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Atmospheric Environment (v.40, #34)

Editorial board (pp. i).

Chemical composition of aerosols over peninsular India during winter by Prabha R. Nair; Susan K. George; S.V. Sunilkumar; K. Parameswaran; Salu Jacob; Annamma Abraham (pp. 6477-6493).

As a part of the campaign conducted for the spatial characterization of aerosols over peninsular India measurements of aerosol mass loading, optical depth and chemical composition have been carried out during the winter month of February 2004. The aerosol characteristics showed significant variation with locations. The aerosol mass loading as well as the optical depth showed high values along the western coastal regions compared to inland locations. Ions of SO₄ and NO₃ are observed to be the major anions present over the entire region with higher mass concentrations at the coastal and close-to-forest regions. The mass fraction of non-sea-salt sulphate was larger at the interior locations. Compared to that in the inland/close-to-forest locations the concentration of Cl and Na are found to be 2–3 times larger in the coastal region. The mass fraction of non-sea-salt K was largest at locations close to forests. Among the metallic components, Fe, Cu, Ca, Zn, Pb etc, which are of continental origin, are found to dominate over inland locations. These measurements over the land are compared with those observed over the Arabian Sea and Indian Ocean during the Indian Ocean Experiment.

Keywords: Sea salt; Non-sea salt; Non-sea-salt sulphate; Continental aerosols; Sea spray; Anthropogenic activity

A study of aerosol optical depth in the central Indian region (17.3–8.6°N) during ISRO-GBP field campaign by Sachchidanand Singh; Bhupender Singh; B.S. Gera; Manoj K. Srivastava; H.N. Dutta; S.C. Garg; Risal Singh (pp. 6494-6503).

We present the ground-based, clear-sky daytime measurements of column aerosol optical depths (AODs) at different wavelengths and the mixing height of atmospheric boundary layers at various locations, conducted during ISRO-GBP aerosol-radiation-trace gases measurements campaign in the central Indian region (17.3–28.6°N and 77.2°–78.2°E) from Delhi to Hyderabad and back, in the month of February 2004. The measurements show AOD variation at 500nm in the range of 0.2–0.5 and Angstrom exponent in the range of 1.0–1.4 throughout the region. The entire experimental region has been classified into four categories depending upon their locations and surroundings, viz., forest, rural, semi-urban, and rural-dusty. The volume size distribution of the aerosol particles at all these categories showed a bi-modal distribution with fine mode dominating around 0.23μm effective radius and the coarse mode dominating around 1μm. The forest site showed minimum AOD and α values with an equal contribution of aerosol particles in the fine and coarse mode. As the fine-mode particle concentration relatively increased at other regions, the α value also went on increasing, along with the increase in AOD. The AOD also showed a latitudinal variation with a minimum occurring at about 23.5°N. During the whole campaign, the average mixing height of planetary boundary layer (PBL) during the daytime was found to be between 650 and 950m.

Keywords: AOD; Central India; Size distribution; MICROTOPS; SODAR

Spatial variations in aerosol characteristics and regional radiative forcing over India: Measurements and modeling of 2004 road campaign experiment by A. Jayaraman; H. Gadhavi; D. Ganguly; A. Misra; S. Ramachandran; T.A. Rajesh (pp. 6504-6515).

Results from a variety of complementary aerosol measurements made as part of the Indian Space Research Organization-Geosphere Biosphere Program (ISRO-GBP) road campaign experiment conducted during Feb 2004 in the central Indian region are reported. An instrumented vehicle fitted with the Micro Pulse Lidar for aerosol vertical profile measurements, nephelometer for scattering and athelometer for absorption coefficients measurements, Microtops II sun-photometer for column aerosol optical depth, Quartz Crystal Microbalance for aerosol mass concentration and Grimm spectrometer for aerosol number concentration was used in the campaign. The synergy of results from these complementary measurements is reflected in the computed aerosol radiative forcing for the region. We show that the large spatial and temporal variations found in the aerosol characteristics over the northwest Indian region are caused mainly by the naturally produced dust particles. The variation in their concentration modulates the overall atmospheric radiative forcing over this region. We also show that apart from the large north to south gradient in aerosol forcing caused due to transport of aerosols from the continent to the Indian Ocean region and reported during INDOEX, there is also a positive gradient in aerosol forcing from west to east, from the Arabian Sea to the Bay of Bengal region. A considerable portion of particles produced from the Indian main land is flushed to the Bay of Bengal region before being transported to the Indian Ocean, causing this west to east gradient.

Keywords: Aerosol vertical profiles; Aerosol scattering and absorption coefficients; Aerosol radiative forcing over central India

Inventory of black carbon and organic carbon emissions from China by Guoliang Cao; Xiaoye Zhang; Fangcheng Zheng (pp. 6516-6527).

We present detailed high-resolution emission inventories of black carbon (BC) and organic carbon (OC) from China in the year 2000. The latest fuel consumption data, including fossil and biomass fuels and socio-economic statistics were obtained from government agencies, mostly at the county level. Some new emission factors (EFs) from local measurements also were used. National and regional summaries of emissions are presented, and gridded emissions at 0.2°×0.2° resolution are shown. Our calculated emissions were 1500 Gg for BC and 4100 Gg for OC, mainly due to the burning of coal and biofuels. The carbonaceous aerosol emissions estimated here are higher than those in previous studies, mainly because coal burning by rural industries and residences were previously underestimated. More carbonaceous aerosols are emitted from eastern China than western China. A strong seasonal dependence is observed for emissions, with peaks in May and October and low emissions in April and July; this seasonality is mainly due to patterns in residential heating and agriculture waste open burning.

Keywords: Carbonaceous aerosol; China; Emission inventory; Seasonality

A statistical comparison of survival and replacement analyses for the use of censored data in a contaminant air database: A case study from the Canadian Arctic by Emma F. Eastoe; Crispin J. Halsall; Janet E. Heffernan; Hayley Hung (pp. 6528-6540).

The data sets of four semi-volatile organic compounds (phenanthrene, PCB-28,p,p′-DDE andα-endosulfan) from a multi-year Canadian Arctic air monitoring programme were examined to test the effect of both including and removing censored data (i.e. data that fall below analytical detection limits) on time-trend models. Two approaches were taken with the data, one that included all censored values, known as a survival analysis, and the other with censored values replaced with a fixed constant, referred to here as a replacement analysis. Initially, the results from the time-trend models (depicting seasonality and year-on-year trends) from the two analyses, where replacement involved a small amount of data that fell below instrumental detection limits, showed very few differences. This was effectively due to the small quantity of censoring apparent in each of the data sets (the data sets of 2 compounds had <10% censoring). However, when the degree of censoring was artificially increased to 50% for two of the compounds (phenanthrene andp,p′-DDE), differences in modelled trend results were evident. By comparing the results of the trend models fitted under both survival and replacement analyses with these highly censored data sets to the actual observed data, it was evident that the survival analysis produced time series models that were far more robust given the quantity of censoring. The application of a Kaplan–Meier (K–M) estimator as a diagnostic tool confirmed the survival analysis approach for producing more robust trend models for both compounds. As a result, we recommend survival analysis and the retention of all censored data within a given data set and this justifies the current approach of retaining all censored data within the Canadian arctic air databases. Blank correction of these types of databases and/or simple exclusion of censored data, could confound time-series analysis.

Keywords: Semi-volatile organic compounds; Pollutants; Censor; Database; Kaplan–Meier plot; Arctic

On relationships between urban and rural near-surface meteorology for diffusion applications by Ashok K. Luhar; Akula Venkatram; S.-M. Sang-Mi Lee (pp. 6541-6553).

Dispersion of releases in urban areas can be estimated with information on micrometeorological variables in the urban boundary layer. However, this information is not generally available. On the other hand, meteorological measurements are routinely made in rural surroundings (e.g. airports). We examine empirical relationships between urban and rural meteorological variables using data from the Basel UrBan Boundary Layer Experiment (BUBBLE), conducted during June and July 2002 around Basel, Switzerland, and present two methods to estimate urban micrometeorology using measurements from rural sites. The first method is based on a two-dimensional internal boundary-layer model that uses rural variables as upwind inputs. It assumes that the urban Obukhov length is the same as that in the rural area in unstable conditions and that it is very large (neutral) in stable rural conditions. The second method uses a three-dimensional prognostic model called TAPM in which upwind rural observations are assimilated. Urban variables estimated from TAPM compare well with observations. This performance is slightly better than that of the internal boundary-layer model.

Keywords: Urban meteorology; Internal boundary layer; Urban–rural differences; TAPM; Urban dispersion; BUBBLE experiment

Origin of atmospheric lead in Johannesburg, South Africa by F. Monna; M. Poujol; R. Losno; J. Dominik; H. Annegarn; H. Coetzee (pp. 6554-6566).

The origin of lead in the atmosphere of Johannesburg, South Africa was investigated on the basis of elemental and lead isotopic analyses of coals, mine dumps, gasoline, and about 30 epiphytic lichen samples. Lead predominantly comes from automotive exhausts in urban and suburban areas, as leaded antiknock additives were still in use in South Africa at the time of the study. Although dust emissions from the numerous mine-tailing dumps were expected to contribute significantly to the heavy metal budget, the southern townships that are surrounded by the dumps (such as Soweto and other historically Black residential areas) do not appear to be more than partially influenced by them, and this influence seems to be geographically limited. Domestic coal burning, suspected to account for the total lead content in the air, is also recognised, but only acts as a minor source of lead, even in townships.

Keywords: Lichen; Lead isotope; Pollution; Mine dump; Mixing model

Emissions of reduced sulfur compounds (RSC) as a landfill gas (LFG): A comparative study of young and old landfill facilities by K.-H. Ki-Hyun Kim (pp. 6567-6578).

To offer some insights into the processes associated with odor release from a strong source environment, concentrations of reduced sulfur compounds (RSCs) in landfill gas (LFG) were measured at two landfill (LF) facilities within a small city boundary through four seasons. The LF sites investigated in this study are distinguished in that the young LF (namely, YLF) was selected to represent a site of active RSC emissions, while the old LF (namely, OLF) was selected for its weak RSC emissions. The LFG composition, when analyzed for a number of RSCs (hydrogen sulfide (H₂S), methyl mercaptan (CH₃SH), dimethyl sulfide ((CH₃)₂S), carbon disulfide (CS₂) and dimethyl disulfide ((CH₃)₂S₂)), was consistently predominated by H₂S from both sites. The mean and SD value of H₂S in the YLF were measured to be 139,070±144,340ppb, while its counterparts in the OLF being 3.86±3.41ppb. The emission concentration levels of H₂S were found to be distinguished from those of the other RSCs, depending on the LF aging. The H₂S results for both LF sites, when compared across seasons, were generally characterized as notable enhancement during summer relative to other seasons. The comparative analysis of relative composition between RSCs and other LFG constituents (such as CH₄, CO₂, and VOC) consistently indicate that the relative proportion of RSCs is substantially larger during the active LF stage (YLF) than in the inactive one (OLF).

Keywords: Hydrogen sulfide; Sulfur gas; Malodor; VOC; Landfill

The variation of characteristics and formation mechanisms of aerosols in dust, haze, and clear days in Beijing by Ying Wang; Guoshun Zhuang; Yele Sun; Zhisheng An (pp. 6579-6591).

A 4-year campaign from 2001 to 2004 monitoring PM_2.5 and TSP in the spring season in urban Beijing, China was performed to study the variation of characteristics and the different formation mechanisms of aerosols in dust, haze, and clear days. A total of 315 aerosol samples were collected and used in this study. The aerosols were more basic in dust days and more acidic in haze days. The ions presented in the order ofSO42->Ca²⁺≫NO3->Cl⁻>NH4+>Na⁺ in dust days, and ofSO42->NO3->NH4+≫Cl⁻>Ca²⁺>K⁺ in haze days. Ions has been classified into three groups, “Na⁺, Mg²⁺, Ca²⁺�?, “K⁺,SO42-, Cl⁻�?, and “NO3-,NH4+�?, representing crust, pollution-crust, and pollution species, respectively. Crust and pollution ions were the main ion fractions in dust and haze days, respectively. The variation of Ca²⁺/Al showed that the increase of dust in dust and haze days was from soil and construction, respectively. “CaCO₃, CaSO₄, and (NH₄)₂SO₄�? and “(NH₄)₂SO₄, NH₄NO₃, and Ca(NO₃)₂�? were the major species in dust and haze days, respectively. The formation of CaSO₄ on airborne soil particles and the formation of (NH₄)₂SO₄ and NH₄NO₃ were the predominant pathways of sulfate and nitrate formations in dust and haze days, respectively. Sulfate might be mainly formed through heterogeneous reactions in the aqueous surface layer on the pre-existing particles, while nitrate mainly through homogeneous gas-phase reactions in the spring season in Beijing. The formation of sulfate and nitrate was accelerated in dust and haze days.

Keywords: Aerosol; Speciation; Formation mechanism; Dust; Haze; Beijing

The flux of methyl chloride along an elevational gradient of a coastal salt marsh, Eastern China by Jinxin Wang; Rongjin Li; Yingyan Guo; Pei Qin; Shucun Sun (pp. 6592-6605).

Salt marshes have been suggested to be a large potential source for methyl chloride (CH₃Cl) that is the major natural carrier of chlorine to the stratosphere. However, the global budget of this trace gas is uncertain, and the empirical field data are still lacking. In this study, CH₃Cl fluxes were measured seasonally using static flux chambers from April 2004 to January 2005, along an elevational gradient of a coastal salt marsh in eastern China. To estimate the contribution of higher plants to the flux, plant aboveground biomass was experimentally removed and the flux difference between the treatment and the intact was examined. In addition, the flux was analyzed in relation to soil and weather conditions.Along the elevational gradient, the salt marsh generally functioned as a net sink in the growing season (from April to October 2004). The flux of CH₃Cl ranged between −1.27 and −29.33μmolm⁻²d⁻¹ (positive for emission and negative for consumption), and the maximum negative rates occurred at the mudflat and the cordgrass ( Spartina alterniflora) marsh. However, the measurements made during inundation indicated that the mudflat was a net source of the gas. In the non-growing season (from November to March), the vegetated flat, when frozen, was a minor source of methyl chloride, with an emission rate ranging from 0.27 to 9.13μmolm⁻²d⁻¹. However, the measurements made during non-frozen periods indicate that the mudflat was a minor sink of methyl chloride. Overall, the study marsh was a large net sink for the gas because the magnitude of the consumption rates was lager than that of emission, and because the duration of the growing season was longer than that of the non-growing season. Plant aboveground biomass had a great effect on the flux. Comparative analyses showed that higher plants were present as an important source of CH₃Cl, and it could balance 17.26–67.66% of the soil consumption. The net CH₃Cl consumption rate was negatively correlated to soil dissolved salt content and light intensity, but it was positively correlated to soil temperature, soil organic matter content, and ambient atmospheric concentration of CH₃Cl. This suggests that the overall net consumption of CH₃Cl observed in the study marsh may result from the high ambient atmospheric concentration that ranged between 1.3 and 58.5ppb, and enriched soil organic matter that feed the soil microorganisms using CH₃Cl as a sole source for both carbon and energy.

Keywords: Cordgrass; Methyl chloride; Plant biomass; Soil uptake; Salt marsh; Seasonal variation

Interfacial properties of mixed films of long-chain organics at the air–water interface by Jessica B. Gilman; Heikki Tervahattu; Veronica Vaida (pp. 6606-6614).

Organic molecules residing at the air–water interface of atmospheric aerosols will have a critical and direct effect on the aerosols’ chemical, physical, and optical properties. It is important to study the interfacial properties of such compounds in order to accurately assess these effects. In this study, the compositions of two organic binary films at the air–water interface were monitored as a function of exposure time to the ambient atmosphere. One film was composed of tetracosanoic acid (lignoceric acid, CH₃(CH₂)₂₂COOH) and nonacosane (C₂₉H₆₀), and the second film was composed of octadecanoic acid (stearic acid, CH₃(CH₂)₁₆COOH) and octadecane (C₁₈H₃₈). These films were used as simplified proxies for the organic coating on atmospheric aerosols. The effect of lengthening the hydrocarbon chain on the interfacial longevity of the compounds in the mixed organic film at the air–aqueous interface was determined. The results show that octadecane in a mixed film desorbs from the interface after 72h while octadecanoic acid remains. For nonacosane, further lengthening of the carbon chain greatly increased its interfacial longevity so that it was comparable with the fatty acids, which remained stable at the interface for at least 144h. These results are used to explain the preponderance of long-chain fatty acids on the surfaces of collected aerosols and give insight into the degree to which the presence of other long-chain organics may affect the aerosol's chemical and physical properties.

Keywords: Mixed organic films; Atmospheric aerosol; Surfactants; Aqueous interface; Fatty acid; Alkane

Determination of octanol–air partition coefficients and supercooled liquid vapor pressures of PAHs as a function of temperature: Application to gas–particle partitioning in an urban atmosphere by Mustafa Odabasi; Eylem Cetin; Aysun Sofuoglu (pp. 6615-6625).

Octanol–air partition coefficients ( K_OA) for 14 polycyclic aromatic hydrocarbons (PAHs) were determined as a function of temperature using the gas chromatographic retention time method. log K_OA values at 25° ranged over six orders of magnitude, between 6.34 (acenaphthylene) and 12.59 (dibenz[ a,h]anthracene). The determined K_OA values were within factor of 0.7 (dibenz[ a,h]anthracene) to 15.1 (benz[ a]anthracene) of values calculated as the ratio of octanol–water partition coefficient to dimensionless Henry's law constant. Supercooled liquid vapor pressures ( P_L) of 13 PAHs were also determined using the gas chromatographic retention time technique. Activity coefficients in octanol calculated using K_OA and P_L ranged between 3.2 and 6.2 indicating near-ideal solution behavior.Atmospheric concentrations measured in this study in Izmir, Turkey were used to investigate the partitioning of PAHs between particle and gas-phases. Experimental gas–particle partition coefficients ( K_p) were compared to the predictions of K_OA absorption and K_SA (soot–air partition coefficient) models. Octanol-based absorptive partitioning model predicted lower partition coefficients especially for relatively volatile PAHs. Ratios of measured/modeled partition coefficients ranged between 1.1 and 15.5 (4.5±6.0, average±SD) for K_OA model. K_SA model predictions were relatively better and measured to modeled ratios ranged between 0.6 and 5.6 (2.3±2.7, average±SD).

Keywords: PAHs; Vapor pressure; Octanol–air partition coefficient; Gas/particle partitioning

Atmospheric dry deposition of trace elements measured around the urban and industrially impacted NY–NJ harbor by S.-M. Seung-Muk Yi; Lisa A. Totten; Sathyapriya Thota; Shu Yan; John H. Offenberg; Steven J. Eisenreich; Joseph Graney; Thomas M. Holsen (pp. 6626-6637).

Long-term direct trace metal dry deposition measurements were made during 2001 and 2002 at two sites near the NY/NJ Harbor Estuary in New Jersey: Jersey City (JC) and New Brunswick (NB). In addition intensive dry deposition and atmospheric size distribution (ASD) measurements were made between September 2001 and June 2002. Dry deposition samples were obtained using modified MIC-B wet deposition samplers which deployed knife-edge surrogate surfaces during dry periods. ASDs were measured with micro-orifice uniform deposit impactors (MOUDI) and coarse particle rotary impactors (CPRI). The fluxes of trace metals were found to be highest at the JC site and lowest at the NB site. The dry deposition fluxes ranged from 0.030(Cd) to 3800(Al)μgm⁻²d⁻¹ and 0.14(Cd) to 8100(Al)μgm⁻²d⁻¹at NB and JC sites, respectively. Metals of crustal origin were found mostly in the coarse particle fraction and anthropogenic metals were found mostly in the fine particle fraction.For the intensive experiments, overall dry deposition velocities of several trace metals were determined by dividing measured fluxes by measured concentrations in different particle size ranges. For most of the elements, the flux was highly correlated with PM₁₀ and coarse particle concentrations. The overall dry deposition velocities of crustal elements (Al and Mg) varied from 3.7 to 8.7cms⁻¹ with correlation coefficients ranging from 0.50 to 0.84. The best-fit dry deposition velocities for anthropogenic elements (Cr, Mn, Zn, and Pb; Cu, Mo, and Ba; V and Ni) varied more than those for crustal elements (0.52–25 vs. 3.7–8.7cms⁻¹). The dry deposition velocities for most elements obtained using three size ranges were statistically significant with R² values ranging from 0.37 to 0.84 except for V and Ni (0.12).

Keywords: Trace metals; NY/NJ harbor estuary; Atmospheric size distributions; Overall dry deposition velocities; Dry deposition fluxes

Aerosol ion concentration dependence on atmospheric conditions in Chicago by Tinamarie Fosco; Martina Schmeling (pp. 6638-6649).

This study seeks to determine the influence of precursor trace gases and local meteorology, including lake breeze events, on the concentrations of secondary aerosol species in Chicago. For this, two particulate air samples per day were collected onto quartz fiber filters at the Loyola University Chicago Air Station (LUCAS) during the summer months of 2002 and 2003 and subsequently analyzed by ion chromatography for sulfate, nitrate and oxalate. In parallel, mixing ratios of ozone (O₃) and nitrogen oxides (NO and NO₂NO _x) were monitored and weather parameters were recorded. In addition, backward trajectories were obtained to estimate air mass transport to Chicago. Ozone and NO _x mixing ratios as well as sulfate, nitrate and oxalate concentrations varied substantially throughout the study, but three situations could be distinguished based on meteorology and chemistry. Case one had the lowest ozone, NO _x and ion levels due to wind directions constantly from Lake Michigan. Case two comprised of days showing the highest pollutant levels because of to predominantly southwestern air currents and warm temperatures and case three experienced an air stagnation situation in the morning leading to high NO _x mixing ratios and a subsequent lake breeze event. In the last case, elevated ozone mixing ratios and ion concentrations were observed after lake breeze onset indicating pollutant transport.

Keywords: Ion chromatography; Lake breeze; Urban air quality; Secondary aerosol formation; Pollutant transport

Mercury, PM_2.5 and gaseous co-pollutants in the Ohio River Valley region: Preliminary results from the Athens supersite by Reddy L.N. Yatavelli; Jason K. Fahrni; Myoungwoo Kim; Kevin C. Crist; Christopher D. Vickers; Stephen E. Winter; Daniel P. Connell (pp. 6650-6665).

This paper presents preliminary results from an ongoing air quality project at a rural super site in Athens, Ohio (39°18′N, 82°7′W). Athens is located in the heart of the Ohio River Valley region, which is characterized by a high number of coal-fired power plants, chemical plants, and manufacturing industries. Highly time-resolved gaseous elemental mercury (Hg⁰), reactive gaseous mercury (RGM), and particulate mercury (Hg_p) data are reported in this paper. Mercury species are measured using an automated Tekran 2537A CVAFS analyzer and Tekran 1130 and 1135 speciation and particulate modules. Continuous mercury data are reported from 27 July 2004, to 30 July 2005. This study also measured wet deposited mercury; reported here are results from 3 May 2004, until 31 May 2005. The highest mercury deposition occurred during September 2004. This is due in part to a series of unusual weather events featuring transport predominantly from the north, northeast, and southeast. The effects of the remnants of hurricanes Frances and Ivan on air quality data are also apparent during this month. This paper also presents results of PM_2.5, gaseous co-pollutant, and meteorological measurements. Results are compiled into daily and monthly averages to display diurnal and seasonal patterns. Low background concentrations with frequent pollution episodes make this rural site an excellent location to capture transport events into and out of the Ohio River Valley.

Keywords: Hg; ⁰; RGM; Hg; _p; Ambient mercury measurements; Mercury deposition

Source apportionment of PAHs in atmospheric particulates of Dalian: Factor analysis with nonnegative constraints and emission inventory analysis by Xianlie Wan; Jingwen Chen; Fulin Tian; Weijun Sun; Fenglin Yang; Kaoru Saiki (pp. 6666-6675).

Levels of 12 PAH species, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, perylene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene, in atmospheric particulates from urban area of Dalian, China, were determined. The sampling was performed at 15 sites in 1998. For wintertime and summertime, the summation of the 12 PAHs (ΣPAHs) averaged 167 (53.3–561) and 17.9 (1.6–48.9)ngm⁻³, respectively, which were much higher than the levels in other cities worldwide. Factor analysis with nonnegative constraints was used for source apportionment, which showed that PAHs originated from coal-related sources mainly (87%) and traffic emission as a second source (13%) in wintertime, and in summertime, coal-related sources (70%), traffic-related sources (27%), and wood burning (3%). The source apportionment results agree with the actual municipal and industrial layout well. Inventory analysis estimated the total amount of the 12 PAHs emitted by regulated stationary and mobile sources was 9940kg in 1998. Qualitatively, consistent source apportionment results were obtained from the factor analysis with nonnegative constraints and inventory analysis.

Keywords: PAHs; Source contribution; Coal combustion; Traffic emission; Dalian

Thermodynamics of the formation of atmospheric organic particulate matter by accretion reactions—Part 3: Carboxylic and dicarboxylic acids by Kelley C. Barsanti; James F. Pankow (pp. 6676-6686).

The term “accretion reactions�? has been used to describe the collection of reactions by which organic compounds can react with one another and/or other atmospheric constituents, forming products of higher-molecular weight (MW) and lower volatility, and thus increasing their tendency to condense [Barsanti, K.B., Pankow, J.F., 2004. Thermodynamics of the formation of atmospheric organic particulate matter by accretion reactions—Part 1: Aldehydes and ketones. Atmospheric Environment 38, 4371–4382; Barsanti, K.B., Pankow, J.F., 2005. Thermodynamics of the formation of atmospheric organic particulate matter by accretion reactions—Part 2: Dialdehydes, methylglyoxal, and diketones. Atmospheric Environment 39, 6597–6607]. Studies have shown that a significant fraction of atmospheric organic particulate matter (OPM) may be comprised of high-MW/low-volatility compounds [e.g., Havers, N., Burpa, P., Lambert, J., Klockow, D., 1998. Spectroscopic characterization of humic-like substances in airborne particulate matter. Journal of Atmospheric Chemistry 29, 45–54], which would be consistent with the occurrence of such accretion reactions in the atmosphere, [e.g., Jang, M., Czoschke, N. M., Lee, S., Kamens, R. M., 2002. Heterogeneous atmospheric organic aerosol production by acid-catalyzed particle-phase reactions. Science 298, 814–817]. However, many uncertainties exist regarding accretion reactions as they may occur in the atmosphere, including identification of those reactions most likely to contribute to OPM.Barsanti and Pankow (2004, 2005) have developed and applied a general theoretical approach to evaluate the thermodynamic favorabilities of accretion reactions, including the extents to which they may be relevant for OPM formation in the atmosphere. That approach is applied here in the consideration of OPM formation by reactions of four mono- and dicarboxylic acids (acetic, malic, maleic, and pinic) to form esters and amides. It was concluded that for all of the acids considered, ester and amide formation are thermodynamically favored under the assumed conditions. For malic, maleic, and pinic acids, and likely for similar mono- and dicarboxylic acids, significant OPM formation may occur via ester and amide formation in the atmosphere when kinetically favorable.

Keywords: Organic particulate matter; Secondary organic aerosol; SOA; Accretion reactions; Oligomers; Acids; Alcohols; Amides; Esters

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Atmospheric Environment (v.40, #34)