Atmospheric Environment (v.119, #C)

The distribution, pollution level, sources and health risk of Hg, As, Cd, Cu, Cr, Ni, Mn, Fe, Pb, Sb and Zn in urban street dust were investigated. X-ray diffraction analysis of dust samples shows that the mineralogy of airborne dusts is dominated by calcite, dolomite and quartz. The total concentration of trace elements across the sampling sites ranged from 36.8 to 234.3 mg kg−1 for Pb, 0.004–4.504 mg kg−1 for Hg, 160.9–778.3 mg kg−1 for Zn, 245–652 mg kg−1 for Mn, 39.4–117.9 mg kg−1 for Ni, 31.6–105.9 mg kg−1 for Cr, 49.8–232.5 mg kg−1 for Cu, 5.3–8.6 mg kg−1 for As, 0.31–0.85 mg kg−1 for Cd, 0.76–9.45 mg kg−1 for Sb, and 16,300–24,900 mg kg−1 for Fe. The enrichment factor results reveal the following order: Cu > Hg > Sb > Zn > Pb > Ni > Cr > As > Mn > Cd > Fe. Among the measured elements, the highest mobility factor belongs to Pb (79.2%), Hg (74.6%), Zn (64.1%) and Mn (56.4%). According to the calculated Hazard Quotient (HQ) and Hazard Index (HI), special attention should be paid to Hg, Pb, Zn, and Mn in the street dusts of Shiraz. Multivariate statistics indicate that traffic, natural soil particles and industrial activities are likely to be the main sources of heavy metals in Shiraz street dusts.
Keywords: Street dust; Potentially toxic metals; Modified BCR sequential extraction; Human health risk; Shiraz;

Seasonal contribution of mineral dust and other major components to particulate matter at two remote sites in Central Asia by Justin P. Miller-Schulze; Martin Shafer; James J. Schauer; Jongbae Heo; Paul A. Solomon; Jeffrey Lantz; Maria Artamonova; Boris Chen; Sanjar Imashev; Leonid Sverdlik; Greg Carmichael; Jeff DeMinter (11-20).
Dust storms are significant contributors to ambient levels of particulate matter (PM) in many areas of the world. Central Asia, an area that is relatively understudied in this regard, is anticipated to be affected by dust storms due to its proximity to several major deserts that are in and generally surround Central Asia (e.g., the Aral Sea region, the Taklimakan desert in Western China). To investigate the relative importance of mineral dust (dust specifically composed of soil related minerals and oxides) in Central Asia, PM10 and PM2.5, and by difference, coarse particles (particles with diameters between 2.5 and 10 μm) were measured at two sites, Bishkek and Lidar Station Teplokluchenka (Lidar), in the Kyrgyz Republic. Samples were collected every other day from July 2008 to July 2009. Daily samples were analyzed for mass and organic and elemental carbon. Samples were also composited on a bi-weekly basis and analyzed for elemental constituents and ionic components. In addition, samples collected on days with relatively high and low PM concentrations were analyzed before, and separately, from the biweekly composites to investigate the chemical differences between the episodic events. Data from the episodic samples were averaged into the composited averages. Using the elemental component data, several observational models were examined to estimate the contribution of mineral dust to ambient PM levels. A mass balance was also conducted.Results indicate that at both sites, mineral dust (as approximated by the “dust oxide” model) and organic matter (OM) were the dominant contributors to PM10 and PM2.5. Mineral dust was a more significant contributor to the coarse PM (PM10-2.5) during high event samples at both sites, although the relative contribution is greater at the Lidar site (average ± standard deviation = 42 ± 29%) as compared with the Bishkek site (26 ± 16%). Principal Components Analysis (PCA) was performed using data from both sites, and PCA indicated that mineral dust explained the majority of the variance in PM concentrations, and that the major apportioned factors of PM10 and PM2.5 were chemically similar between sites.
Keywords: Mineral dust; Dust storms; Particulate matter;

Under the National Ambient Air Quality Standard released in 2012 (NAAQS-2012), Beijing began to publicize hourly Air Quality Index as well as real time concentrations of 6 pollutants in its web platform to provide detailed information for air quality assessment from 2013. In this study, hourly air quality monitoring data from May 2014 to April 2015 were collected for all 35 monitoring stations in Beijing to analyze the temporal and spatial variations of air pollutants and air quality. It is found that in spatial pattern, the air qualities in southern and northern Beijing are totally different. The association between heavy pollution concentrations and wind situations suggested that neighboring area's air quality has an important role in the air quality of Beijing combining with air quality attainment rates in all 35 monitoring stations and northern China. For temporal variations, late night and early morning are the most polluted time while afternoon is the least polluted time for all pollutants except O3 with most polluted time in afternoon. Summer time in Beijing has the best air quality while winter time has the worst air quality coinciding with the heating season in the winter.
Keywords: Air quality; Air pollution; PM2.5; PM10; O3; SO2; NO2; CO;

A new methodology to assess the performance and uncertainty of source apportionment models in intercomparison exercises by C.A. Belis; D. Pernigotti; F. Karagulian; G. Pirovano; B.R. Larsen; M. Gerboles; P.K. Hopke (35-44).
A new methodology to assess source apportionment model performance in intercomparison exercises, encompassing the preparation of real-world and synthetic datasets and the evaluation of the source apportionment results reported by participants, is described. The evaluation consists of three types of tests: complementary tests, preliminary tests, and performance tests. The complementary tests provide summary information about the source apportionment results as a whole. The preliminary tests check whether source/factors belong to a given source category. Three types of indicators: Pearson correlation (Pearson), standardized identity distance (SID), and weighted difference (WD) are used to test factor/source chemical profiles, while factor/source time series and contribution-to-species values are tested only using the Pearson. The performance tests, based on international standards for proficiency testing, are targeted at evaluating whether the reported biases in the quantification of the factor/source contribution estimates (SCEs) and uncertainties are consistent with previously established quality standards in a fitness-for-purpose approach. Moreover, the consistency of the SCE time series is evaluated using a variant of the RMSE normalised by the reference standard uncertainty.The described methodology facilitates a thorough evaluation of the source apportionment output. The new indicator to compare source or factor profiles presented in this study (SID) is more robust and provides additional information compared to the existing ones.
Keywords: Source apportionment; Receptor models; Intercomparison exercise; Model quality objectives; Testing dataset; Particulate matter;

Observations of tropospheric NO2 using ground based MAX-DOAS and OMI measurements during the Shanghai World Expo 2010 by K.L. Chan; A. Hartl; Y.F. Lam; P.H. Xie; W.Q. Liu; H.M. Cheung; J. Lampel; D. Pöhler; A. Li; J. Xu; H.J. Zhou; Z. Ning; M.O. Wenig (45-58).
During the Shanghai World Expo 2010 ground based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of tropospheric nitrogen dioxide (NO2) were performed to investigate the effects of emission control measures during that time. In this study we measured NO2 using four identical MAX-DOAS instruments in Shanghai from April 2009 to November 2010. We combined our MAX-DOAS data, the Ozone Monitoring Instrument (OMI) satellite observations and meteorological information from the National Centers for Environmental Prediction final reanalysis data (NCEP FNL) in order to investigate the spatial distribution of NO2 over Shanghai and the effects of emission control measures during the Expo. In general, the comparison of cloud screened MAX-DOAS data and OMI observations are in good correlation (Pearson correlation coefficient between 0.67 and 0.93 for the four measurement stations). In addition, we compared the MAX-DOAS and OMI NO2 data from the Shanghai Expo in 2010 to the same time of the year in 2009. The results show that the NO2 columns were reduced up to ∼ 30% in the area of central Shanghai during the Expo but no significant reduction of NO2 levels was found in the nearby industrial area. The overall NO2 reduction from May, July and September 2010 ranged from 7.5% to 14.5%, which is comparable to observations in previous studies. Our results revealed that the NO2 reduction was mainly achieved by emission control policies on transportation sources in the city rather than the controls from nearby provinces.
Keywords: MAX-DOAS; NO2; OMI satellite; Shanghai Expo;

Impact of wildfires on size-resolved aerosol composition at a coastal California site by L.C. Maudlin; Z. Wang; H.H. Jonsson; A. Sorooshian (59-68).
Size-resolved aerosol composition measurements were conducted at a coastal site in central California during the Nucleation in California Experiment (NiCE) between July and August of 2013. The site is just east of ship and marine emission sources and is also influenced by continental pollution and wildfires, such as those near the California–Oregon border which occurred near the end of NiCE. Two micro-orifice uniform deposit impactors (MOUDIs) were used, and water-soluble and elemental compositions were measured. The five most abundant water-soluble species (in decreasing order) were chloride, sodium, non-sea salt (nss) sulfate, ammonium, and nitrate. During wildfire periods, nss K mass concentrations were not enhanced as strongly as other species in the sub-micrometer stages and even decreased in the super-micrometer stages; species other than nss K are more reliable tracers for biomass burning in this region. Chloride levels were reduced in the fire sets likely due to chloride depletion by inorganic and organic acids that exhibited elevated levels in transported plumes. During wildfire periods, the mass size distribution of most dicarboxylic acids changed from unimodal to bimodal with peaks in the 0.32 μm and 1.0–1.8 μm stages. Furthermore, sulfate's peak concentration shifted from the 0.32 μm to 0.56 μm stage, and nitrate also shifted to larger sizes (1.0 μm to 1.8–3.2 μm stages). Mass concentrations of numerous soil tracer species (e.g., Si, Fe) were strongly enhanced in samples influenced by wildfires, especially in the sub-micrometer range. Airborne cloud water data confirm that soil species were associated with fire plumes transported south along the coast. In the absence of biomass burning, cloud condensation nuclei (CCN) composition is dominated by nss sulfate and ammonium, and the water-soluble organic fraction is dominated by methanesulfonate, whereas for the samples influenced by wildfires, ammonium becomes the dominant overall species, and oxalate is the most abundant organic species.
Keywords: MOUDI; Biomass burning; Marine; Aerosol; Composition; Soil; Cloud water;

The air quality is influenced by the potential effects of meteorology at meso- and synoptic scales. While local weather and mixing layer dynamics mainly drive the dispersion of sources at small scales, long-range transports affect the movements of air masses over regional, transboundary and even continental scales. Long-range transport may advect polluted air masses from hot-spots by increasing the levels of pollution at nearby or remote locations or may further raise air pollution levels where external air masses originate from other hot-spots. Therefore, the knowledge of ground-wind circulation and potential long-range transports is fundamental not only to evaluate how local or external sources may affect the air quality at a receptor site but also to quantify it. This review is focussed on establishing the relationships among PM2.5 sources, meteorological condition and air mass origin in the Po Valley, which is one of the most polluted areas in Europe. We have chosen the results from a recent study carried out in Venice (Eastern Po Valley) and have analysed them using different statistical approaches to understand the influence of external and local contribution of PM2.5 sources. External contributions were evaluated by applying Trajectory Statistical Methods (TSMs) based on back-trajectory analysis including (i) back-trajectories cluster analysis, (ii) potential source contribution function (PSCF) and (iii) concentration weighted trajectory (CWT). Furthermore, the relationships between the source contributions and ground-wind circulation patterns were investigated by using (iv) cluster analysis on wind data and (v) conditional probability function (CPF). Finally, local source contribution have been estimated by applying the Lenschow' approach.In summary, the integrated approach of different techniques has successfully identified both local and external sources of particulate matter pollution in a European hot-spot affected by the worst air quality.
Keywords: PM2.5; Local and external contributions; Meteorology-based methods;

Characteristics of atmospheric aerosol optical depth variation in China during 1993–2012 by Xiaofeng Xu; Jinhuan Qiu; Xiangao Xia; Ling Sun; Min Min (82-94).
The long-term variations of atmospheric aerosol optical depth (AOD) over 14 first-class solar radiation stations in China during 1993–2012 are studied. The AOD at 750 nm wavelength is retrieved with the hourly accumulated direct solar radiation by using a broadband extinction method. The retrievals are validated in comparison with AERONET (Aerosol Robotic Network) and MODIS (Moderate Resolution Imaging Spectroradiometer) AOD products. For the comparison with AERONET, the correlation coefficient (R), mean bias error (MBE) and root mean square error (RMSE) of the monthly mean AODs are respectively 0.848, 0.029 and 0.101. Based on the statistical analysis, the monthly, seasonal and annual AOD variation characteristics are categorized as follow: (1) There are three major types of the seasonal AOD variations, which shows the largest seasonal averaged AOD appearing in spring, summer and winter. The smallest seasonal averaged AOD appears mostly in autumn. (2) Beijing and Guangzhou show a significant decreasing trend of the yearly AOD, while an increasing tendency appears in Zhengzhou, Shanghai, Kunming, Kashi and Wuhan. Although no significant variation trends are found, some fluctuations appear in the 20-year period in other cities. (3) The 20-year mean AOD ranges from 0.135 (Lhasa) to 0.678 (Zhengzhou). The aerosol hygroscopic growth contributes a lot to AOD in major cities in the eastern part of China, while not in most cities in the western part. A simple correction method is applied for enhancing the relationship of AOD and PM2.5 concentration.
Keywords: Direct solar radiation; Aerosol optical depth; Relative humidity;

The impact of haze-fog on surface temperature, flow pattern, pollutant dispersion and pedestrian thermal comfort are investigated using computational fluid dynamics (CFD) approach based on a three-dimensional street canyon model under different haze-fog conditions. In this study, light extinction coefficient (K ex ) is adopted to represent haze-fog pollution level. Numerical simulations are performed for different K ex values at four representative time events (1000 LST, 1300 LST, 1600 LST and 2000 LST). The numerical results suggest that the surface temperature is strongly affected by the haze-fog condition. Surface heating induced by the solar radiation is enhanced by haze-fog, as higher surface temperature is observed under thicker haze-fog condition. Moreover, the temperature difference between sunlit and shadow surfaces is reduced, while that for the two shadow surfaces is slightly increased. Therefore, the surface temperature among street canyon facets becomes more evenly distributed under heavy haze-fog conditions. In addition, flow patterns are considerably altered by different haze-fog conditions, especially for the afternoon (1600 LST) case, in which thermal-driven flow has opposite direction as that of the wind-driven flow direction. Consequently, pollutants such as vehicular emissions will accumulate at pedestrian level, and pedestrian thermal comfort may lower under thicker haze-fog condition.
Keywords: Street canyon; Haze-fog; CFD; Diurnal variation; Flow pattern; Thermal environment;

Evaluation of model-predicted hazardous air pollutants (HAPs) near a mid-sized U.S. airport by Lakshmi Pradeepa Vennam; William Vizuete; Saravanan Arunachalam (107-117).
Accurate modeling of aircraft-emitted pollutants in the vicinity of airports is essential to study the impact on local air quality and to answer policy and health-impact related issues. To quantify air quality impacts of airport-related hazardous air pollutants (HAPs), we carried out a fine-scale (4 × 4 km horizontal resolution) Community Multiscale Air Quality model (CMAQ) model simulation at the T.F. Green airport in Providence (PVD), Rhode Island. We considered temporally and spatially resolved aircraft emissions from the new Aviation Environmental Design Tool (AEDT). These model predictions were then evaluated with observations from a field campaign focused on assessing HAPs near the PVD airport. The annual normalized mean error (NME) was in the range of 36–70% normalized mean error for all HAPs except for acrolein (>70%). The addition of highly resolved aircraft emissions showed only marginally incremental improvements in performance (1–2% decrease in NME) of some HAPs (formaldehyde, xylene). When compared to a coarser 36 × 36 km grid resolution, the 4 × 4 km grid resolution did improve performance by up to 5–20% NME for formaldehyde and acetaldehyde. The change in power setting (from traditional International Civil Aviation Organization (ICAO) 7% to observation studies based 4%) doubled the aircraft idling emissions of HAPs, but led to only a 2% decrease in NME. Overall modeled aircraft-attributable contributions are in the range of 0.5–28% near a mid-sized airport grid-cell with maximum impacts seen only within 4–16 km from the airport grid-cell. Comparison of CMAQ predictions with HAP estimates from EPA's National Air Toxics Assessment (NATA) did show similar annual mean concentrations and equally poor performance. Current estimates of HAPs for PVD are a challenge for modeling systems and refinements in our ability to simulate aircraft emissions have made only incremental improvements. Even with unrealistic increases in HAPs aviation emissions the model could not match observed concentrations near the runway airport site. Our results suggest other uncertainties in the modeling system such as meteorology, HAPs chemistry, or other emission sources require increased scrutiny.
Keywords: Aircraft emissions; CMAQ; Formaldehyde; Lower thrust idling emissions; Landing–takeoff;

Dust modeling over Saudi Arabia using WRF-Chem: March 2009 severe dust case by Yongxin Zhang; Yubao Liu; Paul A. Kucera; Badr H. Alharbi; Linlin Pan; Ayman Ghulam (118-130).
This paper documents the performance of the fully coupled WRF-Chem model at 21.6 km and 7.2 km resolution over Saudi Arabia in simulating a severe dust storm event that occurred in March 2009. The comparisons between the model simulations and the observed AOD at the Solar Village AERONET site and the MODIS measurements show that WRF-Chem satisfactorily resolves the arrival, evolution and spatial distributions of the dust storm over Saudi Arabia especially for the fine domain at 7.2 km resolution. The model simulated surface meteorological variables at Riyadh Airport, Hafr Al-Batin Airport, Dammam Airport and Gassim Airport follow the observations in terms of magnitude and temporal evolution although model biases such as deficiencies in simulating the amplitude of diurnal cycles are noted. Higher resolution and shorter initialization time improve the model performance in aerosol optical depth but for surface variables shorter initialization time improves correlation while higher horizontal resolution improves mean biases to some extent. The simulated dust plume is mainly confined between the surface and the 5-km height, with the peak concentrations located in the lowest 500 m. The vertical extent of the dust plume shows gradual decreases during the simulation period when averaged over the entire fine domain and an area centered around Solar Village, and also varies in accordance with the development and decay of the boundary layer.
Keywords: Dust modeling; WRF-Chem; Saudi Arabia;

Evaluation of the performance of different atmospheric chemical transport models and inter-comparison of nitrogen and sulphur deposition estimates for the UK by A.J. Dore; D.C. Carslaw; C. Braban; M. Cain; C. Chemel; C. Conolly; R.G. Derwent; S.J. Griffiths; J. Hall; G. Hayman; S. Lawrence; S.E. Metcalfe; A. Redington; D. Simpson; M.A. Sutton; P. Sutton; Y.S. Tang; M. Vieno; M. Werner; J.D. Whyatt (131-143).
An evaluation has been made of a number of contrasting atmospheric chemical transport models, of varying complexity, applied to estimate sulphur and nitrogen deposition in the UK. The models were evaluated by comparison with annually averaged measurements of gas, aerosol and precipitation concentrations from the national monitoring networks. The models were evaluated in relation to performance criteria. They were generally able to satisfy a criterion of ‘fitness for purpose’ that at least 50% of modelled concentrations should be within a factor of two of measured values. The second criterion, that the magnitude of the normalised mean bias should be less than 20%, was not always satisfied. Considering known uncertainties in measurement techniques, this criterion may be too strict. Overall, simpler models were able to give a good representation of measured gas concentrations whilst the use of dynamic meteorology, and complex photo-chemical reactions resulted in a generally better representation of measured aerosol and precipitation concentrations by more complex models.The models were compared graphically by plotting maps and cross-country transects of wet and dry deposition as well as calculating budgets of total wet and dry deposition to the UK for sulphur, oxidised nitrogen and reduced nitrogen. The total deposition to the UK varied by ±22–36% amongst the different models depending on the deposition component. At a local scale estimates of both dry and wet deposition for individual 5 km × 5 km model grid squares were found to vary between the different models by up to a factor of 4.
Keywords: Nitrogen; Sulphur; Inter-comparison; Acid deposition; Eutrophication; Atmospheric chemical transport model; Model evaluation;

Secondary organic aerosol (SOA) formation from aromatic hydrocarbon photooxidation is highly sensitive to NO concentration. The instantaneous effect of NO on SOA formation from m-xylene photooxidation is investigated in this work by data mining 10 years of aromatic hydrocarbon chamber experiments conducted in the UC Riverside/CE-CERT chamber. First, the effect of sub-ppb NO concentrations on SOA formation is explored. The relationship of SOA growth rate to 1) NO2/NO ratio; 2) instantaneous HC/NO; 3) absolute NO concentration; 4) peroxy radical reaction branching ratio and 5) hydroxyl radical concentration are illustrated. Second, continuous and stepwise NO, NO2 and HONO injection are applied to m-xylene photooxidation experiments to simulate continuous NO sources in an urban area. The influence of these reaction scenarios on radical concentrations and SOA formation is explored. [HO2 •]/[RO2 •] shows a strong correlation with SOA yields in addition to [•OH]/[HO2 •], [•OH], [HO2 •] and [RO2 •]. Enhanced SOA formation is observed when low NO levels (<1 ppb) are artificially maintained by continuous or step-wise injection; consistent with earlier research, SOA formation is observed to be suppressed by large initial NO injections. It is proposed that NO at sub-ppb level enhances •OH formation increasing HO2 • and RO2 • and therefore promoting SOA formation. Further, two NO pathways (one promoting and one suppressing SOA formation) and one extremely low NO phase (NO “free”) are used to demonstrate the evolution of NO impact on SOA formation during photooxidation. This study implies that SOA yields from aromatic hydrocarbon and low NOx photooxidation is previously underestimated due to differences between traditional environmental chamber experiments and atmospheric reactivity.
Keywords: Aromatic hydrocarbon; NOx; Secondary organic aerosol; Kinetic modeling; Radicals;

Sulphuric acid and aerosol particle production in the vicinity of an oil refinery by Nina Sarnela; Tuija Jokinen; Tuomo Nieminen; Katrianne Lehtipalo; Heikki Junninen; Juha Kangasluoma; Jani Hakala; Risto Taipale; Siegfried Schobesberger; Mikko Sipilä; Kai Larnimaa; Henrik Westerholm; Juha Heijari; Veli-Matti Kerminen; Tuukka Petäjä; Markku Kulmala (156-166).
In this paper we introduce in-situ observations of trace gases, aerosol particles and their precursors in the vicinity of an oil refinery and industrial area in Kilpilahti, Southern Finland. We conducted a one-month measurement campaign near the oil refinery during summertime when the sulphur dioxide concentrations at the site are typically the highest. The source areas around the measurement location were divided into three sectors: oil refinery area, industrial area and non-industrial area. The atmospheric concentrations of aerosols and trace gases showed a large temporal variability, when exposed to the different source areas. The median sulphur dioxide concentrations for the oil refinery, industrial and non-industrial area were 1.88 ppbv, 0.75 ppbv and 0.38 ppbv, respectively, and the corresponding sulphuric acid concentrations were 11.5 × 106 molecules/cm3, 4.4 × 106 molecules/cm3 and 1.3 × 106 molecules/cm3. The observed concentrations were similar to what have been measured in urban or industrial sites. The ratio between sulphuric acid and sulphur dioxide was the highest when the air mass was coming from the oil refinery. The correlation between the sulphuric acid and 1–2 nm particle concentrations was significant, but the composition of the particles remained unknown as no neutral sulphuric acid clusters were detected with the mass spectrometer. Only a few new particle formation events were observed during the measurement period, and during these events a large fraction of the particle growth could be explained by sulphuric acid condensation.
Keywords: Sulphuric acid; Atmospheric measurements; New particle formation; Oil refinery; Sulphur dioxide; Mass spectometry;

A new corona discharge (CD) based ion source was developed for a commercial high-resolution time-of-flight chemical ionization mass spectrometer (HRToF-CIMS) (Aerodyne Research Inc.) to measure both gaseous sulfuric acid (H2SO4) and aerosol sulfate after thermal desorption. Nitrate core ions (NO3 ) were used as reagent ions and were generated by a negative discharge in zero air followed by addition of excess nitrogen dioxide (NO2) to convert primary ions and hydroxyl radicals (OH) into NO3 ions and nitric acid (HNO3). The CD-HRToF-CIMS showed no detectable interference from hundreds parts per billion by volume (ppbv) of sulfur dioxide (SO2). Unlike the atmospheric pressure ionization (API) ToF-CIMS, the CD ion source was integrated onto the ion–molecule reaction (IMR) chamber and which made it possible to measure aerosol sulfate by coupling to a filter inlet for gases and aerosols (FIGAERO). Moreover, compared with a quadrupole-based mass spectrometer, the desired HSO4 signal was detected by its exact mass of m/z 96.960, which was well resolved from the potential interferences of HCO3 ⋅(H2O)2 (m/z 97.014) and O⋅H2O⋅HNO3 (m/z 97.002). In this work, using laboratory-generated standards the CD-HRToF-CIMS was demonstrated to be able to detect as low as 3.1 × 105 molecules cm−3 gaseous H2SO4 and 0.5 μg m−3 ammonium sulfate based on 10-s integration time and two times of the baseline noise. The CD ion source had the advantages of low cost and a simple but robust structure. Since the system was non-radioactive and did not require corrosive HNO3 gas, it can be readily field deployed. The CD-HRToF-CIMS can be a powerful tool for both field and laboratory studies of aerosol formation mechanism and the chemical processes that were critical to understand the evolution of aerosols in the atmosphere.
Keywords: Sulfuric acid; Sulfate; Corona discharge; HRToF-CIMS; Hydroxyl radicals;

Pulmonary inflammatory effects of source-oriented particulate matter from California's San Joaquin Valley by Laurel E. Plummer; Christopher M. Carosino; Keith J. Bein; Yongjing Zhao; Neil Willits; Suzette Smiley-Jewell; Anthony S. Wexler; Kent E. Pinkerton (174-181).
The EPA regulates ambient particulate matter (PM) because substantial associations have been established between PM and health impacts. Presently, regulatory compliance involves broad control of PM emission sources based on mass concentration rather than chemical composition, although PM toxicity is likely to vary depending upon PM physicochemical properties. The overall objective of this study was to help inform source-specific PM emission control regulations. For the first time, source-oriented PM was collected from the atmosphere in Fresno, CA, onto 38 source/size substrates. Mice were exposed via oropharyngeal aspiration to equivalent mass doses [50 μg] of two size fractions: ultrafine (Dp < 0.17 μm) and submicron fine (0.17 < Dp < 1 μm) during summer and winter seasons. At 24 h post-exposure, cellular and biochemical indicators of pulmonary inflammation were evaluated in the bronchoalveolar lavage fluid. Significant inflammatory responses were elicited by vehicle, regional background, and cooking PM sources that were dependent on season and particle size. This is the first study of source-oriented toxicity of atmospheric PM and supports source-specific emissions control strategies.
Keywords: Air pollution; PM; Fresno; Ultrafine; Submicron fine;

Characterization of gaseous and semi-volatile organic compounds emitted from field burning of rice straw by Nguyen Thi Kim Oanh; Aungsiri Tipayarom; Thuy Ly Bich; Danutawat Tipayarom; Christopher D. Simpson; David Hardie; L.-J. Sally Liu (182-191).
Rice straw (RS) field burning, commonly practiced in Asia, produces large amounts of toxic air pollutants but has not been comprehensively characterized. This study conducted field and laboratory measurements for gaseous pollutants and semi-VOCs (16 PAHs, 16 chlorinated pesticides and 14 PCBs) in RS burning smoke to determine emission factors (EFs) and emission concentration profiles. Paddy burning experiments were done following common practices used by farmers in Southeast Asia and EFs were estimated using the carbon balance method. Laboratory hood experiments simulated burning of dry RS (moisture content ∼ 5%) and normal RS (moisture ∼ 23–30%). Semi-VOCs were analyzed separately in the particulate (PM) and gas phases, and the levels measured in smoke were compared with those in the paddy background and in general ambient air to identify enrichment of the compounds. Lower EFs of all pollutants were obtained for hood burning dry RS as compared to hood burning normal RS. EFs of all detected pollutants in the field burning were higher than hood burning. The EFs of field burning in mg kg−1 RS were 760 for benzene, 230 for toluene, 510 for SO2, 490 for NO2, 260 for total PAHs (88% in gas phase), 0.11 for total PCBs (59% in gas phase) and 0.23 for OCPs (62% in gas phase). The EF of aldehydes determined in the hood experiment was 80–150 mg kg−1 RS. As compared to ambient air, RS smoke had significant enrichment of light PAHs, fluoranthene in PM and acenaphthylene in gas phase. Smoke had a higher proportion of benzene in BTEX than roadside air. Levels of PCBs, OCPs and aldehydes were higher in the burning smoke compared to ambient air, but there was no significant enrichment of particular compounds. This study provides appropriate ranges of EFs for developing emission inventory of RS spread field burning.
Keywords: Rice straw burning; Emission factor; Concentration profile; Gaseous pollutants; PAHs; Chlorinated compounds;

Biosphere–atmosphere exchange of methane in India as influenced by multiple environmental changes during 1901–2010 by Kamaljit Banger; Hanqin Tian; Bowen Zhang; Chaoqun Lu; Wei Ren; Bo Tao (192-200).
It is highly uncertain on how human and natural environmental factors have altered methane (CH4) emissions from terrestrial ecosystems in India. Using a process-based, Dynamic Land Ecosystem Model (DLEM) driven by climate, land cover and land use change (LCLUC), atmospheric nitrogen deposition (NDEP), atmospheric carbon dioxide (CO2) concentration, and tropospheric ozone (O3) pollution, we examined CH4 flux from terrestrial in India during 1901–2010. The DLEM simulations have shown that total CH4 flux over the country ranged from 2.9 Tg C year−1 to 6.5 Tg C year−1 with significant inter-annual variations driven by climate during 1901–2010. Contemporary CH4 emissions have primarily occurred from rice fields (3.9 ± 0.9 Tg C year−1) while wetlands contributed to 2.1 ± 0.6 Tg C year−1 in the 2000s. During 1901–2010, total CH4 emission from the terrestrial biosphere has increased by ∼2.1 Tg C year−1. LCLUC has increased CH4 emissions by 2.3 Tg C year−1 primarily due to increase in the rice-based cropping systems as well as irrigation expansion during the study period. Elevated CO2 concentration stimulated plant biomass production in both rice fields and wetlands that increased CH4 emissions by 0.7 Tg C year−1. On the contrary, climate change decreased net CH4 emissions by ∼1.2 Tg C year−1 due to negative effects of extreme high temperature as well as occurrences of extreme drought events on plant growth. Our study suggests that LCLUC and elevated CO2 concentration have significantly increased CH4 emissions from terrestrial ecosystems in India.
Keywords: Methane; Climate; India; Carbon dioxide; Land cover;

The effectiveness of air pollution regulations and controls are evaluated based on measured air pollutant concentrations. Air pollution levels, however, are highly sensitive to both emissions and meteorological fluctuations. Therefore, an assessment of the change in air pollutant levels due to emissions controls must account for these meteorological fluctuations. Two empirical methods to quantify the impact of meteorology on pollutant levels are discussed and applied to the 13-year time period between 2000 and 2012 in Atlanta, GA. The methods employ Kolmogorov–Zurbenko filters and linear regressions to detrended pollutant signals into long-term, seasonal, weekly, short-term, and white-noise components. The methods differ in how changes in weekly and holiday emissions are accounted for. Both can provide meteorological adjustments on a daily basis for future use in acute health analyses.The meteorological impact on daily signals of ozone, NO x , CO, SO2, PM2.5, and PM species are quantified. Analyses show that the substantial decreases in seasonal averages of NO x and SO2 correspond with controls implemented in the metropolitan Atlanta area. Detrending allows for the impacts of some controls to be observed with averaging times of as little as 3 months. Annual average concentrations of NO x , SO2, and CO have all fallen by at least 50% since 2000. Reductions in NO x levels, however, do not lead to uniform reductions in ozone. While average detrended summer average maximum daily average 8 h ozone (MDA8h O3) levels fell by 4% (2.2 ± 2 ppb) between 2000 and 2012, winter averages have increased by 12% (3.8 ± 1.4 ppb), providing further evidence that high ozone levels are NO x -limited and lower ozone concentrations are NO x -inhibited. High ozone days (with MDA8h O3 greater than 60 ppb) decreased both in number and in magnitude over the study period.
Keywords: Meteorological detrending; Air pollution trends; KZ filtering; Accountability;

PM10 concentrations exceed the guidelines in some Swedish cities and the limit values will likely be further reduced in the future. In order to gain more knowledge of emission factors for road traffic and concentrations of PM10 and PM2.5, existing monitoring stations in two cities, Gothenburg and Umeå, with international E-road thoroughfares, were complemented with some PM2.5 measurements. Emission factors for PM10 and PM2.5 were estimated using NOX as a tracer. Monitoring data from kerbside and urban background sites in Gothenburg during 2006–2010 and in Umeå during 2006–2012 were used. NOX emissions were estimated from the traffic flow and emission factors calculated from the HBEFA3.1 model. PM2.5 constitutes the finer part of PM10. Emissions of the coarser part of PM10 (PM10–PM2.5) are suppressed when roads are wet and show a maximum during spring when the roads dry up and studded tyres are still used. Less than 1% of the road wear caused by studded tyres give rise to airborne PM2.5–10 particles. The NOX emission factors decrease with time in the used model, due to the renewal of the vehicle fleet. However, the NOX concentrations resulting from the roads show no clear trend. The air dispersion is an important factor controlling the PM concentration near the road. The dispersion has a minimum in winter and during midnight. The average street level concentrations of PM10 and PM2.5 in Gothenburg were 21 ± 20 and 8 ± 6 μg m−3 respectively, which is 36% and 22% higher than the urban background concentrations. Despite the four times lower traffic flow in Umeå compared to Gothenburg, the average particle concentrations were very similar; 21 ± 31 and 7 ± 5 μg m−3 for PM10 and PM2.5 respectively. These concentrations were, however, 108% and 55% higher than the urban background concentrations in Umeå. The emission factors for PM10 decreased with time, and the average factor was 0.06 g km−1 vehichle−1. The emission factors for PM2.5 are very uncertain due to the small increments in PM2.5 concentration at the thoroughfares, and were on average 0.02 g km−1 vehichle−1.
Keywords: PM10; PM2.5; Air dispersion; Gothenburg; Umeå; Traffic-related air pollution;

Seasonal variations in atmospheric concentrations and gas–particle partitioning of PCDD/Fs and dioxin-like PCBs around industrial sites in Shanghai, China by Qingqi Die; Zhiqiang Nie; Feng Liu; Yajun Tian; Yanyan Fang; Hefeng Gao; Shulei Tian; Jie He; Qifei Huang (220-227).
Gas and particle phase air samples were collected in summer and winter around industrial sites in Shanghai, China, to allow the concentrations, profiles, and gas–particle partitioning of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) to be determined. The total 2,3,7,8-substituted PCDD/F and dl-PCB toxic equivalent (TEQ) concentrations were 14.2–182 fg TEQ/m3 (mean 56.8 fg TEQ/m3) in summer and 21.9–479 fg TEQ/m3 (mean 145 fg TEQ/m3) in winter. The PCDD/Fs tended to be predominantly in the particulate phase, while the dl-PCBs were predominantly found in the gas phase, and the proportions of all of the PCDD/F and dl-PCB congeners in the particle phase increased as the temperature decreased. The logarithms of the gas–particle partition coefficients correlated well with the subcooled liquid vapor pressures of the PCDD/Fs and dl-PCBs for most of the samples. Gas–particle partitioning of the PCDD/Fs deviated from equilibrium either in summer or winter close to local sources, and the Junge–Pankow model and predictions made using a model based on the octanol–air partition coefficient fitted the measured particulate PCDD/F fractions well, indicating that absorption and adsorption mechanism both contributed to the partitioning process. However, gas–particle equilibrium of the dl-PCBs was reached more easily in winter than in summer. The Junge–Pankow model predictions fitted the dl-PCB data better than did the predictions made using the model based on the octanol–air partition coefficient, indicating that adsorption mechanism made dominated contribution to the partitioning process.
Keywords: PCDD/Fs; dl-PCBs; Seasonal variations; Gas–particle partitioning;

Retrospective source attribution for source-oriented sampling by K.J. Bein; Y. Zhao; A.S. Wexler (228-239).
Previous work successfully implemented a novel system that uses a single particle mass spectrometer to conditionally sample size-segregated, source-oriented particles from the ambient atmosphere in real-time. The underlying hypothesis is that the composition of individual particles is a metric of particle source and thus sampling particles based on composition should be synonymous with sampling based on source. System operation relies on real-time pattern recognition to control the actuation of different ChemVol samplers, where each ChemVol is associated with a unique composition signature. In the current work, a synthesis of data collected during these studies is used in retrospect to reconcile the actual source combinations contributing to the particles collected by each ChemVol. Source attribution is based on correlations between ChemVol sampling periods and coincident wind direction and temporal emissions patterns, coupled to knowledge of single particle composition and surrounding sources. Residential and commercial cooking, vehicular emissions, residential heating and highly processed regional background PM were identified as the major sources. Results show that real-time patterns in single particle mixing state correctly identified specific sources and that these sources were successfully separated into different ChemVols for both summer and winter seasons.Display Omitted
Keywords: Source-oriented sampling; Source attribution; Single particle mass spectrometry; Fresno air quality; Aerosol health effects;

The impact of meteorological forcings on gas phase air pollutants over Europe by Laura Watson; Gwendoline Lacressonnière; Michael Gauss; Magnuz Engardt; Camilla Andersson; Béatrice Josse; Virginie Marécal; Agnes Nyiri; Stefan Sobolowski; Guillaume Siour; Robert Vautard (240-257).
The impact of meteorological forcings on gas phase air pollutants (ozone and nitrogen dioxide) over Europe was studied using four offline chemistry transport models (CTMs) as part of the IMPACT2C project. This study uses long (20- and 30-year) simulations to evaluate the present-day performance of the CTMs, which is a necessary first step before undertaking any analysis of future air quality impacts. Two sets of meteorological forcings were used for each model: reanalysis of past observation data (ERA-Interim) and Global Climate Model (GCM) output. The results for the simulations forced by reanalysis data were assessed in relation to AirBase v7 measurement data, and it was determined that all four models slightly overpredict annual O3 values (mean biases range between 0.7 and 6.6 ppb) and three out of the four models underpredict observed annual NO2 (mean biases range between −3.1 and −5.2 ppb). The simulations forced by climate models result in spatially averaged monthly concentrations of O3 that are generally between 0 and 5 ppb higher than the values obtained from simulations forced by reanalysis data; therefore it was concluded that the use of climate models introduces an additional bias to the results, but this bias tends not to be significant in the majority of cases. The bias in O3 results appears to be correlated mainly to differences in temperature and boundary layer height between the two types of simulations, whereas the less significant bias in NO2 is negatively correlated to temperature and boundary layer height. It is also clear that the selection of chemical boundary conditions is an important factor in determining the variability of O3 model results. These results will be used as a baseline for the interpretation of future work, which will include an analysis of future climate scenarios upon European air quality.
Keywords: Air quality; Ozone; Reanalysis forcings; Global climate model; Chemistry transport model;

Recent work on emissions testing has focused on developing source specific volatility distributions which could be used to improve emissions inventories. One problem about these volatility profiles is that they are evaluated only at one temperature which is usually 298 K. This study uses a simple statistical model to evaluate the temperature dependence of the source-resolved volatility basis set, considering gasoline and diesel vehicle exhaust. The steps involved (a) fitting a distribution to the emissions data (b) evaluating the goodness of fit using a statistical test (c) updating the volatility bins using the Clausius–Clayperon equation; calculating the heats of vaporization of each volatility class using a regression model (d) assessing how the volatility of different VOC classes-Extremely Low Volatile, Low Volatile, Semi-Volatile, Intermediate Volatile and Volatile Organic Compounds – are affected by temperature. The results indicated that there could be significant changes in gas-particle partitioning of these emissions. For diesel exhaust at 298 K, the fractions are 5.4 × 10−4 (ELVOC), 0.074 (LVOC), 0.76 (SVOC), 0.17 (IVOC) and 10−5 (VOC) respectively. Looking at a window of ∓20 K, the partitioning for 278 K is 3 × 10−3 (ELVOC), 0.26 (LVOC), 0.67 (SVOC), 0.07 (IVOC) with no VOC fraction; while at 318 K it is 1.5 × 10−7 (ELVOC), 9 × 10−3 (LVOC), 0.64 (SVOC), 0.35 (IVOC) and 2 × 10−5 (VOC); demonstrating a significant change with temperature. The parameterizations developed in this work could be used to improve motor vehicle emissions inventory models such as MOVES.
Keywords: Volatility basis sets; Temperature; Statistical model;

Mineralogy and geochemistry of atmospheric particulates in western Iran by Hesam Ahmady-Birgani; Hassan Mirnejad; Sadat Feiznia; Ken G. McQueen (262-272).
This study investigates the mineralogy and physico-chemical properties of atmospheric particulates collected at Abadan (southwestern Iran) near the Persian Gulf coast and Urmia (northwestern Iran) during ambient and dust events over 6 months (winter 2011; spring 2012). Particle sizes collected were: TSP (total suspended particulates); PM10 (particulates <10 μm); and PM2.5 (particulates <2.5 μm). Minerals were identified using X-ray diffraction (XRD); particle morphology and composition were examined by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX). Major minerals detected are calcite, quartz, clay minerals and gypsum, with relative abundance related to sampling site, collection period, wind direction, sampling head, and total sample amount. The anomalously high calcite content appears a characteristic feature originated from calcareous soils of the region. SEM observations indicated a wide range of particle morphologies over the 1–50 μm size range, with spherical, platy, cubic, elongate and prismatic shapes and rounding from angular to rounded. Energy dispersive X-ray analysis of TSP samples from both sites for non-dusty periods indicated that the sampled mineral suite contained Al, Mg, Na, Cl, P, S, Ca, K, Fe, Ti, and Si, mostly reflecting calcite, quartz, aluminosilicates, clays, gypsum and halite. Additionally, As, Pb, Zn, Mn, Sc, Nd, W, Ce, La, Ba and Ni were detected in TSP, PM10 and PM2.5 samples collected during dust events.
Keywords: Atmospheric particulates; Physico-chemical properties; Mineralogy and geochemistry; Persian Gulf; Sea of Makran;

Characterization of aerosols in Beijing during severe aerosol loadings by Hao Chen; Tianhai Cheng; Xingfa Gu; Yu Wu (273-281).
Severe aerosol pollutions in China significantly impact radiative forcing of climate at regional and global scales. Until now, the uncertainties in net climate forcing from severe aerosol pollutions in China are substantial, largely due to the lack of detailed knowledge of radiative properties of severe aerosol pollutions. Here the characteristics of aerosols under severe aerosol pollution days (APs) in Beijing are studied by analyzing the ground-based radiance measurements during the period from 2002 to 2014. We show that the mean single scattering albedo (SSA) values increase by 0.03–0.06 (7%) in APs, and the mean asymmetry (ASY) parameter values increase by 0.03–0.04 (6%) for the four wavelengths of 440–1020 nm. The atmospheric forcing of the APs is 2 times higher than that in other days. Contrary to the RF values, the radiative forcing efficiencies in the APs are 38% lower than those in the other days. Larger values of SSA and ASY under APs represent larger presence of more scattering aerosols and irregular-sized aerosols such as dust and non-absorbing fine mode particles. These particles are also verified by the much lower radiative forcing efficiency values. Analyses are applied on the dataset of the APs over Beijing, to group them into four discrete clusters. The two fine-size absorbing aerosols show larger mean atmospheric radiative forcing values (152.5 W/m2 and 184.5 W/m2 respectively) and forcing efficiency values (83.5 W/m2 and 108.5 W/m2 respectively). The non-absorbing aerosols and coarse aerosols exert large planetary cooling (−86.7 W/m2 and −77.3 W/m2) and low atmospheric heating effect.
Keywords: Severe aerosol loading; Optical properties; Radiative forcing; Climate change;

Vertical distribution of airborne bacterial communities in an Asian-dust downwind area, Noto Peninsula by Teruya Maki; Kazutaka Hara; Fumihisa Kobayashi; Yasunori Kurosaki; Makiko Kakikawa; Atsushi Matsuki; Bin Chen; Guangyu Shi; Hiroshi Hasegawa; Yasunobu Iwasaka (282-293).
Bacterial populations transported from ground environments to the atmosphere get dispersed throughout downwind areas and can influence ecosystem dynamics, human health, and climate change. However, the vertical bacterial distribution in the free troposphere was rarely investigated in detail. We collected aerosols at altitudes of 3000 m, 1000 m, and 10 m over the Noto Peninsula, Japan, where the westerly winds carry aerosols from continental and marine areas. During the sampling period on March 10, 2012, the air mass at 3000 m was transported from the Chinese desert region by the westerly winds, and a boundary layer was formed below 2000 m. Pyrosequencing targeting 16S rRNA genes (16S rDNA) revealed that the bacterial community at 3000 m was predominantly composed of terrestrial bacteria, such as Bacillus and Actinobacterium species. In contrast, those at 1000 m and 10 m included marine bacteria belonging to the classes Cyanobacteria and Alphaproteobacteria. The entire 16S rDNA sequences in the clone libraries were identical to those of the terrestrial and marine bacterial species, which originated from the Chinese desert region and the Sea of Japan, respectively. The origins of air masses and meteorological conditions contribute to vertical variations in the bacterial communities in downwind atmosphere.
Keywords: Airborne bacteria; Asian dust; Bioaerosol; Free troposphere; Phylogenetic analysis;

Characteristics of size-fractionated atmospheric metals and water-soluble metals in two typical episodes in Beijing by Qingqing Wang; Yongliang Ma; Jihua Tan; Naijia Zheng; Jingchun Duan; Yele Sun; Kebin He; Yuanxun Zhang (294-303).
The abundance and behaviour of metals and water-soluble metals (V, Cr, Mn, Fe, Cu, Zn, As, Sr, Ag, Cd, Sn, Sb, Ba and Pb) in size-fractionated aerosols were investigated during two typical episodes in Beijing. Water-soluble inorganic ions (Na+, K+, Mg2+, Ca2+, N H 4 + , F, Cl, SO 4 2 − and NO 3 − ) were also measured. Atmospheric metals and water-soluble metals were both found at high levels; for PM2.5, average As, Cr, Cd, Cu, Mn and Pb concentrations were 14.8, 203.3, 2.5, 18.5, 42.6 and 135.3 ng/m3, respectively, and their water-soluble components were 11.1, 1.7, 2.4, 14.5, 19.8 and 97.8 ng/m3, respectively. Daily concentrations of atmospheric metals and water-soluble metals were generally in accordance with particle mass. The highest concentrations of metals and water-soluble metals were generally located in coarse mode and droplet mode, respectively. The lowest mass of metals and water-soluble metals was mostly in Aitken mode. The water solubility of all metals was low in Aitken and coarse modes, indicating that freshly emitted metals have low solubility. Metal water solubility generally increased with the decrease in particle size in the range of 0.26–10 μm. The water solubility of metals for PM10 was: 50% ≤ Cd, As, Sb, Pb; 26% < V, Mn, Cu, Zn and Sr ≤ 50%; others ≤20%. Most metals, water-soluble metals and their water solubility increased when polluted air mass came from the near west, near north-west, south-west and south-east of the mainland, and decreased when clean air mass came from the far north-west and far due south. The influence of dust-storms and clean days on water-soluble metals and size distribution was significant; however, the influence of rainfall was negligible. Aerosols with high concentrations of SO 4 2 − , K+ and N H 4 + might indicate increased potential for human health effects because of their high correlation with water-soluble metals. Industrial emissions contribute substantially to water-soluble metal pollution as water-soluble metals show higher correlation with Cd, Sn, Sb and Pb that are mainly derived from industrial sources.
Keywords: Water-soluble metals; Size-fractionated; Aerosol; Haze; Beijing;

Magnetic response to air pollution recorded by soil and dust-loaded leaves in a changing industrial environment by Liwan Cao; Erwin Appel; Shouyun Hu; Gang Yin; Hai Lin; Wolfgang Rösler (304-313).
Linfen city is one of the World's most polluted cities due to uncontrolled industrial activities of coal combustion releasing huge amounts of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) into the atmosphere. We used soil and leaves as receptors for atmospheric particulate matter to test the efficiency of magnetic approach for assessing and discriminating past and present pollution. The results indicate that strong magnetic particles in topsoil and leaf samples are mainly low-coercivity magnetite, occurring in a larger grain-size range than in background soil, which is helpful to separate anthropogenic and natural sources. Topsoil magnetic signals reflect pollutants, which accumulated over the last decades. Differences in the vertical distribution of magnetic properties between undisturbed and disturbed (cultivated) soil profiles show that the plowing depth is the most important factor for migration of pollutants in cultivated soils. Magnetic susceptibility (MS) values of leaf samples reflect the present state of pollution and can even trace seasonal changes. Spatial maps of MS identify differences of the past and present environmental conditions caused by the shutdown of industrial sites within the last decade. Correlation coefficients between analyzed HM contents (Fe, Cr, Ni, Cu, Pb) and MS values are significantly positive in leaf samples, and still moderate in topsoil samples. Our results demonstrate the practical and economical value of magnetic techniques for pollution assessment, also for the studied case with a complex pollution history, a relatively high magnetic background and disturbing land use.
Keywords: Environmental magnetism; Heavy metal pollution; Atmospheric pollution; Soil; Leaves; Linfen city;

Linkages between pollution and morbidity have been observed in numerous studies. But race/ethnicity has been underemphasized as a modifier of that association, and few studies have tested for a Hispanic Health Paradox in sensitivity to air pollution.Daily asthma, chronic obstructive pulmonary disease (COPD) and congestive heart failure (CHF) hospital admissions in El Paso, Texas were studied in age groups and insurance groups. Daily PM2.5 and NO2 were calculated from pollution monitors and all models adjusted for apparent temperature and wind speed. Conditional logistic regression for the case-crossover design was used for a between-group comparison and for a within-group comparison for Hispanics.Hispanics were at lower risk than non-Hispanic whites and non-Hispanics of other races for NO2-associated admissions, but at greater risk for PM2.5-associated admissions. While Hispanics were generally protected with regards to NO2, Hispanic children (vs. Elderly) faced increased risk for asthma and uninsured Hispanics (vs. Private) faced increased risk for COPD admissions. While Hispanics were at increased risk of PM2.5-associated admissions, certain characteristics heightened their risks: being a Hispanic child (vs. Elderly) for asthma; being a Hispanic with Medicare (vs. Private) for asthma; and being a Hispanic with private insurance (vs. all other insurance types) for CHF. The main effect of pollution on admissions was more significant for asthma and CHF than for COPD, which had the fewest cases.There was heterogeneity in sensitivity to air pollution based on social characteristics and moderate evidence for a Hispanic Health Paradox in sensitivity to NO2.
Keywords: Air pollution; Effect modification; Hispanic Health Paradox; Case-crossover;

We assess the regional and global integrated radiative forcing on 20- and 100-year time horizons caused by a one-year pulse of present day pollution emissions from 10 megacity areas: Los Angeles, Mexico City, New York City, Sao Paulo, Lagos, Cairo, New Delhi, Beijing, Shanghai and Manila. The assessment includes well-mixed greenhouse gases: carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4); and short-lived climate forcers: tropospheric ozone (O3) and fine mode aerosol particles (sulfate, nitrate, black carbon, primary and secondary organic aerosol). All megacities contribute net global warming on both time horizons. Most of the 10 megacity areas exert a net negative effect on their own regional radiation budget that is 10–100 times larger in magnitude than their global radiative effects. Of the cities examined, Beijing, New Delhi, Shanghai and New York contribute most to global warming with values ranging from +0.03 to 0.05 Wm−2yr on short timescales and +0.07–0.10 Wm−2yr on long timescales. Regional net 20-year radiative effects are largest for Mexico City (−0.84 Wm−2yr) and Beijing (−0.78 Wm−2yr). Megacity reduction of non-CH4 O3 precursors to improve air quality offers zero co-benefits to global climate. Megacity reduction of aerosols to improve air quality offers co-benefits to the regional radiative budget but minimal or no co-benefits to global climate with the exception of black carbon reductions in a few cities, especially Beijing and New Delhi. Results suggest that air pollution and global climate change mitigation can be treated as separate environmental issues in policy at the megacity level with the exception of CH4 action. Individual megacity reduction of CO2 and CH4 emissions can mitigate global warming and therefore offers climate safety improvements to the entire planet.
Keywords: Ozone; Aerosols; Climate change; Radiative forcing; Greenhouse gases; Black carbon;

Airborne volatile organic compounds in urban and industrial locations in four developing countries by Duc Hoai Do; Christophe Walgraeve; Abebech Nuguse Amare; Krishna Rani Barai; Amelia Estigoy Parao; Kristof Demeestere; Herman van Langenhove (330-338).
Volatile organic compounds (VOCs) represent an important class of air pollutants, however their concentration levels in developing countries have scarcely been reported in literature. Therefore, concentration levels of 60 VOCs were determined at 27 urban and industrial locations in seven different cities in Ethiopia, Vietnam, the Philippines and Bangladesh between 2011 and 2014. Active sampling using Tenax TA as a sorbent was employed followed by TD-GC-MS analysis using internal standard calibration. It was found that TVOCs concentration levels in Dhaka, Bangladesh (arithmetic mean: 343 and 399 μg/m3 for urban and industrial campaign, respectively) were more than 10 times higher when compared to TVOCs levels observed in Mekelle, Ethiopia. ∑BTEX concentration at street sites ranges from 36 μg/m3 in Mekelle, to 100 and 250 μg/m3 in Hanoi, Vietnam and Dhaka, Bangladesh, respectively. The indoor to outdoor concentration ratios were found to be dependent on the country, type of environment, VOC compound and outdoor reference location. The highest Ozone Formation Potential (OFP, 2150 μg/m3), calculated from the same set of seven aromatic VOCs, was obtained at the street site in Dhaka. This OFP value is a factor three and four times higher than the OFP value observed at the street sites in Hanoi, and Manila, respectively. Finally, the Cumulative Cancer Risk (CCR) calculated for four carcinogenic VOCs ranged from 97 × 10−6 in urban Mekelle to 299 × 10−6 in urban Dhaka. This work provides for the first time comparisons of CCR in urban and industrial environments in the selected developing countries.
Keywords: VOC; BTEX; Urban; Industrial air; Active sampling; Ozone formation potential; Cancer; Inhalation;

Odor characterization from barns and slurry treatment facilities at a commercial swine facility in South Korea by Sang-Hee Jo; Ki-Hyun Kim; Byong-Hun Jeon; Min-Hee Lee; Yong-Hyun Kim; Bo-Won Kim; Sung-Back Cho; Ok-Hwa Hwang; Satya Sundar Bhattacharya (339-347).
In this study, emission characteristics of major odorants in pig confinement facilities were investigated through comparative analysis between odorant composition and odor intensity. Odorant samples in ambient air were collected from five different paired sampling sites: (1) in- and outside of windowless pig barn, (2) in- and outside of open pig barn, (3) before/after slurry treatment (via liquid fertilization), (4) before/after composting, and (5) two reference background sites on a pig confinement facility. A total of 47 compounds consisting of key offensive odorants (such as reduced sulfur and volatile organic compounds) were measured from each selected site. When the results are compared in terms of odor intensity, a list of odorants (sulfur compounds, volatile fatty acids, phenols, and indoles) were generally seen at enhanced levels on most sites. In two types of pig barn facilities (windowless (‘W’) and open (‘O’)), butyric and valeric acid were the predominant species. The removal efficiency of odorants was quite different between the two slurry treatment approaches of composting and liquid fertilization. Although the efficiencies of odor removal in the former were not sufficient, that of the latter was fairly significant in terms of odor intensity. However, some odorants like hydrogen sulfide, methanethiol, p-cresol, and butyric acid were still retained above the odor threshold level. Accordingly, odorant emissions from animal housing facilities can be characterized most effectively by key odorants such as volatile fatty acids and reduced sulfur species.
Keywords: Pig barn; Swine slurry treatment; Hydrogen sulfide; p-Cresol; Odor pollution;

Smoke dispersion modeling over complex terrain using high resolution meteorological data and satellite observations – The FireHub platform by S. Solomos; V. Amiridis; P. Zanis; E. Gerasopoulos; F.I. Sofiou; T. Herekakis; J. Brioude; A. Stohl; R.A. Kahn; C. Kontoes (348-361).
A total number of 20,212 fire hot spots were recorded by the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument over Greece during the period 2002–2013. The Fire Radiative Power (FRP) of these events ranged from 10 up to 6000 MW at 1 km resolution, and many of these fire episodes resulted in long-range transport of smoke over distances up to several hundred kilometers. Three different smoke episodes over Greece are analyzed here using real time hot-spot observations from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) satellite instrument as well as from MODIS hot-spots. Simulations of smoke dispersion are performed with the FLEXPART-WRF model and particulate matter emissions are calculated directly from the observed FRP. The modeled smoke plumes are compared with smoke stereo-heights from the Multiangle Imaging Spectroradiometer (MISR) instrument and the sensitivities to atmospheric and modeling parameters are examined. Driving the simulations with high resolution meteorology (4 × 4 km) and using geostationary satellite data to identify the hot spots allows the description of local scale features that govern smoke dispersion. The long-range transport of smoke is found to be favored over the complex coastline environment of Greece due to the abrupt changes between land and marine planetary boundary layers (PBL) and the decoupling of smoke layers from the surface.
Keywords: Fire smoke; Injection height; Smoke dispersion modeling; FireHub;

Long-term trend and spatiotemporal variations of haze over China by satellite observations from 1979 to 2013 by Xingying Zhang; Ling Wang; Weihe Wang; Dongjie Cao; Xi Wang; Dianxiu Ye (362-373).
With the fast development of economy and industry in the past thirty years, many large cities in the eastern and southwestern areas of China are experiencing increased haze events and atmospheric pollution, which causes significant impacts on the regional environment, human health, and even climate. The long-term trend and spatiotemporal variations of haze over China during recent 30 years are investigated using TOMS AAI products. In addition, the heavy haze events that occurred in January 2013 over eastern China are explored using AAI products from TOU on board FY-3A. Validation results show that satellite AAI products can be used for haze monitoring since it is sensitive to the carbonaceous aerosol, which is one of the main components of haze. In China, the high AAI values (>1.0) mainly located in the main four areas with intense anthropogenic activities, except for the desert region in Northwestern China. In the eastern and northeastern region, AAI peaks dominate in spring before 2005 since those areas were always affected by dust in spring. However, after 2005, AAI peaks appear in winter over eastern China because of haze. Moreover, in the northeastern region, AAI peaks dominate in winter with a secondary peak in spring because this area is affected by both dust and haze. In the southern region, the AAI peaks always dominate in spring since the high-level air pollution often occur in spring, but a decreasing trend is acquired during recent ten years. Over eastern China and northeastern China, AAI shows an increasing trend during recent 30 years in winter, which reveals that the haze over these areas is strengthen. A case study result shows that the heavy haze events occurred in January 2013 in eastern China can be clearly identified from the AAI products of TOU/FY-3A. The daily coverage area with AAI > 3.0 peaks at five periods at this time, i.e. Jan. 7–8, Jan. 13, Jan. 18, Jan. 23, and, Jan. 28–29, which agrees well with the haze events recorded by in-situ measurements.
Keywords: Haze; Satellite observations; Long-term trend; China;

1H NMR studies of water- and alkaline-soluble organic matter from fine urban atmospheric aerosols by Sónia P. Lopes; João T.V. Matos; Artur M.S. Silva; Armando C. Duarte; Regina M.B.O. Duarte (374-380).
Solution-state 1H NMR spectroscopy was applied to characterize the structural features of water- and alkaline-soluble organic matter (WSOM and ASOM, respectively) sequentially extracted from fine urban atmospheric aerosols collected over different seasons. The objectives of this study were twofold: (i) to compare the functional characteristics of fine aerosol WSOM and the yet unknown ASOM, and (ii) to assess the sources of WSOM and ASOM at an urban location. The 1H NMR analysis confirmed that the WSOM and ASOM fractions hold similar 1H functional groups; however, they differ in terms of their relative distribution throughout the seasons. The winter and autumn samples have a less aliphatic and oxidized character and higher contributions from aromatic groups than those of warmer conditions. The urban aerosol WSOM and ASOM fractions do not fit the established 1H NMR source apportionment fingerprints of marine, secondary, and biomass burning organic aerosols (OAs), exhibiting a smaller relative contribution of carbon-oxygen double bonds, which is indicative of a less oxidized character. These results confirm that the boundaries of the pre-established source categories, especially for secondary and biomass burning OAs, might be different at urban locations, suggesting the need to improve the 1H NMR source apportionment model for including a new fingerprint for urban OAs.Display Omitted
Keywords: Atmospheric aerosols; Water-soluble organic matter; Alkaline-soluble organic matter; 1H NMR spectroscopy; Source apportionment;

The objective of the current work was to develop a statistical method and associated tool to evaluate the impact of oil and natural gas exploration and production activities on local air quality. Nonparametric regression of pollutant concentrations on wind direction was combined with bootstrap hypothesis testing to provide statistical inference regarding the existence of a local/regional air quality impact. The block bootstrap method was employed to address the effect of autocorrelation on test significance. The method was applied to short-term air monitoring data collected at three sites within Pennsylvania's Allegheny National Forest. All of the measured pollutant concentrations were well below the National Ambient Air Quality Standards, so the usual criteria and methods for data analysis were not sufficient. Using advanced directional analysis methods, test results were first applied to verify the existence of a regional impact at a background site. Next the impact of an oil field on local NOx and SO2 concentrations at a second monitoring site was identified after removal of the regional effect. Analysis of a third site also revealed air quality impacts from nearby areas with a high density of oil and gas wells. All results and conclusions were quantified in terms of statistical significance level for the associated inferences. The proposed method can be used to formulate hypotheses and verify conclusions regarding oil and gas well impacts on air quality and support better-informed decisions for their management and regulation.
Keywords: Air pollution; Oil and natural gas; Directional analysis; Statistical methods; Nonparametric regression; Block bootstrap;

Assessing impacts of alternative fertilizer management practices on both nitrogen loading and greenhouse gas emissions in rice cultivation by Zheng Zhao; Yubo Yue; Zhimin Sha; Changsheng Li; Jia Deng; Hanlin Zhang; Maofang Gao; Linkui Cao (393-401).
Nitrogen (N) losses and greenhouse gas (GHG) emissions from paddy rice fields contaminate water bodies and atmospheric environment. A 2-year (2012–2013) field experiment was conducted at a typical paddy rice field in a rural suburb of Shanghai, China. N losses and GHG emissions from the paddy field with alternative fertilizer management practices were simultaneously measured. Four treatments were tested in the experiment: applications of only chemical synthetic fertilizer urea (CT), only organic manure (OT), a combination of the two types of fertilizers (MT) and a control (CK). Results from the field study indicated that CT produced the highest seasonal N loading rate (18.79 kg N/ha) and N2O emissions (1.81 kg N2O/ha) but with the lowest seasonal CH4 emissions (69.09 kg CH4/ha). With organic manure applied, MT and OT respectively reduced N loading by 21.86% and 30.41%, reduced N2O emissions by 28.34% and 69.41%, but increased CH4 emissions by 137% and 310% in comparison with CT. However, the net impact of CH4 and N2O emissions on global warming was enhanced when organic manure was applied. In addition, CT and MT produced the optimal rice yield during the experimental period, while OT treatment led to a yield reduction by 9.29% compared with CT. In conclusion, the impacts of alternative fertilizer management practices on ecosystem services ought to be assessed specifically due to the great variations across rice yields, N loss and GHG emissions.
Keywords: Nitrogen loss; Runoff; Leaching; Methane; Nitrous oxide; Paddy rice field;

The study addresses the identification of multiple point sources, emitting the same tracer, from their limited set of merged concentration measurements. The identification, here, refers to the estimation of locations and strengths of a known number of simultaneous point releases. The source–receptor relationship is described in the framework of adjoint modelling by using an analytical Gaussian dispersion model. A least-squares minimization framework, free from an initialization of the release parameters (locations and strengths), is presented to estimate the release parameters. This utilizes the distributed source information observable from the given monitoring design and number of measurements. The technique leads to an exact retrieval of the true release parameters when measurements are noise free and exactly described by the dispersion model. The inversion algorithm is evaluated using the real data from multiple (two, three and four) releases conducted during Fusion Field Trials in September 2007 at Dugway Proving Ground, Utah. The release locations are retrieved, on average, within 25–45 m of the true sources with the distance from retrieved to true source ranging from 0 to 130 m. The release strengths are also estimated within a factor of three to the true release rates. The average deviations in retrieval of source locations are observed relatively large in two release trials in comparison to three and four release trials.
Keywords: Data assimilation; Fusion field trials; Least-squares; Multiple releases; Source reconstruction;

Volatile organic compounds in the atmosphere of Mexico City by Jessica P. Garzón; José I. Huertas; Miguel Magaña; María E. Huertas; Beatriz Cárdenas; Takuro Watanabe; Tsuneaki Maeda; Shinji Wakamatsu; Salvador Blanco (415-429).
The Mexico City Metropolitan Area (MCMA) is one of the most polluted megacities in North America. Therefore, it is an excellent benchmark city to understand atmospheric chemistry and to implement pilot countermeasures. Air quality in the MCMA is not within acceptable levels, mainly due to high ground levels of ozone (O3). Tropospheric O3 is a secondary pollutant formed from the oxidation of volatile organic compounds (VOCs) in the presence of nitrogen oxides and sunlight. To gain a better understanding of O3 formation in megacities, evaluate the effectiveness of already-implemented countermeasures, and identify new cost-effective alternatives to reduce tropospheric O3 concentrations, researchers and environmental authorities require updated concentrations for a broader range of VOCs. Moreover, in an effort to protect human health and the environment, it is important to understand which VOCs exceed reference safe values or most contribute to O3 formation, as well as to identify the most probable emission sources of those VOCs. In this work, 64 VOCs, including 36 toxic VOCs, were measured at four sites in the MCMA during 2011–2012. VOCs related to liquefied petroleum gas leakages exhibited the highest concentrations. Toxic VOCs with the highest average concentrations were acetone and ethanol. The toxic VOC benzene represented the highest risk to Mexican citizens, and toluene contributed the most to O3 formation. Correlation analysis indicated that the measured VOCs come from vehicular emissions and solvent-related industrial sources.Display OmittedVOC measurements revealed that compounds related to liquefied petroleum gas leakages are the most abundant, the toxic VOC benzene represents the highest risk to citizens, and toluene is the greatest VOC contributor to O3 formation in Mexico City.
Keywords: Volatile organic compound; Toxic volatile organic compound; Ozone; Ozone formation potential;

The methodology is tested using 12 months of CMAQ forecasts of hourly PM2.5, from December 01, 2009 through November 30, 2010. The model domain covers the contiguous USA, and model data are verified against U.S. Environmental Prediction Agency AIRNow PM2.5 observations measured at 716 stations over the CMAQ domain. The model bias is found to have a strong seasonal dependency, with a large positive bias in winter and a small bias in the summer months, and also to have a strong diurnal cycle.Five different post-processing techniques are compared, including a seven-day running mean subtraction, Kalman-filtering, analogs, and combinations of analogs and Kalman filtering. The most accurate PM2.5 forecasts have been found to be produced when applying the Kalman filter correction to the analog ensemble weighted mean, referred to as KFAN. The choice of analog predictors used in the analog search is also found to have a significant effect. A monthly error analysis is computed, in each case using the remaining 11 months of the data set for the analog searches. The improvement of KFAN errors over the raw CMAQ model errors ranges from 44 to 52% for MAE and 13–30% for the correlation coefficient. Since the post-processing analysis is only done at the locations where observations are available, the spreading of post-processing correction information over nearby model grid points is necessary to make forecast contour maps. This spreading of information is accomplished with an eight-pass Barnes-type iterative objective analysis scheme. The final corrected CMAQ forecast over the entire domain is composed of the sum of the original CMAQ forecasts and the KFAN bias information interpolated over the entire domain, and is applied on an hourly basis.
Keywords: Analog forecast; CMAQ; Kalman-filtering; PM2.5;