Atmospheric Environment (v.107, #C)

The variation of chemical characteristics of PM2.5 and PM10 and formation causes during two haze pollution events in urban Beijing, China by Jiajia Gao; Hezhong Tian; Ke Cheng; Long Lu; Mei Zheng; Shuxiao Wang; Jiming Hao; Kun Wang; Shenbing Hua; Chuanyong Zhu; Yong Wang (1-8).
Airborne particles in urban Beijing during haze days and normal days were collected and analyzed in the autumn and winter seasons to reveal the chemical characteristics variations of air pollution. The air quality in haze days was substantially worse than that in normal days. Both the relatively low wind speed and high relative humidity were in favor of the accumulation of pollution species and new formation of secondary PM2.5 in the atmosphere. Elevated concentrations of elements and water-soluble inorganic ions were found on haze days for both PM10 and PM2.5. Particularly, the crustal element, such as Fe, in both PM10 and PM2.5 were substantially higher in autumn normal days and winter haze days than those in autumn haze days and winter normal days, indicating that the abundance of Fe in autumn haze days mainly be originated from crustal dust while in winter haze days it might be primarily emitted from anthropogenic sources (iron and steel smelting) instead of road dust. Secondary ion species (SO4 2−, NO3 , NH4 +) in particles were generated much more during haze episodes, and contributed a higher proportion in PM2.5 than in PM10 during the two sampling periods. Moreover, HYSPLIT model was used to explain the possible transport of airborne particles from distant sources. By comparing with south-type trajectory, west-type trajectory entrained larger amounts of primary crustal pollutants, while, south-type trajectory was comprised of a higher mass of anthropogenic pollution species. The results of back trajectory analysis indicated that the elevated concentration of aerosol and its chemical components during haze days might be caused by the integrated effects of accumulation under stagnant meteorological condition and the transport emissions of pollutants from anthropogenic sources surrounding Beijing city.
Keywords: PM2.5; PM10; Haze; Elemental species; Water soluble inorganic ions (WSIIs); Beijing;

Methane is a potent greenhouse gas (GHG) that is now included in both California State and San Francisco Bay Area (SFBA) bottom-up emission inventories as part of California's effort to reduce anthropogenic GHG emissions. Here we provide a top-down estimate of methane (CH4) emissions from the SFBA by combining atmospheric measurements with the comparatively better estimated emission inventory for carbon monoxide (CO). Local enhancements of CH4 and CO are estimated using measurements from 14 air quality sites in the SFBA combined together with global background measurements. Mean annual CH4 emissions are estimated from the product of Bay Area Air Quality Management District (BAAQMD) emission inventory CO and the slope of ambient local CH4 to CO. The resulting top-down estimates of CH4 emissions are found to decrease slightly from 1990 to 2012, with a mean value of 240 ± 60 GgCH4 yr−1 (at 95% confidence) in the most recent (2009–2012) period, and correspond to reasonably a constant factor of 1.5–2.0 (at 95% confidence) times larger than the BAAQMD CH4 emission inventory. However, we note that uncertainty in these emission estimates is dominated by the variation in CH4:CO enhancement ratios across the observing sites and we expect the estimates could represent a lower-limit on CH4 emissions because BAAQMD monitoring sites focus on urban air quality and may be biased toward CO rather than CH4 sources.
Keywords: Methane emissions; Emissions inventory; Greenhouse gas; Inventory verification; Top-down estimates;

The in-cabin environment of a school bus is important for children's health. The pollutants from a bus's own exhaust contribute to children's overall exposure to air pollutants inside the school bus cabin. In this study, we adapted a coupled model originally developed for indoor environment to determine the relative contribution of the bus own exhaust to the in-cabin pollutant concentrations. The coupled model uses CFD (computational fluent dynamics) model to simulate outside concentration and CONTAM (a multi-zone model) for inside the school bus. The model was validated with experimental data in the literature. Using the validated model, we analyzed the effects of vehicle speed and tailpipe location on self-pollution inside the bus cabin. We confirmed that the pollution released from the tailpipe can penetrate into the bus cabin through gaps in the back emergency door. We found the pollution concentration inside school buses was the highest when buses were driven at a medium speed. In addition, locating the tailpipe on the side, behind the rear axle resulted in less self-pollution since there is less time for the suction effect to take place. The developed theoretical framework can be generalized to study other types of buses. These findings can be used in developing policy recommendations for reducing human exposure to air pollution inside buses.
Keywords: School bus; Self-pollution; Coupled model; Exposure mitigation;

Collection and subsequent extraction of particulate matter (PM) from filter substrates is a common requirement for in vivo and in vitro toxicological studies, as well as chemical analyses such as ion chromatography and inductively coupled plasma mass spectrometry. Several filter extraction protocols exist and different laboratories employ different methods, potentially biasing inter-study comparisons. Previous studies have shown significant differences in extraction efficiency between techniques and identified the relevant extraction artifacts. However, a comprehensive inter-comparison of different methods based on the chemical composition of the extracted PM has never been conducted. In the current study, an exhaustive suite of chemical analyses is performed on PM extracted from glass micro-fiber filters using techniques commonly employed in different laboratories: Multi-solvent extraction (MSE) and spin-down extraction (SDE). PM samples were collected simultaneously during field studies conducted in an urban and rural setting using a high-volume PM2.5 sampler. Results show remarkable compositional variance between the PM extracts for all chemical components analyzed, including metals, water soluble ions, polycyclic aromatic hydrocarbons, non-aromatic organics, elemental carbon and organic carbon. Mass closure was greater than 90% for MSE but deviated substantially for SDE. Detailed retrospective gravimetric analysis of archived SDE samples revealed that a process-based loss of PM mass is the root cause of the differences. These losses are shown to be compositionally biased, both externally between different PM mixtures and internally within a given PM mixture. In combination, the results of this study are the first to demonstrate (i) an exhaustive chemical characterization of a single PM extract, (ii) the significance of directly characterizing the extracted PM used in toxicological studies, (iii) the existence of substantial compositional biases between different filter extraction techniques and (iv) the importance of standardizing filter extraction objectives and procedures to avoid introducing study bias into toxicological studies.
Keywords: Filter extraction; Filter sampling; Particulate matter extract; Particulate matter composition; Compositional bias;

Influence of air mass origin on aerosol properties at a remote Michigan forest site by T.M. VanReken; G.R. Mwaniki; H.W. Wallace; S.N. Pressley; M.H. Erickson; B.T. Jobson; B.K. Lamb (35-43).
The northern Great Lakes region of North America is a large, relatively pristine area. To date, there has only been limited study of the atmospheric aerosol in this region. During summer 2009, a detailed characterization of the atmospheric aerosol was conducted at the University of Michigan Biological Station (UMBS) as part of the Community Atmosphere–Biosphere Interactions Experiment (CABINEX). Measurements included particle size distribution, water-soluble composition, and CCN activity. Aerosol properties were strongly dependent on the origin of the air masses reaching the site. For ∼60% of the study period, air was transported from sparsely populated regions to the northwest. During these times aerosol loadings were low, with mean number and volume concentrations of 1630 cm−3 and 1.91 μm3 cm−3, respectively. The aerosol during clean periods was dominated by organics, and exhibited low hygroscopicities (mean κ = 0.18 at s = 0.3%). When air was from more populated regions to the east and south (∼29% of the time), aerosol properties reflected a stronger anthropogenic influence, with 85% greater particle number concentrations, 2.5 times greater aerosol volume, six times more sulfate mass, and increased hygroscopicity (mean к = 0.24 at s = 0.3%). These trends are have the potential to influence forest–atmosphere interactions and should be targeted for future study.
Keywords: Aerosol; Trajectory analysis; Hygroscopicity;

Field study of air purifying paving elements containing TiO2 by Andrea Folli; Michael Strøm; Thomas Pilegaard Madsen; Trine Henriksen; Jan Lang; Johan Emenius; Tore Klevebrant; Åsa Nilsson (44-51).
This paper reports the results of a field test study concerning the use of photocatalytic paving elements in Denmark to mitigate nitrogen oxides pollution. Prior to the installation, the photocatalytic concrete elements were tested in the lab, where conversions of NO reached values as high as 78% with low amount of NO2 formed. Once installed, nitrogen oxides concentration, temperature and relative humidity were monitored every minute for more than a year. The results of the field tests showed that under ideal weather and irradiation conditions, i.e. summer months, the monthly average NO concentration (based on day and night values) in proximity of the photocatalytic area was around 22% lower than the reference area. The close correlation between performance data and solar UV irradiance revealed that at such a latitude (55.68° N) adequate NO (hence NOx) conversions (monthly average) are achieved for total UV irradiance exceeding 600 kJ m−2 day−1. Within this period, data relative to the solar noon showed instantaneous NO abatement in some cases higher than 45%, corresponding to a total NOx abatement higher than 30%.Display Omitted
Keywords: Photocatalytic pavement; Titanium dioxide; Selectivity; Nitrogen oxides; UV irradiance; Solar irradiance; Field study table of content entry;

Due to their low vapor pressure, semi-volatile organic compounds (SVOCs) can absorb onto other compartments in indoor environments, including settled dust. Incidental ingestion of settled dust-bound SVOCs contributes to the majority of daily non-dietary exposure to some SVOCs by human beings. With this pathway in mind, an integrated kinetic model to estimate indoor SVOC was developed to better predict the mass-fraction of SVOC associated with settled dust, which is important to accurately assess the non-dietary ingestion exposure to SVOC. In this integrated kinetic model, the aerosol dynamics were considered, including particle penetration, deposition and resuspension. The newly developed model was evaluated by comparing the predicted mass-fraction of SVOC associated with the settled dust (X dust ) and the measured X dust from previous studies. Sixty X dust values of thirty-eight different SVOCs measured in residences located in seven countries from four continents were involved in the model evaluation. The X dust value predicted by the integrated kinetic model correlated linearly with the measured X dust : y = 0.93x + 0.09 (R 2  = 0.73), which indicates that the predicted X dust by the integrated kinetic model are in good match with the measured data. This model may be utilized to predict SVOC concentrations in different indoor compartments, including dust-bound SVOC.
Keywords: SVOCs; Aerosol dynamics; Settled dust; Kinetic sorption;

Herbicides have been widely used to control weeds in croplands; however, their effects on greenhouse gas emissions remain unclear. The effects of three wheat herbicides (acetochlor, AC; tribenuron-methyl, TBM; fenoxaprop-p-ethyl, FE) and two rice herbicides (butachlor, BC; bensulfuron-methyl, BSM) on N2O and CH4 emissions were investigated in this study. In the wheat growing season, applications of AC and FE + TBM significantly reduced N2O emissions by 31% compared with no herbicide use (p = 0.001). In the rice growing season, the application of BC significantly reduced CH4 emissions by 58% (p = 0.022), and BSM significantly reduced N2O emissions by 27% (p = 0.040); however, no significant difference among treatments with regard to the aggregate emissions of N2O and CH4 in the CO2 equivalent for the 100-year horizon was observed (p > 0.05). Relative to control plots, which were not treated with herbicides, the combined application of the herbicides FE and TBM in the wheat season led to a significant decrease in greenhouse gas intensity (GHGI) by ∼41% (p = 0.002), and the application of BC together with BSM reduced GHGI by 22% in the rice season, although this reduction was not statistically significant (p = 0.158). Further investigation suggested that the inhibitory effect of herbicides on N2O emissions in the wheat field could be ascribed to low soil ammonium nitrogen and less abundance of denitrifying bacteria. The inhibitory effects of separate applications of BC on CH4 emissions in rice fields, in contrast, were linked to high soil nitrate nitrogen and urease activity.
Keywords: Methane; Nitrous oxide; Herbicides; Mitigation; Cropland;

Long-term NOx trends over large cities in the United States during the great recession: Comparison of satellite retrievals, ground observations, and emission inventories by Daniel Q. Tong; Lok Lamsal; Li Pan; Charles Ding; Hyuncheol Kim; Pius Lee; Tianfeng Chai; Kenneth E. Pickering; Ivanka Stajner (70-84).
National emission inventories (NEIs) take years to assemble, but they can become outdated quickly, especially for time-sensitive applications such as air quality forecasting. This study compares multi-year NOx trends derived from satellite and ground observations and uses these data to evaluate the updates of NOx emission data by the US National Air Quality Forecast Capability (NAQFC) for next-day ozone prediction during the 2008 Global Economic Recession. Over the eight large US cities examined here, both the Ozone Monitoring Instrument (OMI) and the Air Quality System (AQS) detect substantial downward trends from 2005 to 2012, with a seven-year total of −35% according to OMI and −38% according to AQS. The NOx emission projection adopted by NAQFC tends to be in the right direction, but at a slower reduction rate (−25% from 2005 to 2012), due likely to the unaccounted effects of the 2008 economic recession. Both OMI and AQS datasets display distinct emission reduction rates before, during, and after the 2008 global recession in some cities, but the detailed changing rates are not consistent across the OMI and AQS data. Our findings demonstrate the feasibility of using space and ground observations to evaluate major updates of emission inventories objectively. The combination of satellite, ground observations, and in-situ measurements (such as emission monitoring in power plants) is likely to provide more reliable estimates of NOx emission and its trend, which is an issue of increasing importance as many urban areas in the US are transitioning to NOx-sensitive chemical regimes by continuous emission reductions.
Keywords: NOx; Emission; Trend; Air quality forecast; Recession; OMI NO2; Ozone; AQS; NAQFC;

An assessment of the influence of sulfidic mine wastes on rainwater quality in a semiarid climate (SE Spain) by A. Alcolea; C. Fernández-López; M. Vázquez; A. Caparrós; I. Ibarra; C. García; M. Zarroca; R. Rodríguez (85-94).
This study assessed the influence of the Sierra Minera de CartagenaLa Unión mining wastes on the surrounding areas, due to the sediment transport in the atmosphere. Monitoring of 15 weather stations located in the Campo de Cartagena land (SE Spain) was performed in the period December, 2004–March, 2008. A total of 920 rainfall water samples were collected and analyzed in this study. The network of weather stations covered a wide range of soil use and human activities (industrial, urban, agricultural, and mining sites). The physicochemical characterization involved determination of pH, EC, major ions, and the metals of interest in the soluble fraction of rainwater. Precipitations had an alkaline pH (7.0–7.9) and, compared to World Health Organization guidelines for drinking-water quality, samples were characterized by low EC (76–930 μS/cm), Ni (0.1–8 μg/L), Cu (3–88 μg/L), As (0.04–2 μg/L), Na+ (3–16 mg/L), K+ (0.41–30 mg/L), Ca2+ (6–51 mg/L), Mg2+ (up to 5 mg/L), Cl (4–23 mg/L), NO3 (1–30 mg/L), and SO4 2− (4–35 mg/L) values. In certain locations, Zn, Cd, and Pb exceeded the guideline limits. A downward trend of H+, Zn, Cd, and Pb concentrations in total depositions was observed while the distance to the area affected by mining activities increased in the first 20 km. Rainwater quality was found to be just subtly affected by the metal-sulfide abandoned minesites, but without presenting a current threat to neither public health nor natural ecosystem. Nevertheless, greater attention should be paid in the future projections of climate change, where a significant increase in aridity may favor the atmospheric transport of pollutant particles.
Keywords: Rainwater pollution; Total deposition; Sierra Minera de Cartagena – La Unión; Sulfidic mine waste; Short-range transport;

We have studied the seasonal and tidal variation of methane (CH4) and nitrous oxide (N2O) emission from the intertidal sediment of Bhitarkanika mangrove in the east coast of India. Seasonal variability study was conducted at five sites (three replicate of each site) inside the core area of the national park during three different seasons (summer, monsoon and winter) whereas tidal variation was studied at three different sites outside the core area during monsoon and winter season. Both CH4 and N2O emission from the intertidal sediment were significantly higher under the low tide condition during the winter season. During the study period CH4 emission from five different sites was ranged between 0.08 and 2.30 mg m−2 h−1 and the N2O emission was ranged between 9.0 and 187.58 μg m−2 h−1. Average seasonal N2O emission (μg m−2 h−1) from five different sites followed the order: winter (115.60 ± 21.90) > summer (45.29 ± 7.78) > monsoon (16.98 ± 2.54). CH4 and N2O emission was also recorded significantly higher during the winter season over the tidal cycle of three sampling locations. The CH4 emission was negatively correlated with sediment salinity (r = −0.91, P < 0.05) and SO4 –2 (r = −0.89, P < 0.05) concentration whereas; the N2O emission was positively correlated with sediment salinity (r = 0.48) and NO3 –N (r = 0.88, P < 0.05) concentration during the monsoon season. Positive correlation of N2O emission with the sediment NO3 –N indicates possible influence of upstream anthropogenic activities on N2O emission from the mangrove sediment. In general, methylamine utilizing methanogen and denitrifying bacterial population was significantly higher during winter season in the mangrove sediment. The study concludes that the CH4 and N2O emission from the sediment at different sites during different seasons are influenced by allochthonous carbon and nitrogenous materials.
Keywords: Methane emission; Nitrous oxide emission; Seasonal; Tidal; Mangrove;

Greenhouse gas emissions from coastal freshwater wetlands in Veracruz Mexico: Effect of plant community and seasonal dynamics by José Luis Marín-Muñiz; María E. Hernández; Patricia Moreno-Casasola (107-117).
Wetlands play an important role in modulating atmospheric concentrations of Greenhouse Gases (GHGs), such as methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2). Despite the fact that ∼30% of wetlands in the world occur in tropical latitudes, little is known about GHG emissions from these ecosystems and the variables that control such emissions. We investigated the CH4, N2O and CO2 emissions in tropical freshwater marshes (FM) and swamps (FS) on the coastal plain of Veracruz, Mexico. GHGs were measured every two months using the closed chamber technique from April 2010 to February 2012 (CH4 and N2O) and during the last year for CO2. The ranges of the emissions were 20–2000 mg C–CH4 m−2 d−1, −2–16 mg N–N2O m−2 d−1 and 0.5–18 g C–CO2 m−2d−1. There were not significant differences in the emissions between FM and FS (P  = 0.314, 0.528 and 0.213 for CH4, N2O, and CO2, respectively). However, significant differences (P < 0.001) in CH4 and CO2 emissions were found in the different seasons. During the rainy and windy seasons, the water level was higher than during dry season, this enhanced reduced conditions in the soils and caused significantly higher (P < 0.05) CH4 emissions (>364 mg m−2 d−1) than during dry season (<150 mg m−2 d−1). The opposite was observed for CO2 emissions, during dry season, wetland soils were more aerobic and CO2 fluxes increased (FM: 11 ± 2, FS: 12 ± 1 g m−2 d−1). N–N2O emissions (FM: 1.5 ± 0.96, FS: 2.4 ± 0.9 mg m−2 d−1) were similar during different climatic season (P  = 0.056). Based on the global warming potential, CH4 was the main contributor to total GHGs emission during the rainy and windy seasons (75–93%), while CO2 was predominant during the dry season (79.6%) and N2O contributed with less than 7% in the three seasons. Water level and redox potential were found to be main factors influencing GHG emissions in these wetlands.Display Omitted
Keywords: Marshes; Swamps; Methane; Nitrous oxide; Carbon dioxide;

In the paper a novel hybrid model combining air mass trajectory analysis and wavelet transformation to improve the artificial neural network (ANN) forecast accuracy of daily average concentrations of PM2.5 two days in advance is presented. The model was developed from 13 different air pollution monitoring stations in Beijing, Tianjin, and Hebei province (Jing-Jin-Ji area). The air mass trajectory was used to recognize distinct corridors for transport of “dirty” air and “clean” air to selected stations. With each corridor, a triangular station net was constructed based on air mass trajectories and the distances between neighboring sites. Wind speed and direction were also considered as parameters in calculating this trajectory based air pollution indicator value. Moreover, the original time series of PM2.5 concentration was decomposed by wavelet transformation into a few sub-series with lower variability. The prediction strategy applied to each of them and then summed up the individual prediction results. Daily meteorological forecast variables as well as the respective pollutant predictors were used as input to a multi-layer perceptron (MLP) type of back-propagation neural network. The experimental verification of the proposed model was conducted over a period of more than one year (between September 2013 and October 2014). It is found that the trajectory based geographic model and wavelet transformation can be effective tools to improve the PM2.5 forecasting accuracy. The root mean squared error (RMSE) of the hybrid model can be reduced, on the average, by up to 40 percent. Particularly, the high PM2.5 days are almost anticipated by using wavelet decomposition and the detection rate (DR) for a given alert threshold of hybrid model can reach 90% on average. This approach shows the potential to be applied in other countries’ air quality forecasting systems.
Keywords: PM2.5 forecasting; Artificial neural networks; Air mass trajectory based geographic model; Wavelet transformation;

Source apportionment of gaseous and particulate PAHs from traffic emission using tunnel measurements in Shanghai, China by Ying Liu; Siyao Wang; Rainer Lohmann; Na Yu; Chenkai Zhang; Yi Gao; Jianfu Zhao; Limin Ma (129-136).
Understanding sources and contributions of gaseous and particulate PAHs from traffic-related pollution can provide valuable information for alleviating air contamination from traffic in urban areas. On-road sampling campaigns were comprehensively conducted during 2011–2012 in an urban tunnel of Shanghai, China. 2–3 rings PAHs were abundant in the tunnel's gas and particle phases. Diagnostic ratios of PAHs were statistically described; several were significantly different between the gas and particle phases. Principal component analysis (PCA), positive matrix factorization (PMF), bivariate correlation analysis and multiple linear regression analysis (MLRA) were applied to apportion sources of gaseous and particulate PAHs in the tunnel. Main sources of the gaseous PAHs included evaporative emission of fuel, high-temperature and low-temperature combustion of fuel, accounting for 50–51%, 30–36% and 13–20%, respectively. Unburned fuel particles (56.4–78.3%), high-temperature combustion of fuel (9.5–26.1%) and gas-to-particle condensation (12.2–17.5%) were major contributors to the particulate PAHs. The result reflected, to a large extent, PAH emissions from the urban traffic of Shanghai. Improving fuel efficiency of local vehicles will greatly reduce contribution of traffic emission to atmospheric PAHs in urban areas. Source apportionment of PM10 mass was also performed based on the organic component data. The results showed that high-temperature combustion of fuel and gas-to-particle condensation contributed to 15–18% and 7–8% of PM10 mass, respectively, but 55–57% of the particle mass was left unexplained. Although the results from the PCA and PMF models were comparable, the PMF method is recommended for source apportionment of PAHs in real traffic conditions. In addition, the combination of multivariate statistical method and bivariate correlation analysis is a useful tool to comprehensively assess sources of PAHs.
Keywords: Atmospheric pollution; Yan'an East Road Tunnel; PM10; PAHs; PMF; PCA;

Size-resolved global emission inventory of primary particulate matter from energy-related combustion sources by E. Winijkul; F. Yan; Z. Lu; D.G. Streets; T.C. Bond; Y. Zhao (137-147).
Current emission inventories provide information about the mass emissions of different chemical species from different emitting sources without information concerning the size distribution of primary particulate matter (PM). The size distribution information, however, is an important input into chemical transport models that determine the fate of PM and its impacts on climate and public health. At present, models usually make rather rudimentary assumptions about the size distribution of primary PM emissions in their model inputs. In this study, we develop a global and regional, size-resolved, mass emission inventory of primary PM emissions from source-specific combustion components of the residential, industrial, power, and transportation sectors for the year 2010. Uncertainties in the emission profiles are also provided. The global size-resolved PM emissions show a distribution with a single peak and the majority of the mass of particles in size ranges smaller than 1 μm. The PM size distributions for different sectors and world regions vary considerably, due to the different combustion characteristics. Typically, the sizes of particles decrease in the order: power sector > industrial sector > residential sector > transportation sector. Three emission scenarios are applied to the baseline distributions to study the likely changes in size distribution of emissions as clean technologies are implemented.
Keywords: Mass size distribution; PM emissions; Combustion sources; Global size-resolved emission inventory;

Assessment of long-term measurements of particulate matter and gaseous pollutants in South-East Mediterranean by Petros Mouzourides; Prashant Kumar; Marina K.-A. Neophytou (148-165).
This work examines long-term measurements of major criteria pollutants concentrations in an urban station in South-Eastern Mediterranean, in Nicosia – Cyprus, which is susceptible both to transboundary air pollution transport from Sahara-dust events as well as to evaporative transport of sea-sprays. The work investigates in particular the role of such multi-scale contributions in the urban air quality measurements, which are important considerations in the assessment of the effectiveness of any mitigation policies implemented by regulatory authorities. Attention is drawn in the regional-scale component of the particulate matter concentrations (PM10; ≤10 μm in diameter) and its contribution in the local measurements. Hourly averaged data of CO, NOx and PM10 concentrations as well as of meteorological parameters were collected from the Air Quality Monitoring Station (AQMS) of the University of Cyprus over a period of more than 5 years (2008–13) and were analysed. Scanning Electron Microscope (SEM) was used to identify chemical characteristics of PM10 and to attribute it to possible sources. A total of 321 days over the entire period were found to exceed the daily limit value of 50 μg/m3 for PM10 concentrations which corresponds to ∼19% of the actual monitored time. Numerical simulations using the Dust REgional Atmospheric Model from Barcelona Supercomputing Center (BSC/DREAM) gave a strong indication that PM10 exceedances were associated with the high regional background dust concentrations during westerly winds. It was also found that despite the implementation of tighter regulations for vehicular and industrial emissions in Europe, the monthly average concentration values of criteria pollutants do not exhibit any falling trend.
Keywords: Urban air quality monitoring; Background pollutant concentration; Transboundary pollution; Pollution concentration exceedances; Nicosia – Cyprus; Scanning Electron Microscope;

Breakthrough emissions that dominate diurnal evaporative emissions from gasoline vehicles were observed in continuous 3-day diurnal breathing loss (DBL) tests. These measurements were conducted on nine vehicles for the Japanese market. Two of these vehicles, made by US and European manufacturers, also meet regulations in their countries of origin. Four vehicles exhibited marked emissions caused by breakthrough emissions during the experimental period, all made by Japanese manufacturers. Using our experimental results, we estimate the total diurnal evaporative emissions from gasoline vehicles in Japan to be 32,792 t y−1. The compositions of the breakthrough and permeation emissions were analyzed in real time using proton transfer reaction plus switchable reagent ion mass spectrometry to estimate the ozone formation potential for the evaporative emissions. The real-time measurements showed that the adsorption of hydrocarbons in a sealed housing evaporative determination unit can result in underestimation, when concentrations are only monitored before and after a DBL test. The composition analysis gave an estimated maximum incremental reactivity (MIR) 20% higher for the breakthrough emissions than for the gasoline that was tested, while the MIR for the permeation emissions was almost the same as the MIR for the fuel. Evaporative emissions from gasoline vehicles in Japan were found to contribute 4.2% to emissions from stationary sources using a mass-based estimate, or 6.1% of emissions from stationary sources using a MIR-based estimate.
Keywords: Evaporative emissions; Breakthrough emissions; Gasoline passenger car; PTR+SRI-MS; Ozone formation potential;

A tailor-made diffusive sampler was developed for the determination of atmospheric Volatile Organic Compounds (VOCs) and the validation of the sampler was carried out under field conditions. All parts of the diffusive sampler which are reusable after a proper cleaning process were made of plastic material (delrin). The reusability of the sampler brings an important advantage considering its lower cost. Activated carbon was used as adsorbent and VOCs adsorbed on the activated carbon were analyzed by GC–MS (gas chromatography equipped with mass selective detector). A comprehensive validation study including detection limit, precision, bias, recovery, self-consistency, shelf life, storage stability, reusability was carried out in accordance with the related European standards ((EN) 13528-1 (2000) and 13528-2 (2000)). Also, a comparison was performed with some commercial diffusive samplers such as 3 M OVM 3500 and Radiello to test the performance of the new diffusive sampler in different environments such as urban area and road tunnel. Uptake rates for the measured VOCs were determined and they were evaluated together with the meteorological parameters (temperature, humidity, wind speed). According to the validation results; all the parameters evaluated for the sampler comply with the related standards and this is an indication of the reliability of the sampler for the sampling of VOCs in the atmosphere.
Keywords: Field validation; Anadolu diffusive sampler; Volatile organic compounds;

The role of fossil fuel combustion on the stability of dissolved iron in rainwater by Joan D. Willey; Robert J. Kieber; Joshua J. Humphreys; Briana C. Rice; Mark J. Hopwood; G. Brooks Avery; Ralph N. Mead (187-193).
The concentration of dissolved Fe(II) has decreased in coastal NC rainwater because of less complexation and stabilization of Fe(II) (aq) by automobile and coal combustion emissions. Better emission control has removed stabilizing organic ligands hence dissolved Fe(II) currently occurs more as inorganic iron, which is not protected against oxidation. Increasing rainwater pH allows oxidation by molecular O2 in addition to H2O2 and also increases the ratio of the ion pair Fe(OH)+ to Fe(II) free ion, which increases the oxidation rates by both H2O2 and molecular oxygen. The concentration of H2O2 in rain has increased; hydrogen peroxide is the primary oxidant of inorganic Fe(II) in precipitation. The East Coast of the USA is also receiving less rain of terrestrial origin, which tends to be higher in dissolved iron and organic compounds. All these factors operate in the same direction and contribute to the lower concentrations and lack of stability of Fe(II) in rainwater currently observed. Results of this study suggest that wet deposition of soluble Fe(II) is an episodic, temporally variable factor in the iron cycle in oceanic regions adjacent to developed or developing coastal regions.
Keywords: Rainwater trends; Iron speciation; Fossil fuel exhaust; Marine iron cycle;

A clustering algorithm for sample data based on environmental pollution characteristics by Mei Chen; Pengfei Wang; Qiang Chen; Jiadong Wu; Xiaoyun Chen (194-203).
Environmental pollution has become an issue of serious international concern in recent years. Among the receptor-oriented pollution models, CMB, PMF, UNMIX, and PCA are widely used as source apportionment models. To improve the accuracy of source apportionment and classify the sample data for these models, this study proposes an easy-to-use, high-dimensional EPC algorithm that not only organizes all of the sample data into different groups according to the similarities in pollution characteristics such as pollution sources and concentrations but also simultaneously detects outliers. The main clustering process consists of selecting the first unlabelled point as the cluster centre, then assigning each data point in the sample dataset to its most similar cluster centre according to both the user-defined threshold and the value of similarity function in each iteration, and finally modifying the clusters using a method similar to k-Means. The validity and accuracy of the algorithm are tested using both real and synthetic datasets, which makes the EPC algorithm practical and effective for appropriately classifying sample data for source apportionment models and helpful for better understanding and interpreting the sources of pollution.
Keywords: Environmental pollution; High-dimensional sample data; Pollution characteristics; Clustering algorithm;

Long-term atmospheric visibility, sunshine duration and precipitation trends in South China by Wenhui Liao; Xuemei Wang; Qi Fan; Shengzhen Zhou; Ming Chang; Zhimin Wang; Yu Wang; Qiulan Tu (204-216).
The fast industrialization and urbanization in South China have led to increasing concentration of aerosols, which has caused the degradation of atmospheric visibility and substantially impacted on cloud properties and the initiation of precipitation in this region. Therefore, it is valuable to study the spatial and temporal trends of atmospheric visibility, sunshine duration and precipitation in recent years in the region to understand how aerosols affect the environment. In this article, meteorological data of 28 stations in South China were obtained from the China Meteorological Data Sharing Service System and were analyzed using several different statistical methods. The stations were divided into four categories: prefecture, county, neighbor, and remote stations. The data show a decrease of visibility in 93% of the stations during 1980–2012, among which the neighbor stations have recorded the fastest average decrease of −1.8 km/decade. The average visibility for all the stations over the 33 years is 16.8 km and the total average decreasing rate is −1.3 km/decade. The percentages of “high” visibility in prefecture, county and neighbor stations decreased dramatically, while the percentages of “low” visibility in aforementioned stations were much higher than those in the remote stations. As for the sunshine duration, the neighbor stations have recorded the rapidest decrease in the recent 30 years, while the data of the prefecture stations showed the most significant change during 1957–2012. The annual average daily rainfall of rainy days shows a significant increase during 1978–1985 in the dry seasons and 1990–2000 in the wet seasons, respectively. The percentage of rainy days per year had been decreasing linearly during 1980–2010. Light rain days had been decreasing in all the types of stations, though such change is the smallest in remote stations. Meanwhile, torrential rain and rainstorm days have been increasing, especially in the prefecture stations. By using the empirical orthogonal function (EOF) and detrended cross-correlations analysis (DCCA), we may conclude that visibility and rainfall have cross-correlation, which shows more complex multifractal structure in Guangzhou (a prefecture station) than in Gaoyao (a neighbor station) and Lianping (a remote station).
Keywords: Sunshine duration; Multifractal structure; Cross-correlation;

Characterisation of particulate matter in different types of archives by Ludmila Mašková; Jiří Smolík; Petr Vodička (217-224).
To determine the composition of particulate matter (PM) in the indoor environments of four different types of archives (three naturally ventilated and one filtered), intensive size-resolved sampling was performed for four seasons of the year. For reconstituting indoor PM, nine aerosol components were considered. Organic matter was the dominant component of both fine and coarse fractions and represented approximately 50–80% of the PM. In the fine fraction, the next most abundant components were elemental carbon and sulphate, and in the coarse fraction the next most abundant were crustal matter, sulphate and nitrate. The resulting mass closure explained 95(±13)% and 115(±38)% of the gravimetric indoor PM in the fine and coarse size fractions, respectively. The results revealed that all the particles found indoors can be considered to be potentially threatening to the stored materials. The results also showed that the most important source of indoor PM in the naturally ventilated archives was penetration from the outdoor air, whereas in the filtered archive, the concentrations of particles were strongly reduced. In naturally ventilated archives the influence of domestic heating, road traffic and local sources (industrial pollution, camp fires) was observed. Furthermore, activities of the staff were identified as an indoor source of coarse particles in all archives.
Keywords: Indoor particles; Chemical composition; Mass closure; Archive;

Predominance of single bacterial cells in composting bioaerosols by Amandine Galès; Valérie Bru-Adan; Jean-Jacques Godon; Karine Delabre; Philippe Catala; Arnaud Ponthieux; Michel Chevallier; Emmanuel Birot; Jean-Philippe Steyer; Nathalie Wéry (225-232).
Bioaerosols emitted from composting plants have become an issue because of their potential harmful impact on public or workers’ health. Accurate knowledge of the particle-size distribution in bioaerosols emitted from open-air composting facilities during operational activity is a requirement for improved modeling of air dispersal. In order to investigate the aerodynamic diameter of bacteria in composting bioaerosols this study used an Electrical Low Pressure Impactor for sampling and quantitative real-time PCR for quantification. Quantitative PCR results show that the size of bacteria peaked between 0.95 μm and 2.4 μm and that the geometric mean diameter of the bacteria was 1.3 μm. In addition, total microbial cells were counted by flow cytometry and revealed that these qPCR results corresponded to single whole bacteria. Finally, the enumeration of cultivable thermophilic microorganisms allowed us to set the upper size limit for fragments at an aerodynamic diameter of ∼0.3 μm. Particle-size distributions of microbial groups previously used to monitor composting bioaerosols were also investigated. In collected the bioaerosols, the aerodynamic diameter of the actinomycetes Saccharopolyspora rectivirgula-and-relatives and also of the fungus Aspergillus fumigatus, appeared to be consistent with a majority of individual cells. Together, this study provides the first culture-independent data on particle-size distribution of composting bioaerosols and reveals that airborne single bacteria were emitted predominantly from open-air composting facilities.
Keywords: Bioaerosol; Compost; Particle-size distribution; Aerodynamic diameter of bacteria; qPCR; Flow cytometry;

Quantifying the influences of atmospheric stability on air pollution in Lanzhou, China, using a radon-based stability monitor by Scott D. Chambers; Fenjuan Wang; Alastair G. Williams; Deng Xiaodong; Hua Zhang; Giovanni Lonati; Jagoda Crawford; Alan D. Griffiths; Antonietta Ianniello; Ivo Allegrini (233-243).
Commercially-available “stability monitors” based on in situ atmospheric radon progeny measurements remain underutilised as a tool for urban pollution studies, due in part to difficulties experienced in relating their standard output directly to the atmospheric mixing state in a consistent manner. The main confounding factor has been a lack of attention to the fact that the observed near-surface atmospheric radon concentration includes large synoptic and fetch-related components in addition to the local stability influence. Here, a technique recently developed for stability classification using a research-quality dual-flow-loop two-filter radon detector is adapted for use with a commercially-available radon-based stability monitor. Performance of the classification scheme is then tested in Lanzhou, China, a topographically-complex region renowned for low mean annual wind speeds (0.8 m s−1) and winter stagnation episodes. Based on an 11-month composite, a factor of seven difference is estimated between peak NOx concentrations in the city's industrial region and a rural background location under stable conditions. The radon-based scheme is evaluated against the Pasquil-Gifford “radiation” (PGR) scheme, and assigns pollutant concentrations more consistently between defined atmospheric stability states than the PGR scheme. Furthermore, the PGR scheme consistently underestimates all peak pollutant concentrations under stable conditions compared with the radon-based scheme, in some cases (e.g. CO in the industrial region) by 25%.
Keywords: Atmospheric stability; Air pollution; Radon; Stability monitor; Pasquil-Gifford;

Aerosol Modeling System (AMS) that is consisted of the Asian Dust Aerosol Model2 (ADAM2) and the Community Multi-scale Air Quality (CMAQ) modeling system has been employed to document the geographical distributions of both the annual averaged Asian dust aerosol and the anthropogenic aerosols concentrations and their total depositions in the East Asia region for the year 2010. It is found that AMS simulates quite well the monitored PM10 concentration with a root mean square error (RMSE) of 9.2 μg m−3 and a normalized mean square error (NMSE) of 5.5% in South Korea and the RMSE of less than 33 μg m−3 with a NMSE of less than 7.8% at the monitoring sites in China. The annual mean surface (column integrated) aerosol concentrations in the East Asia region affect in a wide region as a complex mixture of the Asian dust (AD) aerosol and the anthropogenic aerosol (AA), more predominated by the AD aerosol in the Asian dust source region of northern China and Mongolia with the annual mean (column integrated) PM10 concentration of more than 200 μg m−3 (350 mg m−2). Whereas AA is dominated in the high pollutant emission regions of southern and eastern China and northern India with the annual mean surface (column integrated) concentration of more than 110 μg m−3 (140 mg m−2) in eastern China. On the other hand the mixed aerosols (AD + AA) are dominated in the downwind regions of the Yellow Sea, the East China Sea, the Korean peninsula, Japan, and the Northwest Pacific Ocean. It is also found that the annual total deposition of aerosols in the model domain is 4.9 × 108 t (3.7 × 108 t by AD aerosol and 1.2 × 108 t by AA), of which 66% (3.2 × 108 t) is found to be contributed by the dry deposition (3.1 × 108 t by AD aerosol and 1.3 × 107 t by AA) and 34% (1.7 × 108 t) by the wet deposition (1.0 × 108 t by AA and 6.6 × 107 t by AD aerosol), suggesting significant impacts of aerosols on environment and the terrestrial and marine eco-systems in East Asia.
Keywords: Aerosol Modeling System (AMS); Aerosol deposition; Anthropogenic aerosol; Asian Dust Aerosol Model2 (ADAM2); Column integrated aerosol concentration; Community Multi-scale Air Quality (CMAQ);

Dry deposition of PM2.5 sulfate above a hilly forest using relaxed eddy accumulation by Kazuhide Matsuda; Ichiro Watanabe; Kou Mizukami; Satomi Ban; Akira Takahashi (255-261).
Sulfur compounds continue to be an important component of atmospheric deposition in East Asia. In order to better understand the dry deposition of PM2.5 sulfate, which is one of the most significant transboundary air pollutants in this region, we measured the dry deposition flux of PM2.5 sulfate above a hilly forest of the Field Museum Tamakyuryo (FM Tama) site in suburban Tokyo. We used the relaxed eddy accumulation (REA) method and took measurements during the summer, from 26 July to 2 August 2013, and the autumn, from 18 to 22 November 2013. We primarily focused on the evaluation of dry deposition above a forest on complex terrain. The total flux and 80% of the runs showed downward flux. The deposition velocities measured by the REA method during times when the wind direction was from a relatively uniform sloping surface over the forest were more reasonable than those measured when the wind direction was from a more complex surface. Using a resistance model that includes the effect of growth of hygroscopic aerosols, we inferred the deposition velocities during two experimental periods. When the fluxes were averaged for a long time (i.e., about 2 weeks) the inferred fluxes and deposition velocities were in reasonable agreement with the measurements. Although averages over long periods showed good agreement, the measured deposition velocities were distributed in a wider range than those inferred by the model. An increased range of deposition velocities was associated with flux footprints from complex terrain. It is possible that the agreements between measured and inferred fluxes or deposition velocities at the site are because the depositions of sulfate are largely controlled by surface factors rather than aerodynamic resistance.
Keywords: Deposition velocity; Aerosol; REA; Complex terrain; EANET;

Quantification of PAHs and oxy-PAHs on airborne particulate matter in Chiang Mai, Thailand, using gas chromatography high resolution mass spectrometry by Christophe Walgraeve; Somporn Chantara; Khajornsak Sopajaree; Patrick De Wispelaere; Kristof Demeestere; Herman Van Langenhove (262-272).
An analytical method using gas chromatography high resolution mass spectrometry was developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) and 12 oxygenated PAHs (of which 4 diketones, 3 ketones, 4 aldehydes and one anhydride) on atmospheric particulate matter with an aerodynamic diameter less than 10 μm (PM10). The magnetic sector mass spectrometer was run in multiple ion detection mode (MID) with a mass resolution above 10 000 (10% valley definition) and allows for a selective accurate mass detection of the characteristic ions of the target analytes. Instrumental detection limits between 0.04 pg and 1.34 pg were obtained for the PAHs, whereas for the oxy-PAHs they ranged between 0.08 pg and 2.13 pg. Pressurized liquid extraction using dichloromethane was evaluated and excellent recoveries ranging between 87% and 98% for the PAHs and between 74% and 110% for 10 oxy-PAHs were obtained, when the optimum extraction temperature of 150 °C was applied. The developed method was finally used to determine PAHs and oxy-PAHs concentration levels from particulate matter samples collected in the wet season at 4 different locations in Chiang Mai, Thailand (n = 72). This study brings forward the first concentration levels of oxy-PAHs in Thailand. The median of the sum of the PAHs and oxy-PAHs concentrations was 3.4 ng/m3 and 1.1 ng/m3 respectively, which shows the importance of the group of the oxy-PAHs as PM10 constituents. High molecular weight PAHs contributed the most to the ∑PAHs. For example, benzo[ghi]perylene was responsible for 30–44% of the ∑PAHs. The highest contribution to ∑oxy-PAHs came from 1,8-napthalic anhydride (26–78%), followed by anthracene-9,10-dione (4–27%) and 7H-benzo[de]anthracene-7-one (6–26%). Indications of the degradation of PAHs and/or formation of oxy-PAHs were observed.
Keywords: Oxy-PAHs; OPAHs; PAHs; PM10; Chiang Mai; Gas chromatography; High resolution mass spectrometry; PLE; Pressurized liquid extraction;

Ultrafine particle emissions by in-use diesel buses of various generations at low-load regimes by L. Tartakovsky; V. Baibikov; P. Comte; J. Czerwinski; A. Mayer; M. Veinblat; Y. Zimmerli (273-280).
Ultrafine particles (UFP) are major contributors to air pollution due to their easy gas-like penetration into the human organism, causing adverse health effects. This study analyzes UFP emissions by buses of different technologies (from Euro II till Euro V EEV – Enhanced Environmentally-friendly Vehicle) at low-load regimes. Additionally, the emission-reduction potential of retrofitting with a diesel particle filter (DPF) is demonstrated. A comparison of the measured, engine-out, particle number concentrations (PNC) for buses of different technological generations shows that no substantial reduction of engine-out emissions at low-load operating modes is observed for newer bus generations. Retrofitting the in-use urban and interurban buses of Euro II till Euro IV technologies by the VERT-certified DPF confirmed its high efficiency in reduction of UFP emissions. Particle-count filtration efficiency values of the retrofit DPF were found to be extremely high – greater than 99.8%, similar to that of the OEM filter in the Euro V bus.
Keywords: Ultrafine particles; Diesel engine; Diesel particle filter; Filter retrofitting;

Do N-isotopes in atmospheric nitrate deposition reflect air pollution levels? by Fabian Beyn; Volker Matthias; Armin Aulinger; Kirstin Dähnke (281-288).
Dry and wet deposition of atmospheric reactive nitrogen compounds mostly originate from anthropogenic NH3 and NOX sources. Regarding land-borne pollutants, coastal environments usually have a lower pollution level than terrestrial/urban areas, which have a greater anthropogenic imprint. To investigate this spatial characteristic, we measured NO 3 − and NH 4 + deposition and N isotopes of NO 3 − (δ15N– NO 3 − ) in 94 and 88 wet and dry deposition samples, respectively, at a coastal (List on Sylt) and a terrestrial/urban site (Geesthacht) in Germany from May 2012 to May 2013. A higher total N deposition rate was observed in Geesthacht (10.4 vs. 8.9 kg N ha−1 yr−1) due to higher NH 4 + deposition, which can be explained by more agricultural influence. Surprisingly, overall NO 3 − fluxes were higher at the coastal site than at the terrestrial/urban site. We assume that sea-salt aerosols and the increased influence of NOX emissions from ships in most recent times compensate the higher terrestrial/urban pollution level and thus lead to higher NO 3 − fluxes in dry and comparable fluxes in wet deposition at the coastal site, despite a much lower impact of land-based sources. In line with this, overall mean N isotopes values of NO 3 − show higher values in List than in Geesthacht in dry (+3.1 vs. +1.9‰) as well as in wet deposition (−0.1 vs. −1.0‰). This surprising result can mainly be attributed to an emerging source of NOX, ship emissions, which have a distinctly higher impact at the coastal site. The usage of heavy oil and possibly new technologies in marine engines, which emit more enriched 15N in comparison to older engines, caused the spatial isotopic differences.
Keywords: Atmospheric nitrate deposition; Nitrogen isotopes; Pollution level;

Influence of an urban canopy model and PBL schemes on vertical mixing for air quality modeling over Greater Paris by Youngseob Kim; Karine Sartelet; Jean-Christophe Raut; Patrick Chazette (289-306).
Impacts of meteorological modeling in the planetary boundary layer (PBL) and urban canopy model (UCM) on the vertical mixing of pollutants are studied. Concentrations of gaseous chemical species, including ozone (O3) and nitrogen dioxide (NO2), and particulate matter over Paris and the near suburbs are simulated using the 3-dimensional chemistry-transport model Polair3D of the Polyphemus platform. Simulated concentrations of O3, NO2 and PM10/PM2.5 (particulate matter of aerodynamic diameter lower than 10 μm/2.5 μm, respectively) are first evaluated using ground measurements. Higher surface concentrations are obtained for PM10, PM2.5 and NO2 with the MYNN PBL scheme than the YSU PBL scheme because of lower PBL heights in the MYNN scheme. Differences between simulations using different PBL schemes are lower than differences between simulations with and without the UCM and the Corine land-use over urban areas. Regarding the root mean square error, the simulations using the UCM and the Corine land-use tend to perform better than the simulations without it. At urban stations, the PM10 and PM2.5 concentrations are over-estimated and the over-estimation is reduced using the UCM and the Corine land-use. The ability of the model to reproduce vertical mixing is evaluated using NO2 measurement data at the upper air observation station of the Eiffel Tower, and measurement data at a ground station near the Eiffel Tower. Although NO2 is under-estimated in all simulations, vertical mixing is greatly improved when using the UCM and the Corine land-use. Comparisons of the modeled PM10 vertical distributions to distributions deduced from surface and mobile lidar measurements are performed. The use of the UCM and the Corine land-use is crucial to accurately model PM10 concentrations during nighttime in the center of Paris. In the nocturnal stable boundary layer, PM10 is relatively well modeled, although it is over-estimated on 24 May and under-estimated on 25 May. However, PM10 is under-estimated on both days in the residual layer, and over-estimated on both days over the residual layer. The under-estimations in the residual layer are partly due to difficulties to estimate the PBL height, to an over-estimation of vertical mixing during nighttime at high altitudes and to uncertainties in PM10 emissions. The PBL schemes and the UCM influence the PM vertical distributions not only because they influence vertical mixing (PBL height and eddy–diffusion coefficient), but also horizontal wind fields and humidity. However, for the UCM, it is the influence on vertical mixing that impacts the most the PM10 vertical distribution below 1.5 km.
Keywords: Urban air quality modeling; PM10 vertical distribution; PBL parameterization; Urban canopy model; Eddy–diffusion coefficient; Polyphemus; Greater Paris;

Impact of biodiesel and renewable diesel on emissions of regulated pollutants and greenhouse gases on a 2000 heavy duty diesel truck by Kwangsam Na; Subhasis Biswas; William Robertson; Keshav Sahay; Robert Okamoto; Alexander Mitchell; Sharon Lemieux (307-314).
As part of a broad evaluation of the environmental impacts of biodiesel and renewable diesel as alternative motor fuels and fuel blends in California, the California Air Resources Board's (CARB) Heavy-duty Diesel Emission Testing Laboratory conducted chassis dynamometer exhaust emission measurements on in-use heavy-heavy-duty diesel trucks (HHDDT). The results presented here detail the impact of biodiesel and renewable diesel fuels and fuel blends as compared to CARB ULSD on particulate matter (PM), regulated gases, and two greenhouse gases emissions from a HHDDT with a 2000 C15 Caterpillar engine with no exhaust after treatment devices. This vehicle was tested over the Urban Dynamometer Driving Schedule (UDDS) and the cruise portion of the California HHDDT driving schedule. Three neat blend stocks (soy-based and animal-based fatty acid methyl ester (FAME) biodiesels, and a renewable diesel) and CARB-certified ultra-low sulfur diesel (CARB ULSD) along with their 20% and 50% blends (blended with CARB ULSD) were tested. The effects of blend level on emission characteristics were discussed on g·km−1 basis. The results showed that PM, total hydrocarbon (THC), and carbon monoxide (CO) emissions were dependent on driving cycles, showing higher emissions for the UDDS cycles with medium load than the highway cruise cycle with high load on per km basis. When comparing CARB ULSD to biodiesels and renewable diesel blends, it was observed that the PM, THC, and CO emissions decreased with increasing blend levels regardless of the driving cycles. Note that biodiesel blends showed higher degree of emission reductions for PM, THC, and CO than renewable diesel blends. Both biodiesels and renewable diesel blends effectively reduced PM emissions, mainly due to reduction in elemental carbon emissions (EC), however no readily apparent reductions in organic carbon (OC) emissions were observed. When compared to CARB ULSD, soy- and animal-based biodiesel blends showed statistically significant increases in nitrogen oxides (NO x ) emissions for 50% or higher biodiesel blends. The 20% blends of the biodiesels showed no statistically significant effect on NO x emissions on any cycle. In contrast, renewable diesel slightly decreased NO x emissions and the degree of reduction was statistically significant for 50% or higher blends over the UDDS cycle, but not at the 20% blends. The highway cruise cycles did not show a statistically strong NO x emission trend with increasing blend level of renewable diesel. Biodiesel and renewable fuel impacts on two greenhouse gases, CO2 and N2O emissions were of lower magnitude when compared to other regulated pollutants emissions, showing a change in their emissions within approximately ±3% from the CARB ULSD.
Keywords: Biodiesel; Renewable diesel; Regulated pollutants; Elemental carbon; Chassis dynamometer;

In the present study mesoscale meteorological flow and planetary boundary layer (PBL) parameters over the complex topographic region of Jharkhand state of tropical India are simulated using high resolution Advanced Research WRF (ARW) mesoscale model to study their role in the air pollution dispersion characteristics using a Lagrangian Particle Dispersion Model (FLEXPART). Eight fair weather days in different seasons (winter, pre-monsoon, monsoon, and post-monsoon) are chosen. Sensitivity experiments are conducted with two non-local [Yonsei University (YSU), Asymmetric Convective Model version 2 (ACM2)] and three local turbulence kinetic energy (TKE) closure [Mellor- Yamada Nakanishi and Niino Level 2.5 PBL (MYNN2), Mellor-Yamada-Janjic (MYJ), and quasi-normal scale elimination (QNSE)] PBL parameterisations to study the evolution of PBL parameters and thermodynamic structure. Simulated parameters are validated with available in situ meteorological observations at three stations in the study region. Results indicate that the low-level flow field is highly influenced by the topography and widely varies in different seasons. Simulated vertical PBL structure varied across seasons with shallow boundary layers (1–1.7 km) during winter, monsoon and post-monsoon seasons, deep mixed layers (2–2.7 km) in pre-monsoon season. Simulations in various seasons revealed that ACM2 followed by MYNN2 and YSU reproduced various PBL features such as topographic flows, surface layer fluxes, meteorological variables and the thermo-dynamical structure reasonably well indicating the suitability of the above PBL schemes for air quality simulations over the region. This is corroborated with the error statistics as well. Simulations with FLEXPART using ARW derived meteorology revealed higher dilution potential of the atmosphere in monsoon and pre-monsoon compared to post monsoon and winter seasons over the region. Results also indicate the ACM2, MYNN2 and YSU produce relatively larger dispersion than the QNSE and MYJ.
Keywords: ARW model; FLEXPART; Planetary boundary layer; Complex terrain;

Contribution of coherent structures to momentum and concentration fluxes over a flat vegetation canopy modelled in a wind tunnel by Boris Conan; Sandrine Aubrun; Bruno Coudour; Khaled Chetehouna; Jean-Pierre Garo (329-341).
Coherent structures dominate the shear flow in and above the vegetation canopy, affecting the transport of passive scalars. Their detailed understanding is therefore of great interest for a number of environmental studies such as organic gas exchange, pollution dispersion, or forest fire propagation. In the present study, a forest embedded in an atmospheric boundary layer was reproduced in a wind tunnel. An area source was installed to mimic the volatile organic compounds emission coming from the vegetation. A fast gas analyser combined to a triple hot-wire anemometer were used to measure simultaneously and at the same point the momentum and the concentration fluxes above the canopy. This particular set-up enabled the complex scalar exchange mechanism to be studied in the well defined and stationary boundary conditions of a laboratory experiment simulating neutral atmospheric conditions. Measurements showed that the contribution of coherent structures to the momentum and the concentration flux was 80% and 60% respectively. Contributions were found to be nearly constant with height. The combination of velocity and concentration measurements enabled the determination of the mean concentration of the coherent structures. Results highlights the preponderant role of ejections in releasing highly concentrated gas pockets above the forest canopy. These releases were measured to be, in average, 40% more concentrated than the average gas concentration at the same height. It is shown that 70% of the extreme events observed are linked to an ejection process.
Keywords: Atmospheric boundary-layer simulation; Forest canopy turbulence; Coherent turbulent structures; Concentration fluctuations; Concentration flux; Gas dispersion; Wind-tunnel experiment;

PM2.5 emissions from open biomass burning (BB) in Northeast Asia (NEA: China, Mongolia, Korea, and Japan) during 2000–2013 were estimated using satellite-derived data (GFASv1.0 and GFED3). The annual mean BB PM2.5 emission in NEA during the study period was 660 Gg yr−1, in which considerable inter-annual variability was observed. In general, PM2.5 emissions in NEA were the highest in spring (Mar.–May), likely due to the burning of crop residues and forest fire. The contribution of PM2.5 from open BB in Northeast Asia was less than 10% of the anthropogenic PM2.5 emission, except in Mongolia, wherein BB emission was the predominant source of PM2.5. Although the emissions calculated by GFASv1.0 were significantly higher than GFED3 by a factor of 2.66 (Mongolia) to 10.9 (South Korea) due to difficulty in small fire detection by GFED3, they generally showed consistent temporal variation on average. In general, statistically significant long-term trends of open BB PM2.5 emissions were not observed in NEA, except in South Korea.
Keywords: Biomass burning; PM2.5; GFASv1.0; GFED3; Satellite;

Traffic activity encompasses the number, mix, speed and acceleration of vehicles on roadways. The temporal pattern and variation of traffic activity reflects vehicle use, congestion and safety issues, and it represents a major influence on emissions and concentrations of traffic-related air pollutants. Accurate characterization of vehicle flows is critical in analyzing and modeling urban and local-scale pollutants, especially in near-road environments and traffic corridors. This study describes methods to improve the characterization of temporal variation of traffic activity. Annual, monthly, daily and hourly temporal allocation factors (TAFs), which describe the expected temporal variation in traffic activity, were developed using four years of hourly traffic activity data recorded at 14 continuous counting stations across the Detroit, Michigan, U.S. region. Five sites also provided vehicle classification. TAF-based models provide a simple means to apportion annual average estimates of traffic volume to hourly estimates. The analysis shows the need to separate TAFs for total and commercial vehicles, and weekdays, Saturdays, Sundays and observed holidays. Using either site-specific or urban-wide TAFs, nearly all of the variation in historical traffic activity at the street scale could be explained; unexplained variation was attributed to adverse weather, traffic accidents and construction. The methods and results presented in this paper can improve air quality dispersion modeling of mobile sources, and can be used to evaluate and model temporal variation in ambient air quality monitoring data and exposure estimates.
Keywords: Classification; Freeways; Highways; Mobile sources; Traffic; Vehicles;

Land-use regression panel models of NO2 concentrations in Seoul, Korea by Youngkook Kim; Jean-Michel Guldmann (364-373).
Transportation and land-use activities are major air pollution contributors. Since their shares of emissions vary across space and time, so do air pollution concentrations. Despite these variations, panel data have rarely been used in land-use regression (LUR) modeling of air pollution. In addition, the complex interactions between traffic flows, land uses, and meteorological variables, have not been satisfactorily investigated in LUR models. The purpose of this research is to develop and estimate nitrogen dioxide (NO2) panel models based on the LUR framework with data for Seoul, Korea, accounting for the impacts of these variables, and their interactions with spatial and temporal dummy variables. The panel data vary over several scales: daily (24 h), seasonally (4), and spatially (34 intra-urban measurement locations). To enhance model explanatory power, wind direction and distance decay effects are accounted for. The results show that vehicle-kilometers-traveled (VKT) and solar radiation have statistically strong positive and negative impacts on NO2 concentrations across the four seasonal models. In addition, there are significant interactions with the dummy variables, pointing to VKT and solar radiation effects on NO2 concentrations that vary with time and intra-urban location. The results also show that residential, commercial, and industrial land uses, and wind speed, temperature, and humidity, all impact NO2 concentrations. The R2 vary between 0.95 and 0.98.
Keywords: Land-use regression; Panel models; Nitrogen dioxide; Vehicle-kilometers-traveled; Solar radiation;

Quantification of disproportionate contribution made by signalised traffic intersections (TIs) to overall daily commuting exposure is important but barely known. We carried out mobile measurements in a car for size–resolved particle number concentrations (PNCs) in the 5–560 nm range under five different ventilation settings on a 6 km long busy round route with 10 TIs. These ventilation settings were windows fully open and both outdoor air intake from fan and heating off (Set1), windows closed, fan 25% on and heating 50% on (Set2), windows closed, fan 100% on and heating off (Set3), windows closed, fan off and heating 100% on (Set4), and windows closed, fan and heating off (Set5). Measurements were taken sequentially inside and outside the car cabin at 10 Hz sampling rate using a solenoid switching system in conjunction with a fast response differential mobility spectrometer (DMS50). The objectives were to: (i) identify traffic conditions under which TIs becomes hot–spots of PNCs, (ii) assess the effect of ventilation settings in free–flow and delay conditions (waiting time at a TI when traffic signal is red) on in–cabin PNCs with respect to on–road PNCs at TIs, (iii) deriving the relationship between the PNCs and change in driving speed during delay time at the TIs, and (iv) quantify the contribution of exposure at TIs with respect to overall commuting exposure. Congested TIs were found to become hot–spots when vehicle accelerate from idling conditions. In–cabin peak PNCs followed similar temporal trend as for on–road peak PNCs. Reduction in in–cabin PNC with respect to outside PNC was highest (70%) during free–flow traffic conditions when both fan drawing outdoor air into the cabin and heating was switched off. Such a reduction in in–cabin PNCs at TIs was highest (88%) with respect to outside PNC during delay conditions when fan was drawing outside air at 25% on and heating was 50% on settings. PNCs and change in driving speed showed an exponential–fit relationship during the delay events at TIs. Short–term exposure for ∼2% of total commuting time in car corresponded to ∼25% of total respiratory doses. This study highlights a need for more studies covering diverse traffic and geographical conditions in urban environments so that the disparate contribution of exposure at TIs can be quantified.Display Omitted
Keywords: Particle number concentration; Number size distribution; In–vehicle exposure; Respiratory deposition doses; Traffic intersections;