Atmospheric Environment (v.128, #C)

Atmospheric emission inventory of hazardous air pollutants from China's cement plants: Temporal trends, spatial variation characteristics and scenario projections by Shenbing Hua; Hezhong Tian; Kun Wang; Chuanyong Zhu; Jiajia Gao; Yilin Ma; Yifeng Xue; Yong Wang; Shiheng Duan; Junrui Zhou (1-9).
A multiple-year comprehensive emission inventory of typical hazardous air pollutants (HAPs) from China's cement industry for the period 1980–2012, has been established by using technology-based dynamic emission factors and detailed annual plant-specific cement production from different types of kilns. Our results show that the total emissions of various HAPs (SO2, NOX, CO, PM, Hg, Cd, Cr, Pb, Zn, As, Ni and Cu) have rapidly increased by about 1–21 times at an annual average growth rate of 1–10% over the past three decades. Remarkably uneven spatial allocation features of these pollutants among provinces are observed. HAPs emissions are primarily concentrated in the eastern and coastal provinces due to the concentration of cement plants and their huge volume of coal consumption. We predict the future emission trends of HAPs through 2050 based on industry construction and policy guidance, and our scenario analysis indicates that HAPs emissions will drop substantially because of the combined effects of cement production yields reduction and the increasing application rate of various air pollution control devices. The study suggests that highlighted attention should be paid to this energy-intensive industry to ensure stricter emission standards are implemented for these HAPs emissions in the future.Display Omitted
Keywords: Hazardous air pollutants; Emission inventory; Cement production; Temporal trend; Spatial distribution; Scenario analysis;

Variation of correlations between factors and culturable airborne bacteria and fungi by Min Gao; Xu Yan; Tianlei Qiu; Meilin Han; Xuming Wang (10-19).
Bioaerosols, including their characteristics and overall changes correlated with environmental factors, have the potential to impact human health and influence atmospheric dynamics. In this study, the varying interrelationship between the concentration and diameter of culturable bioaerosols and twelve factors including PM2.5 (AQI), PM10 (AQI), sampling time, sampling season, temperature, relative humidity, dew, pressure, wind, O3, NO2, and SO2 is determined for twelve months during non-haze and haze days in Beijing. Results of principal component analysis (PCA) indicated that the influence of factors on culturable bioaerosols is mainly associated with haze levels, sampling time, and season. Multiple linear regressions showed that the correlation between PM10 (AQI) or temperature and culturable bioaerosols varied at different haze levels. The seasonal influence of PM2.5 (AQI) was observed in culturable bioaerosol concentrations, but not their diameters. A temporal relationship between PM10 (AQI) and culturable bioaerosol concentration was detected during rush hour. SO2 and NO2 show positive and negative correlations with culturable bioaerosol concentrations in the morning/evening and mid-day, respectively. These results are useful for accurately evaluating the health effects of exposure to bioaerosols.Display Omitted
Keywords: Haze level; Meteorological parameters; Air pollutants; Culturable bioaerosols; Beijing;

Asian dust effect on cause-specific mortality in five cities across South Korea and Japan by Saori Kashima; Takashi Yorifuji; Sanghyuk Bae; Yasushi Honda; Youn-Hee Lim; Yun-Chul Hong (20-27).
Desert dust is considered to be potentially toxic and its toxicity may change during long-range transportation. In Asian countries, the health effects of desert dust in different locations are not well understood. We therefore evaluated the city-combined and city-specific effects of Asian dust events on all-cause and cause-specific mortality in five populous cities in South Korea (Seoul) and Japan (Nagasaki, Matsue, Osaka and Tokyo). We obtained daily mean concentrations of Asian dust using light detection and ranging (lidar) between 2005 and 2011. We then evaluated city-specific and pooled associations of Asian dust with daily mortality for elderly residents (≥65 years old) using time-series analyses. Each 10 μg/m3 increase in the concentration of same-day (lag 0) or previous-day (lag 1) Asian dust was significantly associated with an elevated pooled risk of all-cause mortality (relative risk (RR): 1.003 [95% CI: 1.001–1.005] at lag 0 and 1.001 [95% CI: 1.000–1.003] at lag 1) and cerebrovascular disease (RR: 1.006 [95% CI: 1.000–1.011] at lag 1). This association was especially apparent in Seoul and western Japan (Nagasaki and Matsue). Conversely, no significant associations were observed in Tokyo, which is situated further from the origin of Asian dust and experiences low mean concentrations of Asian dust. Adverse health effects on all-cause and cerebrovascular disease mortality were observed in South Korea and Japan. However, the effects of Asian dust differed across the cities and adverse effects were more apparent in cities closer to Asian dust sources.
Keywords: Asian dust storm; Air pollution; Cerebrovascular disease; Epidemiology; Mortality; East Asia;

Simulating reactive nitrogen, carbon monoxide, and ozone in California during ARCTAS-CARB 2008 with high wildfire activity by Chenxia Cai; Sarika Kulkarni; Zhan Zhao; Ajith P. Kaduwela; Jeremy C. Avise; John A. DaMassa; Hanwant B. Singh; Andrew J. Weinheimer; Ronald C. Cohen; Glenn S. Diskin; Paul Wennberg; Jack E. Dibb; Greg Huey; Armin Wisthaler; Jose L. Jimenez; Michael J. Cubison (28-44).
Predictions of O3, CO, total NOy and individual NOy species (NO, NO2, HNO3, PAN, alkyl nitrates and aerosol nitrate) from a fine resolution regional air quality modeling system for the South Coast Air Basin (SoCAB) and San Joaquin Valley Air Basin (SJVAB) of California are presented and evaluated for the 2008 ARCTAS-CARB campaign. The measurements of the chemical compounds from the fire plumes during the field campaign allow for the evaluation of the model's ability to simulate fire-influenced air masses as well. In general, the model successfully simulated the broad spatial distribution of chemical compounds in both air basins as well as the variation within the basins. Using inventories that reflect 2008 emissions levels, the model performed well in simulating NOx (NO + NO2) in SoCAB. Therefore, the under prediction of O3 over these areas is more likely caused by uncertainties with the VOC emissions, chemistry, or discrepancies in the meteorology. The model did not capture the relatively high levels of O3, and some reactive nitrogen species that were measured off shore of the SoCAB, indicating potential missing sources or the transport from on shore to off shore was not successfully captured. In SJVAB, the model had good performance in simulating different chemical compounds in the Fresno and Arvin areas. However, enhanced concentrations of O3, NOx, HNO3 and PAN near dairy farms were significantly underestimated in the model. Negative biases also exist for O3 and HNO3 near oil fields, suggesting larger uncertainties associated with these emission sources. While the model simulated the total NOy mixing ratios reasonably well, the prediction for partitioning between individual compounds showed larger uncertainties in the model simulation. Although the fire emissions inventory was updated to include the latest emissions estimates and speciation profiles, our model shows limited improvement in simulating the enhancement of O3, CO, and PAN under fire impact as compared to a previous version of the modeling system. Further improvements in simulating fire emissions, especially the timing and the plume injection heights, are desired in order to better simulate the impact of fires.
Keywords: Ozone; Carbon monoxide; Reactive nitrogen; San Joaquin valley; South coast air basin; Wildfires;

Particulate pollution transport episodes from Eurasia to a remote region of northeast Mediterranean by E. Triantafyllou; M. Giamarelou; E. Bossioli; P. Zarmpas; C. Theodosi; C. Matsoukas; M. Tombrou; N. Mihalopoulos; G. Biskos (45-52).
Long-range transportation of air pollutants from industrial and urban environments can significantly affect the quality of the air in remote regions. In this study, we investigate episodes of particulate transport (PT) from Eurasia to the remote environment of Northeastern Mediterranean, i.e., the region of the North Aegean Sea (NAS), during the summer when the synoptic Etesian wind conditions prevail. A temporary monitoring station was set up at a remote region on the island of Lemnos, which is located at the center of the NAS at a distance of ca. 250 km from the continent. Measurements of the aerosol particle size distributions, the total number and mass concentrations, as well as the chemical composition of the particles were conducted from 27 August to 10 September 2011. During this period, the wind speeds were high (typically higher than 5.5 ms−1) with a direction that mostly ranged from north to northeast (68% frequency). Winds having direction ranging from northwest to south were less frequent (7% frequency), while the rest of the cases were characterized as calm (i.e., wind speeds less than 1 m s−1; 25% frequency). Seven PT episodes were observed during the sampling period. When the wind direction was northeastern we observed up to a six-fold increase in particle number concentration of nucleation mode, while the peak size of the particles decreased from 100 to 20 nm. Interestingly, the nucleation-mode particles grew from ca. 15 to 25 nm with rates of ca. 9.0 nm h−1, which are representative of polluted areas. Analysis of the chemical composition of particle samples collected on filters during the PT episodes shows that the concentration of sulfates and nitrates increased by ca. 60%, while the OC/EC ratio increased by ca. 22% compared to the rest of the sampling period. Back-trajectory analysis for the period during the episodes shows that the air masses arriving at the station passed over the greater Istanbul area and the Black Sea 9 to 12 h before reaching our station. These observations provide strong evidence that the air quality in the remote region of the NAS can be significantly affected by the transportation of particulate pollution during the summer period, having potentially important effects upon human health and climate in the region.
Keywords: Air pollution; Long-range transport; Aerosol particle concentrations; Particle size distributions; Particle chemical composition;

Interpretation of satellite retrievals of PM2.5 over the southern African Interior by Melanie A. Kneen; David J. Lary; William A. Harrison; Harold J. Annegarn; Tom H. Brikowski (53-64).
A case study is presented for using an unsupervised classification (Self-Organizing Map) of a global PM2.5 data product assembled from satellite retrievals (SeaWIFS, MODIS Terra and MODIS Aqua) and ground observations. The PM2.5 data products are available, on a daily basis, from August 1997 to the present, with 10 km resolutions and global coverage. In this study, a sub-set of the PM2.5 retrievals (collected over the southern African Interior) has been averaged over ten-day intervals for a period of ten years. These averaged sub-sets have been clustered using self-organizing maps to generate spatial and seasonal “PM2.5 climates” and air quality interpretations over southern Africa. Results are an indirect validation of the satellite based data product against available regional ground-based and airborne studies. The final PM2.5 aerosol climatology shows that the data product provides credible PM2.5 estimates for a region that is lacking routine aerosol monitoring data.Display Omitted
Keywords: Regional air pollution; PM2.5 particulate matter; Aerosol retrievals; Aerosol climatology; SeaWIFS; MODIS;

Air quality simulation of NOX over the tropical coastal city Chennai in southern India with FLEXPART-WRF by Srikanth Madala; K.B.R.R. Hari Prasad; C.V. Srinivas; A.N.V. Satyanarayana (65-81).
Chennai is a rapidly growing metropolitan coastal city in southern India with several major sources of pollution. The complex coastal meteorology influences the pollutant transport in different seasons. In this study, the air quality pattern in Chennai with respect of NOX over different seasons are simulated with FLEXPART-WRF Lagrangian Particle Dispersion Model (LPDM) considering release inventory of industrial, vehicular and domestic sources of pollution from seven different locations in Chennai. The meteorological fields for dispersion calculation are simulated using Advanced Research WRF (ARW) mesoscale model at a high resolution (3 km). Air quality data in the study region available at six different places are used for comparing model outputs over 12 days in each season (winter, pre-monsoon, monsoon and post-monsoon). The Hanna diffusion scheme in FLEXPART-WRF is modified with new seasonal empirical turbulent intensity relationships derived as a function of atmospheric stability from turbulence data. Simulated concentrations are evaluated by varying the diffusion schemes (Hanna, modified Hanna) in FLEXPART and the planetary boundary layer (PBL) schemes [YSU, ACM2 and MYNN2] in ARW. Simulations revealed distinct seasonal variation of dispersion patterns of NOX due to seasonal flow-field variation in the study region. It is found that, the new turbulence intensity relationships provide better comparisons for concentrations of NOX relative to the default Hanna relationship. Further, simulations using ACM2 PBL significantly reduced the negative bias and errors in concentration due to capturing the flow-field and other meteorological variables well. The study demonstrates the utility of FLEXPART for air quality modeling in the coastal city.
Keywords: Air quality; FLEXPART-WRF; Planetary boundary layer; Coastal region;

Indoor environmental quality in French dwellings and building characteristics by Sarka Langer; Olivier Ramalho; Mickaël Derbez; Jacques Ribéron; Severine Kirchner; Corinne Mandin (82-91).
A national survey on indoor environmental quality covering 567 residences in mainland France was performed during 2003–2005. The measured parameters were temperature, relative humidity, CO2, and the indoor air pollutants: fourteen individual volatile organic compounds (VOC), four aldehydes and particulate matter PM10 and PM2.5. The measured indoor concentrations were analyzed for correlations with the building characteristics: type of dwelling, period of construction, dwelling location, type of ventilation system, building material, attached garage and retrofitting. The median night time air exchange rate (AER) for all dwellings was 0.44 h−1. The night time AER was higher in apartments (median = 0.49 h−1) than in single-family houses (median = 0.41 h−1). Concentration of formaldehyde was approximately 30% higher in dwellings built after 1990 compared with older ones; it was higher in dwellings with mechanical ventilation and in concrete buildings. The VOC concentrations depended on the building characteristics to various extents. The sampling season influenced the majority of the indoor climate parameters and the concentrations of the air pollutants to a higher degree than the building characteristics. Multivariate linear regression models revealed that the indoor–outdoor difference in specific humidity, a proxy for number of occupants and their indoor activities, remained a significant predictor for most gaseous and particulate air pollutants. The other strong predictors were outdoor concentration, smoking, attached garage and AER (in descending order).
Keywords: Indoor air quality; Building characteristics; Sampling season; Air exchange rate; Organic compounds; Particles;

Identification of products formed during the heterogeneous nitration and ozonation of polycyclic aromatic hydrocarbons by Richard E. Cochran; Haewoo Jeong; Shokouh Haddadi; Rebeka Fisseha Derseh; Alexandra Gowan; Josef Beránek; Alena Kubátová (92-103).
The 3- and 4-ring polycyclic aromatic hydrocarbons (PAHs) are the most abundant of PAHs in air particulate matter (PM). Thus we have investigated heterogeneous oxidation of 3- and 4-ring PAHs in a small-scale flow reactor using quartz filter as a support. Four representative PAHs, anthracene, phenanthrene, pyrene, and fluoranthene, were exposed to either NO2, O3 or NO2+O3 (NO3/N2O5) with a goal to identify and attempt quantification of major product distribution. A combination of gas chromatography with mass spectrometry (GC–MS) with/without derivatization and liquid chromatography with high resolution MS (LC-HRMS) was used for identification. For the first time, a comprehensive characterization of a broad range of products enabled identifying ketone/diketone, aldehyde, hydroxyl, and carboxylic acid PAH derivatives. Exposure to NO3/N2O5 (formed by reacting NO2 with O3, a more powerful reactant than either O3 or NO2) produced additional compounds not observed with either oxidant alone. Multiple isomers of nitrofluoranthene and, for the first time, nitrophenanthrene were identified. In addition hydroxy-nitro-PAH derivatives were observed for the reaction of anthracene with NO3/N2O5. Monitoring of specific common ions such as those of 176 and 205 m/z attributed to carbonyl phenanthrene and deprotonated phenanthrene ions respectively was shown to be a useful tool for identification of multiple pyrene oxidation products.Display Omitted
Keywords: Heterogeneous PAH oxidation; Product identification; Flow reactor; High resolution mass spectrometry;

PM chemical composition and oxidative potential of the soluble fraction of particles at two sites in the urban area of Milan, Northern Italy by Maria Grazia Perrone; Jun Zhou; Mery Malandrino; Giorgia Sangiorgi; Cristiana Rizzi; Luca Ferrero; Josef Dommen; Ezio Bolzacchini (104-113).
Recent epidemiological evidence support the hypothesis that health effects from inhalation of air particles are governed by more than just particle mass, since specific chemical components have been identified as important contributors to mortality and hospitality admissions.We studied the chemical composition and the oxidative potential (OP) of total suspended particle (TSP) samples from Milan at two sites with different traffic loads: a site in the low emission zone (LEZ) and a traffic site (TR) outside. Two a-cellular assays; dithiothreitol (OPDTT) and 2′,7' dichlorofluorescin (OPDCFH) were used to characterize the OP of the soluble fraction of particles.TSP samples from LEZ showed significantly lower concentrations of traffic-related chemical components compared to TR. The decrease in the concentrations from TR to LEZ was maximum for EC, with a LEZ/TR ratio of 0.64 (±0.18), and a significant reduction (p < 0.01) was also observed for PAHs (LEZ/TR = 0.73 ± 0.16), elements (Mn, Cu, Zn, Cd, Pb: LEZ/TR ranged between 0.64 and 0.82), OC (LEZ/TR = 0.85 ± 0.12) and NH4 + (LEZ/TR = 0.92 ± 0.07).OP measures, expressed as OP/m3 or OP/mg, were comparable between sites both for OPDTT and OPDCFH, thus not showing any significant impact of local traffic on OP values at sites. OPDTT and OPDCFH showed contrasting seasonal and daily trends, indicating that the two a-cellular assays gave complementary information on the OP of particles in Milan. The two OP assays resulted to be sensitive to different chemical properties of PM samples. OPDTT correlated positively only with Global Radiation (Spearman's rs = 0.38, p < 0.05), which could be considered as a proxy for high concentrations of secondary oxidizing organics, while OPDCFH was related to various PM chemical species, mainly correlated with total mass (rs = 0.65; p < 0.01), elements (e.g. Zn, rs = 0.67; As, rs = 0.65; p < 0.01) and the sum of sulfate and nitrate (rs = 0.63; p < 0.01), a proxy for secondary aerosol.
Keywords: Particulate matter; Chemical speciation; Urban area; Redox activity; DTT; DCFH;

Chemical characterization and mass closure of PM10 and PM2.5 at an urban site in Karachi – Pakistan by Imran Shahid; Magdalena Kistler; Azam Mukhtar; Badar M. Ghauri; Carlos Ramirez-Santa Cruz; Heidi Bauer; Hans Puxbaum (114-123).
A mass balance method is applied to assess main source contributions to PM2.5 and PM10 levels in Karachi. Carbonaceous species (elemental carbon, organic carbon, carbonate carbon), soluble ions (Ca++, Mg++, Na+, K+, NH4 +, Cl , NO3 , SO4 ), saccharides (levoglucosan, galactosan, mannosan, sucrose, fructose, glucose, arabitol and mannitol) were determined in atmospheric fine (PM2.5) and coarse (PM10) aerosol samples collected under pre-monsoon conditions (March–April 2009) at an urban site in Karachi (Pakistan). The concentrations of PM2.5 and PM10 were found to be 75 μg/m3 and 437 μg/m3 respectively. The large difference between PM10 and PM2.5 originated predominantly from mineral dust. “Calcareous dust” and „siliceous dust” were the over all dominating material in PM, with 46% contribution to PM2.5 and 78% to PM10–2.5. Combustion particles and secondary organics (EC + OM) comprised 23% of PM2.5 and 6% of PM10–2.5. EC, as well as OC ambient levels were higher (59% and 56%) in PM10–2.5 than in PM2.5. Biomass burning contributed about 3% to PM2.5, and had a share of about 13% of “EC + OM” in PM2.5. The impact of bioaerosol (fungal spores) was minor and had a share of 1 and 2% of the OC in the PM2.5 and PM10–2.5 size fractions. In case of secondary inorganic aerosols, ammonium sulphate (NH4)2SO4 contributes 4.4% to PM2.5 and no detectable quantity were found in fraction PM10–2.5. The sea salt contribution is about 2% both to PM2.5 and PM10–2.5.
Keywords: Particulate matter; Biomass burning; Aerosol characterization; Urban pollution;

A consistent modeling framework with nested global and regional chemical transport models (CTMs) is used to separate and quantitatively assess the relative contributions to projections of future U.S. ozone pollution from the effects of emissions changes, climate change, long-range transport (LRT) of pollutants, and differences in modeling design. After incorporating dynamic lateral boundary conditions (LBCs) from a global CTM, a regional CTM's representation of present-day U.S. ozone pollution is notably improved, especially relative to results from the regional CTM with fixed LBCs or from the global CTM alone. This nested system of global and regional CTMs projects substantial surface ozone trends for the 2050's: 6–10 ppb decreases under the ‘clean’ A1B scenario and ∼15 ppb increases under the ‘dirty’ A1Fi scenario. Among the total trends of future ozone, regional emissions changes dominate, contributing negative 25–60% in A1B and positive 30–45% in A1Fi. Comparatively, climate change contributes positive 10–30%, while LRT effects through changing chemical LBCs account for positive 15–20% in both scenarios, suggesting introducing dynamic LBCs could influence projections of the U.S. future ozone pollution with a magnitude comparable to effects of climate change alone. The contribution to future ozone projections due to differences in modeling design, including model formulations, emissions treatments, and other factors between the global and the nested regional CTMs, is regionally dependent, ranging from negative 20% to positive 25%. It is shown that the model discrepancies for present-day simulations between global and regional CTMs can propagate into future U.S. ozone projections systematically but nonlinearly, especially in California and the Southeast. Therefore in addition to representations of emissions change and climate change, accurate treatment of LBCs for the regional CTM is essential for projecting the future U.S. ozone pollution.
Keywords: Regional climate-air quality modeling; Future US ozone projections; Dynamic lateral boundary conditions; Model discrepancies propagation;

Extreme ozone events: Tail behavior of the surface ozone distribution over the U.S. by Pakawat Phalitnonkiat; Wenxiu Sun; Mircea Dan Grigoriu; Peter Hess; Gennady Samorodnitsky (134-146).
The ground level ozone concentration over the continental United States is analyzed from the point of view of modern Extreme Value Theory using ozone data from the Clean Air Status and Trends Network (CASTNET) at 25 measurement sites. At each site the data is analyzed separately for two time periods (1992–2002 and 2003–2013) approximately separated by the NOX SIP call. The Generalized Pareto Distribution is fit to extremes of the ozone concentration by using a combination of maximum likelihood estimates (MLEs) and Hill estimates. The data is appropriately transformed prior to extreme value analysis and data in the right tail is separated from that in the middle part of the distribution. This analysis is compared to current approaches by using synthetic data. Under a variety of conditions the procedure using the MLE approach is likely to underestimate the tail of the distribution. The analysis of the CASTNET ozone data shows that at some locations the ozone probability distribution is not exponentially bounded, and thus can be characterized as heavy tailed, and that at other locations this distribution is not heavy and is bounded to the right so that the ozone concentration is bounded for any return period. The tails of the distribution of ozone concentration become heavier following the NOX SIP call at most of the sites with heavy tails prior to this call.
Keywords: Extremes; EVT; Hill estimator; GPD; Ozone; Air pollution;

Dust aerosols are an important component of the climate system and a challenge to incorporate into weather and climate models. Information on the location and magnitude of dust emission remains a key information gap to inform model development. Inadequate surface observations ensure that satellite data remain the primary source of this information over extensive and remote desert regions. Here, we develop estimates of the relative magnitude of active dust emission over the Sahara desert based on data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Utilising the unique vertical profile of aerosol characteristics provided by CALIOP our algorithm identifies emission from aerosol extinction and lidar backscatter in the near surface layers. From the long-term CALIOP archive of day and night-time orbits over 2006–13 we construct coarse resolution maps of a new dust emission index (DEI) for the Sahara desert during the peak summer dust season (June to September). The spatial structure of DEI indicates highest emission over a broad zone focused on the border regions of Southern Algeria, Northern Mali and northwest Niger, displaced substantially (∼7°) to the east of the mean maximum in satellite-derived aerosol optical depth. In this region night-time emission exceeds that during the day. The DEI maps substantially corroborate recently derived dust source frequency count maps based on back-tracking plumes in high temporal resolution SEVIRI imagery. As such, a convergence of evidence from multiple satellite data sources using independent methods provides an increasingly robust picture of Saharan dust emission sources. Various caveats are considered. As such, quantitative estimates of dust emission may require a synergistic combined multi-sensor analysis.
Keywords: Sahara; Dust; Aerosol; Preferential sources; CALIOP; Lidar;

Anthracene and pyrene photolysis kinetics in aqueous, organic, and mixed aqueous-organic phases by Jarod N. Grossman; Adam P. Stern; Makena L. Kirich; Tara F. Kahan (158-164).
Condensed phases in the atmosphere, such as cloud droplets and aerosols, often contain both water and organic matter (OM). Reactivity can differ significantly between aqueous and organic phases. We have measured photolysis kinetics of the polycyclic aromatic hydrocarbons (PAHs) anthracene and pyrene in several organic solvents and in water, as well as in miscible and phase-separated aqueous-organic mixtures at atmospherically-relevant wavelengths. Photolysis rate constants generally increased with increasing solvent polarity; photolysis of both PAHs was more than ten times faster in water than in octanol. Local polarity had a much greater effect on PAH photolysis kinetics than changes in PAH absorptivity or singlet oxygen concentrations. Photolysis kinetics in homogeneous aqueous-organic mixtures varied monotonically with2 OM volume fraction. Kinetics in immiscible (phase-separated) solutions were more complex, with different dependences on OM content observed in stagnant and turbulent solutions. Our results suggest that OM could greatly affect the photochemical lifetimes of PAHs in atmospheric condensed phases such as aerosols, even if the OM does not itself absorb photons.Display Omitted
Keywords: Photochemistry; Sea surface microlayer; Particulate matter; Core–shell; Dissolved organic matter;

Multi-phase (gaseous, particulate and rain) samples were collected simultaneously for the first time at a high-elevation mountain site in China during March to May 2009. The site, located in the free troposphere, is used to investigate the gas-particle partitioning, precipitation scavenging of polycyclic aromatic hydrocarbons (PAHs). The total measured concentrations of 15 USEPA PAHs varied from 2.67 to 137.00 ng/m3 (average of 24.10 ng/m3). Partitioning of PAHs between gaseous and particulate phases (log Kp) was well-correlated with the supercooled liquid vapor pressure in all samples (R2 = 0.730–0.985), but the slopes (−0.154 to −0.424) were significantly deviated from the expected value of −1. The observed Kp values were better predicted by the Dual model than the Koa model, pointing to the importance of soot carbon for PAH partitioning. The scavenging ratios varied among the individual PAH compound, ranged from 4.47 × 103 (BaA) to 1.02 × 105 (ACY). Particle scavenging was the dominant removal process, accounting over 75% of the total scavenging (except for BbF) for individual PAH compound. Relationships of Wp-particle fraction, Wp-supercooled vapor pressure were analyzed. The results suggested the particle scavenging by precipitation is less efficient for PAHs with higher molecular weights, while more volatile PAHs with lower molecular weights deposited on larger atmospheric particles were scavenged more efficiently. The efficiency of Wp was found to be increased with rain intensity. For gas scavenging, the dissolution and adsorption mechanisms shift their relative importance with different supercooled vapor pressure.
Keywords: PAHs; Free troposphere; Multi-phase sampling; Gas-particle partitioning; Precipitation scavenging;

Observations of atmospheric monoaromatic hydrocarbons at urban, semi-urban and forest environments in the Amazon region by Sarah L. Paralovo; Guilherme C. Borillo; Cybelli G.G. Barbosa; Ana Flavia L. Godoi; Carlos I. Yamamoto; Rodrigo A.F. de Souza; Rita V. Andreoli; Patrícia S. Costa; Gerson P. Almeida; Antonio O. Manzi; Christopher Pöhlker; Ana M. Yáñez-Serrano; Jürgen Kesselmeier; Ricardo H.M. Godoi (175-184).
The Amazon region is one of the most significant natural ecosystems on the planet. Of special interest as a major study area is the interface between the forest and Manaus city, a state capital in Brazil embedded in the heart of the Amazon forest. In view of the interactions between natural and anthropogenic processes, an integrated experiment was conducted measuring the concentrations of the volatile organic compounds (VOCs) benzene, toluene, ethylbenzene and meta, ortho, para-xylene (known as BTEX), all of them regarded as pollutants with harmful effects on human health and vegetation and acting also as important precursors of tropospheric ozone. Furthermore, these compounds also take part in the formation of secondary organic aerosols, which can influence the pattern of cloud formation, and thus the regional water cycle and climate. The samples were collected in 2012/2013 at three different sites: (i) The Amazon Tall Tower Observatory (ATTO), a pristine rain forest region in the central Amazon Basin; (ii) Manacapuru, a semi-urban site located southwest and downwind of Manaus as a preview of the Green Ocean Amazon Experiment (GoAmazon 2014/15); and (iii) the city of Manaus (distributed over three sites). Results indicate that there is an increase in pollutant concentrations with increasing proximity to urban areas. For instance, the benzene concentration ranges were 0.237–19.6 (Manaus), 0.036–0.948 (Manacapuru) and 0.018–0.313 μg m−3 (ATTO). Toluene ranges were 0.700–832 (Manaus), 0.091–2.75 μg m−3 (Manacapuru) and 0.011–4.93 (ATTO). For ethylbenzene, they were 0.165–447 (Manaus), 0.018–1.20 μg m−3 (Manacapuru) and 0.047–0.401 (ATTO). Some indication was found for toluene to be released from the forest. No significant difference was found between the BTEX levels measured in the dry season and the wet seasons. Furthermore, it was observed that, in general, the city of Manaus seems to be less impacted by these pollutants than other cities in Brazil and in other countries, near the coastline or on the continent. A risk analysis for the health of Manaus' population was performed and indicated that the measured concentrations posed a risk for development of chronic diseases and cancer for the population of Manaus.
Keywords: BTEX; Manaus; The Amazon Tall Tower Observatory (ATTO); Amazon forest; Green ocean Amazon experiment (GoAmazon); Health risk;

Simulating aerosols over Arabian Peninsula with CHIMERE: Sensitivity to soil, surface parameters and anthropogenic emission inventories by S. Naseema Beegum; Imen Gherboudj; Naira Chaouch; Florian Couvidat; Laurent Menut; Hosni Ghedira (185-197).
A three dimensional chemistry transport model, CHIMERE, was used to simulate the aerosol optical depths (AOD) over the Arabian Peninsula desert with an offline coupling of Weather Research and Forecasting (WRF) model. The simulations were undertaken with: (i) different horizontal and vertical configurations, (ii) new datasets derived for soil/surface properties, and (iii) EDGAR-HTAP anthropogenic emissions inventories. The model performance evaluations were assessed: (i) qualitatively using MODIS (Moderate-Resolution Imaging Spectroradiometer) deep blue (DB) AOD data for the two local dust events of August 6th and 23rd (2013), and (ii) quantitatively using AERONET (Aerosol Robotic Network) AOD observations, CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) aerosol extinction profiles, and AOD simulations from various forecast models. The model results were observed to be highly sensitive to erodibility and aerodynamic surface roughness length. The use of new datasets on soil erodibility, derived from the MODIS reflectance, and aerodynamic surface roughness length (z0), derived from the ERA-Interim datasets, significantly improved the simulation results. Simulations with the global EDGAR-HTAP anthropogenic emission inventories brought the simulated AOD values closer to the observations. Performance testing of the adapted model for the Arabian Peninsula domain with improved datasets showed good agreement between AERONET AOD measurements and CHIMERE simulations, where the correlation coefficient (R) is 0.6. Higher values of the correlation coefficients and slopes were observed for the dusty periods compared to the non-dusty periods.
Keywords: CHIMERE; Chemistry transport model; Aerosol optical depth; EDGAR-HTAP emissions; Surface roughness length; Soil erodibility;

The paper was aimed at assessing the health risk in the populations of three Silesian cities: Bielsko-Biała, Częstochowa and Katowice exposed to the inhalation intake of cadmium, nickel and arsenic present in airborne particulate matter. In order to establish how the exposure parameters affects risk a probabilistic risk assessment framework was used. The risk model was based on the results of the annual measurements of As, Cd and Ni concentrations in PM2.5 and the sets of data on the concentrations of those elements in PM10 collected by the Voivodship Inspectorate of Environmental Protection over 2012–2013 period. The risk was calculated as an incremental lifetime risk of cancer (ILCR) in particular age groups (infants, children, adults) following Monte Carlo approach. With the aim of depicting the effect the variability of exposure parameters exerts on the risk, the initial parameters of the risk model: metals concentrations, its infiltration into indoor environment, exposure duration, exposure frequency, lung deposition efficiency, daily lung ventilation and body weight were modeled as random variables. The distribution of inhalation cancer risk due to exposure to ambient metals concentrations was LN (1.80 × 10−6 ± 2.89 × 10−6) and LN (6.17 × 10−7 ± 1.08 × 10−6) for PM2.5 and PM10-bound metals respectively and did not exceed the permissible limit of the acceptable risk. The highest probability of contracting cancer was observed for Katowice residents exposed to PM2.5 – LN (2.01 × 10−6 ± 3.24 × 10−6). Across the tested age groups adults were approximately one order of magnitude at higher risk compared to infants. Sensitivity analysis showed that exposure duration (ED) and body weight (BW) were the two variables, which contributed the most to the ILCR.
Keywords: Cancer risk; Monte Carlo; Particulate matter; Metals; Silesia region; Probabilistic assessment;

Valley heat deficit as a bulk measure of wintertime particulate air pollution in the Arve River Valley by Charles Chemel; Gabriele Arduini; Chantal Staquet; Yann Largeron; Dominique Legain; Diane Tzanos; Alexandre Paci (208-215).
Urbanized valleys are particularly vulnerable to particulate air pollution during the winter, when ground-based stable layers or cold-air pools persist over the valley floor. We examine whether the temporal variability of PM10 concentration in the section of the Arve River Valley between Cluses and Servoz in the French Alps can be explained by the temporal variability of the valley heat deficit, a bulk measure of atmospheric stability within the valley. We do this on the basis of temperature profile and ground-based PM10 concentration data collected during wintertime with a temporal resolution of 1 h or finer, as part of the Passy-2015 field campaign conducted around Passy in this section of valley. The valley heat deficit was highly correlated with PM10 concentration on a daily time scale. The hourly variability of PM10 concentrations was more complex and cannot be explained solely by the hourly variability of the valley heat deficit. The interplay of the diurnal cycles of emissions and local dynamics is demonstrated and a drainage mechanism for observed nocturnal dilution of near-surface PM10 concentrations is proposed.
Keywords: PM10; Temperature inversions; Drainage flows;

Analytical dispersion model for the chain of primary and secondary air pollutants released from point source by Laurynas Juodis; Vitold Filistovič; Evaldas Maceika; Vidmantas Remeikis (216-226).
An analytical model for dispersion of air pollutants released from a point source forming a secondary pollutant (e.g. chemical transformation or parent-daughter radionuclide chain) is formulated considering the constant wind speed and eddy diffusivities as an explicit function of downwind distance from the source in Cauchy (reflection-deposition type) boundary conditions. The dispersion of pollutants has been investigated by using the Gaussian plume dispersion parameters σ y and σ z instead of the diffusivity parameters K y and K z . For primary pollutant it was proposed to use the derived dry deposition factor instead of the source depletion alternative. An analytical solution for steady-state two-dimensional pollutant transport in the atmosphere is presented. Derived formulas include dependency from effective release height, gravitational and dry deposition velocities of primary and secondary pollutants, advection, surface roughness length and empirical dispersion parameters σ y and σ z . Demonstration of analytical solution application is provided by calculation of 135Xe and 135C air activity concentrations and the applicability of the model for the solution of atmospheric pollution transport problems.
Keywords: Atmospheric dispersion; Analytical model; Point source; Secondary pollutant; Contaminant transport; Gaussian plume solution;

Trimethylamine (TMA) enters the atmosphere from a variety of sources and is a ubiquitous atmospheric organic base. The atmospheric reaction mechanism of TMA with key atmospheric oxidants is important to predict its distribution and environmental behavior in the particle phase. While previous studies have extensively focused on the production of particle amine salts (i.e. trimethylamine-N-oxide (TMAO)) using chamber experiments, the atmospheric behavior of TMAO in the environment is still poorly understood. Ambient fine particulate matter (PM2.5) was collected at two sampling sites in Beijing from March 10 to May 10, 2012. We analyzed the samples for water-soluble ions, crystal metals, TMA, and TMAO. Water-soluble ions (e.g. SO 4 2 − , NO 3 − , NH 4 + ), TMA, and TMAO were measured using ion chromatography, while crystal metal (e.g. Al, Fe, Mn) in PM2.5 was quantified by inductively coupled plasma mass spectrometry (ICP-MS). Two dust storms (DS) occurred during the sampling period on March 28 and April 28. Mineral dust impacted PM2.5 mass and composition greatly during dust storm days, as it contributed approximately 1.2–4.0 times greater on dust storm days versus non-dust storm days. We found TMAO concentrations were highly associated with aluminum in PM2.5. Further, we applied the density functional theory (DFT) method to confirm that aluminum plays a catalytic effect in the reaction of TMA with ozone (O3). Our work improves understanding of the effect of crystal metals on secondary aliphatic amine aerosol formation in the atmosphere.
Keywords: Trimethylamine-N-oxide; PM2.5; Dust storm; Density functional theory;

Characterization of water-soluble organic matter in urban aerosol by 1H-NMR spectroscopy by Marie-Cecile G. Chalbot; Priyanka Chitranshi; Gonçalo Gamboa da Costa; Erik Pollock; Ilias G. Kavouras (235-245).
The functional and 13C isotopic compositions of water-soluble organic carbon (WSOC) in atmospheric aerosol were determined by nuclear magnetic resonance (1H-NMR) and isotope ratio mass spectrometry (IRMS) in an urban location in the Southern Mississippi Valley. The origin of WSOC was resolved using the functional distribution of organic hydrogen, δ13C ratio, and positive matrix factorization (PMF). Three factors were retained based on NMR spectral bins loadings. Two factors (factors 1 and 3) demonstrated strong associations with the aliphatic region in the NMR spectra and levoglucosan resonances. Differences between the two factors included the abundance of the aromatic functional group for factor 1, indicating fresh emissions and, for factor 3, the presence of resonances attributed to secondary ammonium nitrate and low δ13C ratio values that are indicative of secondary organic aerosol. Factors 1 and 3 added 0.89 and 1.08 μgC m−3, respectively, with the highest contribution in the summer and fall. Factor 2 retained resonances consistent with saccharides and was attributed to pollen particles. Its contribution to WSOC varied from 0.22 μgC m−3 in winter to 1.04 μgC m−3 in spring.Display Omitted
Keywords: Organic aerosol; Biomass burning; NMR; Secondary organic aerosol;

This study aims to develop adaptive neuro-fuzzy inference system (ANFIS) for forecasting of daily air pollution concentrations of five air pollutants [sulphur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3) and particular matters (PM10)] in the atmosphere of a Megacity (Howrah). Air pollution in the city (Howrah) is rising in parallel with the economics and thus observing, forecasting and controlling the air pollution becomes increasingly important due to the health impact. ANFIS serve as a basis for constructing a set of fuzzy IF-THEN rules, with appropriate membership functions to generate the stipulated input–output pairs. The ANFIS model predictor considers the value of meteorological factors (pressure, temperature, relative humidity, dew point, visibility, wind speed, and precipitation) and previous day's pollutant concentration in different combinations as the inputs to predict the 1-day advance and same day air pollution concentration. The concentration value of five air pollutants and seven meteorological parameters of the Howrah city during the period 2009 to 2011 were used for development of the ANFIS model. Collinearity tests were conducted to eliminate the redundant input variables. A forward selection (FS) method is used for selecting the different subsets of input variables. Application of collinearity tests and FS techniques reduces the numbers of input variables and subsets which helps in reducing the computational cost and time. The performances of the models were evaluated on the basis of four statistical indices (coefficient of determination, normalized mean square error, index of agreement, and fractional bias).Display Omitted
Keywords: ANFIS model; Air quality forecasting; Forward search; Collinearity;

Icing severity forecast algorithm under both subjective and objective parameters uncertainties by Feng Zhang; Zhen Huang; Huiju Yao; Weihao Zhai; Tongfeng Gao (263-267).
Based on the traditional deterministic methods for estimating the airplane icing severity, a probabilistic method under considering subjective and objective parameters uncertainties is proposed. In that method, all meteorological observation data are described as random variables, then Monte Carlo method is performed to forecast the probability of airplane icing. In the process of forecasting the airplane icing severity level, the membership function is introduced to describe the subjective uncertainty. Finally, the generalized probabilistic solution formula of estimating the airplane icing severity level is derived. The proposed probabilistic model and solutions for forecasting the airplane icing severity level are proved to be reasonable and applicable by a real airplane icing case.
Keywords: Icing forecast model; Icing severity level; Probabilistic forecast; Membership function; Monte Carlo simulation method;

Distribution of bacteria in inhalable particles and its implications for health risks in kindergarten children in Hong Kong by Wenjing Deng; Yemao Chai; Huiying Lin; Winnie W.M. So; K.W.K. Ho; A.K.Y. Tsui; R.K.S. Wong (268-275).
Health risks in children caused by bacteria in indoor environments have attracted much attention in recent years. There are many harmful bacteria, and children have greater health risks than adults in the same environment. To investigate the association between children's health risks and the distribution and concentration of bacteria in particulate matter smaller than 2.5 μm in indoor and outdoor air at three kindergartens in Hong Kong, quantitative polymerase chain reaction was used to determine the concentration of bacteria, and the terminal restriction fragment length polymorphism method targeting 16S ribosomal RNA genes was used to predict the phylogenetic airborne bacterial community structures. The bacterial concentrations indoors were higher than those outdoors in the three kindergartens, but no obvious differences were found (P > 0.05). Statistical analysis showed that the different schools had significantly different concentrations (P < 0.05). The abundance of bacteria in schools downtown (in Kowloon) was the greatest, reaching 3.3 × 103 to 4.95 × 104 cells per m3. However, the results showed no significant differences between the microbial populations obtained indoors and those obtained outdoors. The dominant genera were very similar among the six samples. Our results suggest that the majority of the inhalable bacteria were harmless to humans. Only a small fraction of microbial pathogens were identified, and their relative abundance appeared to increase as the concentration of particulate matter pollution increased. Analysis of these bacteria can give important clues regarding the exposure of kindergarten children to bacteria in indoor and outdoor air.The bacterial concentrations indoors were higher than those outdoors at all three kindergartens. The higher bacterial concentration was a result of more human activities in a limited area. Our results suggest that the majority of the inhalable bacteria were harmless to humans. Only a few microbial allergens and pathogens were identified and the concentrations were very low.Display Omitted
Keywords: Bacteria; Inhalable particles; Health risks; Kindergarten children;

Resolving detailed molecular structures in complex organic mixtures and modeling their secondary organic aerosol formation by Kevin A.S. Goodman-Rendall; Yang R. Zhuang; Aviv Amirav; Arthur W.H. Chan (276-285).
Characterization of unresolved complex mixtures (UCMs) remains an ongoing challenge towards developing detailed and accurate inputs for modeling secondary organic aerosol (SOA) formation. Traditional techniques based on gas chromatography/electron impact-mass spectrometry induce excessive fragmentation, making it difficult to speciate and quantify isomers precisely. The goal of this study is to identify individual organic isomers by gas chromatography/mass spectrometry with supersonic molecular beam (SMB-GC/MS, also known as GC/MS with Cold EI) and to incorporate speciated isomers into an SOA model that accounts for the specific structures elucidated. Two samples containing atmospherically relevant UCMs are analyzed. The relative isomer distributions exhibit remarkably consistent trends across a wide range of carbon numbers. Constitutional isomers of different alkanes are speciated and individually quantified as linear, branched – for the first time by position of branching – multiply branched, or unsaturated – by degree of ring substitution and number of rings. Relative amounts of exact molecular structures are used as input parameters in an SOA box model to study the effects of molecular structures on SOA yields and volatility evolution. Highly substituted cyclic, mono-substituted cyclic, and linear species have the highest SOA yields while branched alkanes formed the least SOA. The rate of functionalization of a representative UCM is found to be in agreement with current volatility basis set (VBS) parameterizations based on detailed knowledge of composition and known oxidation mechanisms, confirming the validity of VBS parameters currently used in air quality models.
Keywords: Kinetic modeling; Structural elucidation; Aerosol formation from complex mixtures; Supersonic molecular beam; Cold EI;

An algorithm able to identify and characterize episodes of different aerosol types above sea surfaces of the greater Mediterranean basin (GMB), including the Black Sea and the Atlantic Ocean off the coasts of Iberia and northwest Africa, is presented in this study. Based on this algorithm, five types of intense (strong and extreme) aerosol episodes in the GMB are identified and characterized using daily aerosol optical properties from satellite measurements, namely MODIS-Terra, Earth Probe (EP)-TOMS and OMI-Aura. These aerosol episodes are: (i) biomass-burning/urban-industrial (BU), (ii) desert dust (DD), (iii) dust/sea-salt (DSS), (iv) mixed (MX) and (v) undetermined (UN). The identification and characterization is made with our algorithm using a variety of aerosol properties, namely aerosol optical depth (AOD), Ångström exponent (α), fine fraction (FF), effective radius (reff) and Aerosol Index (AI).During the study period (2000–2007), the most frequent aerosol episodes are DD, observed primarily in the western and central Mediterranean Sea, and off the northern African coasts, 7 times/year for strong episodes and 4 times/year for extreme ones, on average. The DD episodes yield 40% of all types of strong aerosol episodes in the study region, while they account for 71.5% of all extreme episodes. The frequency of occurrence of strong episodes exhibits specific geographical patterns, for example the BU are mostly observed along the coasts of southern Europe and off the Atlantic coasts of Portugal, the MX episodes off the Spanish Mediterranean coast and over the Adriatic and northern Aegean Sea, while the DSS ones over the western and central Mediterranean Sea. On the other hand, the extreme episodes for all but DD aerosol display more patchy spatial patterns. The strong episodes exhibit AOD at 550 nm as high as 1.6 in the southernmost parts of central and eastern Mediterranean Sea, which rise up to 5 for the extreme, mainly DD and DSS, episodes. Although more than 90% of all aerosol episodes last 1 day, there are few cases, mainly extreme DD episodes, which last up to 4 days. Independently of their type, the Mediterranean aerosol episodes occur more frequently in spring (strong and extreme episodes) and summer (strong episodes) and most rarely during winter. A significant year by year variability of Mediterranean aerosol episodes has been identified, more in terms of their frequency than intensity. An analysis of 5-day back trajectories for the most extreme episodes provides confidence on the obtained results of the algorithm, based on the revealed origin and track of air masses causing the episodes. The 25 and 6% of all strong and extreme episodes, respectively, are MX, thus highlighting the co-existence of different aerosol types in the greater Mediterranean. The intensity of both MX and DSS episodes exhibits similar patterns to those of DD strong ones, indicating that desert dust is a determinant factor for the intensity of aerosol episodes in the Mediterranean, including DSS and MX episodes.
Keywords: Aerosol episodes; Aerosol type; Dust; Sea-salt; Frequency; Intensity; Satellites; Mediterranean;