Atmospheric Environment (v.47, #C)

Bioactive and total endotoxins in atmospheric aerosols in the Pearl River Delta region, China by Jessica Y.W. Cheng; Esther L.C. Hui; Arthur P.S. Lau (3-11).
Endotoxin, a toxic and pyrogenic substance in gram-negative bacteria in atmospheric aerosols was measured over a period of one year at Nansha, Guangzhou and Hong Kong in the Pearl River Delta region, China. Atmospheric aerosols were collected by high-volume samplers. The bioactive endotoxin levels in the samples were determined using the Limulus Amebocyte Lysate (LAL) assay after extraction with pyrogen-free water while the total endotoxin levels were measured by quantifying the biomarker, 3-hydroxy fatty acids (3-OHFAs) with GC–MS. Results showed that there was no significant difference (0.19 < p < 0.81) in the bioactive endotoxin level in PM10 among sites (average concentrations ranged from 0.34 to 0.39 EU m−3). However, Hong Kong showed a significantly lower (p < 0.05) total endotoxin level in PM10 (average of 17.4 ng m−3) compared with Nansha's 29.4 ng m−3 and Guangzhou's 32.7 ng m−3. The bioactive endotoxins were found to be associated with the coarse mode (PM2.5-10) of the particulates of natural origins while the total endotoxins were associated more with the fine mode (PM2.5) of the particulates of anthropogenic origins. When normalized with particulate mass, the endotoxin loading is much higher in summer as a result of the increased growth of the bacteria when climatic conditions are favorable. The chemically determined total endotoxins were 3–4 orders of magnitude higher than the bioactive endotoxins quantified using the LAL assay. Correlation analyses between the bioactive endotoxins and 3-OHFAs with different carbon length were analyzed. Results showed that the correlations detected vary among sites and particulate sizes. Although no generalization between the total and bioactive endotoxins can be drawn from the study, the levels reported in this study suggests that the discrepancies between the two measurement approaches, and the bioactive potential of 3-OHFAs with individual carbon chains deserve further investigation.► The atmospheric endotoxin levels over a period of one year in 3 cities in Pearl River Delta region were studied. ► Higher bioactive endotoxins were found in coarse mode aerosols. ► More total endotoxins were found in fine mode aerosols. ► Bioactive and total endotoxins had different spatial and seasonal variations. ► First field study with parallel LAL and chemical assay for endotoxins.
Keywords: Airborne endotoxin; Limulus Amebocyte Lysate (LAL) assay; 3-Hydroxy fatty acid; Biomarker; Pearl River Delta;

Evaluation of vehicle emission inventories for carbon monoxide and nitrogen oxides for Bogotá, Buenos Aires, Santiago, and São Paulo by Laura Gallardo; Jerónimo Escribano; Laura Dawidowski; Néstor Rojas; Maria de Fátima Andrade; Mauricio Osses (12-19).
We use concurrent morning peak observations of carbon monoxide (CO) and nitrogen oxides (NOx) to evaluate mobile emissions estimates for CO and NOx at Bogotá (Colombia), Buenos Aires (Argentina), Santiago (Chile) and São Paulo (Brazil). In all cities, molar ratios of CO to NOx decrease over the last 10–15 years. These ratios are not captured by available inventories. Comparison among inventories suggests that major uncertainties are linked to inadequate emission factors for CO and inadequate activity data for NOx. These results, in combination with previous studies, suggest that current NOx emissions are overestimated by a factor of up to 3 in Santiago and São Paulo, and Buenos Aires shows a slight overestimate by 20%. In the case of Bogotá we suspect that the current CO emission inventory is overestimated. Available observations provide valuable information, as exemplified hereby, but more careful attention must be paid to calibration and continuity of the stations.► We use observed CO to NOx molar ratios to evaluate mobile emissions at four South American cities. ► CO to NOx molar ratios decrease over the last 10–15 years, mostly due to reductions in CO emissions. ▶ The observed ratios are not captured by available inventories. ▶ Major uncertainties are linked to CO emission factors and inadequate activity data for NOx. ▶ The evidence indicates overestimates of current NOx emissions.
Keywords: Urban mobile emissions; CO; NOx; South America;

Bacterial abundance and viability in long-range transported dust by Kazutaka Hara; Daizhou Zhang (20-25).
Transports of bacteria in the atmosphere relate to climate and global hydrological cycles by acting as nuclei of ice-cloud formation, and affect the ecosystems and public health in the downwind ecosystems. Here we present quantitative investigations of airborne bacterial cells coupled with LIVE/DEAD BacLight assay in southwestern Japan to show that airborne bacteria were widespread with Asian dust. Total bacterial cell concentrations in dust varied between 1.0 × 106 and 1.6 × 107 cells m−3, which were one to two orders higher than those in non-dusty air and were correlated with the concentrations of aerosol particles larger than 1 μm. The ratio of viable bacterial cells to total bacterial cells (viability) of bacteria in dust ranged from 16 to 40%, which was quite smaller than the viability in non-dusty air. However viable bacterial cell concentrations in dust, 2.5 × 105 – 3.8 × 106 cells m−3, were similar to or higher than those in non-dusty air. Dust is thus a substantial source of airborne bacterial cells as well as mineral particles. These quantitative results suggest Asian dust is one of the processes for dispersal of airborne bacteria in the global atmosphere.Display Omitted► Quantitative investigation of airborne bacteria in Asian dust plumes was conducted. ► The abundance of viable and non-viable bacteria significantly increased during dust episodes. ► Bacterial abundance in dust plumes closely correlated with dust concentration. ► Bacterial viability in dust plumes was quite smaller than that in non-dusty air. ► Viable bacterial abundance in dust plumes was comparable to that in non-dusty air.
Keywords: Airborne bacteria; Bioaerosol; Asian dust; Epifluorescent microscopy;

Due to the high costs and deployment difficulties associated with automated sampling technologies, few investigations have been published on atmospheric mercury in typical urban and rural areas in developing countries. In this study, a novel passive sampler for gaseous elemental mercury was developed and applied to characterize trends in atmospheric mercury levels across an urban–rural transect. The sampling transect originated in the city of Beijing and extended ∼150 km southward into a rural region. Field deployment was conducted during September–October (autumn) and November–December (winter) in 2010. The mercury concentrations in air obtained using the passive sampler were consistent with synchronous automated measurements performed during the field deployment. The results demonstrated that atmospheric mercury concentrations increased along the urban–rural gradient in the following order in both of the two periods: urban > suburban > rural (populated) > rural (farmland).► A novel passive sampler was designed for gaseous elemental mercury sampling. ► The passive sampler was sufficient for long-term measurement of gaseous mercury. ► Urban–rural gradient was observed in both heating and non-heating seasons.
Keywords: Passive sampler; Gaseous elemental mercury; Atmospheric; Urban–rural gradient;

Spatial and seasonal variations of biogenic tracer compounds in ambient PM10 and PM1 samples in Berlin, Germany by Sandra Wagener; Marcel Langner; Ute Hansen; Heinz-Jörn Moriske; Wilfried R. Endlicher (33-42).
PM10 and PM1 aerosol samples were collected between February and October, 2010 at three sites in Berlin that were characterized by different vegetation influences. The aim of the study was to determine the spatial and seasonal variations of several, mainly biogenic secondary and primary tracers in an urban area. Selected tracers including isoprene and α-pinene markers, fatty acids and levoglucosan were detected with GC-MS. The highest median concentrations, up to 45.1 ng m−3, were found for the combustion product levoglucosan. The concentration range of the secondary compounds was 0.3 ng m−3 for the isoprene markers 2-methyltetrols up to 35.7 ng m−3 for malic acid. The occurrence of these compounds was mainly affected by the seasons, which could be described by three patterns. Whereas secondary compounds were mainly characterized by significantly higher concentrations during the warmer months, levoglucosan showed significantly higher concentrations during the colder months. No significant concentration differences between the two periods were rather observed for the primary compounds but also for the α-pinene degradation product pinonic acid. The secondary compounds and levoglucosan could be associated with the fine mode (particles with an aerodynamic diameter (AD) < 1 μm), while primary compounds are rather associated with the coarse mode (AD > 1 μm). Spatial variations were emphasized with a tendency toward higher concentrations for most compounds at sites that were influenced by vegetation, especially evident for the PM10 fraction. Besides concentration differences, spatial variations could also be described by differences in seasonal behavior and the size distribution, indicating major complexity in the composition of biogenic PM within the city of Berlin.► Biogenic tracers were measured in ambient PM samples at three sites in Berlin. ► The occurrence of tracers is strongly affected by the season. ► Higher concentrations are observed at sites influenced by vegetation. ► Spatial variations can be seen in concentrations, time series and size distribution.
Keywords: Biogenic aerosol; Secondary organic aerosol; Urban air quality; Berlin;

Measurements of aerosol scattering properties obtained during the period from March 2006 to December 2010 at Valencia (Spain) have been analyzed. The total aerosol scattering (σ sp ) and backscattering (σ bsp ) coefficients were measured using a TSI Model 3563 three-wavelength integrating nephelometer. From the measurements of σ sp and σ bsp , it was possible to determine also the scattering Ångström exponent (α s ). For the entire measurement period, the mean values (±standard deviation) at 550 nm are: 80 ± 50 Mm−1 for σ sp ; 8 ± 5 Mm−1 for σ bsp ; and 1.6 ± 0.3 for α s . These results indicate a moderate polluted atmosphere characterized by fine particles. The daily variation for all seasons shows clear patterns in the scattering properties of the atmospheric aerosols, due to the traffic and the evolution of the boundary layer throughout the day. This influence of traffic was analyzed, observing different daily patterns for weekdays (Monday–Friday) and weekends (Saturday and Sunday).► Scattering properties of atmospheric aerosols in western Mediterranean are analyzed. ► The annual variation of data from an integrating nephelometer is analyzed. ► Results show a moderate polluted atmosphere characterized by fine particles. ► The daily variation of the scattering properties of aerosols is also analyzed. ► Results show clear patterns due to traffic and the evolution of the boundary layer.
Keywords: Atmospheric aerosol; Light scattering; Integrating nephelometer; Climatology;

Impact of Santiago de Chile urban atmospheric pollution on anthropogenic trace elements enrichment in snow precipitation at Cerro Colorado, Central Andes by F. Cereceda-Balic; M.R. Palomo-Marín; E. Bernalte; V. Vidal; J. Christie; X. Fadic; J.L. Guevara; C. Miro; E. Pinilla Gil (51-57).
Seasonal snow precipitation in the Andes mountain range is evaluated as an environmental indicator of the composition of atmospheric emissions in Santiago de Chile metropolitan area, by measuring a set of representative trace elements in snow samples by ICP-MS. Three late winter sampling campaigns (2003, 2008 and 2009) were conducted in three sampling areas around Cerro Colorado, a Central Andes mountain range sector NE of Santiago (36 km). Nevados de Chillán, a sector in The Andes located about 500 km south from the metropolitan area, was selected as a reference area. The experimental results at Cerro Colorado and Nevados de Chillán were compared with previously published data of fresh snow from remote and urban background sites. High snow concentrations of a range of anthropogenic marker elements were found at Cerro Colorado, probably derived from Santiago urban aerosol transport and deposition combined with the effect of mining and smelting activities in the area, whereas Nevados de Chillán levels roughly correspond to urban background areas. Enhanced concentrations in surface snow respect to deeper samples are discussed. Significant differences found between the 2003, 2008 and 2009 anthropogenic source markers profiles at Cerro Colorado sampling points were correlated with changes in emission sources at the city. The preliminary results obtained in this study, the first of this kind in the southern hemisphere, show promising use of snow precipitation in the Central Andes as a suitable matrix for receptor model studies aimed at identifying and quantifying pollution sources in Santiago de Chile.► Snow precipitation reflects urban atmospheric pollution of Santiago de Chile. ► Snow is enriched with anthropogenic elemental pollutants. ► Results are promising for assignment and tracking of urban pollution sources.Winter snow precipitation in the Central Andes mountain range reflects urban atmospheric emissions of Santiago de Chile by significant enrichment of anthropogenic elements. The preliminary results obtained in this study are promising for assignment and tracking of pollution sources by exploiting chemical information collected in the snow.
Keywords: Trace elements; Atmospheric pollution; Snow; Santiago de Chile; Central Andes;

An investigation on spatial distribution, possible pollution sources, and affecting factors of heavy metals in the urban soils of Weinan (China) was conducted using geographic information system (GIS) technique and multivariate statistics. The results indicated that the levels of 10 heavy metals (Pb, Cr, Ba, Zn, V, Mn, Co, Cu, Ni and As) distribution measured by wavelength dispersive X-ray fluorescence spectrometry (WDXRF) in urban soil of Weinan were As varied from 2.60 to 11.50 mg kg−1, Co was 8.00-14.50 mg kg−1, Cr from 74.90 to 157.00 mg kg−1, Cu from 14.60 to 34.70 mg kg−1, Ba from 413.00 to 1137.60 mg kg−1, Mn from 431.30 to 653.70 mg kg−1, Ni from 20.80 to 35.8 mg kg−1, Pb from 19.00 to 89.50 mg kg−1, V from 63.80 to 89.50 mg kg−1, Zn from 44.50 to 196.80 mg kg−1, respectively. The mean enrichment factors (EFs) decreased in the order of Pb > Cr > Ba > Cu > Zn > Ni > V > Mn > Co > As, indicating Ba, Cu, Pb, Cr and Zn were significant enriched in the study areas. Spatial distribution maps of heavy metal contents, based on geostatistical analysis and GIS mapping, indicated that Pb and Cr had similar patterns of spatial distribution, likewise, between Ba, Cu and Zn, and among As, Co, Mn, V as well. Multivariate statistical analysis (correlation analysis, principal component analysis, and clustering analysis) showed distinctly different associations among the studied metals, suggesting that the heavy metals, Ba, Cu, Pb, Cr and Zn were associated with anthropic activities (industrial sources, combined with coal combustion as well as traffic factor), whereas Mn, V, Co, As and Ni in study area mainly controlled by parent materials and therefore had natural sources. A comprehensive environmental management strategy should be concerned by the local government to address soil pollution in urban areas.► Multivariate statistics and GIS are useful tool to identify pollutant in urban soil. ► The urban soil of Weinan was polluted by Ba, Cu, Pb, Cr and Zn. ► They significant enriched due to the anthropic activities input. ► Whereas Mn, V, Co, As and Ni with the normal level attributed to parent material.
Keywords: Multivariate analysis; Heavy metal; Contamination assessment; Geostatistical analysis; X-ray fluorescence spectrometry; Weinan; Urban soil;

We develop an inventory of global N2O emissions from natural ecosystem soils using an artificial neural network approach and field observational data of N2O fluxes. We estimate that the global soil N2O source strength from natural ecosystems is 3.37 Tg (1 Tg = 1012 g) N per year with an uncertainty ranging from 1.96 to 4.56 Tg N per year in 2000. While our global estimate is lower than other existing estimates, the spatial patterns of our simulated N2O emissions agree with other existing studies. There was a large spatial and seasonal variability in the soil N2O emissions due to the variation in soil type, vegetation and climate conditions. Consistent with other studies, we confirm that warm and moist tropical soils are the major source of atmospheric N2O. As a result of the low temperatures, the high latitude ecosystems have significantly low emission rates and contribute little (less than 0.10 Tg N per year) to the global N2O source. The simulated annual global N2O emissions are found to be most sensitive to variation in precipitation. This study uses the most current available data for N2O fluxes and their associated environmental variables to quantify the global N2O emissions, and provides an independent global inventory of this important trace gas, which will facilitate future studies of atmospheric chemistry and climate feedbacks at the global scale.► A global soil N2O emission inventory is developed. ► Neural network approach is used. ► The study calls for more site level N2O measurements.
Keywords: Global N2O emissions; Artificial neural network; Ecosystems; Greenhouse gas;

Ozone effects on yield quality of spring oilseed rape and broccoli by Karine Vandermeiren; Maarten De Bock; Nele Horemans; Yves Guisez; Reinhart Ceulemans; Ludwig De Temmerman (76-83).
The impact of elevated tropospheric ozone (O3) on the quality of spring oilseed rape (Brassica napus cv Ability) and broccoli (Brassica oleracea L. cv Italic cv Monaco) was assessed during a three year Open – Top Chamber (OTC) experiment. Current ambient O3 levels were compared to an increase of 20 and 40 ppb during 8 h per day over the entire growing season. The qualitative responses were expressed as a function of the accumulated hourly O3 concentrations over a threshold of 40 ppb (AOT40) and the phytotoxic O3 dose above a threshold of 6 nmol s−1 m−2 projected leaf area (POD6).Our results provide clear evidence that O3 has an influence on the qualitative attributes of the harvested products of these Brassica species. The responses were comparable whether they were expressed as a function of the accumulated O3 concentrations or of the modelled O3 uptake. The protein concentration of oilseed rape seeds and broccoli heads was significantly increased in response to O3. There was also a shift in the fatty acid composition of the vegetable oil derived from seeds of oilseed rape. Oleic acid (18:1) declined significantly (p < 0.05) in favour of linoleic acid (18:2) (p < 0.01). There was no change in the relative proportion of linolenic acid (18:3). The suppression of monounsaturated fatty acids (p < 0.05) coincided with a positive response of the % saturated fatty acids (p < 0.05). In rapeseed oil the observed decrease in vitamin E content was due to a reduction of γ-tocopherol (TOC, p < 0.001). α-TOC, the most active form of vitamin E in humans, was not influenced by O3. There was no change in the glucosinolate (GSL) content of oilseed rape seeds. In broccoli an important shift occurred from indolic to aliphatic GSLs although the total GSL concentration was not changed. The increase in the aliphatic/indolic GSL ratio (p < 0.001) may be important in relation to the anticarcinogenic properties of these vegetables. The vitamin C (ascorbate – ASC) and α-TOC concentrations of broccoli were not influenced by O3; glutathione (GSH) was slightly increased in response to a higher O3 uptake (p < 0.05).The consequences of these changes with regard to food and feed quality and human health are discussed.► O3 has an effect on food and feed quality of oilseed rape and broccoli. ► O3 increases the ratio of aliphatic/indolic glucosinolates in broccoli vegetables. ► O3 increases the protein concentration of rapeseed meal and broccoli vegetables. ► There is a shift in the fatty acid composition of rape seed oil. ► The vitamin E concentration in the seeds of oilseed rape is decreased.
Keywords: Brassica napus; Brassica oleracea; Proteins; Fatty acids; Antioxidants; Glucosinolates;

7Be behaviour in the atmosphere of the city of Granada January 2005 to December 2009 by F. Piñero García; M.A. Ferro García; M. Azahra (84-91).
This paper focuses on 7Be concentration in the atmospheric surface aerosols of the Spanish city of Granada, in the southern Iberian Peninsula. We analyze the effects of meteorological conditions in the geographical zone over the period 2005–2009. A prediction model is suggested to describe the behaviour of atmospheric aerosols containing 7Be. The model was applied from January to May 2010 and shows that temperature, relative humidity and precipitation are the meteorological factors responsible for the behaviour of atmospheric aerosols. The statistical significance of the results was 99%. This study helps understanding of the atmosphere of Granada as well as the climate variables responsible for transportation and deposition of atmospheric aerosols. Moreover, in case of a massive release of radionuclides into the atmosphere, the results of this study will help predict behaviour in this city and other continental areas with a similar climate.► Factors controlling 7Be in aerosol’s Granada: temperature, humidity and rain. ► The trend shows a cyclical and seasonal behaviour. ► Scavenging of 7Be is affected by precipitation and humidity. ► The higher values of 60% of humidity produce a very marked decrease in the 7Be. ► Higher temperature interval increases the vertical transport in the troposphere.
Keywords: 7Be; Ground-level air; Seasonal variations; Meteorological factors; Atmospheric deposition;

Reactive nitrogen emissions from crop and livestock farming in India by Viney P. Aneja; William H. Schlesinger; Jan Willem Erisman; Sailesh N. Behera; Mukesh Sharma; William Battye (92-103).
The rapid increase in anthropogenic nitrogen emissions to the atmosphere is matter of concern for the environment, as these may lead to photochemical air pollution, reduced visibility, eutrophication of surface waters, changes in biodiversity, acid rain, stratospheric ozone depletion, and global warming. In this study, ambient emissions of reactive nitrogen (ammonia and nitrous oxide) from animal and crop farming are analyzed for the base year 2003. This objective was achieved by the systematic development of a spatially resolved emissions inventory on a Geographic Information System (GIS) platform. Emissions of ammonia (NH3) and nitrous oxide (N2O) were estimated: (i) from livestock; 1705 Gg/yr and 214 Gg yr−1 and (ii) fertilizer applications; 2697 Gg yr−1 and 326 Gg yr−1. These estimated emissions were compared and contrasted with global, U.S., and European emissions of reactive nitrogen; emissions from India were second only to China. From the spatially resolved emission inventory, it was observed that the state of Uttar Pradesh has the highest NH3 emission (522 Gg yr−1) followed by the state of Maharashtra (425 Gg yr−1) both from animal and crop farming. Similarly the State of Uttar Pradesh has the highest N2O emission (70 Gg yr−1) followed by the state of Maharashtra (47 Gg yr−1).► Agricultural operations emit significant amounts of reactive nitrogen compounds. ► Estimating nitrogen compounds emissions in India from agricultural sources. ► Comparison of agricultural nitrogen compounds emissions in India with global, U.S., and European emissions. ► Suggestions for developing an appropriate regulatory framework to control these emissions.
Keywords: Reactive nitrogen; Agricultural emissions; Fertilizer application; Animal operations; India;

Hydrochloroethers in the troposphere: Kinetics with Cl atoms, lifetimes and atmospheric acceptability indices by Pablo R. Dalmasso; Raúl A. Taccone; Jorge D. Nieto; Pablo M. Cometto; Silvia I. Lane (104-110).
Rate constants for the gas-phase reactions of chlorine atoms with 2-chloroethyl ethyl ether (k 1) and bis(2-chloroethyl) ether (k 2) were determined for the first time using a conventional relative rate technique. Experiments were carried out at (298 ± 2) K and atmospheric pressure using synthetic air as bath gas. The decay rates of the hydrochloroethers were measured relative to those of n-pentane and n-heptane. The following rate constants were derived in units of cm3 molecule−1 s−1: k 1 = (1.7 ± 0.5) × 10−10 and k 2 = (1.0 ± 0.3) × 10−10. The rate constants obtained are compared with previous literature data to indicate reactivity trends and are used to estimate the global atmospheric lifetimes (τ global) of the studied hydrochloroethers. Radiative forcing efficiencies (RE) of the ethers were determined from their integrated IR absorption cross-sections. Using τ global and RE, estimations were made of atmospheric hazard indices of the two chlorinated ethers such as the ozone depletion potential (ODP) and the global warming potential (GWP).► Rate constants for reactions of Cl with two hydrochloroethers. ► Reactivity trends are discussed. ► Atmospheric lifetimes and global warming potentials of the ethers are calculated.
Keywords: Hydrochloroethers; Chlorine atoms; Gas-phase kinetics; Atmospheric acceptability;

Objective classification of air quality monitoring sites over Europe by Mathieu Joly; Vincent-Henri Peuch (111-123).
The observation sites that make up air quality monitoring networks can have very different characteristics (topography, climatology, distance to emission sources, etc), which are partially described in the meta-information provided with data sets. At the scale of Europe, the description of the sites depends on the institute(s) in charge of the air quality monitoring in each country, and is based on specific criteria that can be sometimes rather subjective. The purpose of this study is to build an objective, homogeneous, and pollutant-specific classification of European air quality monitoring sites, primarily for the purpose of model verification and chemical data assimilation.Most studies that tackled this issue so far were based on limited data sets, and often took into account additional external data such as population density, emission estimates, or land cover maps. The present study demonstrates the feasibility of a classification only based on the past time series of measured pollutants. The underlying idea is that the true fingerprint of a given monitoring site lies within its past observation values. On each site to be categorized, eight indicators are defined to characterize each pollutant time series (O3, NO2, NO, SO2, or PM10) of the European AirBase and the French BDQA (Base de Données de Qualité de l’Air) reference sets of validated data over the period 2002–2009. A Linear Discriminant Analysis is used to best discriminate the rural and urban sites. After projection on the Fisher axis, ten classes are finally determined on the basis of fixed thresholds, for each molecule.The method is validated by cross-validation and by direct comparison with the existing meta-data. The link between the classes obtained and the meta-data is strongest with NO, NO2, and PM10. Across Europe, the classification exhibits interesting large-scale features: some contrasts between different regions depend on the pollutant considered. Comparing the classes obtained for different pollutants at the same site reveals an interesting consistency between the separate classifications. The robustness of the method is finally assessed by comparing the classifications obtained for two distinct subsets of years. The robustness – and thus the skill of the objective classification – is satisfying for all of the species, and is highest with NO and NO2.► We classify air quality monitoring sites on the basis of their past measurements. ► We use hourly data at the European scale over the period 2002–2009. ► The objective classification is based on a Linear Discriminant Analysis. ► The classification is specific for each pollutant, but results are coherent. ► The classes obtained for two distinct periods are consistent.
Keywords: Air quality; Classification; Monitoring; Representativeness; Pollutant; European AirBase;

Atmospheric monitoring of a perfluorocarbon tracer at the 2009 ZERT Center experiment by Natalie Pekney; Arthur Wells; J. Rodney Diehl; Matthew McNeil; Natalie Lesko; James Armstrong; Robert Ference (124-132).
Field experiments at Montana State University are conducted for the U.S. Department of Energy as part of the Zero Emissions Research and Technology Center (ZERT) to test and verify monitoring techniques for carbon capture and storage (CCS). A controlled release of CO2 with an added perfluorocarbon tracer was conducted in July 2009 in a multi-laboratory study of atmospheric transport and detection technologies. Tracer plume dispersion was measured with various meteorological conditions using a tethered balloon system with Multi-Tube Remote Samplers (MTRS) at elevations of 10 m, 20 m, and 40 m above ground level (AGL), as well as a ground-based portable tower with monitors containing sorbent material to collect the tracer at 1 m, 2 m, 3 m, and 4 m AGL. Researchers designed a horizontal grid of sampling locations centered at the tracer plume source, with the tower positioned at 10 m and 30 m in both upwind and downwind directions, and the MTRS spaced at 50 m and 90 m downwind and 90 m upwind. Tracer was consistently detected at elevated concentrations at downwind sampling locations. With very few exceptions, higher tracer concentrations correlated with lower elevations. Researchers observed no statistical difference between sampling at 50 m and 90 m downwind at the same elevation. The US EPA AERMOD model applied using site-specific information predicted transport and dispersion of the tracer. Model results are compared to experimental data from the 2009 ZERT experiment. Successful characterization of the tracer plume simulated by the ZERT experiment is considered a step toward demonstrating the feasibility of remote sampling with unmanned aerial systems (UAS’s) at future sequestration sites.► Perfluorocarbon tracer was co-injected with CO2 at a sequestration testing site. ► Tracer atmospheric dispersion was measured using ground- and aerial-based samplers. ► We observed elevated concentrations at sampling locations downwind of release point. ► AERMOD predicted tracer transport and dispersion with good agreement to measurements. ► This work advances development of monitoring plans for future sequestration sites.
Keywords: Carbon sequestration; Geosequestration; Perfluorocarbon tracer; AERMOD; Unmanned aerial systems; Bozeman; Montana;

Emissions from open vegetation fires contribute significantly to global atmospheric dynamics. However, the value of improved quantification of areas burned and knowledge of the composition and structure of biomass fuel is compromised in current emissions modelling and measurement by inadequate understanding of the chemistry of biomass combustion. Physical models of the behaviour of open vegetation fires also have relied on over-simplified combustion chemistry. Considerable knowledge of the thermal degradation and combustion of cellulose, the major constituent of the terrestrial biomass, exists but has yet to make an impact in the fields of atmospheric emissions monitoring and open vegetation fire behaviour modelling. This article provides an interpretive summary of the current knowledge of the chemistry and dynamics of the processes of thermal degradation and combustion of cellulosic biomass and discusses the role of these processes in determining the emissions from, and behaviour of, open fires in such fuels. The important role of competitive thermal decomposition is emphasised, as a driver and regulator of emissions and fire spread (short-term, local effects) and global carbon distributions (long-term, global effects).► The thermoconversion chemistry of cellulosic biomass is reviewed interpretively. ► Competition between char and volatile formation controls biomass combustion reactions. ► Thermal and chemical feedbacks between reactions influence the competition outcomes. ► Outcomes lead to flaming or glowing combustion with different emissions and behaviour. ► Emissions monitoring could be improved by incorporating this basic knowledge.
Keywords: Atmospheric emissions; Competitive thermokinetics; Cellulose; Bushfire behaviour; Wildfire spread; Open fires;

Surface ozone-temperature relationships in the eastern US: A monthly climatology for evaluating chemistry-climate models by D.J. Rasmussen; A.M. Fiore; V. Naik; L.W. Horowitz; S.J. McGinnis; M.G. Schultz (142-153).
We use long-term, coincident O3 and temperature measurements at the regionally representative US Environmental Protection Agency Clean Air Status and Trends Network (CASTNet) over the eastern US from 1988 through 2009 to characterize the surface O3 response to year-to-year fluctuations in weather, for the purpose of evaluating global chemistry-climate models. We first produce a monthly climatology for each site over all available years, defined as the slope of the best-fit line (m O3-T) between monthly average values of maximum daily 8-hour average (MDA8) O3 and monthly average values of daily maximum surface temperature (T max). Applying two distinct statistical approaches to aggregate the site-specific measurements to the regional scale, we find that summer time m O3-T is 3–6 ppb K−1 (r  = 0.5–0.8) over the Northeast, 3–4 ppb K−1 (r  = 0.5–0.9) over the Great Lakes, and 3–6 ppb K−1 (r  = 0.2–0.8) over the Mid-Atlantic. The Geophysical Fluid Dynamics Laboratory (GFDL) Atmospheric Model version 3 (AM3) global chemistry-climate model generally captures the seasonal variations in correlation coefficients and m O3-T despite biases in both monthly mean summertime MDA8 O3 (up to +10 to +30 ppb) and daily T max (up to +5 K) over the eastern US. During summer, GFDL AM3 reproduces m O3-T over the Northeast (m O3-T  = 2–6 ppb K−1; r  = 0.6–0.9), but underestimates m O3-T by 4 ppb K−1 over the Mid-Atlantic, in part due to excessively warm temperatures above which O3 production saturates in the model. Combining T max biases in GFDL AM3 with an observation-based m O3-T estimate of 3 ppb K−1implies that temperature biases could explain up to 5–15 ppb of the MDA8 O3 bias in August and September though correcting for excessively cool temperatures would worsen the O3 bias in June. We underscore the need for long-term, coincident measurements of air pollution and meteorological variables to develop process-level constraints for evaluating chemistry-climate models used to project air quality responses to climate change.► We construct records of O3-temperature relationships over the eastern US. ► Observed O3-temperature relationships are used to evaluate a chemistry climate model. ► The model reproduces observed summer O3 sensitivity to temperature over the Northeast. ► We find modeled temperature biases to partially explain excess-modeled summer O3. ► Lasting long-term measurements are needed to support process-oriented model evaluation.
Keywords: Ozone; Temperature; Climate; Global climate models; Model evaluation;

Secondary organic aerosol formation from the photo-oxidation of benzene by Esther Borrás; Luis Antonio Tortajada-Genaro (154-163).
The production of condensate compounds from the degradation of benzene by OH radical chemistry was studied. Secondary organic aerosol (SOA) formation was investigated in the EUPHORE (European Photoreactor) simulation chambers. Experiments were performed under different OH-production conditions – addition of H2O2, NO or HONO –, in a high-volume reactor, with natural light and in the absence of seed aerosols. The consumption of precursor/reagents, the formation of gas-phase and particulate-phase products and the temporal evolution of aerosol were monitored. Several aerosol physical properties – mass concentration, overall aerosol yield, particle size distribution and density – were determined and found to be clearly dependent on OH radical production and NOx concentrations. Furthermore, the use of one and/or two products gas-particle partitioning absorption models allowed us to determine the aerosol yield curves. The SOA yield ranged from 1.6 to 9.7 %, with higher SOA formation under low-NOx conditions. Chemical characterization of the SOA was carried out, determining multi-oxygenated condensed organic compounds by a method based on the gas chromatography-mass spectrometry technique. Several ring-retaining and ring-cleavage products were identified and quantified. The compounds with the highest percentage contribution to the total aerosol mass were 4-nitrobenzene-1,2-diol, butenedioic acid, succinic acid and trans-trans-muconic. In addition, a multigenerational study was performed comparing with the photo-oxidations of phenol and catechol. The results showed that although the mass concentration of SOA produced was different, the physical and chemical properties were quite similar. Finally, we suggest a general mechanism to describe how changes in benzene degradation pathways – rate of OH generation and concentration of NOx – could justify the variation in SOA production and properties.Display Omitted► SOA yields from the photo-oxidation of benzene, phenol and catechol were 1.6–53%. ► Mass concentration, size distribution, density and composition were determined. ► Aerosol properties were found clearly dependent on OH production and NOx levels. ► Yield models informed about the source and nature of SOA intermediates. ► Multi-oxygenated products (ring-cleavage/ring-retaining) are relevant SOA components.
Keywords: Benzene; Phenol; Catechol; SOA yield; Multi-oxygenated compounds;

Long-term concentrations of airborne cadmium in metropolitan cities in Korea and potential health risks by Atilla Mutlu; Byeong-Kyu Lee; Gee-Hyeong Park; Bong-Gwan Yu; Chi-Hyeon Lee (164-173).
The long-term concentrations of cadmium (Cd) in total suspended particulate (TSP) were calculated from data obtained from 30 ambient air-monitoring stations (AAMSs) located in seven metropolitan cities throughout Korea. The annual mean levels of Cd in TSP in port cities, industrial cities, and an inland city showed a decreasing trend over the 7-year study period. The overall highest average concentration was observed in Incheon with an annual mean of 3.92 ± 1.62 ng m−3, followed by Ulsan and Busan. The long-term Cd mean levels from international port and/or industrial cities (Incheon, Ulsan, Busan) were much higher than those from inland cities (Seoul, Daegu, Daejeon, and Gwangju). Temporal analysis indicated that there were no significant differences among Cd levels in different seasons. However, in Incheon, the seasonal average concentrations of Cd in spring, winter, and fall were 5.20 (±3.27) ng m−3, 4.01 (±0.93) ng m−3, and 3.5 (±0.77) ng m−3, respectively, which were significantly higher levels than those measured in the other cities for the corresponding seasons. These high concentrations in Incheon are likely due to the combined effects of local industries, traffic, ship emissions, and long-range transported PM from the northeastern industrial regions of China. The long-term summer average concentration in Ulsan, the largest industrial city, was 4.58 ± 1.15 ng m−3, which was significantly higher than the other seasonal values and also the summer averages of the other cities. This can be explained by downwind location effects of prevailing winds that pass through the industrial and port sectors of Ulsan. Excess cancer risk (ECR) estimates indicated that the carcinogenic risk due to inhaled Cd is 7, 6, and 4 persons per million of population in Incheon, Ulsan, and Busan, respectively.Display Omitted► We analyzed the long-term concentrations of airborne Cd in Korea. ► The port/industry cities showed higher Cd values than the inland cities. ► The highest excess cancer risk by inhalation of airborne Cd was 15 × 10−6.
Keywords: Cadmium; TSP; Ports; Industrial; Excess cancer risk;

Influence of regional pollution and long range transport over western India: Analysis of ozonesonde data by Shuchita Srivastava; S. Lal; M. Naja; S. Venkataramani; S. Gupta (174-182).
Four years (April 2003 – July 2007) of ozonesonde observations over Ahmedabad have been studied for the first time using ten days backward trajectories in the boundary layer (lower 2 km) and lower troposphere (2.5–4 km). Ozone data are classified according to the residence times of air-masses over the North-Western India (NWI), marine and Northern Africa/Southern Europe (NASE) regions. Ozone increases linearly with increasing residence days over the NWI region for about six days with maximum increase rate (boundary layer ∼4.5 ± 1.1 ppbv/day, lower troposphere ∼3.4 ± 0.8 ppbv/day) during spring and minimum during winter (boundary layer ∼0.7 ± 0.8 ppbv/day, lower troposphere ∼0.8 ± 0.7 ppbv/day). The analysis of surface ozone over Ahmedabad confirms that ozone increase with residence days is largely due to photochemical build up. The estimated background ozone corresponding to zeroth residence day is found to be significantly lower during summer-monsoon (∼26.3 ± 3.3 ppbv) than winter (∼47.7 ± 3.2 ppbv) within the boundary layer. The air masses mainly influenced by NWI region, marine and NASE regions are termed as regionally polluted, marine and long range transport (LRT) respectively. The regionally polluted ozone is found to be higher than the average ozone during spring and summer-monsoon by 22–41% within the boundary layer and by 9–12% in the lower troposphere. The marine air shows lower ozone by 38% and 10% during spring and summer seasons respectively in the boundary layer. LRT plays a significant role in the lower troposphere during spring and summer seasons with an ozone enhancement of 9% and 27% respectively. The present work suggests that regional pollution and long range transport have significant influence on the seasonal distribution of ozone in the lower troposphere whereas the background ozone levels in summer-monsoon are mainly influenced by marine air mass over this region.► Investigation of O3 distribution in lower 4 km over Ahmedabad. ► Estimation of O3 increase rate with residence days over polluted Indian region. ► Influence of marine air on the distribution of ozone in the boundary layer. ► Quantification of ozone in regionally polluted air and Long range transport.
Keywords: Ozonesonde; Boundary layer; Lower troposphere; Regional pollution; Long range transport;

Ammonia emissions and emission factors of naturally ventilated dairy housing with solid floors and an outdoor exercise area in Switzerland by Sabine Schrade; Kerstin Zeyer; Lorenz Gygax; Lukas Emmenegger; Eberhard Hartung; Margret Keck (183-194).
From an agricultural and environmental policy perspective there is a pressing need for up-to-date emission data on ammonia (NH3) from dairy farming. The main aim of this study was to determine NH3 emissions for the most common dairy farming situation in Switzerland of loose housing with an outdoor exercise area. Measurements were taken on six commercial farms, in naturally ventilated cubicle loose housing systems with solid floors and an outdoor exercise area located alongside the housing. The variation in climate over the course of a year was covered by a total of twelve measuring periods, in two out of three seasons (summer, transition period, winter) per farm. A tracer ratio method with two tracer gases (SF6, SF5CF3) was employed to determine emissions from two areas of different source intensity. A variety of accompanying parameters was used to characterise each measuring situation and to derive the relevant influencing variables. The daily average NH3 emission across all farms varied from 31 to 67 g LU−1 d−1 in summer, from 16 to 44 g LU−1 d−1 in the transition period, and from 6 to 23 g LU−1 d−1 in winter (1 LU = 500 kg live weight). From a linear mixed-effects model the wind speed in the housing (p < 0.001) and the interaction of outside temperature and the urea content of the tank milk (p < 0.001) emerged as significant variables influencing NH3 emission.A model-based calculation with bootstrapped variance components was used to calculate yearly averaged emission factors for two mountain and plain regions and two wind speeds (0.3 and 0.5 m s−1). The model input was based on milk urea contents from commercial dairy farms and air temperatures over a five-year period. The calculated NH3 emission factors, which thus accounted for regional differences due to climatic conditions and feeding levels, ranged between 22 and 25 g LU−1 d−1.► NH3 emissions were determined for naturally ventilated dairies with outdoor areas. ► A tracer ratio method with SF6 and SF5CF3 enabled to quantify NH3 emissions. ► NH3 emission was influenced by wind speed, temperature and tank milk urea content. ► A multi-site sampling approach depicted seasonal and farm effects. ► NH3 emission factors for naturally ventilated dairies ranged from 22-25 g LU−1 d−1.
Keywords: Ammonia emission; Natural ventilation; Dairy housing; Outdoor exercise area; Tracer gas; Emission factor;

Measurements of fog composition at a rural site by Derek J. Straub; James W. Hutchings; Pierre Herckes (195-205).
Studies that focus on fog chemistry in the United States have been limited to relatively few locations. Apart from measurements along the East and West coasts and extensive analysis of radiation fog in the Central Valley of California, fog composition has been characterized in only a handful of other locations. To complement and expand the existing fog chemistry data that are currently available, a new field campaign was established at a rural location in Central Pennsylvania to produce a unique, long term record of fog composition. From 2007 to 2010, 41 fog events were sampled with an automated Caltech Heated Rod Cloudwater Collector (CHRCC). The collected samples were analyzed primarily for pH and major inorganic ions. Dissolved organic carbon (DOC) and trace metals were analyzed in selected samples and N-nitrosodimethylamine (NDMA) was quantified in two samples. Sample composition varied widely during the study period. Sulfate concentrations ranged from 15 to 955 (median = 123) μN and pH varied between 3.08 and 7.41 (median = 5.77). In terms of volume weighted averages, ammonium was the most abundant ionic species followed by sulfate, calcium, and nitrate. For the subset of samples in which DOC was analyzed, concentrations ranged from 2.2 to 22.6 mgC l−1. Comparisons with regional precipitation chemistry measurements reveal the influence of local agricultural and soil sources on fog composition. The sum of sulfate, nitrate, and ammonium measured in the present study is considerably lower than the majority of radiation, precipitation, and coastal fogs collected in the United States although the ammonium/(nitrate + sulfate) ratio is similar to those found in the Central Valley of California.► 41 fog samples were collected and analyzed for pH, inorganic ions, and DOC. ► Ammonium was the most abundant ion followed by sulfate, calcium, and nitrate. ► The sum of inorganic ions was lower than in fog sampled in most other U.S. locations. ► Local sources are important for potassium, ammonium, and calcium. ► Ammonium/(nitrate + sulfate) ratios are similar to those in the Central Valley of CA.
Keywords: Fog chemistry; Inorganic ions; Dissolved organic carbon; Pennsylvania; Mid-Atlantic region;

Regional and global modeling estimates of policy relevant background ozone over the United States by Christopher Emery; Jaegun Jung; Nicole Downey; Jeremiah Johnson; Michele Jimenez; Greg Yarwood; Ralph Morris (206-217).
Policy Relevant Background (PRB) ozone, as defined by the US Environmental Protection Agency (EPA), refers to ozone concentrations that would occur in the absence of all North American anthropogenic emissions. PRB enters into the calculation of health risk benefits, and as the US ozone standard approaches background levels, PRB is increasingly important in determining the feasibility and cost of compliance. As PRB is a hypothetical construct, modeling is a necessary tool. Since 2006 EPA has relied on global modeling to establish PRB for their regulatory analyses. Recent assessments with higher resolution global models exhibit improved agreement with remote observations and modest upward shifts in PRB estimates. This paper shifts the paradigm to a regional model (CAMx) run at 12 km resolution, for which North American boundary conditions were provided by a low-resolution version of the GEOS-Chem global model. We conducted a comprehensive model inter-comparison, from which we elucidate differences in predictive performance against ozone observations and differences in temporal and spatial background variability over the US. In general, CAMx performed better in replicating observations at remote monitoring sites, and performance remained better at higher concentrations. While spring and summer mean PRB predicted by GEOS-Chem ranged 20–45 ppb, CAMx predicted PRB ranged 25–50 ppb and reached well over 60 ppb in the west due to event-oriented phenomena such as stratospheric intrusion and wildfires. CAMx showed a higher correlation between modeled PRB and total observed ozone, which is significant for health risk assessments. A case study during April 2006 suggests that stratospheric exchange of ozone is underestimated in both models on an event basis. We conclude that wildfires, lightning NO x and stratospheric intrusions contribute a significant level of uncertainty in estimating PRB, and that PRB will require careful consideration in the ozone standard setting process.► PRB ozone is important in EPA’s standard setting process. ► As PRB is hypothetical, modeling is necessary but must be informed by observations. ► Global and regional ozone modeling was performed and evaluated against observations. ► Model spatial resolution is important for PRB emissions, chemistry and transport. ► High resolution PRB predictions can be more than 10 ppb higher than global modeling.
Keywords: Policy relevant background; Ozone; Photochemical modeling; GEOS-Chem; CAMx;

Energy and ozone fluxes over sea ice by Jennifer B.A. Muller; James R. Dorsey; Michael Flynn; Martin W. Gallagher; Carl J. Percival; Dudley E. Shallcross; Alexander Archibald; Howard K. Roscoe; Rachel W. Obbard; Helen M. Atkinson; James D. Lee; Sarah J. Moller; Lucy J. Carpenter (218-225).
We present surface layer measurements made over Hudson Bay sea ice during February/March 2008 from the COBRA (Impact of combined iodine and bromine release on the Arctic atmosphere) experiment which formed part of the International OASIS (Ocean-Atmosphere-Sea Ice-Snowpack) IPY programme. All components of the local surface energy balance were measured and it was defined by net radiative cooling throughout most of the day, mainly balanced by the conductive heat flux from the warmer sea water to the cooler sea ice at the surface, and a small net radiative warming for a few hours after midday. Unique ground-level ozone fluxes were measured by eddy covariance and deposition velocities ranged from +0.5 mm s−1 (deposition) to −1.5 mm s−1 (emission). Ozone profile measurements suggested ozone flux divergence within the surface layer. The observed bi-directional fluxes and flux divergence with height reveal the complexity of surface ozone fluxes in the Arctic spring time surface layer, and show that ozone exchange with the sea ice surface is best probed using the eddy covariance method alongside frequent or continuous profile measurements. In this study, the local in-situ ozone-halogen photochemistry was identified as weakly controlling the measured ozone flux, whereas horizontal advection and vertical mixing were considered more important in influencing fluxes. Under these conditions, several measurement sites would be desirable in order to quantify the contribution of advection to the local surface exchange.► Radiative, turbulent and conductive energy fluxes were measured over sea ice. ► Net radiative cooling, balanced by conductive heat, defined surface energy balance. ► Surface ozone fluxes by eddy covariance were bi-directional over sea ice. ► Ozone flux divergence in surface layer revealed chemical and dynamical complexity. ► Horizontal advection & vertical mixing important in influencing surface fluxes.
Keywords: Eddy covariance; Ozone surface exchange; Heat flux; Net radiation; Arctic; Hudson Bay;

Sudden increase in the total ozone density due to secondary ozone peaks and its effect on total ozone trends over Korea by Sang Seo Park; Jhoon Kim; Hi Ku Cho; Hanlim Lee; Yeonjoo Lee; Koji Miyagawa (226-235).
Total column ozone (TCO) amounts observed by the Dobson spectrophotometer from 1985 to 2008 in Seoul and vertical ozone profiles obtained with the ozonesonde from 1995 to 2007 in Pohang were used to investigate the relationship between the occurrence of Secondary Ozone Peak (SOP) in the Upper Troposphere/Lower Stratosphere (UT/LS) layer and the enhancement in TCO over the Korean Peninsula. Based on Hybrid Single-Particle, Lagrangian Integrated Trajectory (HYSPLIT) simulations, the advection of a northern mid-latitudinal ozone-rich airmass from the northwest is closely related to SOP occurrences, which consequently lead to enhancements in the amount of ozone in both the UT/LS and the total column at stations in Korea. In addition, both the frequency of the northwesterly advection and the northern mid-latitudinal ozone amount are revealed to affect the amount of ozone in the UT/LS and total column by up to 7 DU. The relationship between the SOP occurrence frequency and the long-term TCO trend was investigated with observed data collected in all seasons. The UT/LS ozone enhancements, which are largely affected by SOP occurrences, are considered to be positively related to the TCO trend from 1985 to 2008 over the Korean Peninsula.► Total ozone enhancement is related to the Secondary Ozone Peak (SOP). ► The SOP occurs the layer in the Upper Troposphere/Lower Stratosphere. ► The SOP occurrence is caused by the advection of ozone-rich airmass in high latitude. ► Temporal variation of SOP occurrence changes long-term total ozone trend over Korea.
Keywords: Total column ozone trend; Secondary ozone peak; Upper troposphere lower stratosphere; Ozone;

Air quality impacts of motor vehicle emissions in the south coast air basin: Current versus more stringent control scenario by Susan Collet; Toru Kidokoro; Yukihiro Sonoda; Kristen Lohman; Prakash Karamchandani; Shu-Yun Chen; Hiroaki Minoura (236-240).
States are working to comply with the ozone National Ambient Air Quality Standards (NAAQS). Often, regulations restricting vehicle emissions are promulgated in order to attain compliance with the NAAQS. Currently, more stringent vehicle emission regulations are being considered by government agencies. This paper compares emissions from passenger cars and light duty trucks under the current California Low Emission Vehicle (LEV II) standards to a control scenario which was anticipated in 2008 to become LEV III (referred to as “more stringent control” in this paper) and determines if the scenario would result in additional improvements to air quality in California’s South Coast Air Basin. The air quality modeling was performed using the Community Multi-scale Air Quality Model (CMAQ) for years 2005, 2014 and 2020.The more stringent control sensitivity study simulated a scenario in which all new passenger cars and light duty trucks in the California South Coast Air Basin in year 2016 achieve Super Ultra-Low Emission Vehicle (SULEV) tail pipe emissions, zero evaporative emissions and more stringent aggressive driving requirements.The total on-road vehicles emissions difference when averaged across the South Coast Air Basin showed the more stringent scenario compared to LEV II to have reductions of 1% for oxides of nitrogen (NO x ), 1% for as reactive organic gases (ROG) and 5% for carbon monoxide (CO) in 2030.LEV II modeled ozone levels in the western areas of the basin increased in 2014 and 2020 as compared to 2005, because these areas are VOC-sensitive and the reductions in NO x emissions in these regions are larger than the VOC reductions. In other areas of the South Coast Basin, ozone is reduced by 1.5% or less. The more stringent control scenario modeled levels of ozone have a maximum decrease from LEV II levels by 1% or less in 2014 and 1.5% or less in 2020.► Emissions were modeled for LEV II and a scenario anticipated in 2008 to become LEV III. ► The subject was passenger cars and light duty trucks in California South Coast Air Basin. ► The new scenario average emission reductions were 2% for NO x and ROG and 5% for CO in 2030. ► LEV II modeled ozone levels in the western areas increase 30% in 2014 and 2020 from 2005. ► The anticipated scenario modeled ozone decreased from LEV II by 1% in 2014 and 1.5% in 2020.
Keywords: Air quality; Motor vehicle emissions; South coast air basin; NAAQS; Ozone; ROG; CO; NO x ; CMAQ; LEV II; LEV III; SULEV; Zero evap; 2005; 2014; 2020;

Vegetation fires in the himalayan region – Aerosol load, black carbon emissions and smoke plume heights by Krishna Prasad Vadrevu; Evan Ellicott; Louis Giglio; K.V.S. Badarinath; Eric Vermote; Chris Justice; William K.M. Lau (241-251).
In this study, we investigate the potential of multi-satellite datasets for quantifying the biomass burning emissions from the Himalayan region. A variety of satellite products were used for characterizing fire events including active fire counts, burnt areas, aerosol optical depth (AOD) variations, aerosol index and smoke plume heights. Results from the MODerate-resolution Imaging Spectroradiometer (MODIS) fire product suggest March–June as the major fire season with the peak during the April. An average of 3908 fire counts per year were recorded with sixty four percent of the fires occurring in the low elevation areas in the Himalayan Region. We estimate average burnt areas of 1129 sq. km, with the black carbon emissions of 431 Mg, per year. The mean AOD (2005–2010) was 0.287 ± 0.105 (one sigma) with peak values in May. Correlation analysis between the fire counts and AOD resulted in a Pearson correlation coefficient of 0.553; the correlation between the FRP and AOD is relatively weaker (r = 0.499). Planetary boundary layer height retrieved from the Modern Era Retrospective-Analysis For Research And Applications (MERRA) product suggests typical PBL height of 1000–1200 m during the April–May peak biomass burning season. Cloud-Aerosol Lidar Orthogonal Polarisation (CALIOP) retrievals show the extent of smoke plume heights beyond the planetary boundary layer during the peak biomass burning month of April. However, comparison of fires in the Himalayan region with other regions and comparisons to aerosol index data from the Ozone Monitoring Instrument (OMI) suggest smoke plumes reaching less than 3 km. Our results on fires and smoke plume height relationships provide valuable information for addressing aerosol transport in the region.► MODIS data was useful in characterizing the number of fire events, seasonality, burnt areas as well as intensity. ► Fire events resulted in increased aerosol optical depth, with peak during May. ► Fire counts correlated well with AOD. ► Satellite data revealed smoke plume heights reaching beyond 5-km in the Himalayan region.
Keywords: Vegetation fires; Biomass burnt; Emissions; India;

Variation in ozone exposure in the landscape of southern Sweden with consideration of topography and coastal climate by J. Klingberg; P.E. Karlsson; G. Pihl Karlsson; Y. Hu; D. Chen; H. Pleijel (252-260).
Ozone concentrations ([O3]) and meteorological parameters were measured with a mobile monitoring station at two coastal and five inland sites in southwest Sweden. Three of the five inland sites were located topographically low and two high compared to the surrounding landscape. In addition, [O3] data from six permanent monitoring stations in southern Sweden were analysed in relation to the positions of the measurement sites in the landscape. [O3] was also measured with passive diffusion samplers at two other sites. Both the diurnal temperature range (DTR) and the diurnal [O3] range (DOR) were to a large extent explained by the strength of the nocturnal temperature inversions at the sites. To investigate the influence of topography, the relative altitude of the sites was defined as the average altitude within a 3 km radius subtracted from the altitude of the site. Statistically significant relationships were obtained for average [O3] as well as DOR with relative altitude. Inland low sites experienced stronger nocturnal temperature inversions, lower average [O3] and larger DOR compared to inland high and coastal sites. Relative altitude was found to be superior to site altitude in explaining the variation of average [O3] and DOR in the landscape. This study underlines the importance of including local topography, as well as vicinity to the coast, in modelling [O3] and in O3 environmental risk assessments.► Local topography and coastal climate are important sources of [O3] variation. ► Night-time [O3] varies substantially over short geographical distances. ► Landscape variation in [O3] depends on strength of nocturnal temperature inversions. ► Relative altitude is superior to altitude in explaining the diurnal dynamics of O3.
Keywords: Diurnal ozone range; Diurnal temperature range; Temperature inversion; Local topography; Southern Sweden;

Determining source impacts near roadways using wind regression and organic source markers by David A. Olson; Ram Vedantham; Gary A. Norris; Steven G. Brown; Paul Roberts (261-268).
Concentrations of 13 organic source markers (10 polycyclic aromatic hydrocarbons and 3 hopanes) are reported from time-integrated samples (24-h and sub-daily) collected near a highway in Las Vegas, NV. Sample selection for assessing source impacts from the roadway was completed using the wind regression model Air Pollution Transport to Receptor model (EPA APTR 1.0). The model uses a kernel smoothing method for estimating source sectors (sector apportionment) of chemicals across wind speeds and wind directions. The model was applied using semi-continuous (5-min averaging time) pollutant data (black carbon (BC), CO, NO2, and NOx) and meteorological data. Using simple screening criteria to identify source impacts (>30% sector apportionment from the roadway and errors in the estimated sector apportionment <30%), sector apportionment results were consistent with organic source marker concentrations representative of motor vehicle exhaust (e.g., benzo(g,h,i)perylene and hopane). Results demonstrated the use of APTR to identify source-impacted time intervals when compared with filter samples analyzed for organic source markers.► We used the wind regression model Air Pollution Transport to Receptor model (EPA APTR 1.0) to estimate source impacts. ► We report concentrations of 10 PAHs and 3 hopanes from samples collected near a highway in Las Vegas, NV. ► The wind regression model used 5-min pollutant data (BC, CO, NO2, and NOx) and meteorological data. ► Sector apportionment results compared well with source-impacted filter samples analyzed for organic source markers.
Keywords: Source apportionment; Motor vehicles; Hopanes; Polycyclic aromatic hydrocarbons (PAHs);

Biomass burning aerosols observed in Eastern Finland during the Russian wildfires in summer 2010 – Part 1: In-situ aerosol characterization by H. Portin; T. Mielonen; A. Leskinen; A. Arola; E. Pärjälä; S. Romakkaniemi; A. Laaksonen; K.E.J. Lehtinen; M. Komppula (269-278).
Biomass burning smoke and associated aerosol particles from wildfires near Moscow, Russia during summer 2010 had a significant impact on air quality both in the close vicinity of the burning area and to a lesser extent in other parts of Eastern Europe. Smoke was also observed in Eastern Finland, about 1000 km northwest of the fire area, in city of Kuopio, at Puijo tower atmospheric measurement station and at the city of Kuopio air quality monitoring sites. The origin of air masses was confirmed by remote sensing observations and trajectory analyses. Despite the distance between Kuopio and the fire area and a travel time of 1–2 days, exceptional physical and optical properties of aerosol particles were evident. During smoke events, aerosol particles twice as large (geometric mean diameter 158 nm) as in background conditions (geometric mean diameter 76.3 nm) were observed and they contained record-breaking amounts of black carbon, up to 1.23 μg m−3, which exceeds typical values by a factor of 12. Thus, absorption coefficient was significantly different when compared to background summer conditions (8.12 Mm−1 vs. 0.651 Mm−1). Also scattering coefficients experienced a remarkable increase, on average from 12.0 Mm−1, 7.2 Mm−1 and 4.2 Mm−1 to 245 Mm−1, 169 Mm−1 and 111 Mm−1 for blue, green and red light, respectively. The amount of particulate mass also experienced a multifold increase. Depending on the measurement site, PM2.5 grew from 3 to 6 μg m−3 to 34–48 μg m−3 and PM10 from 4 to 17 μg m−3 to 40–76 μg m−3. Trace gas concentrations were also affected by the smoke presence, especially carbon monoxide, which is commonly used as a tracer for biomass burning smoke. The concentration of nitric oxide, nitrogen dioxide, ozone and sulfur dioxide was affected only moderately and partly masked by the emissions from local pollutant sources.► Smoke from wildfires around Moscow was observed in Kuopio, Eastern Finland. ► Smoke affected air quality, by e.g. reducing visibility and increasing PM2.5. ► Aerosol particles in smoky air were twice as large as in background conditions. ► Light absorption and scattering properties of the particles were extraordinary. ► Smoke also affected trace gas concentrations, particularly carbon monoxide.
Keywords: Biomass burning; Particulate matter; Black carbon; Light scattering;

Biomass burning aerosols observed in Eastern Finland during the Russian wildfires in summer 2010 – Part 2: Remote sensing by T. Mielonen; H. Portin; M. Komppula; A. Leskinen; J. Tamminen; I. Ialongo; J. Hakkarainen; K.E.J. Lehtinen; A. Arola (279-287).
In the summer 2010 extensive wildfires in the western parts of Russia emitted massive amounts of smoke and aerosols into the atmosphere. These smoke plumes also drifted to Finland over 1000 km away from the fires. The smoke plumes were detected in Kuopio (Eastern Finland) with a wide range of instruments on two specific days: July 29 and August 8. The plumes were studied with several spaceborne instruments: MODIS, OMI, AIRS and CALIOP. Furthermore, a ground-based remote sensing instrument (Cimel) was also used in the analysis. Our results show that ground-based and spaceborne instruments were in good agreement on the Aerosol optical depth (AOD550) values during the episode (July–mid August). The correlation coefficient between MODIS and AERONET measurements done in Kuopio was 0.98 and the mean difference was 0.005 (AERONET AOD being larger). Spaceborne measurements of carbon monoxide provided a clear indicator for biomass burning aerosols. Particle mass (PM2.5) and AERONET AOD550 measurements were also in good agreement with a correlation coefficient of 0.87. Single scattering albedo (SSA675) values derived from AERONET measurements and calculated from in-situ absorption and scattering measurements had similar values close 0.9. On average, the daily in-situ SSA values were 0.02 smaller than the corresponding AERONET values. CALIOP provided vertical profiles of the smoke plumes for the two most polluted days in Kuopio. In July the plume was located close to the surface (mainly below 2 km) while in August the plume had two elevated layers: one between 1 and 2 km and the other between 2.5 and 4 km.► We studied the 2010 Russian wildfires with remote sensing instruments. ► Ground-based and spaceborne instruments were in good agreement. ► Combined ground-based and spaceborne measurements describe the episode thoroughly.
Keywords: Biomass burning emissions; Remote sensing; Aerosols;

A general analytical model for characterizing emission and sorption of formaldehyde and volatile organic compounds (VOCs) in single-layer building materials is developed. Compared with traditional models, the present model can be applicable for four kinds of typical physical processes, i.e., emission in ventilated and airtight chambers, and sorption in these two types of chambers. Based on the general analytical model, a novel method is proposed to determine the characteristic parameters (the diffusion coefficient, D m, and the material/air partition coefficient, K) of formaldehyde and VOC sorption in ventilated and airtight chambers. It establishes a linear relationship between the logarithm of dimensionless excess concentration and sorption time, and the D m and K can be conveniently obtained from the slope and intercept of the regression line. The results of applying the present model are compared with the experimental data in the literature. The good agreement between them not only validates the model but also demonstrates that the measured characteristic parameters are accurate and reliable. The general analytical model should prove useful for unified characterization and prediction of emission/sorption in building materials as well as for parameter measurement.► A general analytical model for formaldehyde and VOC emission/sorption is developed. ► A novel method is proposed to determine the characteristic parameters of sorption. ► The model and the parameter measurement method are validated with experimental data.
Keywords: Indoor air quality; Volatile organic compounds; Formaldehyde; Emission; Sorption; Building material;

Atmospheric pollution in a semi-urban, coastal region in India following festival seasons by T. Nishanth; K.M. Praseed; K. Rathnakaran; M.K. Satheesh Kumar; R. Ravi Krishna; K.T. Valsaraj (295-306).
The traditional Vishu festival in the state of Kerala in South India is celebrated in April with extensive coordinated fireworks display. The influence of these celebrations on the immediate and long-term air quality and impact on the health and well being of the public needs research. The combustion clouds contain harmful fumes (sulfur dioxide, oxides of nitrogen) and particulate matter released at the surface. This study is focused on the influence of fireworks on the air quality at Kannur, India, during Vishu in April 2010 and 2011. Elevated concentrations of various air pollutants such as O3, NO2, NO and PM10 were measured during the intense usage of fireworks. Surprisingly, the organic analysis of the Particulate Matter (PM) samples collected on Vishu day revealed the emission of a variety of hazardous organic compounds during the fireworks display. One of the unique observations in this work is the nighttime production of O3 by the photodissociation of NO2 from the flash of firecrackers. The concentration of O3 was observed to increase two fold over the control days of observation during the same month. Moreover, the concentrations of NO2, and PM10 increased by 100%. The concentration of NO was reduced by four fold during the event. A scheme based on the organic combustion from fireworks and peroxyl radical mediation is proposed for the nighttime production of ozone. The diurnal profile of all pollutants except NO showed higher concentrations starting from the Vishu eve on April 14 to Vishu day on April 15 and this pattern repeated for years 2010 and 2011. The fireworks activities have been increasing every year and generation of pollutants at their increased levels for short duration can potentially cause adverse health impacts on a regional scale in a highly populated region.► First report on the air quality during Vishu festival in Kerala, India. ► Nighttime ozone formation from the intense flash of fireworks. ► A sharp decline in NO and enhancement in NO2 during the episode. ► Spectral analysis of firecrackers. ► Emission of variety of organics from firecrackers.
Keywords: Air quality; Ozone; NOx; PM10; Fireworks; Kerala;

Seasonal heterogeneity in aerosol types over Dibrugarh-North-Eastern India by Binita Pathak; Pradip Kumar Bhuyan; Mukunda Gogoi; Kalyan Bhuyan (307-315).
Columnar aerosol properties retrieved from Multi-Wavelength solar Radiometer (MWR) measurements during the period 2001–2010 over Dibrugarh (27.3°N, 94.6°E, 111 m amsl), North-Eastern India are analyzed to identify the types of aerosols in the atmospheric column. Highest Aerosol optical depth (AOD) characterizes the pre-monsoon (March–May), while lowest AOD has been observed during the post-monsoon (Oct–Nov) season. The Ångström exponent (α) indicates predominance of fine aerosols during post-monsoon and winter (Dec–Feb) and dominance of coarse mode in pre-monsoon and monsoon (June–Sept). NOAA HYSPLIT back trajectory analysis suggests that the seasonal heterogeneity in aerosol characteristics can be attributed to the varying contribution from different source regions. Using the relationship between AOD500 and α, the aerosols can be classified into five main types viz. continental average (CA), marine continental average (MCA), urban/industrial and biomass burning (UB) and desert dust (DD) while the remaining cases are considered as unidentified or mixed type (MT). These aerosol types exhibit seasonal heterogeneity in their contribution depending upon variability in sources. In winter, local production contributes to observed appreciable CA aerosol type, while highest percentage of UB type is attributed to both local and transported aerosols. On the other hand, transported UB and DD types play a significant role in the pre-monsoon season. Post-monsoon season is indicative of background continental average aerosol condition with a significant contribution from CA and MCA aerosols. Monsoon aerosols couldn't be distinguished properly due to different particle growth processes like humidification, hygroscopic growth etc. and hence MT aerosol type is predominant in this season. This is the first ever attempt to classify aerosols over this environment.► The columnar aerosol properties are analyzed over Dibrugarh. ► Column aerosol burden is highly influenced by transported aerosols. ► Five different aerosol types are identified which display significant seasonal variation.
Keywords: Aerosol type; Multi-wavelength solar Radiometer; AOD; Ångström exponent; HYSPLIT;

The reaction of OH radicals with dimethyl sulphide (CH3SCH3, DMS) has been studied in the atmospheric pressure flow tube IfT-LFT at 293 ± 0.5 K in the absence of NO x , [NO x ] ≤ 1010  molecule cm−3. OH radicals were generated either via the photolysis of H2O2 under dry conditions or using the photolysis of O3 at a relative humidity of 50%. PTR-MS and FT-IR spectroscopy served as analytical techniques for product analysis. Observed products were SO2, HCHO, methyl thioformate (MTF), dimethyl sulfoxide (DMSO) and likely dimethyl sulfone (DMSO2). The formation of SO2, HCHO and MTF was clearly inhibited under conditions of a favoured reaction of CH3SCH2O2 radicals with HO2. Experiments in the presence of up to 2 × 1012  molecule cm−3 of O3 showed a small increase of the formation yields of SO2 and HCHO with increasing O3 levels. Modelling runs have been performed using the DMS module from the Master Chemical Mechanism, MCMv3.2, with a few modifications. Generally, the simulation slightly under-predicted the measured yields of HCHO. The SO2 yields observed were roughly in agreement with the modelling results. A qualitative description of the experimentally detected MTF production was achieved by neglecting the MTF formation path via CH3SCH2O2  + HO2 as given originally by MCM. The simulation results described well the amount of consumed O3 by DMS intermediates as well as the impact of O3 on products yields.► Product formation from the reaction OH + DMS was measured in the absence of NO x . ► Influence of O3 on product distribution is investigated. ► Modelling based on MCMv3.2 has been performed.
Keywords: Dimethyl sulphide (DMS); Oxidation; OH radicals; Sulphur dioxide; Simulation;

Characterization of organosulfates in atmospheric aerosols at Four Asian locations by Elizabeth A. Stone; Liming Yang; Liya E. Yu; Maheswar Rupakheti (323-329).
Organosulfates have recently been observed in ambient atmospheres as a component of aerosol organic matter. This study presents the first characterization of organosulfates in Asia and demonstrates their ubiquity and chemical diversity, yet minor contribution to fine particulate mass. Organosulfates were characterized in ambient aerosol by ultra-performance liquid chromatography and high-resolution mass spectrometry, which allowed for experimental determination of molecular formulas and estimation of atmospheric abundance. Aerosols were analyzed from four sites spanning urban and remote locations, including Hanimaadhoo, Maldives, Gosan, Korea, Singapore, and Lahore, Pakistan. Semi-quantitative analysis yielded average estimates of OS accounting for less than 1% of PM2.5 mass, 2.3% of organic carbon, and 3.8% of total sulfate. The majority of the observed compounds were attributed to biogenic secondary organic aerosol from isoprene or monoterpenes. New organosulfates are also reported.► We characterize organosulfates in Asian aerosol for the first time. ► Organosulfates are minor contributors to particulate mass and carbon. ► More than 20 individual organosulfate species were observed. ► Most species were consistent with biogenic secondary organic aerosol. ► Other species were unique to a season or location.
Keywords: Organosulfates; Secondary organic aerosol; Biogenic aerosol; Asia;

We examine transport and chemical transformation of reactive pollutants on an urban street using a computation fluid dynamics (CFD) model coupled with full photochemistry of reactive pollutants. An extensive comparison between simulated results and observations is conducted to evaluate the model, focusing on a field campaign occurred in Dongfeng Middle Street in Guangzhou, China. Observed CO and NO concentrations vary diurnally following traffic volumes. The model captures this observed diurnal variation and magnitudes of CO concentrations successfully. However, simulated NO concentration is three times higher than observation. This high bias is significantly reduced in the sensitivity simulation with lower NO x emissions. We find that oxidation products of O3 photochemistry such as NO2 and O3 vary differently from primary pollutants, indicating important effects of photochemical reactions on their fates. The model appears to reproduce observed O3 and NO2 variability with time and altitude. Our analysis shows that high NO x concentrations in the urban street canyon may efficiently produce aerosol nitrate in the presence of NH3. Simulated inorganic NO3 aerosol concentration reaches up to 0.3 μg m−3 in July but increases an order of magnitude higher at lower temperature that favors partitioning of gas-phase HNO3 to aerosol-phase, implying a serious concern for urban air quality in winter.► We developed a coupled full chemistry-CFD model. ► The model was first applied to an observed case on an urban street canyon. ► The spatial pattern of secondary pollutants differs from the primary. ► Nitrate aerosol would be important for air quality on an urban street.
Keywords: Street canyon; Urban pollution; Air quality; CFD;

In Austria a new guideline is under development to calculate the separation distance between livestock and residential areas to avoid odour annoyance. On the basis of dispersion model calculations for 6 sites by the Austrian odour dispersion model (AODM) a regression model is developed, using a power function S = a Eb . The power function is defined by four input parameters. The basis of the power function is the odour emission rate E (ouE s−1) in the range between 400 ouE s−1 ≤ E ≤ 24 000 ouE s−1. The factor a and the exponent b of the power function are defined by two meteorological parameters, the relative frequency of the wind direction F, the mean wind velocity W of the wind direction for 10° sectors as well as the odour exceedance probability P of the odour impact criterion. One of the requirements for this empirical model is the aspiration to substitute the complex calculation with a dispersion model by the new empirical model. The empirical model can be used in a paper and pencil mode, which enables an evaluation of a planned livestock building in a simple way. For a more detailed assessment, a dispersion model can be applied with the entire meteorological information (e.g., stability of the atmosphere, wind field models), the geometry of the emission source, a time depending odour emission rate, and the orography of the site.► Odour is a major nuisances in the environment often caused by livestock. ► Separation distances are applied to guarantee a certain protection level. ► Empirical guide lines are in use to calculated these separation distances. ► For Austria a new model was developed, based on dispersion modelling. ► Model predictors are: emission, frequency and wind speed, impact criteria.
Keywords: Guideline; Separation distance; Annoyance; Nuisances; Livestock; Odour; Emission rate; Residential area; Dispersion model; Complaint;

Emissions of non-methane volatile organic compounds (NMVOCs) were determined from a swine concentrated animal feeding operation (CAFO) in North Carolina. NMVOCs were measured in air samples collected in SUMMA and fused-silica lined (FSL) canisters and were analyzed using a gas chromatography flame ionization detection (GC–FID) system. Measurements were made from both an anaerobic lagoon and barn in each of the four seasonal sampling periods during the period June 2007 through April 2008. In each sampling period, nine to eleven canister samples were taken from both the anaerobic lagoon and barn over a minimum of four different days during a period of ∼1 week. Measurements of meteorological and physiochemical parameters were also made during the sampling period. In lagoon samples, six NMVOCs were identified that had significantly larger emissions in comparison to other NMVOCs. This included three alcohols (ethanol, 2-ethyl-1-hexanol, and methanol), two ketones (acetone and methyl ethyl ketone (MEK)) and an aldehyde (acetaldehyde). The overall average fluxes for these NMVOCs, ranged from 0.18 μg m−2 min−1 for 2-ethyl-1-hexanol to 2.11 μg m−2 min−1 for acetone, with seasonal fluxes highest in the summer for four (acetone, acetaldehyde, 2-ethyl-1-hexanol and MEK) of the six compounds In barn samples, there were six NMVOCs that had significantly larger concentrations and emissions in comparison to other NMVOCs. These consisted of two alcohols (methanol and ethanol), an aldehyde (acetaldehyde), two ketones (acetone and 2,3-butanedione), and a phenol (4-methylphenol). Overall average barn concentration ranged from 2.87 ppb for 4-methylphenol to 16.12 ppb for ethanol. Overall average normalized barn emission rates ranged from 0.10 g day−1 AU−1 (1 AU (animal unit) = 500 kg of live animal weight) for acetaldehyde to 0.45 g day−1 AU−1 for ethanol. The NMVOCs, 4-methylphenol and 2,3-butanedione, which have low odor thresholds (odor thresholds = 1.86 ppb and 0.068–0.264 ppb for 4-methylphenol, and = 4.37 ppb and 1.42–7.39 ppb for 2-3-butanedione) and an offensive odor were identified in canister samples. Both 4-methylphenol and 2,3-butanedione barn concentrations exceeded their odor thresholds frequently. HAPs were identified in lagoon samples (methanol, acetaldehyde and MEK) and barn samples (methanol, acetaldehyde and 4-methylphenol) that were also classified as NMVOCs with significantly larger lagoon and barn emissions in comparison with other NMVOCs. The overall average lagoon fluxes and overall average normalized barn emissions for NMVOCs reported in this paper were used to estimate their North Carolina swine CAFO emissions. Of the NMVOCs, ethanol was estimated to have the largest North Carolina swine CAFO emission at 206,367 kg yr−1. The barns were found to have higher emissions than the lagoons for all NMVOCs, contributing between 68.6 to ∼100% of individual compounds estimated North Carolina swine CAFO emissions.► Intensification of agriculture has caused air quality impacts. ► There is very limited information on NMVOCs emissions from swine CAFOs. ► This paper provides a comprehensive analysis of NMVOC emissions from a swine CAFO.
Keywords: Non-methane volatile organic compounds; CAFO emissions; Swine;

Aluminum (Al) is an abundant metal in airborne particulate matter. Al concentrations carried by total suspended particulates (TSP) of the Nanjing atmosphere were distinctly higher in soils of industrial areas than the background concentration of the soils. This study aimed to assess the influence of the soils varying in their degree of contamination on the soil-to-plant transfer and translocation of Al to Masson pine (Pinus massoniana L.). A pot experiment was conducted to investigate the phytoavailability and speciation of Al carried by TSP which was collected at urban and industrial sites over a 12-month period in the atmosphere of Nanjing, China. The extractable noncrystalline Al in environmental particulate samples could be operationally fractionated into insoluble (Alin), oxide (Alox), organic (Alor), carbonate (Alca), and exchangeable species (Alex) using Tessier's sequential extraction procedure. The results showed that relatively high Al concentrations in TSP and soil samples were observed at the industrial site due to emissions from a local industry that manufactures Al-based products. The distribution sequence of Al species was quite similar for TSP and soil samples, which was Alin > Alor > Alox > Alca > Alex. The order of industrial particulate matter (IPM) was Alin > Alox > Alca > Alex > Alor. Alor was not detectable. A greater migration of Alex species entered the pine roots and the highest Al contents were accumulated in the roots and declined in the aerial portions. The soil-to-pine Al transfer was extremely low even when grown on industrial Al-contaminated soils. A significant positive correlation was found between the Al contents in pine seedlings and rhizospheric Alex contents. In contrast, there was a strong negative correlation between rhizospheric Alex contents and seedling biomass. For the spiked soils, under the influence of IPM, Al phytoavailability decreased with elevated rhizospheric Al and Alex. Collectively, this study provided evidence of Alex and Alor species dependent Al phytoavailability. Excessive Al carried by IPM lead to a decline in the pine biomass production, and different Al phytoavailabilities showed differentiated responses to IPM addition.► We described the phytoavailability and speciation of Al carried by TSP to the pine. ► The industrial Al-stimulated phytotoxicity in a air-soil-pine system was observed. ► We provided evidence of possible Alex and Alor dependent Al phytoavailability. ► The influence of the spiked soils on the soil-to-pine Al transfer was assessed. ► The Al in pine and pine biomass were mainly associated with rhizospheric Alex.
Keywords: Aluminum speciation; Total suspended particulates (TSP); Soil-to-pine transfer; Phytoavailability; Masson pine (Pinus massoniana L.);

Comparison of CFD and operational dispersion models in an urban-like environment by G. Antonioni; S. Burkhart; J. Burman; A. Dejoan; A. Fusco; R. Gaasbeek; T. Gjesdal; A. Jäppinen; K. Riikonen; P. Morra; O. Parmhed; J.L. Santiago (365-372).
Chemical plants, refineries, transportation of hazardous materials are some of the most attractive facilities for external attacks aimed at the release of toxic substances. Dispersion of these substances into the atmosphere forms a concentration distribution of airborne pollutants with severe consequences for exposed individuals. For emergency preparedness and management, the availability of assessed/validated dispersion models, which can be able to predict concentration distribution and thus dangerous zones for exposed individuals, is of primary importance.Air quality models, integral models and analytical models predict the transport and the turbulent dispersion of gases or aerosols after their release without taking into account in detail the presence of obstacles. Obstacles can modify the velocity field and in turn the concentration field. The Computational Fluid Dynamics (CFD) models on the other hand are able to describe such phenomena, but they need to be correctly set up, tested and validated in order to obtain reliable results.Within the project Europa-ERG1 TA 113.034 "NBC Modelling and Simulation" several different approaches in CFD modelling of turbulent dispersion in closed, semi-confined and urban-like environment were adopted and compared with experimental data and with operational models. In this paper the results of a comparison between models describing the dispersion of a neutral gas in an idealized urban-like environment are presented and discussed. Experimental data available in the literature have been used as a benchmark for assessing statistical performance for each model. Selected experimental trials include some water channel tests, that were performed by Coanda at 1:205 scale, and one full-scale case that was tested in the fall of 2001 at the Dugway Proving Grounds in Utah, using an array of shipping containers. The paper also suggests the adoption of improved statistical parameters in order to better address differences between models, and to have a more straightforward method for comparing models suitable for emergency preparedness aims.► Comparison of CFD and Gaussian/Lagrangian models at laboratory and field scale. ► Statistical performance parameters calculated from experimental data. ► Model ranking on the basis of combination of statistical parameters.
Keywords: CFD modelling; Gas dispersion; Emergency preparedness; Urban area; Model performance;

Nitric oxide and greenhouse gases emissions following the application of different cattle slurry particle size fractions to soil by David Fangueiro; João Coutinho; Fernanda Cabral; Paula Fidalgo; Roland Bol; Henrique Trindade (373-380).
The application to soil of different slurry particle size fractions may lead to variable gaseous soil emissions and associated differential environmental impacts. An incubation experiment was carried out during 70 d to assess the influence on nitric oxide (NO) and greenhouse gas (GHG; i.e. nitrous oxide, carbon dioxide and methane) emissions following incorporation of 4 particle size fractions, obtained through laboratorial separation from cattle slurry, to agricultural sandy loam soil (Dystric Cambisol). The response to these applied slurry fractions (>2000 μm, 2000–500 μm, 500–100 μm, <100 μm) was compared to other experimental treatments, including whole slurry (WS), ammonium sulphate (AS) and an unamended control (CON). The highest value of cumulated NO emissions (6.3 mg NO–N kg−1 dry soil) were observed from the AS treatment. The cumulated amount of NO emitted (∼1 mg NO–N kg−1 dry soil) was not significantly different between slurry fractions, thereby indicating that slurry particle size had no effect on NO emissions. The largest slurry fraction (>2000 μm) induced significantly higher N2O emissions (1.8 mg N2O–N kg−1 dry soil) compared to the other smaller sized fractions (1.0 mg N2O–N kg−1 dry soil). The >2000 μm, fraction, being more than 55% of the slurry by weight, was the major contributor to daily and cumulative N2O emissions. Hence, for N2O, the application of WS to agricultural soil is a better option that amendment with the >2000 μm, fraction. Low CH4 emissions (<200 μg CH4–C kg−1 dry soil d−1) were observed, but only in treatments amended with slurry or its fractions. The CH4 emissions were short-lived and rates returned to control levels within 3 d after the slurry application. Higher CO2 emissions were observed in soils amended with slurry fractions when compared to application with whole slurry. Clearly, slurry separation can increase soil CO2 emissions relative to whole slurry application.Overall, N2O contributed 10–30% to total GHG emissions, while that of methane was negligible. The present study suggested that mechanical separation of slurry into fractions and targeted application of the finest fractions to soil is a potential suitable management tool to reduce GHG emissions. However, the largest fractions have to be used for other purposes as anaerobic digestion rather than applied to soil.► Slurry particle size has no effect on NO emissions following soil application. ► Slurry separation does not increase NO emissions after soil application. ► The grossest slurry fraction is the main contributor to N2O emissions when whole slurry is applied to soil. ► CO2 emissions should not be disregarded since it is still the major contributor to GHG emissions.
Keywords: Gaseous emissions; Carbon; Nitrogen dynamics; Slurry treatment; Particle size fractionation;

Environmental chambers are widely used to test formaldehyde and other volatile organic compound (VOC) emissions from indoor materials and furniture. However, there is a lack of a proven method to assess the precision of the test results of the chamber system. In this paper, we describe a new standard reference, LIFE (liquid-inner tube diffusion-film-emission), to address this problem. This reference has the following salient features: (1) Constant emission rate, with less than 3.0% change with an ambient airflow speed (>0.014 m/s) at furniture emission range (0.1–1.0 mg/m3 in a 30 m3 chamber with air change rate of 1/h) under standard chamber test conditions as specified by ISO 16000-9 (23 °C, 50% RH); (2) Long duration of emissions, on the order of 1000 h; (3) Easy to store, apply and maintain. The design principle and criteria of the LIFE reference are presented. An analytical model and dimensionless analysis were applied to optimize the factors influencing the emission rate, and experiments were conducted to validate the analytical results. In addition, the equivalent emission parameters of the reference, i.e., the initial emittable concentration, the diffusion coefficient and the partition coefficient, were determined through a three-parameter optimizing regression. This can then be used to check the reliability of a chamber method for testing these three parameters. The developed standard reference should prove useful for calibrating chamber systems for indoor material/furniture VOC emissions tests.► An analytical model for liquid-film VOC standard reference is developed. ► A novel VOC standard reference is designed to calibrate chamber test system. ► The equivalent emission parameters of the reference are determined.
Keywords: VOC emission; Standard reference; Chamber; Furniture; Indoor air quality (IAQ);

Cloud condensation nuclei droplet growth kinetics of ultrafine particles during anthropogenic nucleation events by N.C. Shantz; J.R. Pierce; R.Y.-W. Chang; A. Vlasenko; I. Riipinen; S. Sjostedt; J.G. Slowik; A. Wiebe; J. Liggio; J.P.D. Abbatt; W.R. Leaitch (389-398).
Evolution of the cloud condensation nucleus (CCN) activity of 36 ± 4 nm diameter anthropogenic aerosol particles at a water supersaturation of 1.0 ± 0.1% is examined for particle nucleation and growth. During the early stages of one event, relatively few of the anthropogenic particles at 36 nm were CCN active and their growth rates by water condensation were delayed relative to ammonium sulphate particles. As the event progressed, the particle size distribution evolved to larger sizes and the relative numbers of particles at 36 nm that were CCN active increased until all the 36 nm particles were activating at the end of the event. Based on the chemistry of larger particles and the results from an aerosol chemical microphysics box model, the increase in CCN activity of the particles was most likely the result of the condensation of sulphate in this case. Despite the increased CCN activity, a delay was observed in the initial growth of these particles into cloud droplets, which persisted even when the aerosol was most CCN active later in the afternoon. Simulations show that the delay in water uptake is explained by a reduction of the mass accommodation coefficient assuming that the composition of the 36 nm particles is the same as the measured composition of the 60–100 nm particles.► Field study of water uptake and droplet growth kinetics on 36 nm particles. ► Soon after anthropogenic particle nucleation event, particles were not CCN active. ► Particles become more CCN active later on, suggesting sulphate condensation. ► Delays in the initial water uptake suggest organic film inhibits droplet growth. ► Both sulphate and organics are important for growth of particles up to CCN sizes.
Keywords: Aerosols; CCN; Water uptake; Growth kinetics; Nucleation;

Pollutant constituents of exhaust emitted from light-duty diesel vehicles by Hung-Lung Chiang; Yen-Ming Lai; Sheng-You Chang (399-406).
Light-duty diesel exhaust particulate matter and its constituents, including elemental carbon, organic carbon, water-soluble ionic species, elements, and polyaromatic hydrocarbons (PAHs), were measured by a dynamometer study and following the driving pattern of federal test procedure-75 (FTP-75). Fuel consumption of these light-duty diesel vehicles (LDDV) was in the range of 0.106–0.132 l km−1, and the average emission factors of NMHC (non-methane hydrocarbon), CO and NOx for light-duty vehicles were 0.158 (92% of total hydrocarbon), 1.395, and 1.735 g km−1, respectively. The particulate emission factor of LDDVs was 0.172 g km−1, and PM2.5 contributed to 88% of particulate mass. Al, S, Ca, and Fe emission factors were about 0.83–1.24 mg km−1 for PM2.5, and the particulate mass fractions of these elements ranged from 66 to 90% in PM2.5. Nitrate, sulfate, ammonium and nitrite were the major ionic species in diesel PM, and their emission factor ranged from 0.22 to 0.82 mg km−1 for PM2.5. The emission factor of total PAHs was 3.62 mg km−1 in this study, with about 40% in the gas phase and 60% in the particulate phase. Acenaphylene, naphthalene, fluoranthene, pyrene, and anthracene were the dominant PAHs, and their emission factors were more than 0.19 mg km−1. The content of nitro-PAHs was low, with most less than 0.040 mg km−1.► Diesel vehicle pollution is an important issue for air pollution control. ► FTP-75 driving cycle is conducted by dynamometer testing. ► Emission factors of NMHC, CO, NOx are determined for light-duty diesel vehicles. ► Particle constituents are determined for light-duty diesel vehicles.
Keywords: Diesel exhaust; Particulate composition; Emission factor;

Personal exposures to PM2.5 and their relationships with microenvironmental concentrations by Soogil Lim; Jeonghoon Kim; Taehyun Kim; Kiyoung Lee; Wonho Yang; Sangil Jun; Seungdo Yu (407-412).
Personal exposure to particulate matter of aerodynamic diameters less than 2.5 μm (PM2.5) can be affected by various factors. The purpose of this study was to determine the impact of activity pattern and the contribution of each microenvironment to personal PM2.5 exposure. Technicians carried a nephelometer for PM2.5 while engaging in scripted time location activities. The scripted activities of 10 different population groups were based on time activity patterns of the Seoul population in Korea. A total of 58 daily PM2.5 personal exposures were available for analysis. The average PM2.5 personal exposure was 19.8 ± 15.3 μg m−3. The average personal exposure of each population group ranged from 9.8 to 43.1 μg m−3. High peak and average concentrations were observed in restaurants and bars; such high concentrations were due to secondhand smoke and cooking with charcoal on tables. The residential indoor level of the nine microenvironments was the largest contributor to personal exposure. The contributions from residential indoor, non-residential indoor, transportation, and outdoor levels were 36.2%, 53.4%, 6.7%, and 3.7%, respectively. The contributions of microenvironments varied among population groups; these variations suggest that the impact of activity pattern on personal exposure is significant.► Personal exposures to PM2.5 were directly measured with simulating time activity. ► Residence was the most significant contributor to personal exposure to PM2.5. ► Indoor environments like restaurants are critical for public health protection. ► Charcoal cooking and secondhand smoke are important for indoor air quality. ► Understanding time activity patterns are important for personal exposure to PM2.5.
Keywords: PM2.5; Personal exposure; Microenvironment; Apportionment;

Summer/winter variability of the surfactants in aerosols from Grenoble, France by Christine Baduel; Barbara Nozière; Jean-Luc Jaffrezo (413-420).
Many atmospheric aerosols seem to contain strong organic surfactants likely to enhance their cloud-forming properties. Yet, few techniques allow for the identification and characterization of these compounds. Recently, we introduced a double extraction method to isolate the surfactant fraction of atmospheric aerosol samples, and evidenced their very low surface tension (≤30 mN m−1). In this work, this analytical procedure was further optimized. In addition to an optimized extraction and a reduction of the analytical time, the improved method led to a high reproducibility in the surface tension curves obtained (shapes and minimal values), illustrated by the low uncertainties on the values, ±10% or less.The improved method was applied to PM10 aerosols from the urban area of Grenoble, France collected from June 2009 to January 2010. Significant variability was observed between the samples. The minimum surface tension obtained from the summer samples was systematically lower (30 mN m−1) than that of the winter samples (35–45 mN m−1). Sharp transitions in the curves together with the very low surface tensions suggested that the dominating surfactants in the summer samples were biosurfactants, which would be consistent with the high biogenic activity in that season. One group of samples from the winter also displayed sharp transitions, which, together with the slightly higher surface tension, suggested the presence of weaker, possibly man-made, surfactants. A second group of curves from the winter did not display any clear transition but were similar to those of macromolecular surfactants such as polysaccharides or humic substances from wood burning. These surfactants are thus likely to originate from wood burning, the dominating source for aerosols in Grenoble in winter. These observations thus confirm the presence of surfactants from combustion processes in urban aerosols reported by other groups and illustrates the ability of our method to distinguish between different types of surfactants in atmospheric samples.Display Omitted► A method to extract the surfactant fraction of atmospheric aerosols was optimized. ► Aerosols from the urban area of Grenoble, France, contain some strong surfactants. ► The surfactant fraction display significant differences between the summer and the winter. ► In summer, the surfactant fraction seems to be controlled by biosurfactants. ► In winter, macromolecular surfactants from combustion seem to have a significant influence.
Keywords: Aerosols-cloud interactions; CCN properties; Organic compounds; Surfactants;

Low volatility terpenoids emitted from consumer products can react with ozone on surfaces and may significantly alter concentrations of ozone, terpenoids and reaction products in indoor air. We measured the reaction probability and a second-order surface-specific reaction rate for the ozonation of dihydromyrcenol, a representative indoor terpenoid, adsorbed onto polyvinylchloride (PVC), glass, and latex paint coated spheres. The reaction probability ranged from (0.06–8.97) × 10−5 and was very sensitive to humidity, substrate and mass adsorbed. The average surface reaction probability is about 10 times greater than that for the gas-phase reaction. The second-order surface-specific rate coefficient ranged from (0.32–7.05) × 10−15 cm4 s−1 molecule−1and was much less sensitive to humidity, substrate, or mass adsorbed. We also measured the ozone deposition velocity due to adsorbed dihydromyrcenol on painted drywall in a room-sized chamber, Based on that, we calculated the rate coefficient ((0.42–1.6) × 10−15 cm4 molecule−1 s−1), which was consistent with that derived from bench-scale experiments for the latex paint under similar conditions. We predict that more than 95% of dihydromyrcenol oxidation takes place on indoor surfaces, rather than in building air.► The surface reaction rate of ozone with dihydromyrcenol was quantified. ► Indoor surfaces substantially increase ozone–dihydromyrcenol conversion rates. ► Ozone–dihydromyrcenol conversion was dominated by their surface reaction. ► Low-reactivity compounds can lead to enhanced ozone flux to indoor surfaces.
Keywords: Indoor air; Ozone; Dihydromyrcenol; Surface reactions; Kinetics;

An analysis of the time series of the maximum daily ozone hole area over Antarctica for each year during the period 1979–2009 is presented, based on the entropy S defined in a new time domain termed natural time domain, that captures characteristics of the dynamics of the ozone hole complex system. The results obtained show that the entropy in natural time for scales 3–7 years and its value under time reversal for all scales (3–15 years) almost stabilizes during the last several years. On the other hand, characteristic features of this entropy are clearly found before the unprecedented event of the major, sudden stratospheric warming and the subsequent break-up of the Antarctic ozone hole into two holes in September 2002. In particular, the following precursory changes have been identified: First, for scales larger than 8 years, the entropy in natural time exhibits a gradual increase after around 1999. Second, from 2000 to 2001, the entropy in natural time under time reversal shows an increase for all scales (3–15 years) except for the scale of 13 years. Third, the values of the entropy change in natural time almost coincide at 2000 for the short scales 3–7 years and then decrease. The analysis in the natural time domain is also applied on the eddy heat flux, which is proportional to the vertically propagating wave activity affecting the ozone hole over Antarctica. The results drawn confirm those deduced from the ozone hole area diagnostics.► We study the dynamical evolution of the Antarctic ozone hole with a new tool. ► We make use of the entropy defined in a new time domain termed natural time domain. ► Precursory changes found before the ozone hole split over Antarctica in 2002.
Keywords: Dynamics; Ozone; Entropy; Natural time analysis;

Spatio-temporal variations in aerosol optical and cloud parameters over Southern India retrieved from MODIS satellite data by G. Balakrishnaiah; K. Raghavendra kumar; B. Suresh Kumar Reddy; K. Rama Gopal; R.R. Reddy; L.S.S. Reddy; C. Swamulu; Y. Nazeer Ahammed; K. Narasimhulu; K. KrishnaMoorthy; S. Suresh Babu (435-445).
Remote sensing of global aerosols has generated a great scientific interest in a variety of applications related to global warming and climate change. The spatial and temporal variations in aerosol particles over Southern India were described in the present study and the impact of these variations on various optical properties of clouds, using Moderate Resolution Imaging Spectroradiometer (MODIS) data retrieved from the Terra satellite. High mean Aerosol Optical Depth (AOD) values were observed in almost all regions during the summer season, whereas in Pune, Visakhapatnam and Hyderabad, high AOD values were noticed during the monsoon season. The Ångström exponent that increases with AOD is opposite to what would be the case if swelling of particles due to hygroscopic growth near cloudy areas played a major role in the MODIS data. We then analyzed the relationships between AOD and four other cloud parameters, namely water vapor (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP). Regional correlation maps and time series plots for aerosol (AOD) and cloud parameters were produced to provide a better understanding of aerosol–cloud interaction. The correlation between AOD and CF was greater than 0.51 in Visakhapatnam, 0.45 in Thiruvanantapuram, 0.42 in Pune and whereas in Bangalore, Hyderabad and Anantapur, it is 0.17, 0.39 and 0.12, respectively. The analyses showed strong positive correlations between AOD and WV for all cities investigated. The correlation between AOD and CF was positive for all selected cities. AOD showed a negative correlation with CTP and CTT in Southern Indian regions.► The spatio-temporal variations of aerosols have been investigated using MODIS. ► High mean AOD was observed in almost all regions during the summer. ► The correlation between CF and AOD was found to be higher at coastal stations. ► AOD and WV have a stronger positive correlation at higher latitudes. ► CTP, CTT vs AOD showed negative correlation.
Keywords: MODIS; Aerosol optical depth; Ångström exponent; Water vapor; Cloud parameters;

Photochemical analyses of ozone and related compounds under various environmental conditions by Sang-Keun Song; Yoo-Keun Kim; Zang-Ho Shon; Jae-Yong Ryu (446-458).
The photochemical characteristics of ozone (O3) and its main precursors (e.g. NOx and VOCs) were investigated in relation to the photochemical O3 budget and O3–NOx–VOC sensitivity, based on a modeling approach using data sets observed during intensive field campaigns conducted under various environmental conditions (i.e. urban (Seoul), rural (Yang Pyeong), landfill (Dae Gu), coastal (Gwang Yang), and remote sites (Jeju Island). The production of O3 under most environmental conditions (especially, spring season at the urban site) was found to be more strongly sensitive to VOCs than NOx. At the landfill site and during summer at the rural and coastal sites, the production of O3 was partially sensitive to NOx. On the other hand, despite the remote air on Jeju Island, the production of O3 was mainly VOC-sensitive (high NOx levels), but in part NOx-sensitive (low NOx levels), due to the transport processes from different environmental regions (e.g. heavily and less polluted locations).► We investigated the photochemical characteristics of O3 and its main precursors. ► O3 production at the urban site was more sensitive to VOCs than NOx. ► O3 production at the landfill site was partially sensitive to NOx. ► O3 production at the rural and coastal sites in summer was in part sensitive to NOx. ► On Jeju Island, O3 production was mainly VOC-sensitive, but in part NOx-sensitive.
Keywords: Photochemical production; Environmental conditions; NOx-sensitive; VOC-sensitive; O3;

Mixing ratios of ozone (O3), carbon monoxide (CO), methane (CH4) and few light non methane hydrocarbons (NMHCs) were measured on board the ocean research vessel Sagar Kanya over the Bay of Bengal and the Arabian Sea during the spring of 2006 as a part of an Integrated Campaign for Aerosol, gases and Radiation Budget (ICARB). North-westerly winds prevailing during this period transport large amount of anthropogenic pollutants from the Indo-Gangetic Plain (IGP) to the northern part of Bay of Bengal. The south-westerly and north-westerly winds carried cleaner marine air having lower abundance of pollutants over the southern Bay of Bengal and Arabian Sea. Ozone, CH4, CO, ethane and n-butane are found to be well correlated with each other over the northern Bay of Bengal indicating their common co-located sources. The latitudinal gradients of these species are found to be significant (O3 ∼ 5.4 ppbv deg−1, CH4 ∼ 5.3 ppbv deg−1, CO ∼ 10 ppbv deg−1, ethane ∼ 93.2 pptv deg−1 and n-butane ∼ 59.7 pptv deg−1) over this region. Surprisingly, and in contrast to over the Bay of Bengal, the mixing ratios of these trace gases over the Arabian Sea are found comparatively higher over the southern region than over the northern region leading to negative latitudinal gradients. The short lived species with oceanic sources like ethene and propene show large variability and higher mixing ratios over southern parts of both the marine regions. These observations are compared with previous measurements made over these marine regions and the results obtained from the 3D MOZART chemistry transport model. The present study shows that the two marine regions adjacent to the Indian subcontinent are completely different from the perspective of surface level distributions of these species.► First time near simultaneous measurements of trace gases over Bay of Bengal and Arabian Sea. ► Measurements of ozone, CO, CH4 and various non-methane hydrocarbons during pre-monsoon season. ► Outflow of pollutants from Indo-Gangetic Plain over the Northern Bay of Bengal. ► Strong positive latitudinal gradients over Bay of Bengal and negative gradients over Arabian Sea. ► Comparison with a 3D chemistry transport model and CO obtained from MOPITT.
Keywords: Ozone; NMHCs; Transport; Bay of Bengal; Arabian Sea;

This study aims to determine spatial patterns of an air pollutant dispersion and its temporal trends using proper orthogonal decomposition (POD) basis functions. The POD method is a model reduction technique for complex nonlinear problems and POD basis functions contain essential dynamics and physics of original problem. In the present work, the POD basis functions are applied to identify the dominant modes of carbon monoxide (CO) concentration in ambient air. For this purpose, CO concentration data for 15 monitoring stations over mega city of Tehran for 1339 days (1 Jan. 2006 to 31 Aug. 2009) are used. Data of monitoring stations are interpolated to generate 100 × 100 grid point network. Generated grid based data for all days create a time series of data that is the basic for constructing the POD basis functions. POD basis functions are obtained using eigenvectors of correlation matrix that is obtained using correlation of time series of data. The few number of the POD basis functions corresponding to the few first largest eigenvalues of correlation matrix are dominant modes. The results indicate that the first 7 largest eigenvalues of correlation matrix are 99 percent of the first 100 largest eigenvalues. This indicates that the first 7 POD basis functions out of 1339 capture the essential physics of CO distribution over region. Distribution of the first POD basis function over the city shows that the central and west-central parts of the city are more affected by CO pollutant. In addition, using the recorded data and the POD basis functions the temporal variation of each POD basis function is obtained. Results for the temporal variations of the POD basis functions show that the largest temporal trend belongs to the first POD basis function.► POD method applied to identify dominant spatial and temporal mode of CO pollutant. ► Daily averaged concentrations of CO data for 1339 days are used as snapshots. ► Eigenvalue and eigenvector analysis showed that 7 modes are more dominant. ► Distribution of the first mode affects the central and west-central, of the city.
Keywords: Air pollutant; POD basis modes; Spatial patterns; Orthogonal decomposition;

Formaldehyde and acetaldehyde concentrations over the Eastern half of the United States are simulated with a 3-D air quality model to identify the most important chemical precursors under January and July conditions. We find that both aldehydes primarily result from photochemical production, although 25% or more result from direct emissions in urban areas during winter. Isoprene is the major precursor of formaldehyde in most areas during summer, contributing 20–60% of total production, with the magnitude being spatially variable. Other alkenes from anthropogenic and/or biogenic emissions dominate formaldehyde production in winter, contributing 60–85% of total formation, and are prominent contributors in summer. Alkenes, including biogenic alkenes, dominate acetaldehyde production during both seasons. These conclusions are based on the degradation of emitted VOCs described by the SAPRC07TB chemical mechanism, but even this detailed model has difficulty reproducing observed values better than a factor of 2. The substantial role of isoprene and other alkenes in aldehyde formation emphasizes that we examine and improve emission estimates of these compounds. Until we can estimate the emissions and understand the chemistry of VOC precursors to aldehyde formation with greater certainty, it will be difficult to accurately predict atmospheric concentrations of aldehydes and develop strategies to reduce their concentrations.► Over 80% of ambient formaldehyde and acetaldehyde is from photochemical production. ► Isoprene contributes to summer formaldehyde, but the amount is highly variable. ► Alkenes are the major contributor to ambient acetaldehyde concentrations.
Keywords: Formaldehyde; Acetaldehyde; HAPs; Photochemical production; Isoprene;

Determining spatial variability in PM2.5 source impacts across Detroit, MI by Rachelle M. Duvall; Gary A. Norris; Janet M. Burke; David A. Olson; Ram Vedantham; Ron Williams (491-498).
Intra-urban variability in air pollution source impacts was investigated using receptor modeling of daily speciated PM2.5 measurements collected at residential outdoor locations across Detroit, MI (Wayne County) as part of the Detroit Exposure and Aerosol Research Study (DEARS) during summer and winter from 2004 to 2006. Six areas were selected for the residential monitoring in the DEARS to capture impacts from different sources including local industry, motor vehicles, and upwind regional sources. PM2.5 measurements were also collected at the Allen Park, MI Chemical Speciation Network (CSN) site for comparison with the residential outdoor sites. Sources impacting PM2.5 were quantified using the EPA Chemical Mass Balance Model (CMB 8.2). Published source profiles were used as input to CMB along with a mixed industrial profile and a steel manufacturing profile obtained by applying the EPA Positive Matrix Factorization Model (PMF 4.0) to CSN data from a Midwestern U.S. site with industrial sources similar to Detroit.Major PM2.5 sources impacting the Allen Park and residential monitoring areas during DEARS included motor vehicles (24–36% by mass), secondary sulfate/coal combustion (17–35%), secondary nitrate (16–37%) and organic matter (17–21%). Road dust, steel manufacturing, and mixed industrial sources contributed less than 11% by mass. CMB source contribution estimates for Allen Park during the DEARS generally compared well to CMB estimates from the collocated year-long CSN measurements using the same source profiles. CMB source contributions during DEARS showed similar contributions across the residential monitoring areas for secondary sulfate/coal combustion and secondary nitrate consistent with regional impacts for these sources. Contributions from motor vehicles, steel manufacturing, and mixed industrial sources varied across the DEARS monitoring areas, indicating impacts from local sources within the Detroit airshed that may not be well characterized by the Allen Park monitoring location.► PMF-generated source profiles can be used in the CMB model. ► PM2.5 sources can be quantified for exposure studies using many receptor models. ► EMAs were differentially impacted by localized PM sources. ► Allen Park does not represent areas in Detroit close to industry or diesel sources.
Keywords: Particulate matter; Source apportionment; Chemical mass balance; Positive matrix factorization; DEARS; Detroit, MI;

Diurnal and seasonal variation of mercury species at coastal-suburban, urban, and rural sites in the southeastern United States by Udaysankar S. Nair; Yuling Wu; Justin Walters; John Jansen; Eric S. Edgerton (499-508).
Observations for the 2005–2008 time period from three Southeastern Aerosol Research and Characterization (SEARCH) air quality monitoring sites are examined for diurnal and seasonal variation in concentrations of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle bound mercury (HgP < 2.5 μm). The sites are located at 1) a suburban-coastal location near Pensacola, Florida (OLF), 2) an urban location in Birmingham, Alabama (BHM), and 3) a rural location west-northwest of Atlanta, Georgia (YRK). Average concentrations of GEM at both OLF and YRK are 1.35 ng m−3, whereas at BHM it is 2.12 ng m−3. All sites show increase in GEM concentration during the morning hours (0.023 and 0.011 ng m−3hr−1 at OLF and YRK between 6 and 10 AM, 0.038 ng m−3hr−1 at BHM between 5 and 10 AM) due to downward mixing of higher concentrations from the residual layer, after which OLF and YRK show negligible variation compared to decrease in concentration at BHM (2.3–1.9 ng m−3 from 10 AM to 6 PM). All sites show seasonal variation of GEM with enhanced concentrations found in winter and spring. Average GOM concentrations are 4.26, 8.55, and 78.2 pg m−3 at OLF, YRK, and BHM, respectively. Seasonally, GOM values are enhanced during fall and spring. All sites undergo a sinusoidal daytime variation of GOM that peaks in the afternoon, while BHM additionally exhibits an early morning enhancement likely caused by vertical mixing. The average HgP concentrations at OLF, YRK, and BHM are 2.49, 4.43, and 39.5 pg m−3, respectively. At OLF, vertical mixing causes an early morning increase in HgP concentration followed by an afternoon decline during all seasons. A daytime increase in HgP is found at YRK for all seasons, while at BHM, nocturnal accumulation followed by a daytime decline is also found for most seasons except winter. In winter, concentrations increase due to vertical mixing in the morning and then decline as the boundary layer grows. Boundary layer processes appear to play an important role in the seasonal and diurnal variation of Hg species and further investigation utilizing a boundary layer process model is warranted.► Multi-year mercury observation analyzed for three sites in southeastern US. ► Magnitude and temporal patterns of GEM are similar at OLF and YRK, dissimilar at BHM. ► Average GOM is lowest at OLF, about doubled at YRK, and much higher at BHM. ► Magnitude of average HgP is about half that of average GOM for all three sites. ► Vertical mixing on various vertical gradients may explain variations in diurnal GEM.
Keywords: Atmospheric mercury; Southeastern U.S.; Diurnal patterns; Boundary layer processes; Seasonal variation;

Numerical investigation on the urban heat island in an entire city with an urban porous media model by Zhangbao Hu; Bingfeng Yu; Zhi Chen; Tiantian Li; Min Liu (509-518).
This paper considers a city to be the porous media with internal heat sources and derives a porous media model for the turbulent flow and heat transfer in the city. The presented model may be an appropriate method for the numerical study of the urban heat island (UHI) in an entire city with appropriate spatial resolution and computing capacity. We proposed a method to convert the building heat source intensity based on ground surface area into that based on building volume. With the method, the heat flux of the building heat source can be consistent with the building density. We adopted the single domain approach to account for the interface conditions and used the spatial distribution of the porosity to define the parameters in the porous urban region and the clear fluid region. The urban porous media model was verified by comparing its numerical results with the volume-averaged results of the micro-scale model. Moreover, the urban porous media model was applied to examine the effects of urban anthropogenic heat and wind speed on the spatial UHI of the urban area and the leeward rural area. The results showed that an increase in anthropogenic heat intensity by 100 W m−2 led to an increase in UHI intensity by 1.683 K. The increase in wind speed had a prominent mitigation effect on the UHI at a lower wind speed, but the decrease rate of UHI intensity decreased as the wind speed increased. The UHI intensity decreased as the height increased and the UHI almost vanished as the height reached five times the height of the urban canopy. The UHI intensity decreased rapidly as the airflow entered the leeward rural area, but the UHI still existed at a distance of 5 km from the urban area.► We consider a city to be the porous media with internal heat sources. ► We derive a porous media model for the numerical study of UHI in an entire city. ► UHI intensity increases by 1.683 K as anthropogenic heat increases by 100 W m−2. ► Increasing wind speed is more effective for mitigating UHI when wind speed is lower. ► UHI almost vanishes when height reaches five times the height of urban canopy.
Keywords: Urban heat island; Anthropogenic heat; Wind speed; Porous media; Simulation;

A regional model of European aerosol transport: Evaluation with sun photometer, lidar and air quality data by J. Meier; I. Tegen; I. Mattis; R. Wolke; L. Alados Arboledas; A. Apituley; D. Balis; F. Barnaba; A. Chaikovsky; M. Sicard; G. Pappalardo; A. Pietruczuk; D. Stoyanov; F. Ravetta; V. Rizi (519-532).
Aerosol transport simulations within Europe were performed with the regional transport model COSMO-MUSCAT for two different time periods, July 19–26, 2006 and February 16–26, 2007. Simulated PM 2.5, backscatter profiles and aerosol optical depths (AODs) were compared to observations, showing good agreements in magnitude, shape and day-to-day variations. Maximum AODs (>0.4) were found over Middle Europe and minimum AODs (<0.13) over the ocean during both time periods, corresponding to regions of high (PM 2.5 > 10 μg m−3) and low (PM 2.5 < 4.0 μg m−3) concentration near the surface. Vertical aerosol distributions were evaluated with lidar measurements from the EARLINET ground network and CALIPSO satellite retrievals. The characteristic vertical distribution and the differences for the summer and the winter cases were represented well by the regional model. Mean differences between −5.0 × 10−7 to−2.0 × 10−7 m−1 sr−1 (summer case) and −2.3 × 10−6 to 1.0 × 10−6 m−1 sr−1 (winter case) from 0.0 to 2.5 km altitude were found between observed (space-based lidar) and simulated backscatter coefficients. For the cases that were investigated in this study different prescriptions of the vertical distribution at the lateral model boundaries resulted in only small differences in aerosol distributions within the interior of the model region.► Simulation of European aerosol for two different time periods. ► Evaluation with observed PM2.5, AOD and backscatter coefficients. ► Lidar profiles were used at the lateral model boundaries. ► Observed AOD values were used to adjust the vertical distributions. ► Usage of a regional transport model.
Keywords: Regional transport model; Aerosol; Europe; PM 2.5; AOD; Vertical backscatter coefficient; Evaluation;

Atmospheric variability and emissions of halogenated trace gases near New York City by Nicholas Santella; David T. Ho; Peter Schlosser; Elaine Gottlieb; William J. Munger; James W. Elkins; Geoffrey S. Dutton (533-540).
Elevated mixing ratios of chlorofluorocarbons (CFC-11 and CFC-12), and sulfur hexafluoride (SF6) have been observed at Lamont-Doherty Earth Observatory (LDEO), located approximately 25 km north of New York City (NYC). Emissions and transport of these gases are of interest because of their global warming potential, the role of CFCs in depletion of stratospheric ozone and information they provide on the transport of atmospheric pollutants. Comparison of trace gas time series with meteorological data indicates that both NYC and the region to the southwest (New Jersey and the Philadelphia –Washington DC area) are significant sources of CFCs, and confirms that NYC is an unusually large source of SF6. From 1996 to 2005 the elevation of CFC-12 mixing ratio above that of the remote (well mixed) atmosphere has decreased on average by 5.2 ± 0.6 ppt y−1, whereas that of CFC-11 has not changed significantly (0.0 ± 2.0 ppt y−1). From 1998 to 2006, the elevation of SF6 mixing ratios above that of the remote atmosphere declined by 0.4 ± 0.1 ppt y−1. Time series of the same gases measured at Harvard Forest, 205 km northeast of LDEO, demonstrate transport of air masses with elevated levels of these gases from their source region to central Massachusetts. Emissions in the local area around LDEO were quantified through analysis of diurnal cycles. Local CFC-12 emissions decreased ca. 95% between 1996 and 2005 while CFC-11 emission decreased ca. 51% during the same period. Local SF6 emissions decreased by 47% between 1998 and 2005.► Long term trace gas time series indicate emission strength and atmospheric transport. ► Transport observed between LDEO and Harvard Forest, 205 km to northeast using trace gases. ► Local emissions derived from diurnal cycles decreased 95% for CFC-12, 51% for CFC-11 and 47% for SF6.
Keywords: Chlorofluorocarbons; Sulfur hexafluoride; Emission estimates; Atmospheric transport;

Azaarenes concentrations in East of France urban atmospheres through the period between April 2006 and February 2007 are described. Sampling sites were chosen to be representative of three different regions and were situated in Strasbourg (“Alsace region”), in Besançon (“Franche-Comté region”) and in Spicheren (“Lorraine region”). In order to compare the seasonal variability, the sampling campaigns have been performed during the four seasons in Strasbourg, and during two opposed seasons (summer and winter) in Besançon and in Spicheren. Moreover, the sampling campaigns have been performed during 6 h time intervals per day (04:00–10:00; 10:00–16:00; 16:00–22:00 and 22:00–04:00) to assess the diurnal variations of azaarenes concentrations. Mean total azaarenes concentrations were 2.8 ng m−3 in Strasbourg, 1.6 ng m−3 in Besançon and 1.0 ng m−3 in Spicheren. Seasonal variations in the azaarenes concentrations occur with the greatest abundance of all species in the colder months when combustion sources are greatest and when azaarene compounds are mainly associated with the particle phase. A diurnal variation of compound concentrations in the three sites, in warm period, has been observed in accordance with the intensity of the vehicle circulation, with highest concentrations during the morning (04:00–10:00) and the evening (16:00–22:00). In cold period, there is no difference of concentration between these two time intervals of high vehicle circulation in Strasbourg site and in Besançon site. Moreover, in Spicheren site, the highest concentrations were observed during the evening. In this way, it seems that the contribution of domestic heating influenced the diurnal variations of some compounds on the three sites.► Azaarenes are very poorly studied organic pollutants in the air. ► First data in Europe, on azaarenes. ► Seasonal and temporal variation of azaarenes. ► Comparison of azaarenes between three urban sites in the east of France.
Keywords: Azaarenes; Ambient air; Seasonal variation; Diurnal variation;

Gas/particle partitioning of low-molecular-weight dicarboxylic acids at a suburban site in Saitama, Japan by Linfa Bao; Mariko Matsumoto; Tsutomu Kubota; Kazuhiko Sekiguchi; Qingyue Wang; Kazuhiko Sakamoto (546-553).
Low-molecular-weight dicarboxylic acids (diacids) exhibit semivolatile behavior in the atmosphere, but their partitioning between the gaseous and particulate phases is still unclear. An annular denuder–filter pack system with a cyclone PM2.5 was employed to investigate the gaseous and particulate phase concentrations of diacids, with high collection efficiency of most target compounds. Saturated diacids, unsaturated diacids, ketocarboxylic acids, and dicarbonyls were determined in gaseous and particulate samples collected from a suburban site in Japan, during 2007 summer, 2008 late-winter and early-winter. The concentrations of gaseous and particulate diacids in early-winter were lower than those in summer, but higher than those in late-winter. Individual diacid in gaseous phase showed a relatively good correlation with ambient oxidants, but a low correlation with NO gas (a primary pollutant). Particulate fraction to the total amount (F P) of individual acid was larger in winter than in summer, and also was larger at night than in the daytime. In the same sample, individual diacid and ketocarboxylic acid had higher particulate phase occurrence (F P > 56% in summer), whereas unsaturated diacid had higher gaseous phase occurrence (F P < 18% in summer). In summer, gas/particle partitioning of diacids varied diurnally; F P values of oxalic and glyoxylic acids increased from their lowest values in the morning to their highest values at night, exhibiting the similar diurnal variation of relative humidity in the atmosphere. The higher humidity at night may lead to the formation of droplets in which water-soluble gaseous phases can dissolve, thus promoting gas-to-particle conversion. These results suggest that gas/particle partitioning of diacids depends not only on the concentrations in the gaseous phase by photochemical oxidation, but also on the characteristics of the atmosphere (e.g., temperature, sunlight, and relative humidity) and the aerosols (e.g., acidity, alkaline composition, and water content).
Keywords: Gas/particle partitioning; Dicarboxylic acids; Oxygenated organic aerosol; Atmospheric sampling; Collection efficiency;

Throughfall and litterfall represent two major pathways which comprise the bulk of the mercury that reaches the forest floor. In an effort to quantify total mercury deposition to forests, throughfall and litterfall samples were collected at three elevations in the Great Smoky Mountains National Park (GSMNP) between April and November in 2008 and 2009. The mean (±standard error) volume-weighted throughfall total mercury concentration across all three sites ranged from 13.62 ng L−1 (±0.86) to 18.23 ng L−1 (±0.77) with a slight trend of higher throughfall mercury concentration at the high elevation spruce-fir sites relative to the low elevation mixed-hardwood site. The mean (±standard error) throughfall total mercury deposition across all sites ranged from 2.07 μg m−2 (±0.09) to 4.09 μg m−2 (±0.38). Mean (±standard error) mass-weighted litterfall concentration ranged from 37.2 ng g−1 (±1.36) to 62.87 ng g−1 (±1.94) and statistically higher (p = 0.02, p < 0.05) mean concentrations were observed at the higher elevation sites. The mean (±standard error) litterfall mercury deposition across all three sites ranged from 10.34 μg m−2 (±0.69) to 29.30 μg m−2 (±0.44). Although, no statistically (p = 0.05, p < 0.05) significant difference was observed between the sites for either throughfall or litterfall deposition, both increased from 2008 to 2009 at the lower elevation site. Mean litterfall deposition (17.93 μg m−2) dominated Hg input for the two years studied over mean throughfall deposition (3.20 μg m−2). Meanwhile, the mean throughfall concentration (17.8 ng L−1) dominated the mean open area precipitation input (6.03 ng L−1) at the high elevation site, suggesting evidence for a dry deposition component from the forest canopy. While the study was limited in scope, the results do provide some basic data that adds to understanding Hg inputs to the terrestrial ecosystem in general and in the GSMNP specifically.
Keywords: Total mercury deposition; Throughfall; Litterfall; Mercury deposition;

New Directions: The need to develop process-based emission forecasting models by Daniel Q. Tong; Pius Lee; Rick D. Saylor (560-561).

Corrigendum to “Highly time- and size-resolved characterization of submicron aerosol particles in Beijing using an Aerodyne Aerosol Mass Spectrometer” [Atmos. Environ. 44 (2010) 131–140] by Junying Sun; Qi Zhang; Manjula R. Canagaratna; Yangmei Zhang; Nga L. Ng; Yele Sun; John T. Jayne; Xiaochun Zhang; Xiaoye Zhang; Douglas R. Worsnop (570).