the concentrations of isoprene in most temperate cities. Furthermore, summertime isoprene ranks highest in OH reactivity and second highest in terms of ozone formation potential (OFP) among 66 measured VOCs.The ratios of isoprene to 1,3-butadiene, an exhaust tracer, were used to estimate the fractions of biogenic and anthropogenic isoprene in the urban area. The results reveal that the biogenic contribution apparently overwhelmed the anthropogenic contribution in summertime, although traffic in the city is heavy. Furthermore, the residual isoprene (mostly biogenic) after daytime photochemical loss persisted into the nighttime and contributed a large fraction to nighttime isoprene. In autumn, daytime isoprene was also predominantly from biogenic sources because the hot and sunny conditions persist into the autumn months. The high biogenic isoprene levels in subtropical urban settings and its coherence with OH diurnal cycles accentuate the significance of biogenic isoprene and its potentially great impact on atmospheric oxidant capacity, urban air quality, and even regional climate.
Keywords: Secondary pollutant; Isoprene; Volatile organic compounds (VOCs); Secondary organic aerosols (SOA); Vehicular tracer;

A pilot study characterizing real time exposures to particulate matter and carbon monoxide from cookstove related woodsmoke in rural Peru by Adwoa A. Commodore; Stella M. Hartinger; Claudio F. Lanata; Daniel Mäusezahl; Ana I. Gil; Daniel B. Hall; Manuel Aguilar-Villalobos; Luke P. Naeher (380-384).
Nearly half of the world's population is exposed to household air pollution (HAP) due to long hours spent in close proximity to unvented cooking fires. We aimed to use PM2.5 and CO measurements to characterize exposure to cookstove generated woodsmoke in real time among control (n = 10) and intervention (n = 9) households in San Marcos, Cajamarca Region, Peru. Real time personal particulate matter with an aerodynamic diameter ≤2.5 μm (PM2.5), and personal and kitchen carbon monoxide (CO) samples were taken. Control households used a number of stoves including open fire and chimney stoves while intervention households used study-promoted chimney stoves. Measurements were categorized into lunch (9 am–1 pm) and dinner (3 pm–7 pm) periods, where applicable, to adjust for a wide range of sampling periods (2.8–13.1 h). During the 4-h time periods, mean personal PM2.5 exposures were correlated with personal CO exposures during lunch (r = 0.67 p = 0.024 n = 11) and dinner (r = 0.72 p = 0.0011 n = 17) in all study households. Personal PM2.5 exposures and kitchen CO concentrations were also correlated during lunch (r = 0.76 p = 0.018 n = 9) and dinner (r = 0.60 p = 0.018 n = 15). CO may be a useful indicator of PM during 4-h time scales measured in real time, particularly during high woodsmoke exposures, particularly during residential biomass cooking.
Keywords: Carbon monoxide; Cookstove; Exposure assessment; Household air pollution; Particulate matter; Peru;

Complex topography influences atmospheric nitrate deposition in a neotropical mountain rainforest by Sandro Makowski Giannoni; Rütger Rollenbeck; Peter Fabian; Jörg Bendix (385-394).
Future increase of atmospheric nitrogen deposition in tropical regions is expected to have negative impacts on forests ecosystems and related biogeochemical processes. In tropical mountain forests topography causes complex streamflow and rainfall patterns, governing the atmospheric transport of pollutants and the intensity and spatial variability of deposition. The main goal of the current study is to link spatio-temporal patterns of upwind nitrogen emissions and nitrate deposition in the San Francisco Valley (eastern Andes of southern Ecuador) at different altitudinal levels. The work is based on Scanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) retrieved-NO2 concentrations, NO x biomass burning emissions from the Global Fire Emissions Database (GFEDv3), and regional vehicle emissions inventory (SA-INV) for urban emissions in South America. The emission data is used as input for lagrangian atmospheric backward trajectory modeling (FLEXTRA) to model the transport to the study area. The results show that NO 3 − concentrations in occult precipitation samples are significantly correlated to long-range atmospheric secondary nitrogen transport at the highest meteorological stations (MSs) only, whereas for NO 3 − concentrations in rain samples this correlation is more pronounced at the lower MSs. We conclude that ion concentrations in occult precipitation at the uppermost MSs are mainly linked to distant emission sources via the synoptic circulation impinging the more exposed higher sites. Lower correlations close to the valley bottom are due to a lower occult precipitation frequency and point to a contamination of the samples by local pollution sources not captured by the used emission data sources.
Keywords: South Ecuador; Atmospheric deposition; Nitrogen; Satellite data; Emission inventories; Complex topography;

A geostatistical approach for producing daily Level-3 MODIS aerosol optical depth analyses by J.A. Ruiz-Arias; J. Dudhia; V. Lara-Fanego; D. Pozo-Vázquez (395-405).
The daily Level-3 MODIS (dL3M) aerosol optical depth product is a global daily spatial aggregation of the Level-2 MODIS aerosol optical depth (10-km spatial resolution) into a regular grid with a resolution of 1° × 1°. Aerosol optical depth is a seminal parameter for surface solar radiation assessment, in particular, for those applications involving direct irradiance. However, the dL3M AOD is prone to data gaps originated mostly by the unfeasibility of retrieving reliable estimates under cloudy conditions. In addition, its usability is also constrained by regional biases owing to some other reasons. In this work we propose a methodology for bias reduction and data-gaps removal of the dL3M AOD dataset. The result is a database of daily regularly-gridded AOD suitable for use in surface solar radiation applications and large-scale and long-term studies involving AOD without requiring a previous costly data assimilation process involving numerical weather prediction models. The method consists of an empirical approach to bias reduction, data-gaps removal by kriging interpolation and, finally, where reliable ground observations are available, an optimal interpolation procedure. The method was tested in the North American region, where it was able to reduce the initial mean error from 0.067 to 0.001, the root mean square error from 0.130 to 0.057, and increase the squared correlation coefficient from 23% to 58%, as compared against ground measurements.
Keywords: Aerosol optical depth; Level-3 MODIS; Surface solar irradiance;

Sampling system influence on gaseous air pollution measurements by L.A. Mittal; D.C. Green; B.P. Sweeney; P.G. Quincey; G.W. Fuller (406-410).
Efficient sampling systems are key components of ambient air pollution measurement systems used for both regulatory and research purposes. Gaseous sampling systems were tested at 83 monitoring sites incorporating three different sampling system designs. The mean sample collection efficiency was 98% for CO, 99.1% for NO2, 88.7% for O3 and 96.7% for SO2. In most cases, the test uncertainties were greater than the 2% threshold for sample losses allowed by the relevant European Standards. These uncertainties were largely due to repeatability and signal noise within the equipment being tested and the low test gas concentrations required to avoid conditioning the sampling system. There is therefore little scope for improving the test uncertainty. For O3, test uncertainties and repeatability issues meant that firm conclusions could not be reached. For other pollutants, manifold systems offered no systematic advantages over simple PTFE tubing. PTFE tubes should therefore be favoured in site design, providing sample residence times can be met. The high average sampling efficiencies of PTFE sample tubes combined with the uncertainties inherent in the test procedure suggest that regular testing is not worthwhile for this type of sampling system providing sample lines are regularly changed or cleaned. Where a manifold is used, periodic maintenance should include cleaning, as well as flow and leak tests.
Keywords: Sampling system; NO2; O3; CO; SO2;

Characterization of volcanic ash from the 2011 Grímsvötn eruption by means of single-particle analysis by K.I. Lieke; T.B. Kristensen; U.S. Korsholm; J.H. Sørensen; K. Kandler; S. Weinbruch; D. Ceburnis; J. Ovadnevaite; C.D. O'Dowd; M. Bilde (411-420).
This work focuses on transport and properties of ash from the Icelandic volcano Grímsvötn that erupted in spring 2011. Atmospheric transport of volcanic ash from the eruption was simulated using the Danish Emergency Response Model of the Atmosphere (DERMA). The arrivals of volcanic particles were detected on-line at Mace Head at the West coast of Ireland during volcanic plume advection identified by high resolution time of flight aerosol mass spectrometry (HR-ToF AMS).Based on DERMA information aerosol particles were collected in Copenhagen, Denmark, before predicted arrival of the ash plume and during a period where ash was present in the air.Analysis of the meteorological conditions shows that the particles collected before arrival of the volcanic ash may serve as a good reference sample allowing identification of significant changes in ambient aerosol properties during the volcanic ash event over Copenhagen. Using single particle analysis in scanning electron microscopy (SEM), data on structure, chemical composition, size and morphology of individual volcanic ash particles from the Grímsvötn eruption after atmospheric transport to Scandinavia are provided. Particles were sliced with Focused Ion Beam (FIB). Element mappings from cross-sections through collected volcanic ash particles reveal inhomogeneous distributions of the elements K, Mg, Fe and Ti.
Keywords: Volcanic ash; Grímsvötn; Particles; DERMA; FIB/SEM; HR-ToF AMS;

Estimation of sulfur dioxide air pollution concentrations with a spatial autoregressive model by Pavlos S. Kanaroglou; Matthew D. Adams; Patrick F. De Luca; Denis Corr; Nazmul Sohel (421-427).
In this paper, we develop a land-use regression model for sulfur dioxide air pollution concentrations. We make use of mobile monitoring data collected in Hamilton, Ontario, Canada, between 2005 and 2010 inclusive. The observed SO2 concentrations are regressed against a comprehensive set of land use and transportation variables. Land use and transportation variables are assessed as the amount of each characteristic within buffers of 50, 100, 200, 400, 800, and 1600 m around pollution observation locations. In the first instance of regression modeling, we apply ordinary least-squares regression. The OLS model R 2 for training data was 0.38, and an R 2 of 0.3 for a 50% held out cross-validation data set. The residuals are spatially correlated with the OLS model as determined with Moran's I. We thus applied a simultaneous autoregressive model, specifically the spatial error model. The resulting model slightly improved fit as determined by a pseudo R 2 = 0.4, improved log-likelihood, and reduced MSE, RMSE, and MAE. The spatial error model residuals were not spatially auto-correlated, resulting in a valid model. SAR modeling is a natural extension to OLS regression models and solves the issue of spatial autocorrelation in model residuals with a one-stage model.Display Omitted
Keywords: Air pollution; Sulfur dioxide; Mobile monitoring; Land use regression; Spatial error model; Hamilton; Ontario; Canada;

Assessment of polyaromatic hydrocarbon emissions from laser printers by Benjamin J. Mullins; Dean Bertolatti; Ryan Mead-Hunter (428-432).
The potential for polyaromatic hydrocarbon (PAH) emissions from laser printers has been examined using a simulated printing process and a detailed chemical analysis of printer toner. We have analysed the PAH content of both carbon black (a toner constituent) and toner before and after heating and have found measurable evaporation and subsequent condensation of PAHs. Based on our analysis we have estimated a maximum possible PAH emission rate of 82.1 μg min 1 of printing for a 10% page coverage. Our VOC emission results agree well with those of other authors. The concentrations of individual PAHs in the emissions were relatively low, however non-trivial, especially long term.
Keywords: PAHs; VOCs; Toner; Ultrafine particles; Printing;

The effect of developing nations' municipal waste composition on PCDD/PCDF emissions from open burning by Lisa Lundin; Brian Gullett; William F. Carroll; Abderrahmane Touati; Stellan Marklund; Heidelore Fiedler (433-441).
Open burning tests of municipal waste from two countries, Mexico and China, showed composition-related differences in emissions of polychlorinated dibenzodioxins and dibenzofurans (PCDDs/PCDFs). Twenty-six burn tests were conducted, comparing results from two laboratory combustion facilities. Waste was shredded to isolate composition-specific effects from those due to random waste orientation. Emissions ranged from 5 to 780 ng toxic equivalent/kg carbon burned (ng TEQ (kg Cb)−1) with an average of 140 ng TEQ (kg Cb)−1 (stdev = 170). The waste from Mexico (17 ng TEQ (kg Cb)−1) had a statistically lower average emission factor than waste from China (240 ng TEQ (kg Cb)−1. This difference was attributed primarily to waste composition differences, although one time-integrated combustion quality measure, ΔCO/ΔCO2, showed statistical significance between laboratories. However, waste composition differences were far more determinant than which laboratory conducted the tests, illustrated using both statistical techniques and comparison of cross-over samples (wastes tested at both facilities). Comparison of emissions from previous waste combustion tests in Sweden and the U.S.A, showed emission factors within the range of those determined for Mexico and China waste. For laboratory-scale combustion, existing emission factors and test methodologies are generally applicable to both developed and developing countries.
Keywords: PCDD/PCDF; Emission; Waste; Open burning; Composition;

A Community Multiscale Air Quality model with the Master Chemical Mechanism is applied to evaluate the reactions of stabilized Criegee Intermediates SCIs with SO2 ( k SCI + SO 2 ) on sulfate aerosols in the eastern United States (US) during the summer of 2006. Surface sulfate concentrations and total sulfate columns increased by as much as 18% and 6%, respectively, when ( k SCI + SO 2 ) was increased from 7 × 10−14 cm3 s−1 to a suggested value of 3.9 × 10−11 cm3 s−1. The episode-average increase of the top-of-atmosphere direct radiative forcing due to the additional sulfate can be as much as −0.7 W m−2 (5%). However, if the SCI + H2O reaction rate constant ( k SCI + H 2 O ) was also increased based on the reported ratio of kSCI+H2O to ( k SCI + SO 2 ) (6.1 × 10−5), the surface sulfate and total sulfate column increases were less than 0.5%, which suggests that the impact of SCIs on sulfate may be insignificant and additional studies are needed to better determine k SCI + H 2 O . Small SCIs such as CH2OO and CH3CHOO, and SCIs from isoprene (MVKOO) and monoterpene (APINBOO) oxidation are the dominant SCIs in the eastern US.
Keywords: Criegee intermediate; CMAQ; Master Chemical Mechanism; Sulfate; Direct radiative forcing;

Multiple linear and higher order equations were developed for the estimation of the PM10 spatial distribution over the broader area of Athens, Greece, based on satellite data. In situ PM10 measurements for the period 2007–2010 were used to calibrate the satellite observations. The latter included Aerosol Optical Thickness (AOT) derived from MODIS (Moderate Resolution Imaging Spectroradiometer) and MERIS (MEdium Resolution Imaging Spectrometer) and AATSR (Advanced Along-Track Scanning Radiometer) sensors, as well as surface relative humidity, surface temperature and K-Index derived from MODIS. The performance of linear and non-linear relationships and the contribution of each satellite-derived parameter were analyzed based on a stepwise validation. Results found that non-linear relations perform better than simple linear, while the K-Index, an estimator of atmospheric static stability, can be used as a proxy of the vertical aerosol mixing. Coefficients of determination around 0.7 were achieved. Seasonal mean PM10 distributions were also computed, revealing an intra-annual variation, which obtained higher values during the summer, along with spatial differences in PM10 concentrations which were attributed to air pollution at the city center and at industrial areas.
Keywords: Particulate matter; MODIS; MERIS/AATSR synergy; Multiple regression;

A monitoring strategy to assess the fugitive emission from a steel plant by M. Amodio; E. Andriani; P.R. Dambruoso; G. de Gennaro; A. Di Gilio; M. Intini; J. Palmisani; M. Tutino (455-461).
An assessment of the fugitive emission impact on ambient air PM, PAHs and metal concentrations was performed in a residential area near the biggest European steel plant. A careful experimental design was developed to characterize fugitive emissions produced by the integrated steel plant. A PM10 and PM2.5 monitoring campaign was conducted at three sampling sites around the steel plant, in order to perform a triangulation in the area surrounding the investigated site and evaluate its impact based on wind direction. Data analysis showed that the transport of air mass, from the steelworks to one of the receptor sites, resulted in ambient air concentrations of Fe, Mn, Zn and PAHs higher than those observed in the other two sites. Principal component analysis allowed the identification of four emission sources: coke ovens stack, mineral park, a crustal source and vanadium source. The first two sources were characterized by high concentrations of PAHs and metals and related to the steelworks, while the vanadium source was probably associated with maritime traffic in the port area. This preliminary monitoring approach proved effective in identifying the fugitive emission contribution of the steel plant to the surrounding air quality.
Keywords: Steel plant; Fugitive emissions; Micro-pollutants; PAHs; Heavy metals; Southern Italy;

Amelioration of the reactive nitrogen flux calculation by a day/night separation in weekly mean air concentration measurements by Kentaro Hayashi; Kazuhide Matsuda; Keisuke Ono; Takeshi Tokida; Toshihiro Hasegawa (462-471).
The low time resolution of air concentration data of atmospheric deposition in regional monitoring networks makes it difficult to estimate fluxes between the land and the atmosphere. The present study was an evaluation of the effects of day/night separation for a low time resolution of air concentration measurements (i.e., weekly mean) for the estimation of reactive nitrogen fluxes. The target chemical species included reactive nitrogen primarily ammonia (NH3) and nitric acid gas (HNO3) and secondarily nitrous acid gas, particulate ammonium, and particulate nitrate in addition to sulfur dioxide (SO2) as a reference. Monitoring was conducted for one year at a single-crop rice paddy field in central Japan. The study period was divided into the cropping and fallow seasons, which were characterized by rice plants or a drained bare soil surface, respectively. The filter-pack method was applied to measure the weekly mean air concentrations with day/night separation for the target species at two heights (6 and 2 m above the ground surface). Both an inferential and a gradient method were applied to calculate the deposition and exchange fluxes, respectively. The day/night separation in a weekly sampling protocol, on average, reduced the underestimation of HNO3 fluxes for the inferential method by 15.2% ± 6.8% and 8.2% ± 6.1% in the cropping and fallow seasons, respectively, and reduced the overestimation of NH3 fluxes for the gradient method by 121% ± 128% in the cropping season. The fluxes calculated using the inferential method agreed relatively well with those calculated using the gradient method for HNO3 and SO2. The use of single-height measurements for air concentrations with day/night separation and flux calculations using the inferential method are recommended as an appropriate way to enhance the quality in calculated fluxes while simultaneously suppress the increase in labor cost.
Keywords: Atmosphere-rice paddy exchange; Dry deposition; Emission; Filter-pack method; Gradient method; Resistance model;

Scenarios of global mercury emissions from anthropogenic sources by P. Rafaj; I. Bertok; J. Cofala; W. Schöpp (472-479).
This paper discusses the impact of air quality and climate policies on global mercury emissions in the time horizon up to 2050. Evolution of mercury emissions is based on projections of energy consumption for a scenario without any global greenhouse gas mitigation efforts, and for a 2 °C climate policy scenario, which assumes internationally coordinated action to mitigate climate change. The assessment takes into account current air quality legislation in each country, as well as provides estimates of maximum feasible reductions in mercury through 2050. Results indicate significant scope for co-benefits of climate policies for mercury emissions. Atmospheric releases of mercury from anthropogenic sources under the global climate mitigation regime are reduced in 2050 by 45% when compared to the case without climate measures. Around one third of world-wide co-benefits for mercury emissions by 2050 occur in China. An annual Hg-abatement of about 800 tons is estimated for the coal combustion in power sector if the current air pollution legislation and climate policies are adopted in parallel.
Keywords: Mercury emissions; Air pollution control; Climate policy; Co-benefits;

Performance in real condition of photonic crystal sensor based NO2 gas monitoring system by M. Rahmat; W. Maulina; E. Rustami; M. Azis; D.R. Budiarti; K.B. Seminar; A.S. Yuwono; H. Alatas (480-485).
In this report we discuss the performance in real condition of an optical based real-time NO2 gas monitoring system. For detecting the gas concentration in the ambient air we have developed an optical sensor based on one-dimensional photonic crystal with two defects that allows the existence of photonic pass band inside the associated photonic band gap. To measure the gas concentration, we dissolve the corresponding NO2 gas into a specific Griess Saltzman reagent solution. The change of gas concentration in the related dissolved-solution can be inspected by the photonic pass band peak variation. It is observed that the wavelength of the photonic pass band peak of the fabricated photonic crystal is nearly coincide with the wavelength of the associated solution highest absorbance. The laboratory test shows that the device works properly, whereas the field measurement test demonstrates accurate results with validation error of 1.56%.
Keywords: Photonic crystal; NO2 gas; Real-time monitoring system;

Emergencies planning and response: Coupling an exposure model with different atmospheric dispersion models by E.Y. Sanchez; J.E. Colman Lerner; A. Porta; P.M. Jacovkis (486-494).
Information on spatial and time dependent concentration patterns of hazardous substances, as well as on the potential effects on population, is necessary to assist in chemical emergency planning and response. To that end, some models predict transport and dispersion of hazardous substances, and others estimate potential effects upon exposed population. Taken together, both groups constitute a powerful tool to estimate vulnerable regions and to evaluate environmental impact upon affected populations.The development of methodologies and models with direct application to the context in which we live allows us to draft a more clear representation of the risk scenario and, hence, to obtain the adequate tools for an optimal response. By means of the recently developed DDC (Damage Differential Coupling) exposure model, it was possible to optimize, from both the qualitative and the quantitative points of view, the estimation of the population affected by a toxic cloud, because the DDC model has a very good capacity to couple with different atmospheric dispersion models able to provide data over time. In this way, DDC analyzes the different concentration profiles (output from the transport model) associating them with some reference concentration to identify risk zones.In this work we present a disaster scenario in Chicago (USA), by coupling DDC with two transport models of different complexity, showing the close relationship between a representative result and the run time of the models. In the same way, it becomes evident that knowing the time evolution of the toxic cloud and of the affected regions significantly improves the probability of taking the correct decisions on planning and response facing the emergency.
Keywords: Chemical incident; Risk analysis; Acute exposure; Pollutant dispersion model;

Comparison of results of an obstacle resolving microscale model with wind tunnel data by David Grawe; K. Heinke Schlünzen; Frauke Pascheke (495-509).
The microscale transport and stream model MITRAS has been improved and a new technique has been implemented to improve numerical stability for complex obstacle configurations. Results of the updated version have been compared with wind tunnel data using an evaluation method that has been established for simple obstacle configurations. MITRAS is a part of the M-SYS model system for the assessment of ambient air quality. A comparison of model results for the flow field against quality ensured wind tunnel data has been carried out for both idealised and realistic test cases. Results of the comparison show a very good agreement of the wind field for most test cases and identify areas of possible improvement of the model. The evaluated MITRAS results can be used as input data for the M-SYS microscale chemistry model MICTM. This paper describes how such a comparison can be carried out for simple as well as realistic obstacle configurations and what difficulties arise.
Keywords: Microscale; Evaluation; Numerical model; Wind tunnel; Urban area; Wind field; MITRAS;

Effect of Asian dust storms on daily mortality in seven metropolitan cities of Korea by Hyewon Lee; Ho Kim; Yasushi Honda; Youn-Hee Lim; Seungmuk Yi (510-517).
The adverse effects of dust storms on health have been a major issue in several countries. A substantial number of studies have found significant associations between dust storms and morbidity such as emergency visits and hospitalizations. However, the results of the studies on the association between dust storms and mortality are inconsistent. In Korea, no study has found statistically significant effect of Asian dust storms on daily mortality. Thus, this study aims to explore the effect of Asian dust storms on daily mortality in Korea during 2001–2009. All analyses were confined to non-accidental mortality. We used generalized additive model with Quasi-Poisson regressions. We considered the lag effect of dust storms up to 7 days and performed subgroup analyses by disease, sex and age. Current day's temperature, relative humidity, barometric pressure, day of the week, season and time trends were controlled for in a basic model. SO2, NO2 and PM10 levels were also added in the further analyses. Meta-analysis was applied for seven metropolitan cities in Korea to estimate the pooled effects of Asian dust storms. We reported results as excessive mortality by percentage due to Asian dust storms. We found significant positive associations between Asian dust storms and mortality at lag 0 (cardiovascular: 2.91%; 95% CI: 0.13, 5.77, male: 2.74%; 95% CI: 0.74, 4.77 and <65 years: 2.52%; 95% CI: 0.06, 5.04), at lag 2 (male 2.4%; 95% CI: 0.43, 4.4 and <65 years: 2.49%; 95% CI: 0.07, 4.97), at lag 3 (total non-accidental: 1.57%; 95% CI: 0.11, 3.06, male: 2.24%; 95% CI: 0.28, 4.25 and <65 years: 2.43%; 95% CI: 0.01, 4.91) and at lag 5 (cardiovascular: 3.7%; 95% CI: 0.93, 6.54 and male: 2.04%, 95 CI: 0.08, 4.04) in the model which adjusted for NO2 additionally. Other models showed similar significant results except the PM10-adjusted model. This is the first study to show the significant relationship between Asian dust storms and mortality in Korea and to present a pooled effect estimate by meta-analysis of multiple cities in a country. Asian dust storms could significantly affect daily mortality in Korea.Display Omitted
Keywords: Asian dust storms; Non-accidental mortality; Lag effects; Pooled effects; Meta-analysis;

The depth of the planetary boundary layer (PBL) and its temporal evolution have important effects on weather, air quality and climate. While there are methods to detect the PBL depth from atmospheric profiles, few can be applied to different types of measurements and cope with changing atmospheric conditions. Many require supporting information from other instruments. In this study, two common methods for PBL depth detection (wavelet covariance and iterative curve-fitting) are combined, modified and applied to long-term time series of radiosonde profiles, micropulse lidar (MPL) measured backscatter and atmospheric emitted radiance interferometer (AERI) data collected at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site. Intercomparison among the three PBL retrieval products shows the robustness of the algorithm. The comparisons were made for different times of day, four seasons, and variable sky conditions. While considerable uncertainties exist in PBL detection using all three types of measurements, the agreement among the PBL products is promising under certain conditions, and the different measurements have complementary advantages. The best agreement in the seasonal cycle occurs in winter, and the best agreement in the diurnal cycle when the boundary-layer regime is mature and changes slowly. PBL depths from instruments with higher temporal resolution (MPL and AERI) are of comparable accuracy to radiosonde-derived PBL depths; AERI excels for shallow PBLs, MPL for cloudy conditions. The new continuous PBL data set can be used to improve model parameterizations of PBL and our understanding of atmospheric transport of pollutants which affect clouds, air quality and human health.
Keywords: Planetary boundary layer; Aerosol; Lidar; Radiosonde; Boundary-layer depth;

Source apportionment and organic compound characterization of ambient ultrafine particulate matter (PM) in the Los Angeles Basin by Sina Hasheminassab; Nancy Daher; James J. Schauer; Constantinos Sioutas (529-539).
In this study, quasi-UFP (PM0.25, dp < 0.25 μm) were collected for 24 h once per week from April 2008 to March 2009 at 10 different locations in the Los Angeles Basin. Samples were chemically analyzed and organic constituents of PM0.25 were grouped into polycyclic aromatic hydrocarbon (PAHs), hopanes and steranes, n-alkanes, and levoglucosan, with concentration levels ranging from 0.16 to 5.5, 0.09 to 2.2, 9.3 to 48, and 2.2 to 106.2 ng m−3 over all sites and seasons, respectively. A molecular marker-based chemical mass balance (MM-CMB) model was applied to estimate the relative contributions from the following primary sources: mobile sources (combined gasoline and diesel vehicles), wood smoke, natural gas combustion, vegetative detritus, and ship emissions. Secondary organic aerosol (SOA) tracers were not included in the model; however their contributions were estimated from non-biomass burning water soluble organic carbon (WSOCnb) and un-apportioned OC from MM-CMB model (“other OC”). High correlation (R 2 = 0.8) between “other OC” and WSOCnb in summer suggests that “other OC” is highly impacted by SOA, however un-apportioned primary sources may contribute to “other OC” as well. Mobile sources were expectedly the major primary contributor to PM0.25, with seasonal average contributions of 31 ± 12% in summer and 57 ± 17% in winter. “Other organic matter” was the second largest contributor to PM0.25 in all seasons, across the basin, with substantially higher contribution during warmer spring and summer seasons (27%), while lowest during cold seasons (13%). Wood smoke was the third major contributor to PM0.25 in winter, whereas its contribution was lowest in summer. As expected, ship emissions displayed the highest contribution at the near-harbor HUD site, and their levels continually decreased as a function of distance from coast. Two other primary sources, vegetative detritus and natural gas combustion, collectively contributed to 1.3 ± 0.8% of PM0.25 on an annual average basis over all sites. Comparison of our results to PM2.5 OC apportionment, conducted at central LA, shows that contribution of mobile sources to PM0.25 OC is more than two times higher than PM2.5 (75% and 30%, respectively), while “other OC” contributed significantly higher to PM2.5 OC compared to PM0.25 (56% and 21%, respectively).
Keywords: UFP; MM-CMB; Organic compounds; Source apportionment; Los Angeles Basin;

Highly elevated emission of mercury vapor due to the spontaneous combustion of refuse in a landfill by Wei Zhu; Jonas Sommar; Zhonggen Li; Xinbin Feng; Che-Jen Lin; Guanghui Li (540-545).
Refuse disposal (e.g., landfilling and incineration) have been recognized as a significant anthropogenic source of mercury (Hg) emission globally. However, in-situ measurements of Hg emission from landfill or refuse dumping sites where fugitive spontaneous combustion occurs have not been reported. Gaseous elemental mercury (Hg0) concentration and emission flux were observed near spontaneous combustions of refuse at a landfill site in southwestern China. Ambient Hg0 concentrations above the refuse surface ranged from 42.7 ± 20.0 to 396.4 ± 114.2 ng m−3, up to 10 times enhancement due to the spontaneous burning. Using a box model with Hg0 data obtained from 2004 to 2013, we estimated that the Hg0 emission from refuse was amplified by 8–40 times due to spontaneous combustion. A micrometeorological flux measurement system based on relaxed eddy accumulation was configured downwind of the combustion sites to quantify the Hg0 emission. Extremely large turbulent deposition fluxes (up to −128.6 μg m−2 h−1, 20 min average) were detected during periods of high Hg0 concentration events over the measurement footprint. The effect of temperature, moisture and light on the air–surface exchange of Hg0 exchange was found to be masked by the overwhelming deposition of Hg0 from the enriched air from the refuse combustion plumes. This research reveals that mercury emission from the landfill refuse can be boosted by fugitive spontaneous combustion of refuse. The emission represents an anthropogenic source that has been overlooked in Hg inventory estimates.Display Omitted
Keywords: Mercury flux; Refuse; Spontaneous combustion; Relaxed eddy accumulation; Box modeling;

FTIR gas-phase kinetic study on the reactions of OH radicals and Cl atoms with unsaturated esters: Methyl-3,3-dimethyl acrylate, (E)-ethyl tiglate and methyl-3-butenoate by Juan P. Colomer; María B. Blanco; Alicia B. Peñéñory; Ian Barnes; Peter Wiesen; Mariano A. Teruel (546-552).
The relative-rate technique has been used to obtain rates coefficients for the reactions of the unsaturated esters methyl-3,3-dimethyl acrylate, (E)-ethyl tiglate and methyl-3-butenoate with OH radicals and chlorine atoms at (298 ± 2) K in synthetic air at a total pressure of (760 ± 10) Torr. The experiments were performed in an environmental chamber using in situ FTIR detection to monitor the decay of the esters relative to different reference compounds. The following room temperature rate coefficients (in units of cm3 molecule−1 s−1) were obtained: k 1(OH + (CH3)2C=CHC(O)OCH3) = (4.46 ± 1.05) × 10−11, k 2(Cl + (CH3)2C=CHC(O)OCH3) = (2.78 ± 0.46) × 10−10, k 3(OH + CH3CH=C(CH3)C(O)OCH2CH3) = (8.32 ± 1.93) × 10−11, k 4(Cl + CH3CH=C(CH3)C(O)OCH2CH3) = (2.53 ± 0.35) × 10−10, k 5(OH + CH2 =CHCH2C(O)OCH3) = (3.16 ± 0.57) × 10−11k 4(Cl + CH2 =CHCH2C(O)OCH3) = (2.10 ± 0.35) × 10−10. With the exception of the reaction of Cl with methyl-3,3-dimethyl acrylate (k 2), for which one determination exists in the literature, this study is the first kinetic study for these reactions under atmospheric pressure. Reactivity trends are discussed in terms of the effect of the alkyl and ester groups attached to the double bond on the overall rate coefficients towards OH radicals. The atmospheric implications of the reactions were assessed by the estimation of the tropospheric lifetimes of the title reactions.Display Omitted
Keywords: Unsaturated esters; Rate coefficients; Addition reactions; Tropospheric chemistry;

Gas-phase products and secondary organic aerosol formation from the ozonolysis and photooxidation of myrcene by Olaf Böge; Anke Mutzel; Yoshiteru Iinuma; Pasi Yli-Pirilä; Ariane Kahnt; Jorma Joutsensaari; Hartmut Herrmann (553-560).
In this study, the ozone and OH-radical reactions of myrcene were investigated in an aerosol chamber (at 292–295 K and 50% relative humidity) to examine the gas-phase oxidation products and secondary organic aerosol (SOA) formation. The ozone reaction studies were performed in the presence and absence of CO, which serves as an OH radical scavenger. In the photooxidation experiments OH radicals were generated by photolysis of methyl nitrite. The ozonolysis of myrcene in the presence of CO resulted in a substantial yield of 4-vinyl-4-pentenal (55.3%), measured as m/z 111 plus m/z 93 using proton transfer reaction-mass spectrometry (PTR-MS) and confirmed unambiguously as C7H10O by denuder measurements and HPLC/ESI-TOFMS analysis of its 2,4-dinitrophenylhydrazine (DNPH) derivative. Additionally, the formation of two different organic dicarbonyls with m/z 113 and a molecular formula of C6H8O2 were observed (2.1%). The yields of these dicarbonyls were higher in the ozonolysis experiments without an OH scavenger (5.4%) and even higher (13.8%) in the myrcene OH radical reaction. The formation of hydroxyacetone as a direct product of the myrcene reaction with ozone with a molar yield of 17.6% was also observed. The particle size distribution and volume concentrations were monitored and facilitated the calculation of SOA yields, which ranged from 0 to 0.01 (ozonolysis in the presence of CO) to 0.39 (myrcene OH radical reaction). Terpenylic acid was found in the SOA samples collected from the ozonolysis of myrcene in the absence of an OH scavenger and the OH radical-initiated reaction of myrcene but not in samples collected from the ozonolysis in the presence of CO as an OH radical scavenger, suggesting that terpenylic acid formation involves the reaction of myrcene with an OH radical. A reaction mechanism describing the formation of terpenylic acid is proposed.
Keywords: Myrcene; Ozonolysis; OH radical; Chamber experiment; Reaction mechanism; SOA;

An improved approach for measuring Henry's law coefficients of atmospheric organics by J. Duncan Kish; Chunbo Leng; Judas Kelley; Joseph Hiltner; Yunhong Zhang; Yong Liu (561-565).
In this work, we present an improved method for Henry's law constant, K H , measurements by coupling a bubble column system with a gas cell/infrared spectrometer. To demonstrate the feasibility of this approach, we measured K H of atmospheric organics from three different classes, namely, toluene (hydrocarbon), sec-butylamine (amine), and cineole (ether). We also reported temperature and ionic strength effects on the K H values of sec-butylamine for the first time. As shown in this work, the method is highly capable of determining K H of atmospheric organic species regardless the presence of heteroatoms and the occurrence of hydration in water. It is very versatile, easy to use, reliable, and efficient. It is also well-suited for undergraduate students to conduct environmental chemical science research during academic semesters.
Keywords: Henry's law constant; Bubble column technique; Infrared gas cell; Temperature dependence; Ionic strength effect;

Seasonal and spatial variation in redox activity of quasi-ultrafine particles (PM0.25) and its association with chemical species was investigated at 9 distinct sampling sites across the Los Angeles metropolitan area. Biologically reactive oxygen species (ROS) assay (generation of ROS in rat alveolar macrophage cells) was employed in order to assess the redox activity of PM0.25 samples. Seasonally, fall and summer displayed higher volume-based ROS activity (i.e. ROS activity per unit volume of air) compared to spring and winter. ROS levels were generally higher at near source and urban background sites compared to rural receptor locations, except for summer when comparable ROS activity was observed at the rural receptor sites. Univariate linear regression analysis indicated association (R > 0.7) between ROS activity and organic carbon (OC), water soluble organic carbon (WSOC) and water soluble transition metals (including Fe, V, Cr, Cd, Ni, Zn, Mn, Pb and Cu). A multivariate regression method was also used to obtain a model to predict the ROS activity of PM0.25, based on its water-soluble components. The most important species associated with ROS were Cu and La at the source site of Long Beach, and Fe and V at urban Los Angeles sites. These metals are tracers of road dust enriched with vehicular emissions (Fe and Cu) and residual oil combustion (V and La). At Riverside, a rural receptor location, WSOC and Ni (tracers of secondary organic aerosol and metal plating, respectively) were the dominant species driving the ROS activity. At Long Beach, the multivariate model was able to reconstruct the ROS activity with a high coefficient of determination (R 2 = 0.82). For Los Angeles and Riverside, however, the regression models could only explain 63% and 68% of the ROS activity, respectively. The unexplained portion of the measured ROS activity is likely attributed to the nature of organic species not captured in the organic carbon (OC) measurement as well as non-linear effects, which were not included in our linear model.
Keywords: PM; Ultrafine; Reactive oxygen species; Water-solubility; Los Angeles basin;

Dynamic changes of CH4 and CO2 emission from grazing sheep urine and dung patches in typical steppe by Xiaoya Wang; Ding Huang; Yingjun Zhang; Wenqing Chen; Chengjie Wang; Xinming Yang; Wei Luo (576-581).
The contribution of livestock excreta to greenhouse gases (GHGs) emissions by sheep grazing in a typical steppe system in Guyuan county, Hebei province of the People's Republic of China was evaluated. Changes of methane (CH4) and carbon dioxide (CO2) fluxes from urine and dung patches excreted by sheep on grassland were measured for the first 144 h during July, August, September and October in 2011. CH4 fluxes from dung patches significantly increased (P < 0.05) within the first 4–8 h, and CO2 fluxes from urine patches significantly increased (P < 0.05) within the first 8 h. Urine patches cumulated the highest CO2 emission (188.89 g m−2) in the first 144 h in August. Cumulative CH4 emissions from urine patches and dung patches were −0.19 to 1.00 and −8.01 to 30.25 mg m−2 during the measurement period, and the control grassland was a net CH4 sink (−14.66 to −0.29 mg m−2). Dung induced the highest CH4 emission (23.46 μg g−2) in July. Significant positive correlations were found between soil temperature and GHGs fluxes (CH4 in grassland: R 2 = 0.32, P < 0.01; CO2 in urine patches: R 2 = 0.20, P < 0.05). Based on our measurement, the CH4 emission produced by the daily excreta per adult sheep grazing in summer was estimated at 15.07 ± 4.90 mg.
Keywords: Greenhouse gas; Grassland; Urine patch; Dung patch;

Summertime PM2.5 aerosols collected from Qinghai Lake (3200 m a.s.l.), a remote continental site in the northeastern part of Tibetan Plateau, were analyzed for dicarboxylic acids (C2–C11), ketocarboxylic acids and α-dicarbonyals. Oxalic acid (C2) is the dominant dicarboxylic acid in the samples, followed by malonic, succinic and azelaic acids. Total dicarboxylic acids (231 ± 119 ng m−3), ketocarboxylic acids (8.4 ± 4.3 ng m−3), and α-dicarbonyls (2.7 ± 2.1 ng m−3) at the Tibetan background site are 2–5 times less than those detected in lowland areas such as 14 Chinese megacities. Compared to those in other urban and marine areas enhancements in relative abundances of C2/total diacids and diacids-C/WSOC of the PM2.5 samples suggest that organic aerosols in the region are more oxidized due to strong solar radiation. Molecular compositions and air mass trajectories demonstrate that the above secondary organic aerosols in the Qinghai Lake atmosphere are largely derived from long-range transport. Ratios of oxalic acid, glyoxal and methylglyoxal to levoglucosan in PM2.5 aerosols emitted from household burning of yak dung, a major energy source for Tibetan in the region, are 30–400 times lower than those in the ambient air, which further indicates that primary emission from biomass burning is a negligible source of atmospheric oxalic acid and α-dicarbonyls at this background site.
Keywords: Oxalic acid; Secondary organic aerosols; PM2.5; Qinghai Lake; Tibet Plateau;

Effects of a shelterbelt on road dust dispersion by Y. Mao; J.D. Wilson; J. Kort (590-598).
The impact of a roadside shelterbelt on the downwind concentration of road dust raised by a passing vehicle was investigated experimentally, and by numerical modelling. With or without the shelterbelt, the gravel dust plume, as measured some 60 m or more downwind from the road, was dominated by small particles (most frequent diameter ≈ 6 μm) whose gravitational settling velocity was negligible compared to the turbulent velocity scale (i.e. friction velocity). The time-averaged concentration of these small particles was not lower in the lee of the shelterbelt than in a nearby, unsheltered area downwind of the road. Standard formulae for spheres in an airstream negotiating obstacles suggest such fine particles may pass through the shelterbelt on the bleed flow with little likelihood of interception and entrapment, because their small inertial time constant mandates that they accelerate with the wind, deviating around foliage. Numerical simulations of the experiment are consistent in some respects with what was observed, and suggest that the shelterbelt may increase the fraction of fine particles remaining airborne one minute after their injection at the road.
Keywords: Air quality; Airborne particulate; Dust control; Environment; PM10; Road dust; Shelterbelts; Windbreaks;

Aerosol particle vertical distributions and optical properties over Singapore by Boon Ning Chew; James R. Campbell; Santo V. Salinas; Chew Wai Chang; Jeffrey S. Reid; Ellsworth J. Welton; Brent N. Holben; Soo Chin Liew (599-613).
As part of the Seven Southeast Asian Studies (7SEAS) program, an Aerosol Robotic Network (AERONET) sun photometer and a Micro-Pulse Lidar Network (MPLNET) instrument have been deployed at Singapore to study the regional aerosol environment of the Maritime Continent (MC). Using coincident AERONET Level 2.0 and MPLNET Level 2.0a data from 24 September 2009 to 31 March 2011, the seasonal variability of aerosol particle vertical distributions and optical properties is examined. On average, the bulk (∼65%) of aerosol extinction is found below 1.5 km with substantial aerosol loading (∼35%) above. Possibly due to the transition from El Niño to La Niña conditions and subsequent reduction in fire events, the MPLNET mean integrated aerosol extinction is observed to be the lowest for July–September 2010, which coincides with the typical MC biomass burning season. On the other hand, the highest mean integrated extinctions are derived for January–March 2010 and 2011, which can be attributed to off-season MC biomass burning smoke and anthropogenic pollution. The seasonal lidar ratios also show higher occurrences ≥60 sr, which are indicative of biomass burning smoke, for October 2009–June 2010, but such occurrences decrease from July 2010 to March 2011 when La Niña conditions prevail. In addition, principal component analysis (PCA) identifies five primary aerosol vertical profile types over Singapore, i.e. strongly-capped/deep near-surface layer (SCD; 0–1.35 km), enhanced mid-level layer (EML; 1.35–2.4 km), enhanced upper-level layer (EUL; 2.4–3.525 km), deep contiguous layer (DCL; 3.525–4.95 km) and deep multi-layer (DML; >4.95 km). PCA also identifies an off-season MC biomass burning smoke event from 22 February to 8 March 2010, which is subsequently examined in detail.
Keywords: AERONET; ENSO; MPLNET; Lidar; Maritime Continent; Southeast Asia;

Investigation of the sources and seasonal variations of secondary organic aerosols in PM2.5 in Shanghai with organic tracers by Jialiang Feng; Man Li; Pan Zhang; Shiyi Gong; Mian Zhong; Minghong Wu; Mei Zheng; Changhong Chen; Hongli Wang; Shengrong Lou (614-622).
One hundred and forty seasonal PM2.5 samples were collected from January 2010 to January 2011 at one urban site and one suburban site simultaneously in a Chinese megacity, Shanghai, to study the concentrations and seasonal variation of secondary organic aerosols (SOA). Concentrations of water-soluble organic carbon (WSOC) were determined together with organic and elemental carbons. Thirteen organic tracers, including the tracer for biomass burning and tracers for SOA from isoprene, α-pinene, β-caryophyllene and toluene, were measured. EC-based method, WSOC-based method, tracer-based method and PMF modeling were used to estimate the seasonal contributions of secondary organic carbon (SOC) in Shanghai, and the results from the different methods were compared and evaluated. Biomass burning was the major contributor to the measured WSOC in the autumn sampling period, while SOA was the major contributor in the other seasons. The concentrations of the SOA tracers in summer were obviously higher than that in other seasons. It was found that SOC estimated with the tracer-based method accounted for only a small part of the SOC from the WSOC-based method in Shanghai, especially for the winter and spring sampling periods. PMF results showed that a large part of the SOC was associated with sulfate and nitrate but not with the SOA tracers.
Keywords: PM2.5; Secondary organic aerosol; WSOC; Organic tracer; Shanghai;

Several studies have shown that a significant amount of daily air pollution exposure, in particular Black Carbon (BC), is inhaled during trips. Assessing this contribution to exposure remains difficult because on the one hand local air pollution maps lack spatio-temporal resolution, at the other hand direct measurement of particulate matter concentration remains expensive. This paper proposes to use in-traffic noise measurements in combination with geographical and meteorological information for predicting BC exposure during commuting trips. Mobile noise measurements are cheaper and easier to perform than mobile air pollution measurements and can easily be used in participatory sensing campaigns.The uniqueness of the proposed model lies in the choice of noise indicators that goes beyond the traditional overall A-weighted noise level used in previous work. Noise and BC exposures are both related to the traffic intensity but also to traffic speed and traffic dynamics. Inspired by theoretical knowledge on the emission of noise and BC, the low frequency engine related noise and the difference between high frequency and low frequency noise that indicates the traffic speed, are introduced in the model. In addition, it is shown that splitting BC in a local and a background component significantly improves the model. The coefficients of the proposed model are extracted from 200 commuter bicycle trips. The predicted average exposure over a single trip correlates with measurements with a Pearson coefficient of 0.78 using only four parameters: the low frequency noise level, wind speed, the difference between high and low frequency noise and a street canyon index expressing local air pollution dispersion properties.
Keywords: Black Carbon; Vehicle noise; Personal exposure; Bicyclists; Traffic;

Satellite observation of abnormal yellow haze clouds over East China during summer agricultural burning season by Minghui Tao; Liangfu Chen; Zifeng Wang; Jinhua Tao; Lin Su (632-640).
Durative haze clouds with unusual yellow color appeared in East China in agricultural burning period during June 8–12 in 2012, causing extreme air pollution in densely populated regions including Jiangsu, Hubei, and the Yangtze River Delta. The spatial variation, vertical structure, optical properties, as well as formation process, were investigated using combined multiple satellite observations, ground measurements, and meteorological data. Different from previous studies, our analysis reveals that the yellow haze clouds were caused by mixing and interaction among airborne dust, fire emissions, and urban pollution under humid conditions. The pollution layers were 3–5 km thick, and their vertical structures were very inhomogeneous, with dust mostly distributed in the upper part and mixing of fires smoke and urban haze concentrated near surface. Compared with fire smoke, the dust-like haze clouds exhibited different optical properties with higher volume depolarization ratio and notable increase in coarse mode aerosols. Although fire emissions and urban pollution may play a more important role in surface pollution, we conclude that dust transport and high humidity were the main reason that the haze pollution was much heavier than that in previous years. In addition, regional concentrated fires only occurred in several days, and fire count was inconsistent with regional average aerosol loading. The long-range transport of fire emissions can be overestimated. In order to avoid such regional pollution event, our results also suggest that the strict measures in fire management should be extended from special periods to normal season.
Keywords: Yellow haze; Agricultural burning; Satellite; Dust transport; East China;

Nitrous oxide and methane fluxes from a rice–wheat crop rotation under wheat residue incorporation and no-tillage practices by Zhisheng Yao; Xunhua Zheng; Rui Wang; Baohua Xie; Klaus Butterbach-Bahl; Jianguo Zhu (641-649).
Crop residue incorporation and no-tillage are recommended as management practices and are being increasingly adopted in the agricultural sector. However, few studies have assessed the extent to which these practices integrate annual carbon and nitrogen trace gas fluxes and grain yield. We investigated the effect of wheat straw incorporation and no-tillage on nitrous oxide (N2O) and methane (CH4) fluxes from a rice–wheat system in southeast China, using year-round field measurements. Compared to the treatment with synthetic nitrogen fertilizers alone, the wheat straw incorporation reduced the N2O emissions by 38% (P < 0.05) and increased the CH4 emissions by 74% (P < 0.05) during the annual rotation cycle. Compared to the conventional tillage, no-tillage prior to wheat sowing enhanced the N2O emissions by an average of 61% (P < 0.05), irrespective of residue incorporation. The CH4-C emissions that were induced by the wheat straw comprised 6% of the residue-carbon incorporated during the rice season. As a result of the stimulating effect of wheat straw incorporation on CH4 fluxes, the annual aggregate emissions of N2O and CH4 with straw incorporation (10.7 Mg CO2-eq ha−1 yr−1 or 725 kg CO2-eq Mg−1 grain yield) were usually higher than those with no residue incorporation (7.6 Mg CO2-eq ha−1 yr−1 or 545 kg CO2-eq Mg−1 grain yield), irrespective of the tillage practice. Nevertheless, the changes in greenhouse gas emissions are notably only the transient response of the rice–wheat system after crop residue incorporation and tillage conversion, which may not necessarily represent equilibrium conditions for this agro-ecosystem over the long term.
Keywords: Methane; Nitrous oxide; Crop residue; Tillage; Rice–wheat cropping system;

Reflectance spectral analyses for the assessment of environmental pollution in the geothermal site of Mt. Amiata (Italy) by Ciro Manzo; Riccardo Salvini; Enrico Guastaldi; Valentina Nicolardi; Giuseppe Protano (650-665).
We studied the environmental impact of geothermal activities in the Mt. Amiata area, using on-site spectral analyses of various ecological components. Analytical techniques were based on the study of the “red-edge”, which represents the spectral feature of the reflectance spectra defined between red and infrared wavelengths (λ) within the range 670–780 nm. Since in the study area the geothermal exploitation causes the drifting of contaminants such as Hg, Sb, S, B, As and H2S (hydrogen sulfide) from power plants, the spectral response of vegetation and lichens depends on their distance from the power stations, and also on the exposed surface, material type and other physical parameters. In the present research, the spectral radiance of targets was measured in the field using an Analytical Spectral Device (ASD) Field-Spec™FR portable radiometer. Spectral measurements were made on vegetation and lichen samples located near to and far from geothermal areas and potential pollution sources (e.g., power plants), with the aim of spatially defining their environmental impact. Observations for vegetation and lichens showed correlation with laboratory chemical analyses when these organisms were under stress conditions. The evaluation of relationships was carried out using several statistical approaches, which allowed to identify methods for identifying contamination indicators for plants and lichens in polluted areas. Results show that the adopted spectral indices are sensitive to environmental pollution and their responses spatialstatically correlated to chemical and ecophysiological analyses within a notable distance.
Keywords: Geothermal activity; Environmental pollution; Reflectance spectra; Red-edge shift; Geostatistics;

Mayenite based supports for atmospheric NO x sampling by Raffaele Cucciniello; Antonio Proto; Federico Rossi; Oriana Motta (666-671).
In order to obtain a class of calcium based sorbent materials for the quantification and possibly the removal of NO x from the atmosphere, we synthesized and characterized various CaO/Mayenite (Ca12Al14O33) substrates having different weight ratio (w/w) composition. Their reactivity towards NO and NO2 was evaluated by means of several experimental techniques: FT-IR and XRD were used to characterize the species formed during the sorption process, while IC and TGA analysis provided information about the dynamics of the sorption process itself. The hydration reaction occurring on the substrate before NO x sorption has also been considered in our investigation. We finally tested the performance and the reliability of the CaO/mayenite materials in field measurements by incorporating the substrate in a passive sampler device. The simultaneous sorption of atmospheric NO2 and NO has been investigated and the role of the carbon dioxide in the NO x – CO2 exchange reactions has been assessed. According to the data reported in this paper and thanks to the fairly low cost of production, CaO/Mayenite substrates represent a good class of inorganic alkaline sorbents for NO x suitable for many applications in atmospheric sampling and remediation.Display Omitted
Keywords: Radial diffusive samplers; NO x ; Mayenite; Calcium oxide; Sol–gel synthesis;

Non-erodible particles have strong influence on the aeolian erosion phenomena. An oblong stockpile model of sand (bimodal granulometry) was implemented to perform wind-tunnel experiments as similar literature works have only carried out experimental investigations on a flat bed of particles. Thus, the influence of the fluid flow structures around the complex obstacle will be analysed. The tested configurations consisted of two different values of non-erodible particles cover rate (10% and 20%), and three free stream velocities (6, 7 and 8 m s−1). Good repeatability was found. The results showed that the largest amount of particles emitted was for the highest wind velocity and the smallest cover rate. The temporal decreasing of emitted mass flux was found steeper for larger amount of non-erodible particles and higher velocity. The mass flux of particles decreases very strongly in the first four minutes of measurements and the cover rate influences this downward sloping. The same analysis applies for the effects of the free stream velocity. The qualitative analysis (high quality photographic system) of the stockpile surface gradual change has shown that non-erodible particles aggregation induces a pavement effect on some areas of the pile. This analysis indicated typical wind erosion zones: high wall friction on the crest line and lateral sides; low wall friction on the windward wall near the ground and on the recirculation downstream the leeward wall. The results and discussions presented here allows for the understanding of the impact of non-erodible particle on dust emissions.
Keywords: Aeolian erosion; Stockpiles; Dust emission; Non-erodible particles; Wind-tunnel;

Relationship between methanesulfonate (MS) in atmospheric particulate and remotely sensed phytoplankton activity in oligo-mesotrophic central Mediterranean Sea by S. Becagli; L. Lazzara; F. Fani; C. Marchese; R. Traversi; M. Severi; A. di Sarra; D. Sferlazzo; S. Piacentino; C. Bommarito; U. Dayan; R. Udisti (681-688).
The coupling between oceanic and atmospheric sulfur cycles is fundamental for the understanding of the role of sulfate particles as potential climate regulators. We discuss existing relationships among methanesulfonate (MS – one of the end products of oxidation of biogenic dimethylsulfide – DMS) in the atmospheric particulate, phytoplankton biomass, and remotely-sensed activity in the central Mediterranean. The MS concentration in the aerosol particles is based on PM10 sampling (from 2005 to 2008) of atmospheric aerosols at the island of Lampedusa (35.5°N, 12.6°E) in the central Mediterranean Sea.The marine primary production in the sea sector surrounding the sampling site is obtained by using Ocean Color remote sensed data (SeaWiFS, MODIS-Aqua). In particular, primary production is calculated using a bio-optical model of sea reflectance and a Wavelength-Depth-Resolved Model (WDRM), fed by elaborated satellite data (chlorophyll concentration in the euphotic layer – Chl, sea surface temperature) and daily solar surface irradiance measurements.The multi-year evolution of MS atmospheric concentration shows a well-defined seasonal cycle with a summer maximum, corresponding to the annual peak of solar radiation and a minimum of phytoplankton biomass (expressed as Chl).Statistically significant linear relationships between monthly means of atmospheric MS and both the phytoplankton productivity index PB (r 2 = 0.84, p < 0.001) and the solar radiation dose (SRD; r 2 = 0.87, p < 0.001) in the upper mixed layer of the sea around Lampedusa are found. These correlations are mainly driven by the common seasonal pattern and suggest that DMS production in the marine surface layer is mainly related to the phytoplankton physiology. High values of PB are also the expression of stressed cells. The main stress factors in Mediterranean Sea during summer are high irradiance and shallow depth of the upper mixed layer, which lead to enhanced DMS emissions and higher MS amounts in the atmosphere.During spring 2005 high biomass and primary productivity values are observed in February and April, just one month before the peaks of atmospheric MS (March and May). The occurrence of anomalously high values at this time is hypothesized to be related to the negative phase of the North Atlantic Oscillation, and to related oceanic and atmospheric processes. The possible role of the taxonomic composition of phytoplankton assemblages is also discussed.
Keywords: Primary productivity; Methanesulfonate; MSA; Aerosol; Central Mediterranean Sea; North Atlantic Oscillation;

A three-year time-series of dust deposition flux measurements in Gran Canaria, Spain: A comparison of wet and dry surface deposition samplers by Patricia López-García; Maria Dolores Gelado-Caballero; Desire Santana-Castellano; Miguel Suárez de Tangil; Cayetano Collado-Sánchez; José Joaquín Hernández-Brito (689-694).
A three-year dataset of particle deposition flux measurements in Gran Canaria, Canary Islands, is presented. As part of this work, a comparison between wet and dry surrogate surfaces to estimate dry deposition fluxes was carried out over a period of more than two years in order to compare the particle collection efficiency of both devices. The selected recipients were buckets placed in two commercial samplers (ARS 1000, MTX Italy) equipped with a rain sensor; one of which was modified to maintain a constant volume of water during the collection time. No relationship was found between dry deposition fluxes and meteorological conditions (such as wind speed), the volume of the deposition container, or the number of days sampled. Dry deposition measurements made using a wet plate were 94% (±7%) of the corresponding measurements made by dry plate, and therefore are no better for the collection of particles. While both systems showed consistent results, with no significant differences in the estimation of total flux, the use of wet plates increased the uncertainty in the measurements and the complexity of the sampling method.During 2009–2012, wet and dry deposition fluxes showed a marked seasonality with a maximum in spring. Dry deposition dominated the particle fluxes (more than 93% of the total flux) and a value of 25.0 ± 0.3 mg m−2 d-1 was measured. Estimated dry deposition velocity was 0.85 ± 0.38 cm s−1, in good agreement with previously reported values.
Keywords: Dry atmospheric deposition; Surrogate plate; Water plate; Settling velocity; Aerosol; Canary Islands;

Semi-volatile organic compounds (SVOCs) have been attracting more and more attentions to many researchers in these years. Because SVOCs have a strong tendency for adsorption to suspended particles, we take the effect of suspended particles into account to study the transport mechanism of SVOCs in the air. We establish a mathematical model to describe the transport mechanism of SVOCs, and study the transport processes of both gas- and particle-phase di-2-ethylhexyl phthalate (DEHP) in Field and Laboratory Emission Cells (FLECs). The predictions by the proposed model not only fit well with the experimental data of previous studies, but also show that the gas-phase DEHP concentration increases rapidly in the first few seconds and increases slowly during the following 200 days due to different transport mechanisms in the two periods. Meanwhile, when the particle radiuses are of the order of micron and the air changes per hour (ACH) is large enough, the characteristic time for DEHP getting gas/particle equilibrium is much longer than the residence time of a particle in the flow field, and thus there is no significant influence of suspended particles on the total concentration of DEHP in the air. Oppositely, the influence of particles on DEHP emission will be enhanced for a cycling air flow system with a small ACH, where increasing ACH will reduce the concentrations of particle-phase SVOCs. Besides, if the particle radiuses are of the order of nanometer, decreasing the particle radiuses will shorter the characteristic time for DEHP getting gas/particle equilibrium, and finally increase the particle-phase concentration of DEHP.
Keywords: Indoor air; Semi-volatile organic compounds; Suspended particle; Transport mechanism; Adsorption;

Decrease in surface ozone concentrations at Mediterranean remote sites and increase in the cities by Pierre Sicard; Alessandra De Marco; Fabien Troussier; Camille Renou; Nicolas Vas; Elena Paoletti (705-715).
Analyzing hourly ozone data from 214 European background sites over the time period 2000–2010, we demonstrated for the first time that the ozone control measures are effective at rural sites, while ozone concentrations are still increasing in the cities. The Western European Mediterranean basin is expected to be more strongly affected by climate change, including ozone pollution, than most of the other regions of the world. At 58% of the rural sites significant decreases were found resulting in an average – 0.43% per year while an increase was recorded in urban and suburban stations (+0.64% year−1 and +0.46% year−1, respectively). At cities ozone average levels increased, but the peak ozone concentrations decreased. In all station types, a significant reduction in the amplitude of peak ozone concentrations was found at more than 75% of stations (98th percentile, −0.77% year−1; hourly peak, −1.14% year−1 and daily average peak, −0.76% year−1). The peak reduction may largely be attributed to the reduction in NO x and VOC emissions within the European Union which started in the early 1990s. The results suggested a convergence of ozone pollution at remote and urban sites all around the Western European Mediterranean basin.
Keywords: Mann–Kendall test; Ground-level ozone; Mediterranean basin; Trend; O3;

Near-field pollutant dispersion in the urban environment involves the interaction of a plume and the flow field perturbed by building obstacles. In the past two decades, micro-scale Computational Fluid Dynamics (CFD) simulation of pollutant dispersion around buildings and in urban areas has been widely used, sometimes in lieu of wind tunnel testing. This paper reviews current modeling techniques in CFD simulation of near-field pollutant dispersion in urban environments and discusses the findings to give insight into future applications. Key features of near-field pollutant dispersion around buildings from previous studies, i.e., three-dimensionality of mean flow, unsteadiness of large-scale flow structure, and anisotropy of turbulent scalar fluxes, are identified and discussed. This review highlights that it is important to choose appropriate numerical models and boundary conditions by understanding their inherent strengths and limitations. Furthermore, the importance of model evaluation was emphasized. Because pollutant concentrations around buildings can vary by orders of magnitudes in time and space, the model evaluation should be performed carefully, while paying attention to their uncertainty. Although CFD has significant potential, it is important to understand the underlying theory and limitations of a model in order to appropriately investigate the dispersion phenomena in question.
Keywords: CFD simulation; Near-field; Pollutant dispersion; Urban environment; Modeling technique;

Measuring odours in the environment vs. dispersion modelling: A review by Laura Capelli; Selena Sironi; Renato Del Rosso; Jean-Michel Guillot (731-743).
Source characterization alone is not sufficient to account for the effective impact of odours on citizens, which would require to quantify odours directly at receptors. However, despite a certain simplicity of odour measurement at the emission source, odour measurement in the field is a quite more complicated task. This is one of the main reasons for the spreading of odour impact assessment approaches based on odour dispersion modelling. Currently, just a very limited number of reports discussing the use of tracer gas dispersion experiments both in the field and in wind tunnels for model validation purposes can be found in literature. However, when dealing with odour emissions, it is not always possible to identify a limited number of tracer compounds, nor to relate analytical concentrations to odour properties, thus giving that considering single odorous compounds might be insufficient to account for effective odour perception. For these reasons, the possibility of measuring of odours in the field, both as a way for directly assessing odour annoyance or for verifying that modelled odour concentrations correspond to the effective odour perception by humans, is still an important objective. The present work has the aim to review the techniques that can be adopted for measuring odours in the field, particularly discussing how such techniques can be used in alternative or in combination with odour dispersion models for odour impact assessment purposes, and how the results of field odour measurements and model outputs can be related and compared to each other.
Keywords: Odour annoyance; Dynamic olfactometry; Odour concentration; Field inspection; Human assessors; Electronic nose;

In this work variability of aerosol optical thickness (AOT) measured at Belsk, Poland is studied as well as modification of AOT during airmass advection towards Belsk. AOT measurements taken at Belsk and at AERONET stations located in eastern Germany, Belarus and Scandinavia are used as well as satellite measurements of AOT taken by MODIS instrument onboard Terra and Aqua satellites. Directions of airmass advection are determined by means of cluster analysis of airmass backward-trajectories.Changes of AOT at Belsk from day to day varies around zero regardless of time lag between measurements. The standard deviation of these measurements increases with increasing time lag. In case of advection from west and north direction such standard deviation is reduced. It gives good perspective for a persistent forecast of next day AOT.Analysis of AOT changes during airmass advection toward Belsk reveals two modes of AOT changes distributions. One of them with small increase of AOT and second one with larger increase of AOT, so-called loading mode. Loading mode dominates in case of advection from south direction whilst the first mode of AOT changes dominates in case of advection from other directions. Mean increase of AOT associated with the first mode is 0.034 ± 0.003. Analysis of backward-trajectories shows that aerosol loading occurs over urban/industrial regions located south and south-west of Belsk. Substantial aerosol loading is found during seasonal biomass burning episodes in Eastern Europe.
Keywords: Aerosol; AOT; Backward-trajectory; Cluster analysis;

Aldehydes in passenger vehicles: An analysis of data from the RIOPA Study 1999–2001 by Ashley E.M. Mapou; Derek G. Shendell; Jennifer H. Therkorn; Youyou Xiong; Qingyu Meng; Junfeng Zhang (751-759).
In-vehicle air quality (IVAQ) can be a major health concern due to factors such as urban sprawl and increased commuting time spent by individuals in vehicles. Few studies, particularly in the U.S., have considered in-vehicle toxic air contaminants, and none to date collected/analyzed field data in multiple communities across multiple climate zones. This study presents analyses of field data collected during the RIOPA Study from participating non-smoking adults for communities in Los Angeles County, CA, Elizabeth, NJ and Houston, TX. A significant difference (p < 0.001) in in-vehicle formaldehyde concentrations was observed, with the median concentration of in-vehicle formaldehyde in the CA communities about twice as high as in the NJ and TX communities. The highest median concentration of in-vehicle acetaldehyde was observed among the TX participants, over 40% higher than the overall study median. Given small sample sizes, the community (state) differences may be driven independently by differences in individual vehicle conditions and driving habits. Positive correlations were found between average community outdoor relative humidity in CA and NJ and in-vehicle formaldehyde and acetaldehyde concentrations. The amount of time car windows were reported as closed was inversely correlated with in-vehicle formaldehyde across study locations, and for in-vehicle acetaldehyde in CA and TX. Average wind speed and varying sky conditions also had suggested associations to in-vehicle formaldehyde and acetaldehyde. In CA and TX, 88% (7/8) of participants with a diagnosis of bronchitis reported at study baseline had in-vehicle formaldehyde concentrations greater than the overall study median. Every participant with diagnoses of both asthma and bronchitis (n = 3) reported at study baseline had in-vehicle formaldehyde and acetaldehyde concentrations above the overall study median; one participant in TX with two seasonal in-vehicle samplings had in-vehicle concentrations > 75th percentile. IVAQ during commuting may vary based on human behavior and meteorological factors. Additional studies are needed to further characterize ways to help reduce in-vehicle aldehyde exposures, especially for people with existing chronic respiratory illnesses who could experience symptom exacerbations upon such exposures.
Keywords: In-vehicle air quality; RIOPA Study; Aldehydes; Formaldehyde; Acetaldehyde; Propionaldehyde;

Atmospheric mercury and fine particulate matter in coastal New England: Implications for mercury and trace element sources in the northeastern United States by Allan Kolker; Mark A. Engle; Bernhard Peucker-Ehrenbrink; Nicholas J. Geboy; David P. Krabbenhoft; Michael H. Bothner; Michael T. Tate (760-768).
Intensive sampling of ambient atmospheric fine particulate matter was conducted at Woods Hole, Massachusetts over a four-month period from 3 April to 29 July, 2008, in conjunction with year-long deployment of the USGS Mobile Mercury Lab. Results were obtained for trace elements in fine particulate matter concurrently with determination of ambient atmospheric mercury speciation and concentrations of ancillary gasses (SO2, NO x , and O3). For particulate matter, trace element enrichment factors greater than 10 relative to crustal background values were found for As, Bi, Cd, Cu, Hg, Pb, Sb, V, and Zn, indicating contribution of these elements by anthropogenic sources. For other elements, enrichments are consistent with natural marine (Na, Ca, Mg, Sr) or crustal (Ba, Ce, Co, Cs, Fe, Ga, La, Rb, Sc, Th, Ti, U, Y) sources, respectively. Positive matrix factorization was used together with concentration weighted air-mass back trajectories to better define element sources and their locations. Our analysis, based on events exhibiting the 10% highest PM2.5 contributions for each source category, identifies coal-fired power stations concentrated in the U.S. Ohio Valley, metal smelting in eastern Canada, and marine and crustal sources showing surprisingly similar back trajectories, at times each sampling Atlantic coastal airsheds. This pattern is consistent with contribution of Saharan dust by a summer maximum at the latitude of Florida and northward transport up the Atlantic Coast by clockwise circulation of the summer Bermuda High. Results for mercury speciation show diurnal production of RGM by photochemical oxidation of Hg° in a marine environment, and periodic traverse of the study area by correlated RGM-SO2(NO x ) plumes, indicative of coal combustion sources.
Keywords: Trace elements; PM2.5; Mercury speciation; Source attribution; Saharan dust; Transport of pollutants; Woods Hole; Cape Cod; Massachusetts; Coastal New England;

N2O as a tracer of mixing stratospheric and tropospheric air based on CARIBIC data with applications for CO2 by S.S. Assonov; C.A.M. Brenninkmeijer; T. Schuck; T. Umezawa (769-779).
Stratosphere–troposphere exchange (STE) affects distributions of trace gases, with ozone (O3) and CO being commonly used to study mixing process in the UTLS (Upper Troposphere and Lower Stratosphere) region. Here we explore the application of N2O as a tracer of stratosphere to troposphere flux for CO2 and its isotopes, using N2O and CO2 mixing ratios including a set of CO2 isotope data for CARIBIC aircraft samples and NOAA-Carbon Cycle flask samples. A frequency distribution of CARIBIC N2O data (mostly UTLS at mid- and high-latitudes) reveals a narrow distribution around a tropospheric maximum at nearly the same N2O mixing ratio as the distribution peak for the station Mauna Loa (MLO) however with a skewing due to STE. We demonstrate that upper-tropospheric and STE-affected air can be distinguished using a threshold value based on the N2O distribution width at MLO. A comparison with the use of O3 is given. N2O is discussed to be a robust and linear (season and latitude independent) tracer of STE mixing proportions. We propose that CARIBIC data coupled with CO2 isotopic data published for the stratosphere and data of NOAA stations can be used as a frame of reference for δ18O(CO2) and Δ17O(CO2) STE fluxes. The Δ17O(CO2) flux is of particular interest as it is thought to constrain estimates of biosphere productivity, atmospheric oxygen cycle and global gross CO2 fluxes. CARBIC data can also help tracing STE flux by deep stratospheric intrusions and a data analysis is given for the Walliguan (WLG) observatory on the Tibetan Plateau.
Keywords: Stratosphere – troposphere flux of CO2 isotopes; Stratospheric tracer–tracer correlations; UTLS and LMS region; Tropospheric N2O; CO2 isotopes;

Optimisation steps of an innovative air sampling method for semi volatile organic compounds by Borislav Lazarov; Rudi Swinnen; Maarten Spruyt; Eddy Goelen; Marianne Stranger; Gilbert Desmet; Eric Wauters (780-786).
This work describes optimisation steps of an innovative method for the measurement several groups of semi-volatile organic compounds (SVOCs) in air, collecting both gaseous and particulate air fractions. It is based on active air sampling on sorption tubes (consisting of polydimethylsiloxane (PDMS) and Tenax TA), followed by thermal desorption and gas chromatography mass spectrometry analysis (TD–GC–MS). The optimised method was validated in the laboratory for the measurement of selected target compounds from the following chemical classes: polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and phthalate esters (PEs). It was applied in different Belgian urban outdoor as well as indoor environments. The new method is characterised by limits of detection in the range of 0.003–0.3 ng m−3 for PAHs, 0.004–0.2 ng m−3 for PCBs, 0.113–0.201 ng m−3 for PBDEs and 0.002–0.2 ng m−3 for PEs, a linearity of 0.996 and a repeatability of less than 10% for all studied compounds.
Keywords: Air monitoring; Semi-volatile organic compounds; Thermal desorption; GC–MS; Mixed bed sampling;

Implications of alternative assumptions regarding future air pollution control in scenarios similar to the Representative Concentration Pathways by Clifford Chuwah; Twan van Noije; Detlef P. van Vuuren; Wilco Hazeleger; Achim Strunk; Sebastiaan Deetman; Angelica Mendoza Beltran; Jasper van Vliet (787-801).
The uncertain, future development of emissions of short-lived trace gases and aerosols forms a key factor for future air quality and climate forcing. The Representative Concentration Pathways (RCPs) only explore part of this range as they all assume that worldwide ambitious air pollution control policies will be implemented. In this study, we explore how different assumptions on future air pollution policy and climate policy lead to different concentrations of air pollutants for a set of RCP-like scenarios developed using the IMAGE model. These scenarios combine low and high air pollution variants of the scenarios with radiative forcing targets in 2100 of 2.6 W m−2 and 6.0 W m−2. Simulations using the global atmospheric chemistry and transport model TM5 for the present-day climate show that both climate mitigation and air pollution control policies have large-scale effects on pollutant concentrations, often of similar magnitude. If no further air pollution policies would be implemented, pollution levels could be considerably higher than in the RCPs, especially in Asia. Air pollution control measures could significantly reduce the warming by tropospheric ozone and black carbon and the cooling by sulphate by 2020, and in the longer term contribute to enhanced warming by methane. These effects tend to cancel each other on a global scale. According to our estimates the effect of the worldwide implementation of air pollution control measures on the total global mean direct radiative forcing in 2050 is +0.09 W m−2 in the 6.0 W m−2 scenario and −0.16 W m−2 in the 2.6 W m−2 scenario.
Keywords: Emission scenarios; Representative Concentration Pathways; Climate change mitigation; Air pollution control; Radiative forcing;

East Asia monsoon's influence on seasonal changes of beryllium-7 and typical POPs in near-surface atmospheric aerosols in mid-latitude city Qingdao, China by Yong-Liang Yang; Nan Gai; Cun-Zhen Geng; Xiao-Hua Zhu; Yong Li; Yuan Xue; Han-Qing Yu; Ke-Yan Tan (802-810).
Near-surface atmospheric aerosols were collected at sampling frequency of 3 d per week for one year from August 2009 to July 2010 in Laoshan District, Qingdao, located in the mid-latitude coastal region of East Asia monsoon region. The samples were analyzed for cosmogenic nuclide beryllium-7 (7Be), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs). The annual average 7Be concentration was 6.83 ± 0.40 mBq m−3, with the variation range from 1.52 to 14.58 mBq m−3. The maximum and minimum levels were observed in September and May, respectively. Autumn and spring were the seasons with high 7Be concentrations and summer was the lowest 7Be season. Enhanced wet precipitation may have caused lower 7Be observed in summer when southeasterlies were prevailing. Higher 7Be concentrations in autumn 2009 were caused by the abnormal atmospheric circulation. Concentrations of HCHs, DDTs, and PCBs followed a trend of being lower in summer and higher in winter. Higher chlorinated PCB isomers were predominant in winter and lower chlorinated PCB isomers were predominant in summer. ∑OCPs generally showed positive correlations with 7Be but were interrupted by the “spring leak maximum” episode for 7Be in the atmosphere in April when the stratosphere–troposphere exchange was enhanced, and in December when abnormally high HCHs were observed. No significant correlation was found between 7Be and PCBs except for PCB28. Seasonal oscillations in 7Be and the ratios of POP/7Be were observed.
Keywords: Beryllium-7; Aerosol; Persistent organic pollutants; Qingdao; East Asia monsoon;

Seasonal trends and spatial variations of PM10-bounded polycyclic aromatic hydrocarbons in Veneto Region, Northeast Italy by Mauro Masiol; Gianni Formenton; Alberto Pasqualetto; Bruno Pavoni (811-821).
The Veneto Region extends for ∼18.4·103 km2 in the northeastern part of the Po Valley and includes mountains, hills, plain and coastal environments with very different and discontinuous anthropogenic pressures. Although many efforts have been made to mitigate air pollution, the European air quality standards for atmospheric pollutants are frequently breached. This study investigates the levels of eight PM10-bound PAHs collected in 21 stations categorized as rural background, urban and suburban backgrounds, traffic and industrial hot-spots during one year (2011). Data were statistically processed to detect the PAH seasonal trends, their relationship with other air pollutants and micro-meteorological parameters and the space variations at a regional scale. Results show that PAHs levels are relatively high in the largest part of the region, with 10 sites exceeding the levels of BaP targeted by the European legislation. Two sites exhibited anomalously high PAHs concentrations and this anomaly became even more evident when considering the population density as a surrogate for the potential anthropogenic pressure. The PAHs levels were found directly proportional to other gaseous pollutants (CO, NO, NO x , SO2) suggesting common polluting sources. The analysis of time trends of PAH concentrations reveals significant coincidences throughout the region, i.e. simultaneous changes are observed in most sites as a consequence of similar emission sources and accumulation/removal processes. In this scenario, the control strategies currently imposed at local level (e.g. traffic limitations) have proven scarcely effective in mitigating air pollution and a real coordination at regional or even interregional level cannot be further postponed. Peculiar features of the PAHs pollution in the Veneto were also identified and some measures for protecting the human health were suggested.Display Omitted
Keywords: PAHs; PM10; Po Valley; Spatial distribution; Seasonal variations; Mitigation strategy;

Air quality prediction using optimal neural networks with stochastic variables by Ana Russo; Frank Raischel; Pedro G. Lind (822-830).
We apply recent methods in stochastic data analysis for discovering a set of few stochastic variables that represent the relevant information on a multivariate stochastic system, used as input for artificial neural network models for air quality forecast. We show that using these derived variables as input variables for training the neural networks it is possible to significantly reduce the amount of input variables necessary for the neural network model, without considerably changing the predictive power of the model. The reduced set of variables including these derived variables is therefore proposed as an optimal variable set for training neural network models in forecasting geophysical and weather properties. Finally, we briefly discuss other possible applications of such optimized neural network models.
Keywords: Pollutants; Neural networks; Stochastic systems; Environmental research;

The recent history of atmospheric As, Cd, Ni, Pb and Zn deposition and the stable Pb isotope signatures were reconstructed from short cores collected at three peat bogs along the St. Lawrence Valley (SLV). The onset of industrial activity was recorded around 1810–1850 AD. As, Cd, Pb and, to a certain extent, Ni deposition rates reached maxima between 1940 and the early 1970s. Trace metals likely originated from coal-burning and ore smelting between 1850 and 1950 AD, and were replaced thereafter, at least in the case of Pb, by the combustion of leaded gasolines until the mid-1980s. Trace metal contents and accumulation rates were greater in the two cores recovered from the southwestern SLV than further northeast, as expected from their proximity to urban and industrial centers of eastern Canada and the U.S. Mid-West and the direction of the prevalent winds. A rapid decrease in metal accumulation rates since the 1970s suggests that mitigation policies were effective in reducing atmospheric metal emissions. Nevertheless, metal accumulation rates and stable Pb isotope signatures have not yet returned to their pre-industrial values.
Keywords: Trace metal pollution; Peat bogs; Industrial Revolution; Lead isotopes; Northeastern America;

On February 29th 2012, China published its new National Ambient Air Quality Standard (CH-NAAQS) aiming at revising the standards and measurements for both gaseous pollutants including ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2), and also particle pollutants including PM10 and PM2.5. In order to understand the air pollution status regarding this new standard, the integrated MM5/CMAQ modeling system was applied over Yangtze River Delta (YRD) within this study to examine the criteria gaseous pollutants listed in the new CH-NAAQS. Sensitivity simulations were also conducted to assess the responses of gaseous pollutants under 8 different sector-dependent emission reduction scenarios in order to evaluate the potential control strategies. 2006 was selected as the simulation year in order to review the air quality condition at the beginning of China's 11th Five-Year-Plan (FYP, from 2006 to 2010), and also compared with air quality status in 2010 as the end of 11th FYP to probe into the effectiveness of the national emission control efforts. Base case simulation showed distinct seasonal variation for gaseous pollutants: SO2, and NO2 were found to have higher surface concentrations in winter while O3 was found to have higher concentrations in spring and summer than other seasons. According to the analyses focused on 3 megacities within YRD, Shanghai, Nanjing, and Hangzhou, we found different air quality conditions among the cities: NO2 was the primary pollutant that having the largest number of days exceeding the CH-NAAQS daily standard (80 μg m−3) in Shanghai (59 days) and Nanjing (27 days); SO2 was the primary pollutant with maximum number of days exceeding daily air quality standard (150 μg m−3) in Hangzhou (28 days), while O3 exceeding the daily maximum 8-h standard (160 μg m−3) for relatively fewer days in all the three cities (9 days in Shanghai, 14 days in Nanjing, and 11 days in Hangzhou). Simulation results from predefined potential applicable emission control scenarios suggested significant air quality improvements from emission reduction: 90% of SO2 emission removed from power plant in YRD would be able to reduce more than 85% of SO2 pollution, 85% NO x emission reduction from power plant would reduce more than 60% of NO2 pollution, in terms of reducing the number of days exceeding daily air quality standard. NO x emission reduction from transportation and industry were also found to effectively reduce NO2 pollution but less efficient than emission control from power plants. We also found that multi-pollutants emission control including both NO x and VOC would be a better strategy than independent NO x control over YRD which is China's 12th Five-Year-Plan (from 2011 to 2015), because O3 pollution would be increased as a side effect of NO x control and counteract NO2 pollution reduction benefit.
Keywords: Yangtze River Delta; Gaseous pollutants; Chinese National Air Quality Standard; CMAQ; Emission control;

Here we demonstrate the sharp seasonal and latitudinal gradient of atmospheric CO2 over East Asia, where there are relatively few ground-based observations. The Greenhouse gases Observing SATellite (GOSAT) column-averaged dry air CO2 mole fraction (xCO2) retrieved by NASA's Atmospheric CO2 Observations from Space (ACOS) (2009–2011) program and GEOS-Chem nested-grid CO2 results are used. The strong anthropogenic emissions mainly from China and intensive vegetation uptake from northeastern Asia lead to a clear seasonal change of the xCO2 between spring maximum and summer minimum (>10 ppm). In particular, the steep latitudinal gradient of summer time xCO2 by 3–5 ppm in the vicinity of the Korean Peninsula (32°N-44°N) is likely attributed to the large difference in CO2 fluxes among industry/cities, northeastern forests and the northwest Pacific region. This study represents the current progress to understand sub-continental scale atmospheric CO2 variabilities with recent satellite retrievals and nested-grid modeling.
Keywords: Atmospheric CO2; East Asia; GOSAT; ACOS/OCO-2; GEOS-Chem;

Model quality objectives based on measurement uncertainty. Part I: Ozone by P. Thunis; D. Pernigotti; M. Gerboles (861-868).
Since models are increasingly used for policy support their evaluation is becoming an important issue. One of the possible evaluations is to compare model results to measurements. Statistical performance indicators then provide insight on model performance but do not tell whether model results have reached a sufficient level of quality for a given application. In a previous work Thunis et al. (2012, referred to as T2012) proposed a Model Quality Objective (MQO) based on the root mean square error between measured and modeled concentrations divided by the measurement uncertainty. In T2012 the measurement uncertainty was assumed to remain constant regardless of the concentration level. In the current work this assumption is overcome by quantifying all possible sources of uncertainty for the particular case of O3. Based on these uncertainty source quantifications, a simple relationship is proposed to formulate the measurement uncertainty which is then used to update the MQO and Model Performance Criteria (MPC) proposed in T2012 with more accurate values. The MQO and MPC calculated based on the European monitoring network AIRBASE data provide insight on the expected model results quality for a given application, depending on the geographical area and station type. These station specific MQOs and MPCs have the main advantage of relating expected model performances to the underlying measurement uncertainties.
Keywords: Model evaluation; Measurement uncertainty; Air quality modeling; GUM;

Model quality objectives based on measurement uncertainty. Part II: NO2 and PM10 by D. Pernigotti; M. Gerboles; C.A. Belis; P. Thunis (869-878).
Estimating measurement uncertainty for NO2 and PM10 is a complex issue that is normally addressed by experimentalists specifically for every type of instrument and measurement. On the other hand, an estimate of the maximum expected measurement uncertainty is needed when a numerical model is to be evaluated against observations, as proposed in Thunis et al. (2012, referred to as T2012). In a companion paper (Thunis et al., 2013, referred to as T2013) a simplified formulation of the measurement uncertainty in function of the measured concentration is proposed and applied to the simpler case of Ozone. In this paper the same approach is applied for NO2 and PM10, but using different techniques for the uncertainty estimation. For NO2 the Guide to the expression of Uncertainty in Measurement JCGM (2008, referred to as GUM) approach is used and applied on each urban AirBase (1997) measurement over the year 2009. For PM10, the method of the Guide for the Demonstration of Equivalence (ECWG, 2010) is used on data obtained with two different PM samplers used in parallel either during specific monitoring campaign or as available within the AirBase database. The resulting concentration dependent measurement uncertainties are then used to update the MQO (Model Quality Objective) and MPC (Model Performance Criteria) proposed in T2012. An estimate of the measurement uncertainty for annual means is proposed as well.
Keywords: Model evaluation; Measurement uncertainty; Air quality modeling; GUM; Equivalence; Model Quality Objective; Model Performance Criteria; NO2; PM10;

New Directions: Elevated layers of anthropogenic aerosols aggravate stratospheric ozone loss? by S.K. Satheesh; K. Krishna Moorthy; J. Srinivasan (879-882).