Atmospheric Environment (v.94, #C)

The concentrations of many harmful metals in air have been continuously decreasing around the world especially in North America and Western Europe, although deviations from such trend have been observed elsewhere such as East Asia. To help understand spatiotemporal factors governing the environmental behavior of hazardous metals, the concentrations of copper (Cu) in total suspended particulate (TSP) fractions were analyzed in the seven major cities in South Korea over a two decadal period (1991 through 2012). Unlike other metal species, there was no distinctive seasonal trend (e.g., spring/winter maximum and summer minimum) in the Cu levels in most South Korean cities. The long-term trend of Cu, if assessed by its annual mean values, recorded two contrasting trends for each decade: the earlier period (from 1991 to early 2000) is characterized by high variabilities with a maximum concentration of 243 ng m−3 (in 2003), while the later period showed an appreciable (several-fold) reduction to the latest (2012) available concentration level of 35.7 ng m−3. As such, the present Cu levels in Korea should approach those commonly seen in moderately clean urban environments elsewhere. The overall results suggest that South Korean regulatory efforts to control particulate matter (PM) emissions have greatly influenced the present Cu levels consistent with the observed temporal trends of airborne PM.
Keywords: Copper (Cu); Toxic metal; Long-term; Spatial; Emission; Atmosphere;

Multivariate methods for indoor PM10 and PM2.5 modelling in naturally ventilated schools buildings by Maher Elbayoumi; Nor Azam Ramli; Noor Faizah Fitri Md Yusof; Ahmad Shukri Bin Yahaya; Wesam Al Madhoun; Ahmed Zia Ul-Saufie (11-21).
In this study the concentrations of PM10, PM2.5, CO and CO2 concentrations and meteorological variables (wind speed, air temperature, and relative humidity) were employed to predict the annual and seasonal indoor concentration of PM10 and PM2.5 using multivariate statistical methods. The data have been collected in twelve naturally ventilated schools in Gaza Strip (Palestine) from October 2011 to May 2012 (academic year). The bivariate correlation analysis showed that the indoor PM10 and PM2.5 were highly positive correlated with outdoor concentration of PM10 and PM2.5. Further, Multiple linear regression (MLR) was used for modelling and R 2 values for indoor PM10 were determined as 0.62 and 0.84 for PM10 and PM2.5 respectively. The Performance indicators of MLR models indicated that the prediction for PM10 and PM2.5 annual models were better than seasonal models. In order to reduce the number of input variables, principal component analysis (PCA) and principal component regression (PCR) were applied by using annual data. The predicted R 2 were 0.40 and 0.73 for PM10 and PM2.5, respectively. PM10 models (MLR and PCR) show the tendency to underestimate indoor PM10 concentrations as it does not take into account the occupant’s activities which highly affect the indoor concentrations during the class hours.
Keywords: Regression models; PCA; PM10; PM2.5; Air pollution;

This thesis presents pilot studies concerning the assessment of the possibility of using organic materials of vegetative origin as indices of heavy metals emissions (Cd, Cr, Cu, Ni, Pb and Zn) from domestic wood-fired fireplaces. Mosses of the Pleurozium schreberi species as well as cellulose and cotton wool were used during the study as the potential indices for the elements emission. It was proved that mosses are more reliable as indices of metals emissions than cellulose or cotton wool. It was found that the quantity of Ni accumulated in the moss tissue is comparable with the concentration of this compound in the dust assessed with the reference method. A correlation between the Ni, Cr, Zn and Pb concentrations defined in the mosses and dust filter was found. It was proved that mosses as adsorbers, more clearly than in the case of cellulose and cotton, react to the change of the size of the particulates emitted.
Keywords: RWC; Fireplace; Heavy metals; Moss; Cellucotton; Cotton;

Characteristics of ultrafine particle sources and deposition rates in primary school classrooms by Rusdin Laiman; Congrong He; Mandana Mazaheri; Samuel Clifford; Farhad Salimi; Leigh R. Crilley; Megat Azman Megat Mokhtar; Lidia Morawska (28-35).
The aim of this work was to investigate changes in particle number concentration (PNC) within naturally ventilated primary school classrooms arising from local sources either within or adjacent to the classrooms. We quantify the rate at which ultrafine particles were emitted either from printing, grilling, heating or cleaning activities and the rate at which the particles were removed by both deposition and air exchange processes. At each of 25 schools in Brisbane, Australia, two weeks of measurements of PNC and CO2 were taken both outdoors and in the two classrooms. Bayesian regression modelling was employed in order to estimate the relevant rates and analyse the relationship between air exchange rate (AER), particle infiltration and the deposition rates of particle generated from indoor activities in the classrooms. During schooling hours, grilling events at the school tuckshop as well as heating and printing in the classrooms led to indoor PNCs being elevated by a factor of more than four, with emission rates of (2.51 ± 0.25) × 1011 p min−1, (8.99 ± 6.70) × 1011 p min−1 and (5.17 ± 2.00) × 1011 p min−1, respectively. During non-school hours, cleaning events elevated indoor PNC by a factor of above five, with an average emission rate of (2.09 ± 6.30) × 1011 p min−1. Particles were removed by both air exchange and deposition; chiefly by ventilation when AER > 0.7 h−1 and by deposition when AER < 0.7 h−1.
Keywords: Air exchange rate; Ultrafine particles; Indoor sources; Emission rate; Deposition rate; Schools;

Feces composition and manure derived methane yield from dairy cows: Influence of diet with focus on fat supplement and roughage type by Henrik Bjarne Møller; Verónica Moset; Maike Brask; Martin Riis Weisbjerg; Peter Lund (36-43).
The objective of the present study was to evaluate the effect of dairy cow diets on feces composition and methane (CH4) potential from manure with emphasis on fat level and roughage type and compare these results with the corresponding enteric CH4 emission. In experiment 1 six different diets, divided into two fat levels (low and high) and three different roughage types (early cut grass silage, late cut grass silage and maize silage), were used. The high fat level was achieved by adding crushed rapeseed. In experiment 2, the influence of increasing the fat level by using three different types of rapeseed: rapeseed cake, whole seed and rapeseed oil against a low fat ration with no rapeseed fat supplementation was studied. The diet and fat level had a significant influence on feces composition and CH4 yield. In general, ultimate CH4 yields (B 0) were 8–9% higher than the present international default values for diets without extra fat and in feces from diets with extra fat supply the yield was 25–31% higher. It was possible to predict the B 0 value from feed and feces characteristics; in fact, the best correlation was obtained by including both feed and feces characteristics. Addition of crude fat to diets to dairy cows reduced enteric CH4 emission but at the same time increased CH4 potential from feces both in terms of organic matter in feces and dry matter intake which might lead to increasing emissions unless proper manure handling such as anaerobic digestion is included. Without subsequent anaerobic digestion to produce energy the positive effect achieved at cow level could be counteracted by increasing manure emissions.
Keywords: Biogas yield; Methane emission; Cattle manure; Rapeseed; Harvesting time; Roughage type;

Exposure to PM2.5 in modern office buildings through elemental characterization and oxidative potential by Tamás Szigeti; Zsófia Kertész; Christina Dunster; Frank J. Kelly; Gyula Záray; Victor G. Mihucz (44-52).
Fifty samples of indoor and outdoor PM2.5 were collected onto quartz fiber and Teflon membrane filters in five office buildings equipped with heating, ventilation and air-conditioning system for 8 h daily in order to coincide with the work shift of employees. Samples were analyzed for i) mass concentration; ii) elemental concentration; and iii) oxidative potential (OP) through antioxidant depletion. The PM2.5 mass concentration exceeded the annual mean guideline of 10 μg m−3 WHO in 50% of the samples. Indoor and outdoor PM2.5 mass concentrations correlated almost linearly. Proton-induced X-ray emission (PIXE) spectrometry was used for the monitoring of 21 elements. Quantitative determination was achieved in the case of Teflon filters only for Al, Si, S, Cl, K, Ca, Ti, Cr, Mn, Fe and Zn at ng m−3 concentration level. Quartz fiber filters were less adequate for the PIXE measurements due to their greater thickness and filamentary structure. Ca, Cr, Zn and Ti had generally higher concentration (mg g−1) indoors. Indoor/outdoor (I/O) OP values were higher than one in 14% and 57% of the samples in the case of ascorbate and reduced glutathione (GSH), respectively. Spatial and temporal variations of OP were observed across the office buildings. The I/O ratios for OP, Cr and Zn concentrations in the case of GSH were higher for three buildings. Significant relationship was observed between GSH oxidation and Cr and Zn concentrations. Thus, employees were exposed to a higher extent to reactive oxygen species in three buildings.
Keywords: Indoor air quality; Occupational health; Office building; Oxidative potential; Particulate matter; Reactive oxygen species;

Exposure to volatile organic compounds: Comparison among different transportation modes by Duc Hoai Do; Herman Van Langenhove; Stephen Izuchukwu Chigbo; Abebech Nuguse Amare; Kristof Demeestere; Christophe Walgraeve (53-62).
The increasing trend of promoting public transportation (bus tram, metro, train) and more environmental friendly and sustainable non fossil-fuel alternatives (walking, cycling etc) as substitutes for auto vehicles brings forward new questions with regard to pollutant levels to which commuters are exposed. In this study, three transportation modes (tram, auto vehicle and bicycle) are studied and concentration levels of 84 volatile organic compounds (VOCs) (hydrocarbons, aromatic hydrocarbons, oxygen containing hydrocarbons, terpenes and halogenated compounds) are measured along a route in the city of Ghent, Belgium. The concentration levels are obtained by active sampling on Tenax TA sorbent tubes followed by thermal desorption gas chromatography mass spectrometry (TD-GC-MS) using deuterated toluene as an internal standard. The median total VOC concentrations for the tram mode (33 μg/m³) is 1.7 times higher than that of the bicycle mode (20 μg/m³) and 1.5 times higher than for the car mode (22 μg/m³). It is found that aromatic hydrocarbons account for a significant proportion in the total VOCs concentration (TVOCs) being as high as 41–57%, 59–72% and 58–72% for the tram, car and bicycle respectively. In all transportation modes, there was a high (r > 0.6) degree of correlation between BTEX compounds, isopropylbenzene, n-propylbenzene, 1,3,5-trimethylbenzene and 1,2,4-trimethylbenzene. When comparing time weighed average concentrations along a fixed route in Ghent, it is found that commuters using the tram mode experience the highest TVOCs concentration levels. However, next to the concentration level to which commuters are exposed, the physical activity level involving the mode of transportation is important to assess the exposure to toxic VOCs. It is proven that the commuter using a bicycle (4.3 ± 1.5 μg) inhales seven and nine times more benzene compared to the commuter using the car and tram respectively, when the same route is followed.
Keywords: VOC; Commuter exposure; Inhalation dose; Tram; Car; Bicycle; Ghent; Belgium;

Computational study on the mechanism and kinetics of Cl-initiated oxidation of vinyl acetate by Jing Li; Haijie Cao; Dandan Han; Mingyue Li; Xin Li; Maoxia He; Shuping Ma (63-73).
A comprehensive theoretical study of chlorine-initiated atmospheric oxidation mechanism of vinyl acetate (VAC, CH2 =CHOC(O)CH3) has been performed by using MPWB1K/6-311 + G(3df,2p)//MPWB1K + G(d,p). Two reaction types (Cl-addition and H-abstraction) and the subsequent reactions for the primary intermediates (IM1 and IM2) have been proposed in the presence of O2 and NO. The calculated results show that the Cl addition–elimination mechanism dominates the reaction between vinyl acetate and Cl. For the Cl addition reactions, the most energetically favorable pathway is the Cl addition to the terminal carbon atom. H-abstraction pathways are not expected to play an important role in the final products formation. The major possible degradation products have been identified. The rate constants and branching ratios of the main reaction channels have been obtained over a wide range of temperatures and pressures by using master equation (ME) calculations. The total rate constants are dependent on pressure and temperature over the whole study range (0.1–10,000 Torr and 200–1000 K). The atmospheric lifetime of vinyl acetate is estimated.
Keywords: Vinyl acetate; Chlorine atoms; Degradation mechanisms; NO x -presence; Rate constants;

Effects of roadway configurations on near-road air quality and the implications on roadway designs by Jonathan T. Steffens; David K. Heist; Steven G. Perry; Vlad Isakov; Richard W. Baldauf; K. Max Zhang (74-85).
This paper presents an analysis of wind tunnel experiments of twelve different roadway configurations and modeling of these configurations using a Large-Eddy Simulation (LES) model, aiming at investigating how flow structures affect the impact of roadway features on near-road and on-road air quality. The presence of roadside barriers, elevated fill and depressed roadways, and combinations of these configurations all reduce ground-level air pollutant concentrations immediately downwind of roadways. However, all of these cases, except the elevated fill configuration, increase pollutant concentrations on the roadway itself. For a roadside barrier with finite length, higher concentrations than those without a barrier are present in a small region near the edge of the barrier, influenced by complex flow in that region which we term “Edge Effects”. The inclusion of multiple roadway features often result in lower downwind pollutant concentrations than those with single roadway features; however, adding features typically offers diminishing returns in concentration reduction. Generally, the effects on concentration, both beneficial and adverse will damp out within 15 multiples of the characteristic height, be it the barrier height or the elevation/depression height of the roadway. Thus, evaluating the trade-off between the air pollutant reductions near the ground and the air pollutant increases on the roadway and elevated above the ground will be important in designing a sustainable transportation system.
Keywords: Emissions; CFD; Sustainable communities; Urban planning;

Volatile organic compound speciation above and within a Douglas fir forest by Nichola Copeland; J. Neil Cape; Eiko Nemitz; Mathew R. Heal (86-95).
Mixing ratios and fluxes of volatile organic compounds (VOCs) were measured by PTR-MS (and GC–MS) and virtual disjunct eddy covariance during a three-week field campaign in summer 2009 within and above a Douglas fir (Pseudotsuga menziesii) forest in Speulderbos, the Netherlands. Measurements included the first non-terpenoid species fluxes and mixing ratios for Douglas fir canopy. Above-canopy emissions of monoterpenes were comparable to previous studies of P. menziesii, with estimated standard emission factors for the first and second halves of the campaign of 0.8 ± 0.4 and 0.8 ± 0.3 μg gdw −1 h−1, and temperature coefficients of 0.19 ± 0.06 and 0.08 ± 0.05 °C−1, respectively. Estimated isoprene standard emission factors for the two halves of the campaign were 0.09 ± 0.12 and 0.16 ± 0.18 μg gdw −1 h−1. Fluxes of several non-terpenoid VOCs were significant, with maximum fluxes greater than has been measured for other coniferous species. α-Pinene was the dominant monoterpene within and above the canopy. Within-canopy mixing ratios of individual species were generally greatest in early evening consistent with reduced vertical mixing and continued temperature-dependent emissions. Acetaldehyde, acetone and monoterpenes had elevated mixing ratios toward the bottom of the canopy (5–10 m) with assumed contribution from the large quantities of forest-floor leaf litter. MBO (2-methyl-3-buten-2-ol) and estragole had peak mixing ratios at the top of the canopy and are known to have coniferous sources. MVK + MACR (methyl vinyl ketone and methacrolein) also had highest mixing ratios at the top of the canopy consistent with formation from in-canopy oxidation of isoprene. The work highlights the importance of quantifying a wider variety of VOCs from biogenic sources than isoprene and monoterpenes.
Keywords: BVOC; PTR-MS; vDEC; Monoterpene; Pinene; Isoprene;

Regular near-surface measurements of aerosol scattering and absorbing coefficients, along with other aerosol and meteorological parameters, were performed during June 2011 to March 2012 at Nainital, central Himalayas in the frameworks of Ganges Valley Aerosol Experiment (GVAX). The spectral scattering (0.45, 0.55 and 0.70 μm) and absorption (0.467, 0.53 and 0.66 μm) coefficients exhibit increased values in November, mostly affected by the biomass-burning aerosols in Indo-Gangetic Plains. Both parameters are considered for fine (D < 1 μm) and sub-10 μm particles (D < 10 μm) revealing the influence of particle size in aerosol properties. Furthermore, estimations of spectral (0.467, 0.55 and 0.66 μm) single scattering albedo (SSA) and aerosol radiative forcing efficiency (ARFE) at 0.55 μm were performed focussing on determination of the role of particle size in spectral SSA and climate implications. The results show relatively high SSA values ranging from 0.90 (±0.09) to 0.95 (±0.01) for D < 10 μm, and from 0.87 (±0.10) to 0.93 (±0.02) for D < 1 μm particles, on monthly basis, suggesting large heterogeneity in the aerosol sources. The SSA for the sub-micron aerosols decreases with wavelength in the majority of the cases, in contrast to the increase for the super-micron particles suggesting different source apportionment for the particle groups. The ARFE at the top of the atmosphere is found to range from −3 to −20 W m−2 with a mean of ∼−17 W m−2 for both particle-size groups; however, during the June–October period, the ARFE for the sub-10 μm particles is found to be more negative than that for the fine aerosols.
Keywords: Ganges Valley aerosol experiment; Scattering-absorption coefficient; Single scattering albedo; Aerosol radiative forcing efficiency; Gangetic Himalayan region;

Complex time series analysis of PM10 and PM2.5 for a coastal site using artificial neural network modelling and k-means clustering by M.A. Elangasinghe; N. Singhal; K.N. Dirks; J.A. Salmond; S. Samarasinghe (106-116).
This paper uses artificial neural networks (ANN), combined with k-means clustering, to understand the complex time series of PM10 and PM2.5 concentrations at a coastal location of New Zealand based on data from a single site. Out of available meteorological parameters from the network (wind speed, wind direction, solar radiation, temperature, relative humidity), key factors governing the pattern of the time series concentrations were identified through input sensitivity analysis performed on the trained neural network model. The transport pathways of particulate matter under these key meteorological parameters were further analysed through bivariate concentration polar plots and k-means clustering techniques. The analysis shows that the external sources such as marine aerosols and local sources such as traffic and biomass burning contribute equally to the particulate matter concentrations at the study site. These results are in agreement with the results of receptor modelling by the Auckland Council based on Positive Matrix Factorization (PMF). Our findings also show that contrasting concentration–wind speed relationships exist between marine aerosols and local traffic sources resulting in very noisy and seemingly large random PM10 concentrations. The inclusion of cluster rankings as an input parameter to the ANN model showed a statistically significant (p < 0.005) improvement in the performance of the ANN time series model and also showed better performance in picking up high concentrations. For the presented case study, the correlation coefficient between observed and predicted concentrations improved from 0.77 to 0.79 for PM2.5 and from 0.63 to 0.69 for PM10 and reduced the root mean squared error (RMSE) from 5.00 to 4.74 for PM2.5 and from 6.77 to 6.34 for PM10. The techniques presented here enable the user to obtain an understanding of potential sources and their transport characteristics prior to the implementation of costly chemical analysis techniques or advanced air dispersion models.Display Omitted
Keywords: Artificial neural network; Air quality modelling; K-means clustering; Marine aerosols;

Novel application of a combustion chamber for experimental assessment of biomass burning emission by Ilaria Lusini; E. Pallozzi; P. Corona; P. Ciccioli; C. Calfapietra (117-125).
Biomass burning is an important ecological factor in the Mediterranean ecosystem and a significant source of several atmospheric gases and particles. This paper demonstrates the performance of a recently developed combustion chamber, showing its capability in estimating the emission from wildland fire through a case study with dried leaf litter of Quercus robur. The combustion chamber was equipped with a thermocouple, a high resolution balance, an epiradiometer, two different sampling lines to collect volatile organic compounds (VOCs) and particles, and a portable analyzer to measure carbon monoxide (CO) and carbon dioxide (CO2) emission. VOCs were determined by gas chromatography–mass spectrometry (GC–MS) after enrichment on adsorption traps, but also monitored on-line with a proton-transfer-reaction mass spectrometer (PTR-MS). Preliminary qualitative analyses of emissions from burning dried leaf litter of Q. robur found CO and CO2 as the main gaseous species emitted during the flaming and smoldering stages. Aromatic VOCs, such as benzene and toluene, were detected together with several oxygenated VOCs, like acetaldehyde and methanol. Moreover, a clear picture of the carbon balance during the biomass combustion was obtained with the chamber used. The combustion chamber will allow to distinguish the contribution of different plant tissues to the emissions occurring during different combustion phases.
Keywords: Forest fires; Combustion chamber; Combustion gases; Volatile organic compounds emission;

A portable and inexpensive method for quantifying ambient intermediate volatility organic compounds by Nicole C. Bouvier-Brown; Erica Carrasco; James Karz; Kylee Chang; Theodore Nguyen; Daniel Ruiz; Vivian Okonta; Jessica B. Gilman; William C. Kuster; Joost A. de Gouw (126-133).
Volatile organic compounds (VOCs) and intermediate volatility VOCs (IVOCs) are gas-phase organic compounds which may participate in chemical reactions affecting air quality and climate. The development of an inexpensive, field-portable quantification method for higher molecular weight VOCs and IVOCs utilizing commercially available components could be used as a tool to survey aerosol precursors or identify and monitor air quality in various communities. We characterized the performance characteristics for the HayeSep-Q adsorbent with a representative selection of anthropogenic and biogenic VOC standards and optimized experimental conditions and procedures for field collections followed by laboratory analysis. All VOCs were analyzed using gas chromatography coupled with mass spectrometry. Precision (average 22%) and accuracy were reasonable and the limit of detection ranged from 10 to 80 pmol/mol (ppt) for the studied compounds. The method was employed at the Los Angeles site during the CalNex campaign in summer 2010 and ambient mixing ratios agreed well (slope 0.69–1.06, R 2 0.67–0.71) with measurements made using an in-situ GC–MS – a distinctly different sampling and quantification method. This new technique can be applied to quantify ambient biogenic and anthropogenic C8–C15 VOCs and IVOCs.
Keywords: Intermediate volatility organic compounds; Aerosol precursor; HayeSep-Q adsorbent;

To examine the formation pathways of two size-resolved water-soluble organic carbon (WSOC) fractions, a total of 16 sets of size-segregated aerosol samples were collected using a 10-stage Micro-Orifice Uniform Deposit Impactor (MOUDI) at a roadway site in Korea from September 29 to October 29, 2010. A XAD7HP (non-ionic aliphatic acrylic polymer) resin column was used to separate the filtered extracts into hydrophilic (WSOCHPI) and hydrophobic (WSOCHPO) WSOC fractions. Also the size distributions of water-soluble inorganic species and oxalate were examined to determine the formation pathways of size-resolved WSOCHPI and WSOCHPO fractions.The size distribution of WSOCHPI showed a dominant mode at 0.55 μm, while the WSOCHPO had dominant modes at both 0.17–0.32 μm and 0.55 μm. On the basis of the size distribution characteristics, it was found that the formation pathways of both WSOCHPI and WSOCHPO were dependent on the particle size; in the condensation mode (0.17–0.32 μm), both the WSOCHPI and WSOCHPO could be produced through atmospheric processes similar to those of SO 4 2 − and oxalate, which were derived from the gas-phase oxidations of organic compounds. In the droplet mode (0.55–1.8 μm), the cloud processing of both the organic compounds and biomass burning emissions could be a major pathway for the WSOCHPI formation. However, the droplet mode WSOCHPO was likely produced through cloud processing and heterogeneous reactions or aerosol-phase reactions. In the coarse mode (>3.1 μm), the WSOCHPI formation was more likely associated with soil-related particles (Ca(NO3)2 and CaSO4) than with sea-salt particles (NaNO3 and Na2SO4).
Keywords: Roadway; Aerosol size distributions; Water-soluble organic carbon (WSOC) fractions; Size-resolved WSOC fractions; Production pathways;

Emission factors from small scale appliances burning wood and pellets by Senem Ozgen; Stefano Caserini; Silvia Galante; Michele Giugliano; Elisabetta Angelino; Alessandro Marongiu; Francesca Hugony; Gabriele Migliavacca; Carmen Morreale (144-153).
Four manually fed (6–11 kW) firewood burning and two automatic wood pellets (8.8–25 kW) residential heating appliances were tested under real-world operating conditions in order to determine emission factors (EFs) of macropollutants, i.e., carbon monoxide (CO), nitrogen oxides (NO x ), non-methane hydrocarbons (NMHC), particulate matter (PM) and trace pollutants such as polycyclic aromatic hydrocarbons (PAH) and dioxins. The results were examined for the influence of different factors (i.e., type of wood, appliance and combustion cycle). The experimental EFs were also compared with the values proposed by the European emission inventory guidebook used in the local inventory in order to evaluate their representativeness of real world emissions. The composite macropollutant EFs for manually fed appliances were: for CO 5858 g GJ−1, for NO x 122 g GJ−1, NMHC 542 g GJ−1, PM 254 g GJ−1, whereas emissions were much lower for automatic pellets appliances: CO 219 g GJ−1, for NO x 66 g GJ−1, NMHC 5 g GJ−1, PM 85 g GJ−1. The highest emissions were generally observed for the open fireplace, however traditional and advanced stoves have the highest overall CO EFs. Especially for the advanced stove real-world emissions are far worse than those measured under cycles used for type testing of residential solid fuel appliances. No great difference is observed for different firewood types in batch working appliances, diversely the quality of the pellets is observed to influence directly the emission performance of the automatic appliances. Benzo(b)fluoranthene is the PAH with the highest contribution (110 mg GJ−1 for manual appliances and 2 mg GJ−1 for automatic devices) followed by benzo(a)pyrene (77 mg GJ−1 for manual appliances and 0.8 mg GJ−1 for automatic devices).
Keywords: Residential wood combustion; Emission factor; Combustion cycle; Pellet; Stoves; Fireplaces;

Mass closure and source apportionment of PM2.5 by Positive Matrix Factorization analysis in urban Mediterranean environment by E. Mantas; E. Remoundaki; I. Halari; P. Kassomenos; C. Theodosi; A. Hatzikioseyian; N. Mihalopoulos (154-163).
A systematic monitoring of PM2.5 was carried out during a period of three years (from February 2010 to April 2013) at an urban site, at the National Technical University of Athens campus. Two types of 24-h PM2.5 samples have been collected: 271 samples on PTFE and 116 samples on quartz filters. Daily PM2.5 concentrations were determined for both types of samples. Total sulfur, crustal origin elements and elements of a major crustal component (Al, Si, Fe, Ca, K, Mg, Ti) trace elements (Zn, Pb, Cu, Ni, P, V, Cr, Mn) and water soluble ions (Cl, NO3 , SO4 2−, Na+, K+, NH4 +, Ca2+, Mg2+) were determined on the PTFE samples. Organic carbon (OC), elemental carbon (EC) and water soluble ions were determined on the quartz samples. For the mass closure six components were considered: Secondary Inorganic Aerosol (SIA), Organic Matter (OM), Elemental Carbon (EC), Dust, Mineral anthropogenic component (MIN) and Sea Salt (SS). SIA and OM contributed in the mass of PM2.5 almost equally: 30–36% and 30% respectively. EC, SS and MIN accounted for 5, 4 and 3% respectively of the total PM2.5 mass. Dust accounted for about 3–5% in absence of dust transport event and reached a much higher percentage in case of dust transport event. These contributions justify at least 80% of the PM2.5 mass. Source apportionment analysis has been performed by Positive Matrix Factorization. The combination of the PMF results obtained by both data sets lead to the definition of six factors: 1. SO4 2−, NH4 +, OC (industrial/regional sources, secondary aerosol) 2. EC, OC, K and trace metals (traffic and heating by biomass burning, locally emitted aerosol). 3. Ca, EC, OC and trace metals (urban-resuspended road dust reflecting exhaust emissions), 4. Secondary nitrates 5. Na, Cl (marine source) 6. Si, Al, Ti, Ca, Fe (Dust transported from Sahara). These factors reflect not only main sources contributions but also underline the key role of atmospheric dynamics and aerosol ageing processes in this Mediterranean environment.
Keywords: Secondary inorganic aerosol; Organic matter; Elemental carbon; Mass closure; Source apportionment; EPA PMF;

A simulation study of atmospheric mercury and its deposition in the Great Lakes by Shanique L. Grant; Myoungwoo Kim; Peng Lin; Kevin C. Crist; Saikat Ghosh; V. Rao Kotamarthi (164-172).
The Great Lakes eco-region is one of the largest sources of fresh water in North America; however it is chronically exposed to heavy metal loadings such as mercury. In this study a comprehensive model evaluation was conducted to determine mercury loadings to the Great Lakes. The study also evaluated the relative impact of anthropogenic mercury emissions from China, regional and global sources on deposition to the Great Lakes. For the 2005 study period, CMAQ 4.7.1 model estimated a total of 6.4 ± 0.5 metric tons of mercury deposited in the Great Lakes. The total deposition breakdown showed a net loading for Lake Superior of 1906 ± 246 kg/year which is the highest of all the lakes. Lake Michigan followed with 1645 ± 203 kg/year and 1511 ± 107 kg/year in Lake Huron. The lowest total deposition was seen in Lakes Erie and Ontario amassing annual totals of 837 ± 107 kg and 506 ± 63 kg, respectively. Wet and dry deposition of mercury were both significant pathways and exhibited strong seasonal variability with higher deposition occurring in the warmer months (June–November) and the lowest in winter. Wet deposition of RGM significantly influenced the deposition proportions accounting for roughly 90% of all mercury deposited. Of the three emission sources (global background, integrated planning management (IPM) and Chinese), global background concentrations represented the maximum impact to deposition loading in the Great Lakes, except for Lake Erie and parts of Lake Michigan. There was minimal seasonality for the global background, but differences in percentage contribution between dry (28–97%) and wet deposition (43–98%) was predicted. The contributions were seen mainly in the northern sections of the Great Lakes further away from IPM point sources. These findings suggest strong localized impact of IPM sources on the southernmost lakes. Deposition as a result of emissions from China exhibited seasonality in both wet and dry deposition and showed significant contributions ranging from 0.2 to 9%.
Keywords: Deposition; Integrated planning management; Reactive gaseous mercury; Chinese emissions;

Seasonal variability of ultra-fine metals downwind of a heavily traveled secondary road by Thomas A. Cahill; David E. Barnes; Nicholas J. Spada (173-179).
Since 2002, we have been studying the impact of a heavily traveled secondary road on an adjacent downwind school located at a stop light controlled intersection. The prior studies were all performed in winter conditions with typically strong inversions, but established significant PM2.5 impacts on the school roughly in accord with theoretical models and the relevant literature. In this project, we have enhanced this effort by extending the study from winter to summer, and adding compositionally-resolved ultra-fine aerosol measurements. Ultra-fine aerosols, including metals derived from both brake wear and zinc in lubricating oil, were present at high concentrations in winter downwind of the roadway but absent at a residential site 500 m upwind. Their concentrations faded to minor levels in spring and early summer, while coarse roadway resuspended dust increased in that period. A comparison of ultra-fine measurements in downtown Sacramento and other California Central Valley sites indicates that these traffic derived aerosols are widely present in urban areas impacted by heavy traffic, freeways and secondary streets, especially where heavy braking is occurring. The potential for health impacts of ultra-fine metals associated with cars braking and accelerating in inversion conditions is a serious health concern based on recent epidemiological studies.
Keywords: Ultra-fine metallic aerosols; Roadway emissions; Seasonal variability; Vehicle brakes;

Quantifying the emissions and air quality co-benefits of lower-carbon electricity production by Steven D. Plachinski; Tracey Holloway; Paul J. Meier; Gregory F. Nemet; Arber Rrushaj; Jacob T. Oberman; Phillip L. Duran; Caitlin L. Voigt (180-191).
The impact of air emissions from electricity generation depends on the spatial distribution of power plants and electricity dispatch decisions. Thus, any realistic evaluation of the air quality impacts of lower-carbon electricity must account for the spatially heterogeneous changes in associated emissions. Here, we present an analysis of the changes in fine particulate matter (PM2.5) associated with current, expected, and proposed energy efficiency and renewable energy policies in Wisconsin. We simulate the state's electricity system and its potential response to policies using the MyPower electricity-sector model, which calculates plant-by-plant reductions in NO x and SO2 emissions. We find that increased efficiency and renewable generation in a 2024 policy scenario substantially reduce statewide emissions of NO x and SO2 (55% and 59% compared to 2008, 32% and 33% compared to 2024 business-as-usual, BAU). PM2.5 is quantified across the Great Lakes region using the EPA Community Multiscale Air Quality (CMAQ) model for some emissions scenarios. We find that summer mean surface concentrations of sulfate and PM2.5 are less sensitive to policy changes than emissions. In the 2024 policy scenario, sulfate aerosol decreases less than 3% over most of the region relative to BAU and 3–13% relative to 2008 over most of Wisconsin. The lower response of these secondary aerosols arises from chemical and meteorological processing of electricity emissions, and mixing with other emission sources. An analysis of model performance and response to emission reduction at five sites in Wisconsin shows good model agreement with observations and a high level of spatial and temporal variability in sulfate and PM2.5 reductions. In this case study, the marginal improvements in emissions and air quality associated with carbon policies were less than the technology, renewable, and conservation assumptions under a business-as-usual scenario. However, this analysis for Wisconsin shows how integrated modeling can quantify the emission and air quality co-benefits associated with carbon reduction measures, and this approach can be applied to other regions and larger geographical scales.

Low-molecular-weight aliphatic amines were measured in the ambient urban background air at the SMEAR III station (Station for Measuring Forest Ecosystem–Atmosphere Relations III) in Helsinki, Finland, from May until late August 2011. The alkyl amines measured were dimethylamine (DMA), ethylamine (EA), trimethylamine (TMA), propylamine (PA), diethylamine (DEA), butylamine (BA) and triethylamine (TEA).Of these amines, DMA + EA and TMA + PA were the most abundant, with average concentrations of 24 and 8 ppt. The ranges of weekly mean concentrations of DMA + EA and TMA + PA were <DL (9.5 ppt) – 55 ppt and 4–27 ppt. The concentrations of all amines in urban background air in Helsinki were lower than at a boreal forest site (SMEAR II), indicating the presence at the latter site of some additional sources. Amine lifetimes are short, varying from 2.3 h to 7.6 h against hydroxyl (OH) radicals. The amine concentrations were scaled against OH reactivity and compared with the OH reactivities of aromatic hydrocarbons and terpenes. The results showed that amines strongly influenced the total OH reactivity, especially at the boreal forest site in May, September and October, showing contributions almost as high as those of monoterpenes.
Keywords: Amines; Urban air; OH reactivity; VOCs;

On-road emission characteristics of CNG-fueled bi-fuel taxis by Zhiliang Yao; Xinyue Cao; Xianbao Shen; Yingzhi Zhang; Xintong Wang; Kebin He (198-204).
To alleviate air pollution and lessen the petroleum demand from the motor vehicle sector in China, natural gas vehicles (NGVs) have been rapidly developed over the last several years. However, the understanding of the real-world emissions of NGVs is very limited. In this study, the emissions from 20 compressed-natural-gas-fueled bi-fuel taxis were measured using a portable emission measurement system (PEMS) under actual driving conditions in Yichang, China. The emission characteristics of the tested vehicles were analyzed, revealing that the average CO2, CO, HC and NO x emissions from the tested compressed-natural-gas (CNG) taxis under urban driving conditions were 1.6, 4.0, 2.0 and 0.98 times those under highway road conditions, respectively. The CO, HC and NO x emissions from Euro 3 CNG vehicles were approximately 40%, 55% and 44% lower than those from Euro 2 vehicles, respectively. Compared with the values for light-duty gasoline vehicles reported in the literature, the CO2 and CO emissions from the tested CNG taxis were clearly lower; however, significant increases in the HC and NO x emissions were observed. Finally, we normalized the emissions under the actual driving cycles of the entire test route to the New European Driving Cycle (NEDC)-based emissions using a VSP modes method developed by North Carolina State University. The simulated NEDC-based CO emissions from the tested CNG taxis were better than the corresponding emissions standards, whereas the simulated NEDC-based HC and NO x emissions greatly exceeded the standards. Thus, more attention should be paid to the emissions from CNG vehicles. As for the CNG-fueled bi-fuel taxis currently in use, the department of environmental protection should strengthen their inspection and supervision to reduce the emissions from these vehicles. The results of this study will be helpful in understanding and controlling emissions from CNG-fueled bi-fuel vehicles in China.
Keywords: Emissions; Vehicle pollution; Motor vehicle; CNG; Yichang;

Temporal variations of O3 and NO x in the urban background atmosphere of the coastal city Jeddah, Saudi Arabia by M.A. Alghamdi; M. Khoder; Roy M. Harrison; A.-P. Hyvärinen; T. Hussein; H. Al-Jeelani; A.S. Abdelmaksoud; M.H. Goknil; I.I. Shabbaj; F.M. Almehmadi; H. Lihavainen; M. Kulmala; K. Hämeri (205-214).
Ozone is a pollutant of major concern because of its well recognized effects upon human health and crop yields. This study analyses in depth a new dataset for ozone from Jeddah, a coastal city in Saudi Arabia within the Middle Eastern region, for which very few ozone data are currently available, collected between March 2012 and February 2013. The measurements presented include NO, NO2 and ozone as well as relevant meteorological variables. The data show a marked seasonal variation in ozone with highest concentrations in the summer months and lowest average concentrations in the winter. Concentrations also show a substantial difference between weekdays and weekends, with higher NO and NO2 on weekdays, but lower concentrations of ozone. Plots of total oxidant versus NO x concentration indicate background concentrations of ozone (at zero NO x ) ranging from 38.2 ppb in January to 59 ppb in May consistent with the northern hemisphere spring maximum in ozone concentrations. The slope of total oxidant/NO x varies from 0.13 in March to 0.68 in August. The two summer months of July and August are anomalous with slopes of around double that of other months, suggesting a higher efficiency of ozone production at lower primary pollutant concentrations arising from much reduced daytime traffic. A substantial weekend/weekday difference in ozone which is higher at weekends appears to be attributable to lower daytime traffic activity and hence reduced emissions of NO x to a “NO x -saturated” atmosphere.
Keywords: Ozone; Oxides of nitrogen; Saudi Arabia; Total oxidant; Weekend effect; Meteorological parameters;

Characteristics and origins of carbonaceous aerosol in the Sichuan Basin, China by Yuan Chen; Shaodong Xie; Bin Luo; Chongzhi Zhai (215-223).
The Sichuan Basin is a low visibility area in southwest China, where the hilly and basin topography, plus humid and stagnant weather, lead to unique pollution patterns. To identify the characteristics and sources of carbonaceous aerosols, one-year record of 24-h PM2.5 samples were analyzed for organic carbon (OC) and elemental carbon (EC) content following the thermal/optical transmission protocol at three cities (Chengdu (CD), Neijiang (NJ), and Chongqing (CQ)) in the region during May 2012 to April 2013. The annual average concentrations were 19.0 ± 13.3 μg OC m−3 and 4.6 ± 2.6 μg EC m−3 in CD, 18.3 ± 8.4 μg OC m−3 and 4.1 ± 1.8 μg EC m−3 in NJ, and 15.2 ± 8.4 μg OC m−3 and 4.0 ± 1.6 μg EC m−3 in CQ, respectively. Organic matter (1.6OC) plus EC contributed about 40% of PM2.5 mass and displayed weak regional uniformity. Relatively high ratios of OC to EC were observed in the region with 4.3 for CD, 4.6 for NJ, and 3.8 for CQ, respectively. OC and EC pollution in the region exhibited interesting season-dependent characteristics with the lowest concentrations and OC/EC ratios in summer, but higher levels in other seasons. Higher OC/EC ratios in spring and autumn resulted from biomass burning, and in winter were from the enhanced secondary organic aerosol formation under favorable conditions. The exceptionally high OC and EC levels in May and October, mostly notable in CD, resulted from the burning of agricultural residues during harvest period. The high K+ concentrations and the high K excess/EC ratios implied the persistent influence of biomass burning throughout the year. Using a novel technique combing the EC tracer method and potassium mass balance in the aerosols, a K/EC ratio of 1.22 was used to retrieve the OC from biomass burning and the estimated contributions were 30.8%, 28.3%, and 21.9% in CD, NJ, and CQ, respectively, while secondary OC contributions to OC were 26.7%, 24.6%, and 25.7% in CD, NJ, and CQ, respectively.
Keywords: Organic carbon; Elemental carbon; Fine particle; Sichuan Basin; SOC; Biomass burning;

Characteristics of tyre dust in polluted air: Studies by single particle mass spectrometry (ATOFMS) by Manuel Dall'Osto; David C.S. Beddows; Johanna K. Gietl; Oluremi A. Olatunbosun; Xiaoguang Yang; Roy M. Harrison (224-230).
There is a paucity of quantitative knowledge on the contributions of non-exhaust (abrasion and re-suspension) sources to traffic emissions. Abrasive emissions can be broadly categorised as tyre wear, brake wear and road dust/road surface wear. Current research often considers road dust and tyre dust as externally mixed particles, the former mainly composed of mineral matter and the latter solely composed of mainly organic matter and some trace elements. The aim of this work was to characterise tyre wear from both laboratory and field studies by using Aerosol Time-Of-Flight Mass Spectrometry (ATOFMS). Real-time single particle chemical composition was obtained from a set of rubber tyres rotating on a metal surface. Bimodal particle number size distributions peaking at 35 nm and 85 nm were obtained from SMPS/APS measurements over the range 6–20,000 nm. ATOFMS mass spectra of tyre wear in the particle size range 200–3000 nm diameter show peaks due to exo-sulphur compounds, nitrate, Zn and ions of high molecular weight (m/z > 100) attributed to organic polymers. Two large ATOFMS datasets collected from a number of outdoor studies were examined. The former was constituted of 48 road dust samples collected on the roads of London. The latter consisted of ATOFMS ambient air field studies from Europe, overall composed of more than 2,000,000 single particle mass spectra. The majority (95%) of tyre wear particles present in the road dust samples and atmospheric samples are internally mixed with metals (Li, Na, Ca, Fe, Ti), as well as phosphate. It is concluded that the interaction of tyres with the road surface creates particles internally mixed from two sources: tyre rubber and road surface materials. Measurements of the tyre rubber component alone may underestimate the contribution of tyre wear to concentrations of airborne particulate matter. The results presented are especially relevant for urban aerosol source apportionment and PM2.5 exposure assessment.
Keywords: Tyre dust; Road surface wear; Non-exhaust emissions; Road traffic; ATOFMS;

Measurements of nitrous acid (HONO) using ion drift-chemical ionization mass spectrometry during the 2009 SHARP field campaign by Misti Levy; Renyi Zhang; Jun Zheng; Annie L. Zhang; Wen Xu; Mario Gomez-Hernandez; Yuan Wang; Eduardo Olaguer (231-240).
We have developed a novel approach for ambient measurements of nitrous acid (HONO) using ion drift-chemical ionization mass spectrometry (ID-CIMS). HONO is ionized using the sulfur hexafluoride anion, representing the first application of this reagent ion under humid tropospheric conditions. During the 2009 Study of Houston Atmospheric Radical Precursors (SHARP) Field Campaign, HONO measurements were continuously conducted from 1 May to 1 June at a site located on the campus of the University of Houston. Diurnally, HONO concentration accumulates in the late afternoon, reaches a nighttime maximum, and declines rapidly after sunrise. The nighttime HONO peaks show close correlations with the NO2 concentration, particle surface area, and soot mass concentration, indicating that the aerosol-phase chemistry likely contributes to HONO formation. A higher nighttime HONO peak concentration typically precedes a higher and earlier ozone peak concentration of the following day, by about 20 ppb higher and four hours earlier than those with a lower preceding HONO peak concentration. Because of its high detection sensitivity and fast-responding time, the ID-CIMS method described in this work may greatly facilitate HONO detection under typical tropospheric conditions.
Keywords: HONO; ID-CIMS; Soot; Aerosol chemistry;

Assessing ozone exposure for epidemiological studies in Malmö and Umeå, Sweden by E. Malmqvist; D. Olsson; A. Hagenbjörk-Gustafsson; B. Forsberg; K. Mattisson; E. Stroh; M. Strömgren; E. Swietlicki; L. Rylander; G. Hoek; H. Tinnerberg; L. Modig (241-248).
Ground level ozone [ozone] is considered a harmful air pollutant but there is a knowledge gap regarding its long term health effects. The main aim of this study is to develop local Land Use Regression [LUR] models that can be used to study long term health effects of ozone. The specific aim is to develop spatial LUR models for two Swedish cities, Umeå and Malmö, as well as a temporal model for Malmö in order to assess ozone exposure for long term epidemiological studies. For the spatial model we measured ozone, using Ogawa passive samplers, as weekly averages at 40 sites in each study area, during three seasons. This data was then inserted in the LUR-model with data on traffic, land use, population density and altitude to develop explanatory models of ozone variation. To develop the temporal model for Malmö, hourly ozone data was aggregated into daily means for two measurement stations in Malmö and one in a rural area outside Malmö. Using regression analyses we inserted meteorological variables into different temporal models and the one that performed best for all three stations was chosen. For Malmö the LUR-model had an adjusted model R 2 of 0.40 and cross validation R 2 of 0.17. For Umeå the model had an adjusted model R 2 of 0.67 and cross validation adjusted R 2 of 0.48. When restricting the model to only including measuring sites from urban areas, the Malmö model had adjusted model R 2 of 0.51 (cross validation adjusted R 2 0.33) and the Umeå model had adjusted model R 2 of 0.81 (validation adjusted R 2 of 0.73). The temporal model had adjusted model R 2 0.54 and 0.61 for the two Malmö sites, the cross validation adjusted R 2 was 0.42. In conclusion, we can with moderate accuracy, at least for Umeå, predict the spatial variability, and in Malmö the temporal variability in ozone variation.
Keywords: Land use regression; Ozone; Air pollution modelling; Epidemiology; Risk assessment;

Analysis of UK and European NO x and VOC emission scenarios in the Defra model intercomparison exercise by Richard Derwent; Sean Beevers; Charles Chemel; Sally Cooke; Xavier Francis; Andrea Fraser; Mathew R. Heal; Nutthida Kitwiroon; Justin Lingard; Alison Redington; Ranjeet Sokhi; Massimo Vieno (249-257).
Simple emission scenarios have been implemented in eight United Kingdom air quality models with the aim of assessing how these models compared when addressing whether photochemical ozone formation in southern England was NOx- or VOC-sensitive and whether ozone precursor sources in the UK or in the Rest of Europe (RoE) were the most important during July 2006. The suite of models included three Eulerian-grid models (three implementations of one of these models), a Lagrangian atmospheric dispersion model and two moving box air parcel models. The assignments as to NOx- or VOC-sensitive and to UK- versus RoE-dominant, turned out to be highly variable and often contradictory between the individual models. However, when the assignments were filtered by model performance on each day, many of the contradictions could be eliminated. Nevertheless, no one model was found to be the 'best' model on all days, indicating that no single air quality model could currently be relied upon to inform policymakers robustly in terms of NOx- versus VOC-sensitivity and UK- versus RoE-dominance on each day. It is important to maintain a diversity in model approaches.
Keywords: Air quality modelling; Model intercomparison; Episodic peak ozone levels; Emission sensitivities; NOx and VOC emissions;

N2O emissions from global transportation by T.J. Wallington; P. Wiesen (258-263).
Direct emissions of N2O from global transportation (land, air, water) are estimated to be 0.142 ± 0.065 Tg N2O–N yr−1 in 2010 with the majority (≈55%) of emissions resulting as an unwanted by-product from catalytic emission control systems of light-duty vehicles. Emissions from global transportation accounted for 3 ± 1% of current estimates of the total anthropogenic emissions. With anticipated improvements in the emission control systems of light-duty vehicles, the emissions of N2O from global transportation are expected to decline to 0.108 ± 0.065 Tg N2O–N yr−1 by 2030 despite a substantial increase in global transportation activity.
Keywords: Nitrous oxide; N2O; Emissions; Transport; Climate change;

Infrequent occurrence of new particle formation at a semi-rural location, Gadanki, in tropical Southern India by V.P. Kanawade; S. Shika; C. Pöhlker; D. Rose; M.N.S. Suman; H. Gadhavi; Ashwini Kumar; S. M. Shiva Nagendra; R. Ravikrishna; Huan Yu; L.K. Sahu; A. Jayaraman; M.O. Andreae; U. Pöschl; S.S. Gunthe (264-273).
We report first measurements of ultrafine particles from a semi-rural location, Gadanki, from tropical Southern India. Measurements of particle number size distributions in the diameter range of 5 nm–32 μm were performed during 2 May–31 July 2012. The mean number concentrations of nucleation (N NUC), Aitken (N AIT), accumulation (N ACCU), and total particles (N TOT) at this site were (1.1 ± 0.9) × 103 cm−3, (2.2 ± 1.3) × 103 cm−3, (1.5 ± 1.2) × 103 cm−3 and (4.8 ± 2.4) × 103 cm−3, respectively, comparable to other rural to semi-rural locations globally and declined as the season progressed, perhaps due to wet removal of aerosols with onset of monsoon in early June. Particle bursts in the nucleation mode size range (5–25 nm), followed by a sustained growth in size were observed very rarely (only 5 out of 79 observation days) at this site, less frequently than at most other locations around the world during May–July. Most factors affecting new particle formation (NPF) were similar on NPF and nonNPF event days, such as condensation sink, relative humidity, temperature, wind speed and direction, and mixing layer height. Thus, the infrequent occurrence of NPF at our site appeared to be linked to lower precursor gas concentrations and weak gas-phase oxidation chemistry due to diminished solar radiation on persistently cloudy days with the onset of the monsoon in early June over this region. The derived particle growth rates (GR > 5 nm) and formation rates of 5 nm particles (J 5) ranged from 2.2 to 4.7 nm h−1 and 0.4–2.4 cm−3 s−1, with a mean and standard deviation of 3.4 ± 0.9 nm h−1 and 1.2 ± 2.3 cm−3 s−1, respectively, comparable to previous investigations at rural to semi-rural locations. The observed behavior in aerosol and meteorological parameters on NPF and nonNPF event days appeared to be distinctive compared to other rural to urban locations across the globe. However, this distinct behavior is limited and restricted to this site and season of the year, and should therefore not be generalized over a larger spatio-temporal scale. This emphasizes the need for long-term aerosol and precursor measurements over this and other regions of India.
Keywords: Nucleation; Particle size distribution; Semi-rural; Tropics;

An integrated PM2.5 source apportionment study: Positive Matrix Factorisation vs. the chemical transport model CAMx by M.C. Bove; P. Brotto; F. Cassola; E. Cuccia; D. Massabò; A. Mazzino; A. Piazzalunga; P. Prati (274-286).
Receptor and Chemical Transport Models are commonly used tools in source apportionment studies, even if different expertise is required. We describe an experiment using both approaches to apportion the PM2.5 (i.e., particulate matter with aerodynamic diameters below 2.5 μm) sources in the city of Genoa (Italy). A sampling campaign was carried out to collect PM2.5 samples daily for approximately six month during 2011 in three sites. The subsequent compositional analyses included the speciation of elements, major ions and both organic and elemental carbon; these data produced a large database for receptor modelling through Positive Matrix Factorisation (PMF). In the same period, a meteorological and air quality modelling system was implemented based on the mesoscale numerical weather prediction model WRF and the chemical transport model CAMx to obtain meteorological and pollutant concentrations up to a resolution of 1.1 km. The source apportionment was evaluated by CAMx over the same period that was used for the monitoring campaign using the Particulate Source Apportionment Technology tool. Even if the source categorisations were changed (i.e., groups of time-correlated compounds in PMF vs. activity categories in CAMx), the PM2.5 source apportionment by PMF and CAMx produced comparable results. The different information provided by the two approaches (e.g., real-world factor profile by PMF and apportionment of a secondary aerosol by CAMx) was used jointly to elucidate the composition and origin of PM2.5 and to develop a more general methodology. When studying the primary and secondary components of PM, the main anthropogenic sources in the area were road transportation, energy production/industry and maritime emissions, accounting for 40%–50%, 20%–30% and 10%–15%, of PM2.5, respectively.
Keywords: PM2.5; Source apportionment; Receptor models; Chemical transport models;

Variation in isotopologues of atmospheric nitric acid in passively collected samples along an air pollution gradient in southern California by Michael D. Bell; James O. Sickman; Andrzej Bytnerowicz; Pamela E. Padgett; Edith B. Allen (287-296).
The sources and oxidation pathways of atmospheric nitric acid (HNO3) can be evaluated using the isotopic signatures of oxygen (O) and nitrogen (N). This study evaluated the ability of Nylasorb nylon filters to passively collect unbiased isotopologues of atmospheric HNO3 under controlled and field conditions. Filters contained in passive samplers were exposed in continuous stirred tank reactors (CSTRs) at high (16 μg/m3) and moderate (8 μg/m3) HNO3 concentrations during 1–4 week deployment times. Filters were concurrently exposed at high and low N deposition sites along a gradient in the Sonoran Desert. Filters deployed in CSTRs at moderate HNO3 concentrations for 1–2 weeks had greater variation of δ 18O relative to the 3–4 week deployments, while high concentration samples were consistent across weeks. All deployment means were within 2‰ of the source solution. The δ 15N of all weekly samples were within 0.5‰ of the source solution. Thus, when deployed for longer than 3 weeks, Nylasorb filters collected an isotopically unbiased sample of atmospheric HNO3. The initial HNO3 samples at the high deposition field sites had higher δ 15N and δ 18O values than the low deposition sites, suggesting either two independent sources of HNO3 were mixing or that heavier isotopologues of HNO3 were preferentially lost from the gas phase through physical deposition or equilibrium chemical reactions. Subsequent HNO3 samples were subject to summer monsoon conditions leading to variation of isotopic signatures of N and O following 2-source mixing dynamics. Both sites mixed with a source that dominated during the two discrete precipitation events. The high number of lightning strikes near the samplers during the monsoon events suggested that lightning-created HNO3 was one of the dominant mixing sources with an approximate isotopic signature of 21.6‰ and −0.6‰ for δ 18O and δ 15N respectively. Two-source mixing models suggest that lightning-created HNO3 made up between 40 and 42% of atmospheric HNO3 at the high deposition sites and 59–63% at the low deposition during the 4 week exposure.
Keywords: Nylasorb nylon filter; Atmospheric deposition; Passive sampler; Nitric acid; δ 15N; δ 18O; Lightning;

In an urban planning context, an assessment indicator for evaluating a city's dispersion potential is beneficial, especially if the city has a complex natural terrain and significant wind variations. A study was conducted to implement an urban canopy drag indicator, taking site wind variation into account by involving both wind speed and direction in the calculations. Hong Kong (HK) was taken as an example due to its complicated natural topography and wind characteristics. A spatial distribution of an urban canopy drag over HK was determined based on wind data from 2004. The urban canopy drag values in three highly urbanized areas in HK, including Kowloon West, Kowloon East and Hong Kong Island North, were obtained and are discussed in detail. A fluid particle tracking program was developed and applied to identify the major wind paths in Kowloon West, with an area of approximately 5.5 × 6 km as an example. We analyzed the diurnal variation in the dispersion times and the major wind paths in the region during both summer and winter. Our results estimated that the horizontal dispersion times of Kowloon West during both winter and summer were approximately 20 min. By combining the wind paths from both seasons, we identified several major wind paths and critical ventilation areas in Kowloon West. This paper demonstrates the potential use of an urban canopy drag indicator for assessing air ventilation and pollutant dispersion in a city planning context.
Keywords: Urban ventilation; Urban canopy drag; Pollutant dispersion;

Effects of alkylate fuel on exhaust emissions and secondary aerosol formation of a 2-stroke and a 4-stroke scooter by Alessandro A. Zardini; Stephen M. Platt; Michael Clairotte; Imad El Haddad; Brice Temime-Roussel; Nicolas Marchand; Irena Ježek; Luka Drinovec; Griša Močnik; Jay G. Slowik; Urbano Manfredi; André S.H. Prévôt; Urs Baltensperger; Covadonga Astorga (307-315).
Regulated and unregulated emissions from a 2-stroke and a 4-stroke scooter were characterized during a legislative driving cycle in a certified laboratory. Scooter exhaust was analyzed at the tailpipe, in a dilution tunnel, and partly collected in a mobile smog chamber for photochemical ageing. We present evidence that the photochemically aged exhaust from a 2-stroke and a 4-stroke scooter produces considerable amounts of secondary organic aerosol: from 1.5 to 22.0 mg/km, and from 5.5 to 6.6 mg/km, respectively. Tests were repeated after replacing the standard petrol and synthetic lube oil with an alkylate fuel (with low content of aromatic compounds) and ultra-clean lube oil (low ash forming potential). We observed emission reduction (with some exceptions) for several gaseous and particulate phase species, in particular for carbon monoxide (from 8% up to 38% and from 31% to 50%, for the 2-stroke and the 4-stroke scooters, respectively), particulate mass (from 32% up to 75% for the 2-stroke scooter), aromatic compounds (89% and 97% for the 2-stroke and the 4-stroke scooter, respectively), and secondary organic aerosol (from 87% to 100% and 99% for the 2-stroke and the 4-stroke scooters, respectively). We attribute the organic aerosol reduction to the low content of aromatics in the alkylate fuel.
Keywords: Emission factors; Secondary organic aerosol production; Chassis dynamometer; Powered two-wheelers;

This study explores the usefulness of stable isotopic composition (δ13C) along with other chemical tracers and air mass trajectory to identify the primary and secondary sources of carbonaceous aerosols. Aerosol samples (n = 84) were collected continuously from April 2003 to April 2004 at Gosan site in Jeju Island, South Korea. The concentrations of total carbon (TC), HCl fumed carbonate-free total carbon (fumed-TC) and their δ13C were measured online using elemental analyzer interfaced to isotope ratio mass spectrometer (EA-IRMS). Similar concentrations of TC and fumed-TC and their similar δ13C values suggest the insignificant contribution of inorganic carbon to Gosan aerosols. The monthly averaged δ13CTC showed the lowest in April/May (−24.2 to −24.4‰), which is related with the highest concentrations of oxalic acid (a secondary tracer). The result indicates an enhanced contribution of TC from secondary sources. The monthly averaged δ13CTC in July/August (−23.0 to −22.5‰) were similar to those in January/February (−23.1‰ to −22.7‰). However, chemical tracers and air mass transport pattern suggest that the pollution source regions in January/February are completely different from those in July/August. Higher δ13C values in July/August are aligned with higher concentration ratios of marine tracers (azelaic acid/TC and methanesulfonate/TC), suggesting an enhanced contribution of marine organic matter to the aerosol loading. Higher δ13C values in January/February are associated with higher concentrations of phthalic acid and K+/TC, indicating more contributions of carbonaceous aerosols from fossil fuel and C4-plant biomass combustion. This study demonstrates that δ13CTC, along with other chemical tracers and air mass trajectory, can be used as a tracer to understand the importance of primary versus secondary pollution sources of carbonaceous aerosols in the atmosphere.
Keywords: Marine aerosol; Air pollution; Organic aerosol; δ13C; Isotopic enrichment; Gosan;

Ambient particle characterization by single particle aerosol mass spectrometry in an urban area of Beijing by Lei Li; Mei Li; Zhengxu Huang; Wei Gao; Huiqing Nian; Zhong Fu; Jian Gao; Fahe Chai; Zhen Zhou (323-331).
To investigate the composition and possible sources of aerosol particles in Beijing urban area, a single particle aerosol mass spectrometer (SPAMS) was deployed from April 22 to May 4, 2011. 510,341 particles out of 2,953,200 sized particles were characterized by SPAMS in combination with the ART-2a neural network algorithm. The particles were classified as rich-K (39.79%), carbonaceous species (32.7%), industry metal (19.2%), dust (5.7%), and rich-Na (1.76%). Industrial emissions related particles, rich-Fe, rich-Pb, and K-nitrate, were the major components of aerosol particles during haze periods, which were mainly from the steel plants and metal smelting processes around Beijing. Under stagnant meterological conditions, these regional emissions have a vital effect on haze formation. Organic carbon (OC) particles were attributed to biomass burning. NaK-EC was likely to come from local traffic emissions. Internally mixed organic and elemental carbon (OCEC) was found to be from possible sources of local traffic emission and biomass burning. It was found that coarse dust particles were mainly composed of four different types of dust particles, dust-Si, dust-Ca, dust-Al, and dust-Ti. It is the first time that SPAMS was used to study a dust storm in Beijing. Our results showed that SPAMS could be a powerful tool in the identification and apportionment of aerosol sources in Beijing, providing useful reference information for environmental control and management.
Keywords: Single particle; Mass spectrometry; Aerosol; Composition; Source apportionment;

The levels of ozone (O3) at a given location in the UK have been reported to be determined by a combination of global (northern hemispheric), regional and local-scale effects. These effects therefore also potentially influence values of the O3 exposure metric, AOT40 (the accumulated ozone exposure over a threshold of 40 ppb). A corresponding background oxidant metric, AOXBT40, is defined, which quantifies the value of AOT40 corrected for the effects of local oxidant sources and the chemical coupling of O3 with emitted NO x (i.e. effectively a remote rural background AOT40 value). Data from the UK automatic monitoring network have been analysed to determine values of AOT40 and AOXBT40 at 39 UK sites for the example year of 2009. The spatial variation of AOXBT40 over the UK is consistent with contributions deriving both directly from the northern hemispheric baseline O3 level and from episodic events during which the baseline is supplemented by regional-scale oxidant formation; and the approximate relative importance of these inputs is estimated. The fractional decrement in AOT40 (AOT40/AOXBT40), shows a well-defined dependence on the average NO x level for the hours that contribute to AOXBT40, consistent with the expected impact of the local-scale chemical coupling of O3 and NO x . The AOXBT40 concept can therefore be used to help characterise the factors that control AOT40 on different spatial scales, and its potential applications in empirical O3 exposure modelling activities and model evaluation are briefly discussed.
Keywords: Monitoring networks; Air quality; Photochemical pollution; Ozone episode; Ozone exposure; Nitrogen dioxide; Nitrogen oxides; Policy models;

Spatial variability of particle number concentrations and NO x in the Karlsruhe (Germany) area obtained with the mobile laboratory ‘AERO-TRAM’ by Rowell Hagemann; Ulrich Corsmeier; Christoph Kottmeier; Rayk Rinke; Andreas Wieser; Bernhard Vogel (341-352).
For the first time in Germany, we obtained high-resolution spatial distributions of particle numbers and nitrogen oxides in an urban agglomeration using a tram system. In comparison to particle numbers the NO x concentration decreased much faster with a significantly steeper gradient when going from the inner city to the surrounding area. In case of NO x the decrease was 70% while for particle number concentration it was only 50%. We found an area in the rural surrounding with a second increase of particle numbers without simultaneous enhanced NO x levels. The source of the high particle numbers could be ascribed to industry emissions about 5–10 km away. The mean spatial distribution of particle number concentration depended on wind direction, wind velocity and boundary layer stability. The dependency was particularly strong in the rural area affected by industrial emissions, where individual wind directions led to concentration differences of up to 25%. The particulate concentration was 40% higher during low wind velocities (1–5 m s−1) than during high wind velocities (>5 m s−1). We observed similar findings for the impact of boundary layer stability on particle numbers concentration. Particle pollution was 40% higher for stable stratification compared to neutral or unstable cases.
Keywords: Mobile measurements; Particle number concentration; Tramway; Urban pollution;

A review of chemical and physical characterisation of atmospheric metallic nanoparticles by Paul Sanderson; Juana Maria Delgado-Saborit; Roy M. Harrison (353-365).
Knowledge of the human health impacts associated with airborne nanoparticle exposure has led to considerable research activity aimed at better characterising these particles and understanding which particle properties are most important in the context of effects on health. Knowledge of the sources, chemical composition, physical structure and ambient concentrations of nanoparticles has improved significantly as a result. Given the known toxicity of many metals and the contribution of nanoparticles to their oxidative potential, the metallic content of the nanoparticulate burden is likely to be an important factor to consider when attempting to assess the impact of nanoparticle exposure on health. This review therefore seeks to draw together the existing knowledge of metallic nanoparticles in the atmosphere and discuss future research priorities in the field. The article opens by outlining the reasons behind the current research interest in the field, and moves on to discuss sources of nanoparticles to the atmosphere. The next section reviews ambient concentrations, covering spatial and temporal variation, mass and number size distributions, air sampling and measurement techniques. Further sections discuss the chemical and physical composition of particles. The review concludes by summing up the current state of research in the area and considering where future research should be focused.
Keywords: Particulate matter; Nanoparticles; Ultrafine particles; Metals;

Aromatic organosulfates in atmospheric aerosols: Synthesis, characterization, and abundance by Sean Staudt; Shuvashish Kundu; Hans-Joachim Lehmler; Xianran He; Tianqu Cui; Ying-Hsuan Lin; Kasper Kristensen; Marianne Glasius; Xiaolu Zhang; Rodney J. Weber; Jason D. Surratt; Elizabeth A. Stone (366-373).
Aromatic organosulfates are identified and quantified in fine particulate matter (PM2.5) from Lahore, Pakistan, Godavari, Nepal, and Pasadena, California. To support detection and quantification, authentic standards of phenyl sulfate, benzyl sulfate, 3- and 4-methylphenyl sulfate and 2-, 3-, and 4-methylbenzyl sulfate were synthesized. Authentic standards and aerosol samples were analyzed by ultra-performance liquid chromatography (UPLC) coupled to negative electrospray ionization (ESI) quadrupole time-of-flight (ToF) mass spectrometry. Benzyl sulfate was present in all three locations at concentrations ranging from 4 to 90 pg m−3. Phenyl sulfate, methylphenyl sulfates and methylbenzyl sulfates were observed intermittently with abundances of 4 pg m−3, 2–31 pg m−3, 109 pg m−3, respectively. Characteristic fragment ions of aromatic organosulfates include the sulfite radical (•SO3 , m/z 80) and the sulfate radical (•SO4 , m/z 96). Instrumental response factors of phenyl and benzyl sulfates varied by a factor of 4.3, indicating that structurally-similar organosulfates have significantly different instrumental responses and highlighting the need to develop authentic standards for absolute quantitation organosulfates. In an effort to better understand the sources of aromatic organosulfates to the atmosphere, chamber experiments with the precursor toluene were conducted under conditions that form biogenic organosulfates. Aromatic organosulfates were not detected in the chamber samples, suggesting that they form through different pathways, have different precursors (e.g. naphthalene or methylnaphthalene), or are emitted from primary sources.
Keywords: Sulfate ester synthesis; Atmospheric aerosol; Mass spectrometry; Toluene;

This study focuses on analyzing the extreme aerosol loading and the mechanisms, source areas and meteorological conditions that favored the abnormal dust exposure towards Arabian Sea during June 2008. The analysis reveals that the spatial-averaged aerosol optical depth (AOD) over Arabian Sea in June 2008 is 0.5 (78.2%) higher than the 2000–2013 mean June value and is mostly attributed to the enhanced dust activity and several (18) dust storms originated from the Sistan region (Iran–Afghanistan borders). Landsat images show that the marshy lakes in Sistan basin got dried during the second half of June 2008 and the alluvial silt and saline material got easily eroded by the intense Levar winds, which were stronger (>15–20 m s−1) than the climatological mean for the month of June. These conditions led to enhanced dust exposure from Sistan that strongly affected the northern and central parts of the Arabian Sea, as forward air-mass trajectories show. The NCEP/NCAR reanalysis reveals an abnormal intensification and spatial expansion of the Indian low pressure system towards northern Arabian Sea in June 2008. This suggests strengthening of the convection over the arid southwest Asia and exposure of significant amount of dust, which can reach further south over Arabian Sea favored by the enhanced cyclonic circulation. MODIS imagery highlighted several dust storms originated from Sistan and affecting Arabian Sea during June 2008, while the SPRINTARS model simulations of increased AOD and dust concentration over Sistan and downwind areas are in agreement with ground-based and satellite observations.
Keywords: Arabian Sea; Severe AOD; Dust storms; Remote sensing; Synoptic meteorology; SPRINTARS;

Spores of fungi in the genus Fusarium may be transported through the atmosphere over long distances. New information is needed to characterize seasonal trends in atmospheric loads of Fusarium and to pinpoint the source(s) of inoculum at both local (farm) and regional (state or country) scales. We hypothesized that (1) atmospheric concentrations of Fusarium spores in an agricultural ecosystem vary with height and season and (2) transport distances from potential inoculum source(s) vary with season. To test these hypotheses, spores of Fusarium were collected from the atmosphere in an agricultural ecosystem in Blacksburg, VA, USA using a Burkard volumetric sampler (BVS) 1 m above ground level and autonomous unmanned aerial vehicles (UAVs) 100 m above ground level. More than 2200 colony forming units (CFUs) of Fusarium were collected during 104 BVS sampling periods and 180 UAV sampling periods over four calendar years (2009–2012). Spore concentrations ranged from 0 to 13 and 0 to 23 spores m−3 for the BVS and the UAVs, respectively. Spore concentrations were generally higher in the fall, spring, and summer, and lower in the winter. Spore concentrations from the BVS were generally higher than those from the UAVs for both seasonal and hourly collections. A Gaussian plume transport model was used to estimate distances to the potential inoculum source(s) by season, and produced mean transport distances of 1.4 km for the spring, 1.7 km for the summer, 1.2 km for the fall, and 4.1 km for the winter. Environmental signatures that predict atmospheric loads of Fusarium could inform disease spread, air pollution, and climate change.
Keywords: Fungi; Pathogen; Aerobiology; Aerobiological sampling; Burkard volumetric sampler; Unmanned aerial vehicle; UAV; Long-distance transport;

A new statistical approach for establishing high-resolution emission inventory of primary gaseous air pollutants by Ying Zhou; Shuiyuan Cheng; Dongsheng Chen; Jianlei Lang; Beibei Zhao; Wei Wei (392-401).
This paper, which aims at the primary gaseous air pollutants (i.e., SO2, NO x , VOCS and CO), is the third paper in the series papers published in Atmospheric Environment to develop new emission estimation models by the regression method. A group of regression models for various industrial and non-industrial sectors were proposed based on an emission investigation case study of Handan region in northern China. The main data requirements of the regression models for industrial sectors were coal consumption, oil consumption, gaseous fuel consumption and annual industrial output. The data requirements for non-industrial sector emission estimations were the population, the number of resident population households, the vehicle population, the area of construction sites, the forestland area, and the orchard area. The models were then applied to Tangshan region in northern China. The results showed that the developed regression models had relatively satisfactory performance. The modeling errors at the regional level for SO2, NO x , VOCS and CO were −16.5%, −10.6%, −11.8% and −22.6%, respectively. The corresponding modeling errors at the county level were 39.9%, 33.9%, 46.3% and 46.9%, respectively. The models were also applied to other regions in northern China. The results revealed that the new models could develop emission inventories with generally lower error than found in previous emission inventory studies. The developed models had the advantages of only using publicly available statistical information for developing high-accuracy and high-resolution emission inventory, without requiring detailed data investigation which is necessary by conventional “bottom-up” emission inventory development approach.
Keywords: Emission inventory; Regression model; County level resolution; Primary gaseous air pollutants;

Estimation of regional background concentration of CO2 at Lin'an Station in Yangtze River Delta, China by Jing-Jiao Pu; Hong-Hui Xu; Jun He; Shuang-Xi Fang; Ling-Xi Zhou (402-408).
A new method of extracting regional background concentration of CO2 in Yangtze River Delta was established based on the observations of both black carbon concentration and meteorological parameters. The concentrations of CO2 and black carbon were observed at Lin'an regional background station from 2009 to 2011. The regional background concentration of CO2 in Yangtze River Delta was obtained by means of this new method, and the impact of human activities on CO2 concentration in this area was also assessed. The results showed that the regional background concentration of CO2 extracted by this approach was comparable to the values obtained by R statistical filter method, and moreover this new method was better at picking up episodes heavily polluted by anthropogenic emissions. The annual regional average background concentration of CO2 in Yangtze River Delta from 2009 to 2011 was approximately 404.7 ± 8.2 ppm, 405.6 ± 5.3 ppm and 407.0 ± 5.3 ppm, respectively, much higher than global average value, indicating the distinct characteristic of this region. The anthropogenic emissions from Yangtze River Delta had significant influence on the concentration of CO2, increasing the value roughly 9.1 ppm higher than the regional background concentration of this area.
Keywords: CO2; Regional background concentration; Black carbon; Yangtze River Delta;

Rainwater is an important natural resource and utilized for various beneficial purposes. However, information on prokaryotes in rainwater is limited. Rainwater samples were collected during three heavy rain events at a suburban site in Seoul in April, May, and July 2011. The highest bacterial abundance (BA) in rainwater was observed in April when airborne bacteria had also been abundant the day before rainwater collection. ATP content in bacterial fraction of the rainwater suggested that the rainwater bacteria were metabolically active. Bacterial community compositions (BCCs) of rainwater samples, analyzed by using 16S rRNA gene-based pyrosequencing, differed considerably among the three rain events. Rainwater bacteria showed potentials of fast growth and drastic shift after incubation in BCCs from fresh rainwater at broad taxonomic levels and the dominant operational taxonomic units (OTUs) level. Presumable marine bacterial OTUs which formed a robust clade with marine bacteria Lacinutrix spp. were at high concentrations in rainwater in April, likely reflecting origin from saline environments. Most of the Flavobacteria sequences unusually high in April rainwater seemed to have marine origins. Further, spore-forming euryhaline marine Firmicutes were isolated from rainwater samples, suggesting possible dispersal of some marine bacteria via rain. A potential human pathogen and Escherichia coli-like sequences were detected in rainwater samples, calling for the need for assessment of health risks of collected rainwater.
Keywords: Abundance; Bacteria; Community composition; Pyrosequencing; Rainwater;

This study combined a three-year time series of air pollutant measurements from the Michigan Air Sampling Network (MASN) with spatially detailed datasets for two two-week periods in September 2008 and June 2009. The objective was to produce monthly pollutant concentration models for the city of Detroit, Michigan, USA from January 2008 through December 2010, in support of a related epidemiological study examining adverse birth outcomes in Detroit. Two gaseous analytes, NO2 (nitrogen dioxide) and total BTEX (benzene, toluene, ethyl-benzene, and xylene), as well as two particulate matter size fractions, PM2.5 and PM10, were investigated. The September 2008 and June 2009 datasets were modeled using ordinary kriging to produce high spatial density concentration maps with 300 m by 300 m resolution across the city. A weighted average was applied to these maps to generate a series of monthly spatial models for each pollutant. Temporal variability was then incorporated by adjusting each monthly spatial model using an average bulk shift derived from MASN time series measurements for the corresponding month over the three-year study period.The resulting models incorporate temporal trends while preserving neighborhood scale spatial variability. Seasonal variation was evident in NO2 models, but not readily discernable in BTEX or PM models across the three year study period. The greatest spatial and temporal variability was observed in the BTEX distributions, which are inferred to be strongly influenced by local sources. The methodology employed assumes that the interpolated monthly models adequately capture spatial variability of the air pollutants across the study area, the spatial distribution of pollutant concentrations remained consistent while their magnitude fluctuated from month to month, and that the available time series measurements reflect temporal trends across the city of Detroit throughout the three-year study period.Display Omitted
Keywords: Urban air quality; Spatial variability; Temporal variability; Spatiotemporal modeling; GeoDHOC; Detroit;

Measurement of the light absorbing properties of diesel exhaust particles using a three-wavelength photoacoustic spectrometer by Xuesong Guo; Tomoki Nakayama; Hiroyuki Yamada; Satoshi Inomata; Kenichi Tonokura; Yutaka Matsumi (428-437).
Diesel-exhaust particles (DEP) are one of the main anthropogenic sources of black carbon (BC) and organic matter (OM). Understanding the optical properties of DEP, including the enhancement of light absorption by BC due to coating and light absorption by OM, is important for evaluating the climate impact of DEP. In this study, a three-wavelength photoacoustic soot spectrometer (405, 532, and 781 nm) was used to investigate the wavelength-dependent optical properties of DEP emitted from a diesel engine vehicle running on a chassis dynamometer in transient driving mode (JE-05) and at a constant speed (either idling or driving at 70 km/h). Optical properties were measured after passing the diluted exhaust through a heater, set at 20, 47, or 300 °C (transient driving mode) or between 20 and 400 °C (constant driving mode). The OM accounted for, on average, ∼40 and ∼35% of the total mass concentration of DEP during the transient and constant driving modes, respectively. In transient driving mode, enhancements of scattering coefficients at 20 and 47 °C, and of the mass concentration of organics, were observed during the high-speed driving period (∼80 km/h) corresponding to driving on a highway. No difference was observed in the absorption coefficients between heated and unheated particles at 781 nm for either the transient (including the high-speed driving period) or constant driving modes. These results indicate a lack of enhancement due to the lensing effect, possibly because the BC was mainly mixed externally with the OM or because it was located at the edges of particles under these experimental conditions. Contributions to total light absorption at 405 nm by the OM were estimated by comparing the wavelength dependence of the absorption coefficients with and without heating. A significant contribution by light-absorbing OM (20 ± 7%) to total light absorption at 405 nm was observed during the high-speed driving period of the JE-05 mode, while the contributions were small during other periods in the JE-05 mode (0 ± 8%) and the constant driving mode (idling: 4 ± 12%; driving at 70 km/h: 0 ± 16%).
Keywords: Aerosol optical property; Diesel exhaust particle (DEP); Black carbon (BC); Lensing effect; Brown carbon; Photoacoustic spectroscopy (PAS);

Impacts of Stabilized Criegee Intermediates, surface uptake processes and higher aromatic secondary organic aerosol yields on predicted PM2.5 concentrations in the Mexico City Metropolitan Zone by Qi Ying; Iris V. Cureño; Gang Chen; Sajjad Ali; Hongliang Zhang; Meagan Malloy; Humberto A. Bravo; Rodolfo Sosa (438-447).
The Community Multiscale Air Quality Model (CMAQ) with the SAPRC-99 gas phase photochemical mechanism and the AERO5 aerosol module was applied to model gases and particulate matter (PM) concentrations in the Mexico City Metropolitan Zone (MCMZ) and the surrounding regions for March 2006 using the official 2006 emission inventories, along with emissions from biogenic sources, biomass burning, windblown dust, the Tula Industrial Complex and the Popocatépetl volcano. The base case model was capable of reproducing the observed hourly concentrations of O3 and attaining CO, NO2 and NO x performance similar to previous modeling studies. Although the base case model performance of hourly PM2.5 and PM10 meets the model performance criteria, under-prediction of high PM2.5 concentrations in late morning indicates that secondary PM, such as sulfate and secondary organic aerosol (SOA), might be under-predicted. Several potential pathways to increase SOA and secondary sulfate were investigated, including Stabilized Criegee Intermediates (SCIs) from ozonolysis reactions of unsaturated hydrocarbons and their reactions with SO2, the reactive uptake processes of SO2, glyoxal and methylglyoxal on particle surface and higher SOA formation due to higher mass yields of aromatic SOA precursors. Averaging over the entire episode, the glyoxal and methylglyoxal reactive uptake and higher aromatics SOA yields contribute to ∼0.9 μg m−3 and ∼1.25 μg m−3 of SOA, respectively. Episode average SOA in the MCMZ reaches ∼3 μg m−3. The SCI pathway increases PM2.5 sulfate by 0.2–0.4 μg m−3 or approximately 10–15%. The relative amount of sulfate increase due to SCI agrees with previous studies in summer eastern US. Surface SO2 uptake significantly increases sulfate concentration in MCMZ by 1–3 μg m−3 or approximately 50–60%. The higher SOA and sulfate leads to improved PM2.5 and PM10 model performance.
Keywords: Stabilized Criegee Intermediates; Secondary sulfate; Secondary organic aerosol; Aromatic hydrocarbon; Sulfur dioxide; Mexico City;

Role of stabilized Criegee Intermediate in secondary organic aerosol formation from the ozonolysis of α-cedrene by Lei Yao; Yan Ma; Lin Wang; Jun Zheng; Alexei Khalizov; Mindong Chen; Yaoyao Zhou; Lu Qi; Fenping Cui (448-457).
Atmospheric ozonolysis of sesquiterpenes is an important source of secondary organic aerosols (SOA). The mechanisms by which Criegee Intermediates (CIs) react to form SOA precursors and the influence of environmental conditions, however, remain unclear. On the basis of environmental chamber experiments coupled with detailed characterization of gas-phase and particle-phase products, we present evidence that a significant fraction of CIs from ozonolysis of α-cedrene are stabilized and bimolecular reactions of these stabilized CIs (SCIs) play a key role in the formation of SOA precursors. Ozonolysis experiments were conducted in a 4.5 m3 collapsible fluoropolymer chamber under various conditions in the presence of the OH radical and SCI scavengers. The size and mass of SOA particles produced during ozonolysis were measured directly and used for calculation of particle effective density and mass yield. Gaseous and particulate products were analyzed by several mass spectrometry methods. A total of 14 compounds in gas phase and 17 compounds in particle phase were tentatively identified. The major gas-phase products are secondary ozonides (SOZ) from intramolecular reactions of SCIs. Multifunctional organic acids are dominant particle-phase products. The measured density of aerosol particles is 1.04 ± 0.03 to 1.38 ± 0.03 g/cm3, and the aerosol mass yield is (23.7 ± 0.4)% to (46.4 ± 6.5)%, depending on reaction conditions. The presence of acetic acid, an SCI scavenger, inhibits new particle formation, but leads to increased aerosol mass yield. In contrast, the addition of SO2 dramatically enhances new particle formation and total aerosol yield. The calculated OH formation yield decreases from (62.4 ± 4.9)% to (9.0 ± 1.6)% upon addition of SCI scavengers CH3COOH and SO2, indicating that a large fraction of excited CIs are collisionally stabilized and unimolecular decomposition of SCIs via the hydroperoxide channel can be suppressed by bimolecular reactions. The reaction of SCIs with SO2 leads to the formation of sulfuric acid, an important nucleation precursor. From the consumption of SO2 added as SCI scavenger, a lower-limit yield of SCIs from α-cedrene ozonolysis is estimated at ∼88%. Our work underscores the key role of SCIs in SOA formation and observed composition of gas- and particle-phase products from α-cedrene ozonolysis. Bimolecular reactions of sesquiterpene CIs with atmospherically relevant species (e.g. SO2, H2O) need to be considered when assessing the atmospheric relevance of ozonolysis of sesquiterpenes.
Keywords: Sesquiterpene; α-Cedrene; Ozonolysis; Secondary organic aerosol; Criegee Intermediate; Reaction mechanism;

Characterizing reduced sulfur compounds emissions from a swine concentrated animal feeding operation by Ian C. Rumsey; Viney P. Aneja; William A. Lonneman (458-466).
Reduced sulfur compounds (RSCs) emissions from concentrated animal feeding operations (CAFOs) have become a potential environmental and human health concern, as a result of changes in livestock production methods. RSC emissions were determined from a swine CAFO in North Carolina. RSC measurements were made over a period of ≈1 week from both the barn and lagoon during each of the four seasonal periods from June 2007 to April 2008. During sampling, meteorological and other environmental parameters were measured continuously. Seasonal hydrogen sulfide (H2S) barn concentrations ranged from 72 to 631 ppb. Seasonal dimethyl sulfide (DMS; CH3SCH3) and dimethyl disulfide (DMDS; CH3S2CH3) concentrations were 2–3 orders of magnitude lower, ranging from 0.18 to 0.89 ppb and 0.47 to 1.02 ppb, respectively. The overall average barn emission rate was 3.3 g day−1 AU−1 (AU (animal unit) = 500 kg of live animal weight) for H2S, which was approximately two orders of magnitude higher than the DMS and DMDS overall average emissions rates, determined as 0.017 g day−1 AU−1 and 0.036 g day−1 AU−1, respectively. The overall average lagoon flux was 1.33 μg m−2 min−1 for H2S, which was approximately an order of magnitude higher than the overall average DMS (0.12 μg m−2 min−1) and DMDS (0.09 μg m−2 min−1) lagoon fluxes. The overall average lagoon emission for H2S (0.038 g day−1 AU−1) was also approximately an order of magnitude higher than the overall average DMS (0.0034 g day−1 AU−1) and DMDS (0.0028 g day−1 AU−1) emissions. H2S, DMS and DMDS have offensive odors and low odor thresholds. Over all four sampling seasons, 77% of 15 min averaged H2S barn concentrations were an order of magnitude above the average odor threshold. During these sampling periods, however, DMS and DMDS concentrations did not exceed their odor thresholds. The overall average barn and lagoon emissions from this study were used to help estimate barn, lagoon and total (barn + lagoon) RSC emissions from swine CAFOs in North Carolina. Total (barn + lagoon) H2S emissions from swine CAFOs in North Carolina were estimated to be 1.22*106 kg yr−1. The barns had significantly higher H2S emissions than the lagoons, contributing ≈98% of total North Carolina H2S swine CAFO emissions. Total (barn + lagoon) emissions for DMS and DMDS were 1–2 orders of magnitude lower, with barns contributing ≈86% and ≈93% of total emissions, respectively. H2S swine CAFO emissions were estimated to contribute ≈18% of North Carolina H2S emissions.
Keywords: Reduced sulfur compounds; Hydrogen sulfide; CAFO emissions; Swine;

Gas phase carbonyl compounds in ship emissions: Differences between diesel fuel and heavy fuel oil operation by Ahmed A. Reda; J. Schnelle-Kreis; J. Orasche; G. Abbaszade; J. Lintelmann; J.M. Arteaga-Salas; B. Stengel; R. Rabe; H. Harndorf; O. Sippula; T. Streibel; R. Zimmermann (467-478).
Gas phase emission samples of carbonyl compounds (CCs) were collected from a research ship diesel engine at Rostock University, Germany. The ship engine was operated using two different types of fuels, heavy fuel oil (HFO) and diesel fuel (DF). Sampling of CCs was performed from diluted exhaust using cartridges and impingers. Both sampling methods involved the derivatization of CCs with 2,4-Dinitrophenylhydrazine (DNPH). The CCs-hydrazone derivatives were analyzed by two analytical techniques: High Performance Liquid Chromatography-Diode Array Detector (HPLC-DAD) and Gas Chromatography–Selective Ion Monitoring–Mass Spectrometry (GC–SIM–MS). Analysis of DNPH cartridges by GC–SIM–MS method has resulted in the identification of 19 CCs in both fuel operations. These CCs include ten aliphatic aldehydes (formaldehyde, acetaldehyde, propanal, isobutanal, butanal, isopentanal, pentanal, hexanal, octanal, nonanal), three unsaturated aldehydes (acrolein, methacrolein, crotonaldehyde), three aromatic aldehyde (benzaldehyde, p-tolualdehyde, m,o-molualdehyde), two ketones (acetone, butanone) and one heterocyclic aldehyde (furfural). In general, all CCs under investigation were detected with higher emission factors in HFO than DF. The total carbonyl emission factor was determined and found to be 6050 and 2300 μg MJ−1 for the operation with HFO and DF respectively. Formaldehyde and acetaldehyde were found to be the dominant carbonyls in the gas phase of ship engine emission. Formaldehyde emissions factor varied from 3500 μg MJ−1 in HFO operation to 1540 μg MJ−1 in DF operation, which is 4–30 times higher than those of other carbonyls. Emission profile contribution of CCs showed also a different pattern between HFO and DF operation. The contribution of formaldehyde was found to be 58% of the emission profile of HFO and about 67% of the emission profile of DF. Acetaldehyde showed opposite behavior with higher contribution of 16% in HFO compared to 11% for DF. Heavier carbonyls (more than two carbon atoms) showed also more contribution in the emission profile of the HFO fuel (26%) than in DF (22%).
Keywords: Carbonyl compounds; DNPH; Ship emission; Heavy fuel oil; GC–SIM–MS;

Aircraft observations of the lower troposphere above a megacity: Alkyl nitrate and ozone chemistry by Eleonora Aruffo; Piero Di Carlo; Cesare Dari-Salisburgo; Fabio Biancofiore; Franco Giammaria; Marcella Busilacchio; James Lee; Sarah Moller; James Hopkins; Shalini Punjabi; Stéphane Bauguitte; Debbie O'Sullivan; Carl Percival; Michael Le Breton; Jennifer Muller; Rod Jones; Grant Forster; Claire Reeves; Dwayne Heard; Hannah Walker; Trevor Ingham; Stewart Vaughan; Daniel Stone (479-488).
Within the framework of the RONOCO (ROle of Nighttime chemistry in controlling the Oxidising Capacity of the atmOsphere) campaign a daytime flight over the metropolitan area of London were carried out to study the nitrogen oxide chemistry and its role in the production and loss of ozone (O 3 ) and alkyl and multifunctional nitrate (ΣANs). The FAAM BAe-146 aircraft, used for these observations, was equipped with instruments to measure the most relevant compounds that control the lower troposphere chemistry, including O 3 , NO, NO 2 , NO 3 , N 2 O 5 , HNO 3 , peroxy nitrates (ΣPNs), ΣANs, OH, and HO 2 . In the London's flight a strong ozone titration process was observed when flying above Reading (downwind of London) and when intercepting the London plume. The coupled cycles of NO x and HO x can have different terminations forming ΣPNs, ΣANs, HNO 3 or peroxides (H2O2, ROOH) altering the O 3 production. In the observations reported here, we found that a strong ozone titration (ΔO 3  = −16 ppb), due to a rapid increase of NO x NO x  = 27 ppb), corresponds also to a high increase of ΣANs concentrations (ΔΣANs = 3 ppb), and quite stable concentrations of HNO3 and ΣPNs. Unexpectedly, compared with other megacities, the production of ΣANs is similar to that of O x (O 3  + NO 2 ), suggesting that in the London plume, at least during these observations, the formation of ΣANs effectively removes active NO x and hence reduces the amount of O 3 production. In fact, we found that the ratio between the ozone production and the alkyl nitrates production (observed) approximate the unity; on the contrary the calculated ratio is 7. In order to explain this discrepancy, we made sensitivity tests changing the alkyl nitrates branching ratio for some VOCs and we investigated the impact of the unmeasured VOCs during the flight, founding that the calculated ratio decreases from 7 to 2 and that, in this condition, the major contribution to the ΣANs production is given by Alkanes. Observations and analysis reported here suggest that in the London plume the high NO x emissions and the chemistry of some VOCs (mainly Alkanes) produce high concentrations of ΣANs competing against the local ozone production.
Keywords: Ozone production; Alkyl nitrates production; Tropospheric chemistry; Urban pollution; Aircraft; London;

Rate coefficients for the gas phase reactions of OH radicals with 2,2,2-trifluoroethylmethacrylate (k 1) 1,1,1,3,3,3-hexafluoroisopropylacrylate (k 2), 1,1,1,3,3,3-hexafluoroisopropylmethacrylate (k 3), and 2,2,2-trifluoroethylacrylate (k 4) were determinated to be k 1 = (2.54 ± 0.12) × 10−11, k 2 = (1.41 ± 0.11) × 10−11, k 3 = (1.65 ± 0.14) × 10−11 and k 4 = (1.25 ± 0.13) × 10−11 cm3 molecule−1 s−1, respectively. Kinetic experiments were performed at room temperature and atmospheric pressure using the relative-rate technique with GC-FID analysis. This study is the first kinetic for these reactions of OH radicals under atmospheric pressure. Additionally, the rate constants obtained are compared with other halogenated and non halogenated acrylates and methacrylates to develop structure/reactivity relationships in terms of the presence of fluorine and ester groups and the hydrocarbon chain length. The atmospheric implications of the reactions were assessed by the estimation of the tropospheric lifetimes of the title reactions.Display Omitted
Keywords: 2,2,2-Trifluoroethylmethacrylate; 1,1,1,3,3,3-Hexafluoroisopropylacrylate; 1,1,1,3,3,3-Hexafluoroisopropylmethacrylate; 2,2,2-Trifluoroethylacrylate; Rate coefficients; Tropospheric chemistry;

The moss bag technique is a simple and economical environmental monitoring tool used to monitor air quality. However, routine use of the method is not possible because the protocols involved have not yet been standardized. Some of the most variable methodological aspects include (i) selection of moss species, (ii) ratio of moss weight to surface area of the bag, (iii) duration of exposure, and (iv) height of exposure. In the present study, the best option for each of these aspects was selected on the basis of the mean concentrations and data replicability of Cd, Cu, Hg, Pb and Zn measured during at least two exposure periods in environments affected by different degrees of contamination. The optimal choices for the studied aspects were the following: (i) Sphagnum denticulatum, (ii) 5.68 mg of moss tissue for each cm−2 of bag surface, (iii) 8 weeks of exposure, and (iv) 4 m height of exposure. Duration of exposure and height of exposure accounted for most of the variability in the data. The aim of this methodological study was to provide data to help establish a standardized protocol that will enable use of the moss bag technique by public authorities.
Keywords: Biomonitoring harmonization; Environmental tool; Heavy metals; Air quality; Atmospheric deposition;

Black carbon and carbon monoxide over Bay of Bengal during W_ICARB: Source characteristics by I.A. Girach; Vijayakumar S. Nair; S. Suresh Babu; Prabha R. Nair (508-517).
The ship borne measurements of near-surface black carbon (BC) and carbon monoxide (CO) were carried out over Bay of Bengal (BoB) during the winter period of 2009 under W_ICARB, the second phase of ‘Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB)’. The CO mixing ratio and BC mass concentration varied in the ranges of 80–480 ppbv and 75–10,000 ng m−3, respectively over this marine region. The BC and CO showed similar variations over northern BoB where airmass from Indo-Gangetic Plain (IGP) region prevailed during the observations period leading to a very strong positive correlation. The association of BC and CO was poor over the eastern and southern part of BoB could be due to the removal of BC aerosols by rain and/or processes of dilution and mixing while transported over to BoB. The highest value of CO observed over eastern BoB was partially due to biomass burning over East Asia. The BC/CO ratio for IGP airmass found to be 20.3 ng m−3 ppb−1 and ∼16 ng m−3 ppb−1 during winter and pre-monsoon, respectively which indicate the role of biomass burning as the source of BC over the region. Based on the emission flux of CO from various inventories and observed BC/CO ratios during pre-monsoon and winter, the BC emission for India is estimated to be in the range of 0.78–1.23 Tg year−1. The analysis of scavenging of BC revealed the loss rate of BC due to relative humidity 0.39 ± 0.08 ng m−3 ppb−1 RH (%)−1 over northern BoB and 0.53 ± 0.04 ng m−3 ppb−1 RH (%)−1 over the southern-BoB during winter.
Keywords: Carbon monoxide; Black carbon; Source characteristics; Emission flux; Humidity effect on BC;

Spatial resolution requirements for traffic-related air pollutant exposure evaluations by Stuart Batterman; Sarah Chambliss; Vlad Isakov (518-528).
Vehicle emissions represent one of the most important air pollution sources in most urban areas, and elevated concentrations of pollutants found near major roads have been associated with many adverse health impacts. To understand these impacts, exposure estimates should reflect the spatial and temporal patterns observed for traffic-related air pollutants. This paper evaluates the spatial resolution and zonal systems required to estimate accurately intraurban and near-road exposures of traffic-related air pollutants. The analyses use the detailed information assembled for a large (800 km2) area centered on Detroit, Michigan, USA. Concentrations of nitrogen oxides (NO x ) due to vehicle emissions were estimated using hourly traffic volumes and speeds on 9700 links representing all but minor roads in the city, the MOVES2010 emission model, the RLINE dispersion model, local meteorological data, a temporal resolution of 1 h, and spatial resolution as low as 10 m. Model estimates were joined with the corresponding shape files to estimate residential exposures for 700,000 individuals at property parcel, census block, census tract, and ZIP code levels. We evaluate joining methods, the spatial resolution needed to meet specific error criteria, and the extent of exposure misclassification. To portray traffic-related air pollutant exposure, raster or inverse distance-weighted interpolations are superior to nearest neighbor approaches, and interpolations between receptors and points of interest should not exceed about 40 m near major roads, and 100 m at larger distances. For census tracts and ZIP codes, average exposures are overestimated since few individuals live very near major roads, the range of concentrations is compressed, most exposures are misclassified, and high concentrations near roads are entirely omitted. While smaller zones improve performance considerably, even block-level data can misclassify many individuals. To estimate exposures and impacts of traffic-related pollutants accurately, data should be geocoded or estimated at the most-resolved spatial level; census tract and larger zones have little if any ability to represent intraurban variation in traffic-related air pollutant concentrations. These results are based on one of the most comprehensive intraurban modeling studies in the literature and results are robust. Additional recommendations address the value of dispersion models to portray spatial and temporal variation of air pollutants in epidemiology and other studies; techniques to improve accuracy and reduce the computational burden in urban scale modeling; the necessary spatial resolution for health surveillance, demographic, and pollution data; and the consequences of low resolution data in terms of exposure misclassification.Exposure estimates at the census tract level do not have the spatial resolution needed for traffic-related air pollutants.Display Omitted
Keywords: Air pollution; Exposure; Exposure misclassification; Traffic;

Measurement of nitrogen dioxide diffusive sampling rates for Palmes diffusion tubes using a controlled atmosphere test facility (CATFAC) by Nicholas A. Martin; Jonathan J. Helmore; Samual White; Ieuan L. Barker Snook; Andy Parish; Linda S. Gates (529-537).
We report measurements of the 28 day NO2 diffusive sampling rates for seven designs of Palmes diffusion tubes (PDTs), which were exposed in a controlled atmosphere test facility (CATFAC) containing traceable concentrations of nitrogen dioxide, nitric oxide and water vapour under defined conditions of temperature (20 °C) and wind speed. One of the aims of the work was to implement low cost modifications to the conventional open tube PDT design, using either meshes or filters. This would potentially reduce some of the undesirable bias effects due to wind, which may lead to an over estimation of the NO2 concentration. Exposure tests in the CATFAC were carried out over a wide concentration range applicable to ambient monitoring, and also over a range of wind speeds at a constant concentration. For a given PDT design, the measured NO2 diffusive sampling rates were found to be effectively constant over the conditions tested. These rates were then applied to NO2 field measurements carried out at a monitoring station in central London, and three of the modified PDT designs were found to deliver improved repeatability and consequently reduced measurement uncertainty over the conventional open tubes.
Keywords: Diffusive sampling rates; Nitrogen dioxide; Wind effects; Palmes diffusion tubes;

Tracing fossil fuel CO2 using Δ14C in Xi'an City, China by Weijian Zhou; Shugang Wu; Wenwen Huo; Xiaohu Xiong; Peng Cheng; Xuefeng Lu; Zhenchuan Niu (538-545).
Radiocarbon can be used to trace fossil fuel CO2 (CO2ff ) in the atmosphere, because radiocarbon has been depleted in fossil fuels. Here we present our study on the spatial distribution and temporal variations of CO2ff in Xi'an City, China using Δ14C of both green foxtail (Setaria viridis, L. Beauv.) leaf samples and urban air samples collected in the recent years. Our results show that the CO2ff indicated by green foxtail ranged from 14.7 ± 1.7 to 52.6 ± 1.7 ppm, reflecting high CO2ff mole fractions in downtown, industrial areas, and at road sites, and low CO2ff mole fractions in public parks. Meanwhile, the monthly CO2ff reflected by air samples showed higher value in winter (57.8 ± 17.1 ppm) than that in summer (20.2 ± 9.8 ppm) due to the enhancement usage of coal burning and the poor dispersion condition of atmosphere. This study displays that the increased fossil fuel emission is associated with the fast development of Xi'an City in China. It is worth mentioning that the green foxtail samples can be used to map out the CO2ff spatial distribution on large scale quickly and conveniently, while the air samples can be used to trace the CO2ff temporal variations with high resolution effectively. Therefore the Δ14C of both green foxtail and air samples is a good indicator of CO2ff emission.
Keywords: Δ14C; Annual plant; Air samples; Fossil fuel CO2; Spatial distribution; Temporal variation;

Quantification of soil respiration in forest ecosystems across China by Xinzhang Song; Changhui Peng; Zhengyong Zhao; Zhiting Zhang; Baohua Guo; Weifeng Wang; Hong Jiang; Qiuan Zhu (546-551).
We collected 139 estimates of the annual forest soil CO2 flux and 173 estimates of the Q 10 value (the temperature sensitivity) assembled from 90 published studies across Chinese forest ecosystems. We analyzed the annual soil respiration (Rs) rates and the temperature sensitivities of seven forest ecosystems, including evergreen broadleaf forests (EBF), deciduous broadleaf forests (DBF), broadleaf and needleleaf mixed forests (BNMF), evergreen needleleaf forests (ENF), deciduous needleleaf forests (DNF), bamboo forests (BF) and shrubs (SF). The results showed that the mean annual Rs rate was 33.65 t CO2 ha−1 year−1 across Chinese forest ecosystems. Rs rates were significantly different (P < 0.001) among the seven forest types, and were significantly and positively influenced by mean annual temperature (MAT), mean annual precipitation (MAP), and actual evapotranspiration (AET); but negatively affected by latitude and elevation. The mean Q 10 value of 1.28 was lower than the world average (1.4–2.0). The Q 10 values derived from the soil temperature at a depth of 5 cm varied among forest ecosystems by an average of 2.46 and significantly decreased with the MAT but increased with elevation and latitude. Moreover, our results suggested that an artificial neural network (ANN) model can effectively predict Rs across Chinese forest ecosystems. This study contributes to better understanding of Rs across Chinese forest ecosystems and their possible responses to global warming.
Keywords: Soil CO2 flux; Temperature sensitivity; Artificial neural network model; Climate change; Carbon cycle;

Sensitivity of air quality to potential future climate change and emissions in the United States and major cities by M. Trail; A.P. Tsimpidi; P. Liu; K. Tsigaridis; J. Rudokas; P. Miller; A. Nenes; Y. Hu; A.G. Russell (552-563).
Simulated present and future air quality is compared for the years 2006–2010 and 2048–2052 over the contiguous United States (CONUS) using the Community Multi-scale Air Quality (CMAQ) model. Regionally downscaled present and future climate results are developed using GISS and the Weather Research Forecasting (WRF) model. Present and future emissions are estimated using MARKAL 9R model. O3 and PM2.5 sensitivities to precursor emissions for the years 2010 and 2050 are calculated using CMAQ-DDM (Direct Decoupled Method). We find major improvements in future U.S. air quality including generally decreased MDA8 (maximum daily 8-hr average O3) mixing ratios and PM2.5 concentrations and reduced frequency of NAAQS O3 standard exceedances in most major U.S. cities. The Eastern and Pacific U.S. experience the largest reductions in summertime seasonal average MDA8 (up to 12 ppb) with localized decreases in the 4th highest MDA8 of the year, decreasing by up to 25 ppb. Results from a Climate Penalty (CP) scenario isolate the impact of climate change on air quality and show that future climate change tends to increase O3 mixing ratios in some regions of the U.S., with climate change causing increases of over 10 ppb in the annual 4th highest MDA8 in Los Angeles. Seasonal average PM2.5 decreases (2–4 μg m−3) over the Eastern U.S. are accounted for by decreases in sulfate and nitrate concentrations resulting from reduced mobile and point source emissions of NO x and SO x .
Keywords: Climate change; Air quality; Sensitivity; CMAQ; Downscaling; Projecting emissions;

Rate coefficients for the gas-phase reactions of Cl atoms with a series of unsaturated biogenic alcohols at 298 ± 3 K and 1 atm have been measured by the relative technique in an environmental chamber with in situ FTIR detection of reactants. The rate coefficients obtained using 1-butene and isobutene as reference compounds were (in units of 10−10 cm3 molecule−1 s−1): k 1((E)-2-hexen-1-ol) = (3.49 ± 0.82), k 2((E)-3-hexen-1-ol) = (3.42 ± 0.79), k 3 ((Z)-3-hexen-1-ol) = (2.94 ± 0.72), k 4((Z)-3-hepten-1-ol) = (3.80 ± 0.86) and k 5((Z)-3-octen-1-ol) = (4.13 ± 0.68). This work constitutes the first kinetic study of the reactions cited above. The rate coefficients are compared with those for other unsaturated alcohols and a correlation between the reactivity of unsaturated alcohols toward Cl atoms and the energy of the HOMO of the unsaturated alcohols is presented. Based on the obtained results, the atmospheric lifetimes of the unsaturated alcohols have been estimated and possible atmospheric implications assessed.Display Omitted
Keywords: (E)-2-hexen-1-ol; (E)-3-hexen-1-ol; (Z)-3-hexen-1-ol; (Z)-3-hepten-1-ol; (Z)-3-octen-1-ol; Chlorine atoms;

Emissions of polychlorinated-p-dibenzo dioxin, dibenzofurans (PCDD/Fs) and polybrominated diphenyl ethers (PBDEs) from rice straw biomass burning by Shun-Shiang Chang; Wen-Jhy Lee; Thomas M. Holsen; Hsing-Wang Li; Lin-Chi Wang; Guo-Ping Chang-Chien (573-581).
Biomass burning in Asia has been widely studied owing to its adverse effects on visibility, human health, and global climate. However the impact of rice straw burning on polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) and polybrominated diphenyl ethers (PBDEs) concentrations is not known. In this study concentrations of these pollutants were measured at a farm site and two nearby sites during rice straw (open) burning and non-burning periods. During non-burning periods atmospheric PCDD/F and PBDE concentrations ranged from 0.0263 to 0.0329 pg I-TEQ/Nm3 and 43.5 to 58.3 pg/Nm3 respectively, and were similar at all of the sites. During rice straw burning periods PCDD/F and PBDE concentrations measured near the combustion (farm) site increased dramatically by six to twenty times. The strong correlation between the natural logarithm of PBDE and PCDD/F concentrations (r = 0.949, p < 0.01) at each site indicates that the elevated PCDD/Fs and PBDEs were due to emissions from the rice straw burning. The calculated emission factors, determined using the burned carbon method and the Industrial Source Complex Short-Term Dispersion Model (ISCST3), ranged from 12.6 to 14.5 ng TEQ/kg Cburned and 11.7 to 14.5 μg/kg Cburned, for PCDD/Fs and PBDEs respectively. The PBDE emission factors were at least 38 times higher than those of PCDD/Fs, revealing that rice straw burning is an important PBDE emission source.
Keywords: Biomass open burning; PCDD/Fs; PBDEs; Ambient air; ISCST3;

Emissions of NO x , SO2 and primary nitrate and sulfate from seven regions in China (North, Northeast, East, Central, South, Southwest and Northwest) were separately tracked in a source-oriented Community Multiscale Air Quality (CMAQ) model to quantify the local and inter-regional contributions to PM2.5 nitrate and sulfate concentrations in different cities and provinces. In January, high concentrations of nitrate (∼30 μg m−3) occurred in the North China Plain (NCP) and the Middle and Lower Yangtze Plain (MLYP), as well as the Sichuan Basin. NO x emissions from North, Central and East China were transported over long distances to form rather uniform concentration of nitrate in the NCP and MLYP regions and significantly impacted nitrate concentrations in downwind regions as far as the Pearl River Delta (PRD) region in South China. Wintertime sulfate concentrations demonstrated a more significant inter-regional southward transport pattern and wider spatial distributions than nitrate. The top-five ranked provinces with combined nitrate and sulfate concentrations (Chongqing, Sichuan, Guizhou, Anhui and Hunan) were all affected by emissions from the North, Central and East China, in addition to their local region emissions. In August, slower northerly and northeasterly wind reduced inter-regional transport. Nitrate and sulfate concentrations peaked in North China as dilution was more severely restricted by mountain ranges further north. Three of the top five high concentration provinces (Tianjin, Hebei and Beijing) were located in North China and had more than 55% of local region contributions. Emissions from North China accounted for ∼20% in the remaining two provinces (Shandong in East China and Henan in Central China). In addition to emissions from North China, ∼30% or more of the nitrate and sulfate concentrations in four of the top five high concentration provinces (Tianjin, Henan, Hebei and Shandong) were due to emissions from East China. Time series of daily regional contributions in three megacities (Beijing, Shanghai and Chongqing) and a large city cluster (PRD) also indicated stronger and more frequent inter-regional transport in winter than in summer. Although the cities were mostly affected by local region emissions, influences of long range transport were especially obvious for sulfate concentration in the PRD region in winter, where emissions from North, East and Central China often accounted for more than 80% of the total concentrations. The results from this study suggest that provincial or region-level emission controls alone may not be sufficient to effectively reduce nitrate and sulfate concentrations in many areas and coordinated local and inter-regional emission control strategies are necessary for the country.
Keywords: Secondary particulate matter; Source-oriented air quality model; CMAQ; Emission source region;

Particle deposition to forests: An alternative to K-theory by Cheng-Wei Huang; Samuli Launiainen; Tiia Grönholm; Gabriel G. Katul (593-605).
It has been known for some time that flux-gradient closure schemes (or K-theory), widely used to model the aerosol sized particle turbulent diffusivity, are problematic within canopies. Reported momentum transport in a zero- or counter-mean velocity gradient flow within open trunk spaces of forests is prototypical of the failure of K-theory. To circumvent this problem, a multi-layered and size-resolved second-order closure model is developed using the mean particle turbulent flux budget as a primary closure for the particle turbulent flux instead of K-theory. The proposed model is evaluated against the multi-level size-resolved particle fluxes and particle concentration measurements conducted within and above a tall Scots pine forest situated in Hyytiälä, Southern Finland. Conditions promoting the failure of K-theory for different particle sizes and canopy layers and the characteristics of the particle transport processes within the canopy sub-layer (CSL) are discussed. Using the model, it is shown that K-theory may still be plausible for modeling the particle deposition velocity when the particle size range is smaller than 1 μm provided the local particle turbulent diffusivity is estimated from the characteristic turbulent relaxation time scale and the vertical velocity variance. Model calculations suggest that the partitioning of particle deposition onto foliage and forest floor appears insensitive to the friction velocity for particles smaller than 100 nm (ultrafine), but decreases with increasing friction velocity for particles larger than 100 nm (accumulation and coarse modes).
Keywords: Atmospheric aerosol particles; Canopy turbulence; Particle flux budget; Second-order closure model; Size-resolved model;

Unusual high values of aerosol optical depth evidenced in the Arctic during summer 2011 by P.R.C. Rahul; S.M. Sonbawne; P.C.S. Devara (606-615).
Climatologically, high Aerosol Optical Depth (AOD500 nm) >0.1 during spring and very low AODs (∼0.05) during the summer months persist over the Arctic. Unusually high values of AOD are unknown to be observed during Arctic summers; however using MICROTOPS II, we report AOD500 nm values >0.1 at Ny-Ålesund (78.9°N, 11.9°E), Spitsbergen, Arctic, during June and July 2011. The AODs derived from the Aerosol Robotic Network (AERONET) at Hornsund (77.0°N, 15.5°E) (close to Ny-Ålesund) also revealed AOD values more than 0.1 during June and July 2011. The size distribution analysis revealed dominance of fine mode particles in June 2011, and fine and coarse mode particles in July 2011. The HYSPLIT trajectories and NCEP wind anomalies showed that these fine and coarse mode particles were a result of long range transport from landmasses around the Arctic.
Keywords: Arctic; Aerosol optical depth;

Reduction of the air traffic's contribution to climate change: A REACT4C case study by Volker Grewe; Thierry Champougny; Sigrun Matthes; Christine Frömming; Sabine Brinkop; Ole Amund Søvde; Emma A. Irvine; Lucia Halscheidt (616-625).
Air traffic alters the atmospheric composition and thereby contributes to climate change. Here we investigate the trans-Atlantic air traffic for one specific winter day and analyse, which routing changes were required to achieve a reduction in the air traffic's contribution to climate change. We have applied an atmosphere-chemistry model to calculate so-called five dimensional climate cost functions (CCF), which describe the climate effect of a locally confined emission. The five dimensions result from the emission location (3D), time (1D) and the type of emission (1D; carbon dioxide, water vapour, nitrogen oxides). In other words, carbon dioxide (CO2), water vapour (H2O) and nitrogen oxides (NO x ) are emitted in amounts typical for aviation at many confined locations and times and their impacts on climate calculated with the atmosphere-chemistry model. The impact on climate results from direct effects, such as the changes in the concentration of the greenhouse gases CO2 and H2O and indirect effects such as contrail cirrus formation and chemical changes of ozone and methane by emissions of NO x . These climate cost functions are used by a flight planning tool to optimise flight routes with respect to their climate impact and economic costs of these routes. The results for this specific winter day show that large reductions in the air traffic’s contribution to climate warming (up to 60%) can be achieved for westbound flights and smaller reductions for eastbound flights (around 25%). Eastbound flights take advantage of the tail winds from the jet stream and hence routings with lower climate impacts have a large fuel penalty, whenever they leave the jet stream. Maximum reduction in climate impact increases the economic costs by 10–15%, due to higher fuel consumption, caused by a longer flight distance and lower flight levels. However, with only small changes to the air traffic routings and flight altitudes, climate reductions up to 25% can be achieved by only small changes in economic costs (less than 0.5%).Relation of economic cost changes and climate impact changes for a one-day trans-Atlantic air traffic. Relations for westbound and eastbound flights are in red and blue, respectively. Three different climate metrics are used: P-AGWP100 (solid line), P-AGWP20 (dotted line), and F-ATR20 (dashed line).Display Omitted
Keywords: Air traffic; Climate mitigation; Contrails; Ozone; Optimisation;

Composition and hygroscopicity of aerosol particles at Mt. Lu in South China: Implications for acid precipitation by Weijun Li; Jianwei Chi; Zongbo Shi; Xinfeng Wang; Bin Chen; Yan Wang; Tao Li; Jianmin Chen; Daizhou Zhang; Zifa Wang; Chune Shi; Liangke Liu; Wenxing Wang (626-636).
Physicochemical properties of aerosol particles were studied at Mt. Lu, an elevated site (115°59′E, 29°35′N, 1165 m) within the acid precipitation area. Northeast winds transport copious amounts of air pollutants and water vapor from the Yangtze River Delta into this acid precipitation area. NH4 + and SO4 2− are the dominant ions in PM2.5 and determine aerosol acidity. Individual particle analysis shows abundant S-rich and metals (i.e. Fe-, Zn-, Mn-, and Pb-rich) particles. Unlike aerosol particles in North China and urban areas, there are little soot and mineral particles at Mt. Lu. Lack of mineral particles contributed to the higher acidity in precipitation in the research area. Nano-sized spherical metal particles were observed to be embedded in 37% of S-rich particles. These metal particles were likely originated from heavy industries and fired-power plants. Hygroscopic experiments show that most particles start to deliquesce at 73–76% but organic coating lowers the particle deliquescence relative humidity (DRH) to 63–73%. The DRHs of these aerosol particles are clearly smaller than that of pure ammonium sulfate particles which is 80%. Since RH in ambient air was relatively high, ranging from 65% to 85% during our study period, most particles at our sampling site were in liquid phase. Our results suggest that liquid phase reactions in aerosol particles may contribute to SO2 to sulfuric acid conversion in the acid precipitation area.Display Omitted
Keywords: Acid precipitation; Hygroscopicity; Aerosol formation; Individual particle;

In order to identify the source term of gas emission in atmosphere, an improved hybrid algorithm combined with the minimum relative entropy (MRE) and particle swarm optimization (PSO) method was presented. Not only are the estimated source parameters obtained, but also the confidence intervals at some probability levels. If only the source strength was required to be determined, the problem can be viewed as a linear inverse problem directly, which can be solved by original MRE method successfully. When both source strength and location are unknown, the common gas dispersion model should be transformed to be a linear system. Although the transformed linear model has some differences from that in original MRE method, satisfied estimation results were still obtained by adding iteratively adaptive adjustment parameters in the MRE-PSO method. The dependence of the MRE-PSO method on prior information such as lower and upper bound, prior expected values and noises were also discussed. The results showed that the confidence intervals and estimated parameters are influenced little by the prior bounds and expected values, but the errors affect the estimation results greatly. The simulation and experiment verification results showed that the MRE-PSO method is able to identify the source parameters with satisfied results. Finally, the error model was probed and then it was added in the MRE-PSO method. The addition of error model improves the performance of the identification method. Therefore, the MRE-PSO method with adjustment parameters proposed in this paper is a potential good method to resolve inverse problem in atmosphere environment.Display Omitted
Keywords: Gas emission; Source term; Minimum relative entropy; Optimization; Atmosphere pollution;

Satellite data of atmospheric pollution for U.S. air quality applications: Examples of applications, summary of data end-user resources, answers to FAQs, and common mistakes to avoid by Bryan N. Duncan; Ana I. Prados; Lok N. Lamsal; Yang Liu; David G. Streets; Pawan Gupta; Ernest Hilsenrath; Ralph A. Kahn; J. Eric Nielsen; Andreas J. Beyersdorf; Sharon P. Burton; Arlene M. Fiore; Jack Fishman; Daven K. Henze; Chris A. Hostetler; Nickolay A. Krotkov; Pius Lee; Meiyun Lin; Steven Pawson; Gabriele Pfister; Kenneth E. Pickering; R. Bradley Pierce; Yasuko Yoshida; Luke D. Ziemba (647-662).
Satellite data of atmospheric pollutants are becoming more widely used in the decision-making and environmental management activities of public, private sector and non-profit organizations. They are employed for estimating emissions, tracking pollutant plumes, supporting air quality forecasting activities, providing evidence for “exceptional event” declarations, monitoring regional long-term trends, and evaluating air quality model output. However, many air quality managers are not taking full advantage of the data for these applications nor has the full potential of satellite data for air quality applications been realized. A key barrier is the inherent difficulties associated with accessing, processing, and properly interpreting observational data. A degree of technical skill is required on the part of the data end-user, which is often problematic for air quality agencies with limited resources. Therefore, we 1) review the primary uses of satellite data for air quality applications, 2) provide some background information on satellite capabilities for measuring pollutants, 3) discuss the many resources available to the end-user for accessing, processing, and visualizing the data, and 4) provide answers to common questions in plain language.
Keywords: Satellite data; Air quality; End-user resources; Remote sensing;

Impact of wood burning on indoor PM2.5 in a primary school in rural Portugal by Nuno Canha; Susana Marta Almeida; Maria do Carmo Freitas; Hubert Th. Wolterbeek; João Cardoso; Casimiro Pio; Alexandre Caseiro (663-670).
A study concerning the chemical characterization of PM2.5 sampled indoors of a primary school, which burns wood for classrooms’ heating, was conducted in a rural area of Portugal. A Partisol sequential sampler was placed inside of a classroom, to collect PM2.5 during the day, which corresponds to the occupied period, and during the night. The collected PM2.5 was characterized by Instrumental Neutron Activation Analysis to determine the concentration of chemical elements and by Ion Chromatography to measure Water Soluble Ions. High PM2.5 concentrations were found principally during the occupied periods (100 ± 71 μg m−3). A source apportionment study was performed by means of Positive Matrix Factorization (PMF) analysis. Results showed that four factors contributed for PM2.5 concentration whereas one factor was associated exclusively with a mixture of indoor sources: wood burning, re-suspension of soil and chalk. During classes, this indoor factor contributed for 60% of the total PM2.5 concentration. This study showed that children are exposed to high levels of PM2.5 and indicated the existence of an indoor air quality problem associated with specific indoor sources and poor ventilation.
Keywords: Primary school; Wood burning; PM2.5; Chemical elements; Water soluble ions; Source apportionment;

Widespread reductions in haze across the United States from the early 1990s through 2011 by J.L. Hand; B.A. Schichtel; W.C. Malm; S. Copeland; J.V. Molenar; N. Frank; M. Pitchford (671-679).
Visibility has improved significantly at many remote areas across the United States since the early 1990s. Trends in visibility were calculated using ambient light extinction coefficients (b ext) estimated from speciated particulate concentrations measured by the IMPROVE (Interagency Monitoring of Protected Visual Environments) network. The 20% haziest b ext levels were computed for each year following Regional Haze Rule guidelines and aggregated over three major regions of the United States. Over the last two decades (1992–2011) the regional mean 20% haziest b ext dropped by 52% (−2.6% yr−1, p < 0.01) in the eastern United States, and by 20% (−1.0% yr−1, p = 0.08) for sites along the West Coast. However, in the Intermountain/Southwest region, the trend was insignificant (−0.2% yr−1, p = 0.36). Over the last decade (2002–2011) the haziest b ext in the Intermountain/Southwest region decreased by 15% (−1.5% yr−1, p = 0.09), compared to a decrease of 35% (−3.5% yr−1, p = 0.06) in the West Coast region and 50% (−5.0% yr−1, p = 0.02) in the East. A novel aspect to this study is the visualization of trends through the simulation of images of national parks and other remote areas for early and current haziest conditions. These images are an effective means for communicating trends and illustrate the dramatic improvement in visibility, especially in the East, where reductions in sulfate concentrations and sulfur dioxide emissions have had a positive impact on visibility degradation. However, while conditions are clearer for regions in the West, less improvement points to the need for understanding the influences on the trends in haziest conditions in those regions.
Keywords: Haze; Visibility; Aerosol trends; Remote aerosols;

Global aerosol change in the last decade: An analysis based on MODIS data by K.B. Mao; Y. Ma; L. Xia; Wendy Y. Chen; X.Y. Shen; T.J. He; T.R. Xu (680-686).
Our understanding of the global aerosol change is rather limited, although it is well known that aerosol forcing could affect the global radiative budget, hydrological processes, carbon, nitrogen and sulfur cycles, as well as climate change. To understand the wide range effects of aerosols, it is key to obtain aerosol characteristics at high spatio-temporal resolutions. In this study, we try to map the global variations of the aerosol optical depth (AOD) using two aerosol products retrieved from MODIS (Moderate Resolution Imaging Spectroradiometer) satellite instrument. It is found that the global average AOD is 0.126 over the last decade (2003–2012). The highest and the lowest AOD occurred in 2007 and 2010, respectively. AOD variations between land and ocean, north and south hemispheres, among seven continents and four oceans were also explored. It is interesting to find that high concentrations of aerosols are mainly distributed in regions where developing countries are located (Asia and Africa), and an increasing trend could also be observed. Seasonal variations of AOD (air quality) can also be noted, which is decreasing in the north hemisphere from spring, summer to autumn and winter, but increasing in the south hemisphere.
Keywords: Globe; Aerosol; Air quality; Climate change;

An open-path Fourier transform infrared (OP-FTIR) spectroscopic technique in combination with a backward Lagrangian stochastic (bLS) dispersion model (WindTrax) can be used to simultaneously measure gaseous emissions of N2O, NH3, CH4 and CO2. We assessed the capability of this technique for measuring NH3 and N2O emissions following the application of calcium nitrate (Ca(NO3)2), Nitrophoska (NPK) and chicken manure on a celery farm at Boneo, Victoria, during April and May 2013. We found that the OP-FTIR/WindTrax method was able to measure the diurnal variation in NH3 flux from the field site following application of chicken manure with measured emissions ranging from approximately 0.1–9.8 kg NH3–N ha−1 day−1. The OP-FTIR/WindTrax method also detected a diurnal variation in N2O flux of 1.5–6.2 kg N2O–N ha−1 day−1 and N2O flux increased in response to application of the Ca(NO3)2. We concluded that the OP-FTIR/WindTrax technique can quantify gaseous N loss from vegetable production systems.
Keywords: Open-path Fourier transform infrared spectroscopy; bLS dispersion model; Ammonia; Nitrous oxide; Greenhouse gas emissions; Vegetable farm;

Indoor PM2.5 in Santiago, Chile, spring 2012: Source apportionment and outdoor contributions by Francisco Barraza; Héctor Jorquera; Gonzalo Valdivia; Lupita D. Montoya (692-700).
Indoor and outdoor PM2.5 sampling campaigns were carried out at Santiago, Chile (6 million inhabitants, 33.5°S, 70.6°W) in spring 2012. A pair of samplers was placed inside each household studied and an additional pair of samplers was placed at a fixed outdoor location for measuring trace elements and elemental (EC) and organic carbon (OC) in Teflon and quartz filters, respectively. A total of 47 households in downtown Santiago were included in this study. Mean outdoor and indoor PM2.5 concentrations were 19.2 and 21.6 μg/m3, respectively. Indoor concentrations of PM2.5 were affected by socioeconomic status (p = 0.048) but no such evidence was found for PM2.5 species, except lead (p = 0.046). Estimated species infiltration factors were 0.70 (±0.19), 0.98 (±0.21), 0.80 (±0.12) and 0.80 (±0.03) for PM2.5, OC, EC and sulfur, respectively. Estimated household infiltration factors had a median of 0.75, mean of 0.78, standard deviation of 0.18 and interquartile range (IQR) 0.67–0.86.For the very first time, Positive Matrix Factorization (PMF3) was applied to an indoor PM2.5 chemical composition data set measured at Santiago. Source identification was carried out by inspection of key species and by comparison with published source profiles; six sources were identified. Three of them were outdoor contributions: motor vehicles with 5.6 (±0.7) μg/m3, street dust with 2.9 (±0.5) μg/m3 and secondary sulfates with 3.4 (±0.5) μg/m3. The indoor sources were: indoor dust with 1.6 (±0.3) μg/m3, cleaning and cooking with 2.3 (±0.3) μg/m3 and cooking and environmental tobacco smoke with 6.1 (±0.7) μg/m3. There is potential for further reducing PM2.5 population exposure in the short term —by improving ventilation of indoor air and controlling indoor sources — and in the long term — with filtration of outdoor air and household improvements to reduce air change rates.Display Omitted
Keywords: Indoor air quality; PM2.5; Sustainable urban development; Household infiltration; Source apportionment;

Airborne hexavalent chromium (Cr(VI)) is a known pulmonary carcinogen and can be emitted from both natural and anthropogenic sources, including diesel emissions. However, there is limited knowledge about ambient Cr(VI) concentration levels and its particle size distribution. This pilot study characterized ambient Cr(VI) concentrations in the New Jersey Meadowlands (NJ ML) district, which is close to the heavily trafficked New Jersey Turnpike (NJTPK) as well as Chromium Ore Processing Residue (COPR) waste sites. Monitoring was simultaneously conducted at two sites, William site (∼50 m from NJTPK) and MERI site (∼700 m from NJTPK). The distance between the two sites is approximately 6.2 km. Ambient Cr(VI) concentrations and PM2.5 mass concentrations were concurrently measured at both sites during summer and winter. The summer concentrations (mean ± S.D. [median]), 0.13 ± 0.06 [0.12] ng/m3 at the MERI site and 0.08 ± 0.05 [0.07] ng/m3 at the William site, were all significantly higher than the winter concentrations, 0.02 ± 0.01 [0.02] ng/m3 and 0.03 ± 0.01 [0.03] ng/m3 at the MERI and William sites, respectively. The site difference (i.e., MERI > William) was observed for summer Cr(VI) concentrations; however, no differences for winter and pooled datasets. These results suggest higher Cr(VI) concentrations may be attributed from stronger atmospheric reactions such as photo-oxidation of Cr(III) to Cr(VI) in the summer. The Cr(VI) distribution as a function of particle size, ranging from 0.18 to 18 μm, was determined at the William site. It was found that Cr(VI) was enriched in the particles less than 2.5 μm in diameter (PM2.5). This finding suggested potential health concerns, because PM2.5 are easily inhaled and deposited in the alveoli. A multiple linear regression analysis confirmed ambient Cr(VI) concentrations were significantly affected by meteorological factors (i.e., temperature and humidity) and reactive gases/particles (i.e., O3, Fe and Mn).
Keywords: Cr(VI); Hexavalent chromium; Particle size; Diesel traffic;

On 11 March 2011 an earthquake off the Pacific coast of the Fukushima prefecture generated a tsunami that hit Fukushima Dai-ichi and Fukushima Da-ini Nuclear Power Plants. From 12 March a significant amount of radioactive material was released into the atmosphere and dispersed worldwide. Among the most abundant radioactive species released were iodine and cesium isotopes. By means of an atmospheric dispersion Lagrangian code and publicly available meteorological data, the atmospheric dispersion of 131I, 134Cs, and 137Cs have been simulated for three months after the event with a spatial resolution of 0.5° × 0.5° globally. The simulation has been validated by comparison to publicly available measurements collected in 206 locations worldwide. Sensitivity analysis shows that release height of the radionuclides, wet deposition velocity, and source term are the parameters with the most impact on the simulation results.The simulation shows that the radioactive plume, consisting of about 200 PBq by adding contributions from 131I, 134Cs, and 137Cs, has been transported over the entire northern hemisphere depositing up to 1.2 MBq m−2 nearby the NPPs to less than 20 Bq m−2 in Europe. The consequent effective dose to the population over a 50-year period, calculated by considering both external and internal pathways of exposure, is found to be about 40 mSv in the surroundings of Fukushima Dai-ichi, while other countries in the northern hemisphere experienced doses several orders of magnitude lower suggesting a small impact on the population health elsewhere.Display Omitted
Keywords: Radioactive materials; Lagrangian atmospheric dispersion; Fukushima accident; Effective dose; Sensitivity; Model evaluation;

In the presented study a comprehensive statistical analysis of the chemical composition of atmospheric particulate matter was carried out. The data were collected from April 2003 to August 2008 with a 7-day time resolution in the Northern Adriatic Port of Koper and analyzed by the Proton Induced X-ray method (PIXE). The Positive Matrix Factorization (PMF) analysis of fifteen chemical elements identified six source factors, three natural-regional sources and three local-anthropogenic sources. Heavy machinery, industry and iron ore factor were marked as anthropogenic sources. Heavy machinery source was represented by the elements V, Ni and Cu. The elements Fe and Mn are attributed to the Iron ore source and were explained by the proximity of the bulk-cargo warehouse and the intense handling of iron ore in Port of Koper. The heavy industry source represented by Pb and Zn was the only anthropogenic factor, which shows clear seasonal pattern. In contrast to the local-anthropogenic source factors, natural and regional source factors show significant negative trend. The reduction of the crustal elements Ca, Ti and Sr, joined in a soil source, and sulfur-biomass source, represented by elements K and S, have been attributed to more intense precipitation and to the negative trend of the North Atlantic Oscillation (NAO) index. The negative trend of the Cl and Br elements was in line with the negative trend of the wind speed above the sea surface and the significant sea-wave height.
Keywords: Positive matrix factorization; PIXE; Particulate matter; FLEXPART; Inter and intra annual analysis; Trend and seasonal decomposition;

The ozone (O3) budget in the boundary layer of the Asia-Pacific region (AP) was studied from 2001 to 2007 using the output of Model of Ozone and Related chemical Tracers, version 4 (MOZART-4). The model-simulated O3 data agree well with observed values. O3 budget analysis using the model output confirms that the dominant factor controlling seasonal variation of O3 differs by region. Photochemistry was found to play a critical role over Japan, the Korean Peninsula and Eastern China. Over the northwestern Pacific Ocean, advective flux was found to drive the seasonal variation of O3 concentrations. The large latitudinal gradient in O3 with a maximum of 52 ppbv over the marine boundary layer around 35°N during the spring was mainly due to chemistry; meanwhile, advection was found to weaken the gradient. The contribution of stratospheric O3 was ranked second (20%) to the local contribution (25%) in Japan and the Korean Peninsula near 35°N. The rate of O3 export from China's boundary layer was the highest (approximately 30%) in low latitudes and decreased with increasing latitude, while the contribution of North America and Europe increased with increasing latitude, from 10% in lower latitudes to 24% in higher latitudes.
Keywords: Boundary layer; Asia-Pacific; Ozone budget; Seasonal variation; Latitudinal gradient;

Relationship between particulate air pollution and meteorological variables in Utah's Salt Lake Valley by C. David Whiteman; Sebastian W. Hoch; John D. Horel; Allison Charland (742-753).
Critical meteorological factors affecting daily particulate concentrations during winter for Utah's urbanized Salt Lake Valley are examined on the basis of forty years of data. In a typical winter, the National Ambient Air Quality Standard for particulate matter with aerodynamic diameter less than 2.5 microns (PM2.5) is exceeded during 6 multi-day events comprising 18 winter days. Multi-day episodes of high stability produce these events, as synoptic-scale high-pressure ridges transit across Utah. The valley heat deficit, a bulk measure of atmospheric stability, exhibits large winter-to-winter variations that are highly related to similar variations in PM2.5. While control strategies have led to downward trends in concentrations for some primary pollutants, no long-term trends in valley heat deficit are evident over the 40 years. PM2.5 concentrations rise gradually over a period of days after a heat deficit threshold is exceeded as the air within the valley becomes decoupled from generally stronger winds aloft. Concentrations climb at a typical rate of about 10 μg m−3 d−1 over a four-day period to about 60 μg m−3 during these episodes. During episodes when PM2.5 concentrations exceed 35 μg m−3, the atmospheric column in the valley is characterized by: temperature below 0 °C; relative humidity in excess of 50%; and light wind speeds. PM2.5 concentrations in excess of 35 μg m−3 are four times more likely when the valley is snow covered than when it is not. A stepwise multiple linear regression based upon selected meteorological variables is used to estimate daily values of PM2.5 during two independent winters. The correlation between observed and estimated PM2.5 for these winters reaches 0.81.
Keywords: PM2.5; Particulates; NAAQS exceedances; Inversions; Climatology; Salt Lake Valley;

General trends of atmospheric mercury concentrations in urban and rural areas in Korea and characteristics of high-concentration events by Young-Ji Han; Jung-Eun Kim; Pyung-Rae Kim; Woo-Jin Kim; Seung-Muk Yi; Yong-Seok Seo; Seung-Hee Kim (754-764).
Long-term measurement of speciated Hg concentrations is the first step toward identifying the seasonal and spatial characteristics of Hg concentrations; however, atmospheric Hg research is scarce in Korea. In this study, total gaseous mercury (TGM), gaseous oxidized mercury (GOM) and particle-bound mercury (PBM) were measured in urban (Seoul) and rural (Chuncheon) areas over a more than 3 year period in order to improve the understanding of speciated Hg transport. The mean concentrations of TGM, GOM and PBM were 3.72 ± 2.96 (0.19–149.84) ng m−3, 11.3 ± 9.5 (0.9–57.3) pg m−3, and 13.4 ± 12.0 (2.1–64.3) pg m−3 at the Seoul site and 2.12 ± 1.47 (0.26–10.75) ng m−3, 2.7 ± 2.7 (0.1–16.9) pg m−3, and 3.7 ± 5.7 (0.1–30.0) pg m−3 in Chuncheon. Both long-range transport and local sources caused high TGM concentration events, while local coal combustion was a main cause of enhancing the GOM and PBM concentrations in Seoul. However, there was no correlation between the pollutants emitted from coal combustion and the speciated Hg concentration in Chuncheon, indicating that other mechanisms were involved in the Hg increase. We found a positive correlation between the GOM and the O3 concentrations and a negative correlation between the GEM and the GOM concentrations, especially on foggy days, suggesting that the oxidation of GEM was an important source for GOM in Chuncheon. In addition, the ratio of PBM/GOM was inversely proportional to the atmospheric temperature and directly proportional to the relative humidity, which suggests that the in-situ formation of PBM through gas-particle partitioning of GOM was important in rural areas.
Keywords: Speciated mercury; Urban; Rural; In-situ formation; Long-range transport;

Ozone and nitrogen effects on yield and nutritive quality of the annual legume Trifolium cherleri by J. Sanz; I. González-Fernández; H. Calvete-Sogo; J.S. Lin; R. Alonso; R. Muntifering; V. Bermejo (765-772).
Two independent experiments were performed in an Open-Top Chamber facility to determine the response of biomass and nutritive quality of the annual legume Trifolium cherleri to increased levels of ozone (O3) and nitrogen (N) deposition, two main drivers of global change. Plants growing in pots were exposed to three O3 treatments: charcoal-filtered air (CFA); non-filtered air, reproducing ambient O3 levels of the site (NFA); and non-filtered air supplemented with 40 nl l 1 (NFA+). Nitrogen was added in biweekly doses to achieve final doses of 5 (N5), 15 (N15) and 30 kg ha 1 (N30), reproducing the N deposition range in the Iberian Peninsula.Ozone negatively affected all the growth-related parameters and increased plant senescent biomass. The pollutant affected subterranean biomass to a greater extent than aerial biomass, resulting in altered aerial/subterranean ratio. Effects in the second experiment followed the same pattern as in the first, but were of lesser magnitude. However, these differences between assays could not be explained adequately by the absorbed O3 fluxes (Phytotoxic Ozone Dose, POD). Concentrations of cell-wall constituents related to nutritive quality increased with the O3 exposure, reducing the Relative Food Value index (RFV) that indicates decreased nutritive quality of the forage.Nitrogen stimulated all growth-related parameters, but increased the aboveground biomass more than the subterranean biomass. No effects of N fertilizer were detected for the nutritive quality parameters. A significant interaction between O3 and N was found in the second experiment. N further enhanced the increase of senescent biomass caused by O3.Results indicate that O3 is a potentially significant environmental stress factor in terms of structure and diversity of Mediterranean pastures.
Keywords: Annual grasslands; Dehesa; Forage quality; Ozone fluxes; Senescence; POD;

Measurements of size- and time-resolved elemental concentrations at a California dairy farm by Yongjing Zhao; Steven S. Cliff; Anthony S. Wexler; Wasim Javed; Kevin Perry; Yuee Pan; Frank M. Mitloehner (773-781).
Airborne particulate matter with aerodynamic size less than 10 μm was collected at a California dairy in fall 2006 using a Rotating Drum Impactor (RDI) sampler in 8 size ranges (i.e., 10–5, 5–2.5, 2.5–1.15, 1.15–0.75, 0.75–0.56, 0.56–0.34, 0.34–0.26, and 0.26–0.09 μm). The RDI samples were analyzed using synchrotron X-ray Fluorescence (XRF) at the Advance Light Source (ALS), Lawrence National Berkeley Laboratory, to derive the concentrations of trace elements Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cu, Fe, Mn, and Zn. During this study, periods of rainfall in early November provided an opportunity to isolate particle emission sources. After the rainfalls, elemental concentrations decreased by about 80% for Mg, Al, Si, and Ti, 70% for Fe and Mn, 65% for Cu, and 60% for K and Ca. By contrast, the concentrations of the elements P, S, Zn and Cl did not decrease as significantly as others. Therefore, it is very likely that the dairy drylot corrals could be a major source of the elements Mg, Al, Si, K, Ca, Ti, Cu, Fe, and Mn under dry condition, but not of elements P, S, Zn and Cl. Elements Mg, Al, Si, K, Ca, Ti, Cu, Fe, and Mn were correlated with each other under both dry and wet conditions (R 2 ranging from 0.47 to 0.99), indicating that they had common emission sources. Highly correlated sub-groups of elements shifted from dry to wet conditions, R 2 > 0.96 among elements Mg, Al, and Si, R 2 > 0.93 among elements K, Ca, Ti, Cu, Fe, and Mn under dry condition, and R 2 > 0.87 among elements Mg, Al, Si, Ti, Fe, and Mn under wet condition, possibly due to the change in emission sources. Size distribution of the observed elements revealed (1) a general trend that elemental concentrations increased with particle size except for S, which had a peak at 1.15 μm and (2) a greater portion of coarse elements (2.5–10 μm) than fine elements (less than 2.5 μm) for all elements except for S and Zn under both dry and wet conditions.
Keywords: Elemental concentrations; RDI sampler; XRF; CAFO; Dairy;

It is widely accepted that concentrations of primary traffic pollutants can vary substantially across relatively small urban areas. Fixed-site monitors have been shown to be largely inadequate for representing concentrations at nearby locations, resulting in the increasing use of spatial modelling or mobile sampling methods to achieve spatial saturation. In this study, we employ the use of a simple bicycle to sample concentrations of ultrafine particles (UFPs), carbon monoxide (CO) and particulate matter (PM10) at two small areas (<2.5 km2) in South Auckland, New Zealand. Portable instruments were mounted inside a custom-built casing at the front of the bicycle and every street within each study area was sampled in a grid-like fashion, at four times of day (07:00, 12:00, 17:00 and 22:00). Each area has a six-lane highway running through its centre and the core aim was to visualise and describe spatial variability of pollutant levels about the highway, main arterials and quieter streets, at periods of contrasting meteorological and traffic conditions. A total of 20 sampling runs in each area (five at each of the four timings) were conducted. Meteorological data were logged continuously at background sites within each study area. Results show that the influence of highway traffic (UFPs, CO) was strongest during the mornings and late evenings when wind speeds were low, while for the midday and afternoon timings, concentrations were highest at the arterial and shopping zones. Concentrations of PM10 appeared to be strongest in the residential areas during mornings and late evenings, suggesting an influence of wood burning for home heating. For all timings combined, for all three pollutants, it appears the arterial roads featuring shops and numerous intersections with traffic lights, had a stronger influence on concentrations than the busier but more free-flowing highways. This study provides not only an insight into microspatial hotspot variation across suburbs, but also how this variation shifts diurnally.
Keywords: Mobile monitoring; Spatial variation; Near roadway; Highway community;

Residential infiltration of fine and ultrafine particles in Edmonton by Jill Kearney; Lance Wallace; Morgan MacNeill; Marie-Eve Héroux; Warren Kindzierski; Amanda Wheeler (793-805).
Airborne indoor particles arise from both indoor sources and ambient particles that have infiltrated indoors. The intra-urban variability of infiltration factors (F inf) is a source of measurement error in epidemiological studies estimating exposure from a central site measurement, hence information on the within and between-home variability of F inf is useful to better characterize ambient PM exposure. The objective of this paper was to estimate magnitudes and predictors of daily residential infiltration factors (F inf) and ambient/non-ambient components of indoor ultrafine particle (UFP) and fine particle (FP) concentrations. FPs and UFPs were measured continuously for 7 consecutive days in 74 Edmonton homes in winter and summer 2010 (50 homes in each season). Simultaneous measurements of outdoor (near-home) FP and ambient (at a central site) UFP concentrations were also measured. Daily infiltration factors were estimated for each home; considerable variability was seen within and between homes. For FPs, seasonal-averaged F inf (the average of the 7 daily F inf estimates) ranged from 0.10 to 0.92 in winter (median = 0.30, n = 49) and 0.31 to 0.99 in summer (median = 0.68, n = 48). For UFPs, the seasonal-averaged F inf ranged from 0.08 to 0.47 across homes in winter (median = 0.21, n = 33 houses) and from 0.16 to 0.94 in summer (median = 0.57, n = 48). The higher median F inf in summer was attributed to a high frequency of open windows. Daily infiltration factors were also estimated based on the indoor/outdoor PM1 sulfur ratio. These estimates were poorly correlated with DustTrak-based FP infiltration factor estimates; the difference may be due to losses of volatile components on the PM1 filter samples. Generalized linear mixed models were used to identify variables significantly associated with F inf and the non-ambient component of indoor FP and UFP concentrations. Wind speed was consistently associated with F inf across all seasons for both FPs and UFPs. The use of an air cleaner was associated with reduced UFP infiltration factors in summer, suggesting a potential method of reducing infiltrated UFPs. Various cooking activities and smoking were associated with the non-ambient component of indoor FP and UFP concentrations. On average, the majority of indoor FPs were of ambient origin while the majority of UFPs were of indoor origin. In summer, more of the indoor FP and UFP concentrations were from ambient origin, compared to winter, due to the higher infiltration factors. The variability in FP and UFP F inf within and between homes may cause substantial exposure misclassification in epidemiological studies using only ambient measurements.
Keywords: Ultrafine particles; Fine particles; Infiltration factor; F inf; Residential; Indoor air quality; Exposure misclassification;

Roadside levels and traffic emission rates of PM2.5 and BTEX in Ho Chi Minh City, Vietnam by Nguyen Tran Huong Giang; Nguyen Thi Kim Oanh (806-816).
A monitoring program was designed and implemented to characterize roadside levels of PM2.5 and BTEX in Ho Chi Minh City, Vietnam, and to generate input data for CALINE (California LINE Source Dispersion Model) inverse modeling. Monitoring was done during Dec 2007–Jan 2008, on both weekdays and weekends, and yielded 284 hourly BTEX samples (adsorption tubes), 24 samples of 8 h-PM2.5 and 42 samples of 24 h-PM2.5 (by MiniVol samplers). The air sampling was done at 8 points on both sides of one street that had an average traffic flow, simultaneously meteorology data and vehicle flows were recorded. Roadside 24 h-PM2.5 levels were 97 ± 31 (53–151) μg m−3, higher on weekdays than weekends. Diurnal BTEX variation patterns were consistent with the diurnal flows of 6 vehicle categories moving on the street. BTEX levels were reduced with the increase in downwind distance from traffic lanes (approximately by 15% for each 5 m increment). Principal component analysis also confirmed the association between roadside pollution levels and traffic. A calculation algorithm was developed to remove the urban background, contributed by other sources than traffic in the selected street, from the roadside measured pollution levels. Urban background contributed a majority of PM2.5 (90–98%) and hourly BTEX (67–97%) with higher contributions at upwind side of the street and at late evening hours when less traffic was observed. CALINE inverse modeling produced explainable fleet hourly emission rates (g km−1 h−1) and vehicle emission factors (EF, mg veh−1 km−1). The obtained EF for gasoline and diesel vehicles were comparable with recent measurements made in Asian cities, as well as with calculated EFs for European and US urban fleets about 10–15 years ago. To minimize the collinearity problem encountered in inverse traffic modeling it is essential that the monitoring is done at different times to capture significant variations in the street traffic compositions.
Keywords: Roadside PM2.5; BTEX; Inverse modeling; Fleet emission rate; Emission factor; Ho Chi Minh City;

Corrigendum to “An observational study of the atmospheric ultra-fine particle dynamics” [Atmos. Environ. 59 (2012) 312–319] by C. Varotsos; J. Ondov; C. Tzanis; F. Öztürk; M. Nelson; H. Ke; J. Christodoulakis (817).