Atmospheric Environment (v.43, #17)

A wide range of environmental particulate matter (PM) both indoor and outdoor and consisting of natural and anthropogenic PM was collected by high volume air filters, electrostatic precipitation, and thermophoretic precipitation directly onto transmission electron microscope (TEM) coated grid platforms. These collected PM have been systematically characterized by TEM, energy-dispersive X-ray spectrometry (EDS) and scanning electron microscopy (SEM). In the El Paso, TX, USA/Juarez, Mexico metroplex 93% of outdoor PM1 is crystalline while 40% of PM1 is carbonaceous soot (including multiwall carbon nanotubes (MWCNTs) and multiconcentric fullerenes) PM. Multiply-replicated cytotoxicity (in vitro) assays utilizing a human epithelial (lung model) cell line (A549) consistently demonstrated varying degrees of cell death for essentially all PM which was characterized as aggregates of nanoparticulates or primary nanoparticles. Cytokine release was detected for Fe2O3, chrysotile asbestos, BC, and MWCNT PM while reactive oxygen species (ROS) production has been detected for Fe2O3, asbestos, BC, and MWCNT aggregate PM as well as natural gas combustion PM.Nanoparticulate materials in the indoor and outdoor environments appear to be variously cytotoxic, especially carbonaceous nano-PM such as multiwall carbon nanotubes, black carbon, and soot nano-PM produced by natural gas combustion.
Keywords: Environmental nanoparticulates; Microstructural characterization of nano-PM; Cytotoxicity assays; Health effects;

Effects of meteorology on diurnal and nocturnal levels of priority polycyclic aromatic hydrocarbons and elemental and organic carbon in PM10 at a source and a receptor area in Mexico City by Diana Guzmán-Torres; Arantza Eiguren-Fernández; Pablo Cicero-Fernández; Marisela Maubert-Franco; Armando Retama-Hernández; Rafael Ramos Villegas; Antonio H. Miguel (2693-2699).
PM10 levels of the 16 US-EPA Priority Pollutant polycyclic aromatic hydrocarbons (PAHs) were measured from March 17 to 31, 2003, in 8-h time bins (morning, afternoon and nighttime) at Merced, a source site dominated by vehicular traffic emissions near the center of Mexico City, and at Pedregal, a receptor area located downwind in a residential area of low traffic. Along with PAH, elemental (EC) and organic carbon (OC), mass, and prevailing meteorological parameters were measured. At the source location, measured concentrations of benzo[a]pyrene (BAP), an agent suspected of being carcinogenic to humans and of causing oxidative DNA damage, reached concentrations as high as 2.04 and 2.11 ng m−3 during the morning of a weekday and the night period of a holiday. Compared with source dominated areas in Central Los Angeles, the BAP levels found in Central Mexico City are approximately 6 times higher. Benzo[ghi]perylene (BGP) levels were, in general, the highest among the target PAH, both at the source (7.2 ng m−3) and the receptor site (2.8 ng m−3), suggesting that, at both locations, exhaust emission by light-duty (LD) vehicles is an important contributor to the atmospheric PAH burden. Higher PAH concentrations were observed during the morning period (5:00–13:00 h) at the source and the receptor site. The concentrations of PAHs found predominantly in the particle-phase (MW > 202) correlated well (r = 0.57–0.71) with the occurrence of surface thermal inversions and with mixing heights (r = −0.57 to −0.72). Organic and elemental carbon ratios also indicated that Pedregal is impacted by secondary aerosols during the afternoon hours.
Keywords: Polycyclic aromatic hydrocarbons; Elemental carbon; Organic carbon; Meteorology; Mexico City; PM10;

Columnar optical properties of tropospheric aerosol by combined lidar and sunphotometer measurements at Taipei, Taiwan by Wei-Nai Chen; Yi-Wei Chen; Charles C.K. Chou; Shih-Yang Chang; Po-Hsiung Lin; Jen-Ping Chen (2700-2708).
Vertical extinction profiles and columnar optical properties (optical depth, Angstrom exponent, lidar ratio, and particle depolarization) of aerosols were obtained by simultaneous measurements with a depolarization lidar and a sunphotometer at Taipei, Taiwan from February 2004 to January 2006. Columnar optical depths are high in Feb–Apr (0.61–0.75) by sunphotometer measurements. Lidar measurements show the contribution of aerosols in the free atmosphere on columnar optical depths are about 44–50% in Feb–Apr and about 26–37% in other months. Back-trajectory analyses and depolarization measurements show almost all of non-spherical aerosols originated from Northwest China which indicate Asian dusts frequently transported to Taipei from dust source regions in the free atmosphere. Aerosols with depolarization lower than 5% are found mostly originated from South China or Southeast Asia. Good correlations between columnar lidar ratio, particle depolarization, and Angstrom exponent are found for cases that columnar water vapor less than 1.5 cm. The effect of water vapor on particle depolarization is briefly discussed.
Keywords: Lidar; Sunphotometer; Aerosol; Lidar ratio; Angstrom exponent; Depolarization;

Analysis of cloud and precipitation chemistry at Whiteface Mountain, NY by Nenad Aleksic; K. Roy; G. Sistla; J. Dukett; N. Houck; P. Casson (2709-2716).
Federal and state programs over the past two decades have resulted in the reduction of emissions of precursors of acid rain. Concomitant with these changes, measured concentrations of acidity in precipitation and in watersheds have shown a downward trend or improvement. However, another pathway for these precursors is through cloud and fog events that often tend to occur at high-elevation regions affecting the fauna and flora as well. In this study we report on long-term measurements of cloud water and precipitation chemistry made from 1994 onwards at a high-elevation location, Whiteface Mountain NY, in the northeastern United States. Trends and inter-relationship between the ions were examined along with ambient SO2 measurements and Adirondack lakes chemistry data.
Keywords: Cloud deposition; Cloud chemistry; Acid deposition; Whiteface Mountain;

Direct quantification of organic acids in aerosols by desorption electrospray ionization mass spectrometry by Mei Li; Hong Chen; Xin Yang; Jianmin Chen; Chunlei Li (2717-2720).
Desorption electrospray ionization mass spectrometry (DESI-MS) is a novel analytical technique for direct surface analysis under ambient conditions. In this work, we report the first application of DESI-MS to the analysis of organic acids in atmospheric aerosols. We took oxalic and oleic acids as two typical representatives of the particulate organic acids. Experimental parameters for DESI-MS were optimized to enhance the signal intensity. Calibrations for both acids showed great linearity over a concentration range of 5 orders of magnitude with correlation coefficients R 2>0.99. The relative standard deviation (RSD) was less than 10% for oxalic acid and within 15% for oleic acid measurement. The detection limits for oxalic acid and oleic acid are about 1 pg mm−2 with 5–10 s sampling time. Mass concentrations of organic acids in both laboratory-generated biomass burning and ambient aerosols were measured by DESI-MS and the results agree well with the ion chromatography (IC) and GC–MS values. This work demonstrates that DESI-MS is a promising method for rapid quantitative analysis of organic acids in atmospheric aerosols.
Keywords: Organic acid; Aerosol; DESI-MS; Quantitative measurement;

Experiments were conducted on a 4-cylinder direct-injection diesel engine using ultralow sulfur diesel blended with biodiesel and ethanol to investigate the gaseous emissions of the engine under five engine loads at the maximum torque engine speed of 1800 rev min−1. Four biodiesel blended fuels and four ethanol blended fuels with oxygen concentrations of 2%, 4%, 6% and 8% were used. With the increase of oxygen content in the blended fuels, the brake thermal efficiency improves slightly.For the diesel-biodiesel fuels, the brake specific HC and CO emissions decrease while the brake specific NO x and NO2 emissions increase. The emissions of formaldehyde, 1,3-butadiene, toluene, xylene and overall BTX (benzene, toluene, xylene) in general decrease, however, acetaldehyde and benzene emissions increase. For the diesel-ethanol fuels, the brake specific HC and CO emissions increase significantly at low engine load, NO x emission decreases at low engine load but increases at high engine load. The emissions of benzene and BTX vary with engine load and ethanol content. Similar to the biodiesel-diesel fuels, the formaldehyde, 1,3-butadiene, toluene and xylene emissions decrease while the acetaldehyde and NO2 emissions increase. Despite having the same oxygen contents in the blended fuels, there are significant differences in the gaseous emissions between the biodiesel-diesel blends and the ethanol-diesel blends.
Keywords: Ultralow sulfur diesel; Biodiesel; Ethanol; Regulated gaseous emissions; Unregulated gaseous emissions;

NH4 +, NO3 , and SO4 2− in roadside and rural size-resolved particles and transformation of NO2/SO2 to nanoparticle-bound NO3 /SO4 2− by Chih-Chung Lin; Kuo-Lin Huang; Shui-Jen Chen; Shaw-Chen Liu; Jen-Hsiung Tsai; Yuan-Chung Lin; Wen-Yinn Lin (2731-2736).
This study investigates ammonium, nitrate, and sulfate (NH4 +, NO3 , and SO4 2−) in size-resolved particles (particularly nano (PM0.01–0.056)/ultrafine (PM0.01–0.1)) and NOx/SO2 collected near a busy road and at a rural site. The average (mass) cumulative fraction of secondary inorganic aerosols (SO4 2−+NO3 +NH4 +) in nano or ultrafine particles at the roadside was found to be three to four times that at the rural site. The above three secondary inorganic aerosol species were present in similar cumulative fractions in particles of size 1–18 μm at both sites; however, dissimilar fractions were observed for Cl, Na+, and K+. The nitrogen ratios (NRs: NR = NO3 −N/(NO3 −N + NO2–N)), sulfur ratios (SRs: SR = SO4 2−−S/(SO4 2−−S + SO2–S)), dNR/DP (derivative of NR with respect to DP (particle diameter)), and dSR/DP (derivative of SR with respect to DP) at the roadside were higher than those at the rural site for nano/ultrafine particles. At both sites (particularly the roadside), the nanoparticles had significantly higher dNR/DP and dSR/DP values than differently sized particles, implying that NO3 /SO4 2− (from NO2/SO2 transformation or NO3 /SO4 2− deposition) were present on these particles.
Keywords: Nanoparticles; Ultrafine; Nitrates; Sulfates;

Simulation of global warming potential (GWP) from rice fields in the Tai-Lake region, China by coupling 1:50,000 soil database with DNDC model by Liming Zhang; Dongsheng Yu; Xuezheng Shi; David C. Weindorf; Limin Zhao; Weixin Ding; Hongjie Wang; Jianjun Pan; Changsheng Li (2737-2746).
Quantifying greenhouse gas (GHG) emissions from wetland ecosystems is a relatively new issue in global climate change studies. China has approximately 22% of the world's rice paddies and 38% of the world's rice production, which are crucial to accurately estimate the global warming potential (GWP) at regional scale. This paper reports an application of a biogeochemical model (DeNitrification and DeComposition or DNDC) for quantifying GWP from rice fields in the Tai-Lake region of China. For this application, DNDC is linked to a 1:50,000 soil database, which was derived from 1107 paddy soil profiles compiled during the Second National Soil Survey of China in the 1980–1990s. The simulated results show that the 2.34 Mha of paddy soil cultivated in rice–wheat rotation in the Tai-Lake region emitted about −1.48 Tg C, 0.84 Tg N and 5.67 Tg C as CO2, N2O, and CH4 respectively, with a cumulative GWP of 565 Tg CO2 equivalent from 1982 to 2000. As for soil subgroups, the highest GWP (26,900 kg CO2 equivalent ha−1 yr−1) was linked to gleyed paddy soils accounting for about 4.4% of the total area of paddy soils. The lowest GWP (5370 kg CO2 equivalent ha−1 yr−1) was associated with submergenic paddy soils accounting for about 0.32% of the total area of paddy soils. The most common soil in the area was hydromorphic paddy soils, which accounted for about 53% of the total area of paddy soils with a GWP of 12,300 kg CO2 equivalent ha−1 yr−1. On a regional basis, the annual averaged GWP in the polder, Tai-Lake plain, and alluvial plain soil regions was distinctly higher than that in the low mountainous and Hilly soil regions. As for administrative areas, the average annual GWP of counties in Shanghai city was high. Conversely, the average annual GWP of counties in Jiangsu province was low. The high variability in soil properties throughout the Tai-Lake region is important and affects the net greenhouse gas emissions. Therefore, the use of detailed soil data sets with high-resolution digital soil maps is essential to improve the accuracy of GWP estimates with process-based models at regional and national scales.
Keywords: Global warming potential (GWP); Tai-Lake region; Paddy soil; DNDC; 1:50,000 soil database;

Vapor- and particulate-phase polycyclic aromatic hydrocarbon (PAH) samples were continuously collected at an urban site in Dalian, China, during the heating and non-heating period. There is strong temperature dependence and obvious seasonal trend for atmospheric PAHs, and significant positive correlations of atmospheric PAHs with SO2 and CO concentrations were observed. Factor analysis model with non-negative constraints (FA–NNC) combined with local and literature PAH source fingerprints was successful in source identification of particulate PAHs in the atmospheric samples. The results suggested that, in heating period, the main pollution sources were identified as coal-fired boiler emission (56%), residential coal combustion (33%) and traffic emissions (11%). As for non-heating period, the main sources were gasoline engine emission, traffic tunnel emission and coal-fired power plant, and the overall source contributions of traffic emission (gasoline engine + traffic tunnel) were 79% and coal-fired power plant 21%. The current results support our previous study and provide new insights. This can be the first attempt to quantitatively apportion air organic pollutants using receptor models combined with local source fingerprints. The source fingerprints can be used as reference data for source apportionment of atmospheric PAHs of China.
Keywords: PAHs; PM10; Vapor phase; Seasonality; FA–NNC;

The impact of vehicular emissions on air depends, among other factors, on the composition of fuel and the technology used to build the engines. The reduction of vehicular emissions requires changes in the fuel composition, and improving the technologies used in the manufacturing of engines and for the after-treatment of gases. In general, improvements to diesel engines have targeted not only emission reductions, but also reductions in fuel consumption. However, changes in the fuel composition have been shown to be a more rapid and effective alternative to reduce pollution. Some factors should been taken into consideration when searching for an alternative fuel to be used in diesel engines, such as emissions, fuel stability, availability and its distribution, as well as its effects on the engine durability. In this work, 45 fuel blends were prepared and their stability was evaluated. The following mixtures (v/v/v) were stable for the 90-day period and were used in the emission study: diesel/ethanol – 90/10%, diesel/ethanol/soybean biodiesel – 80/15/5%, diesel/ethanol/castor biodiesel – 80/15/5%, diesel/ethanol/residual biodiesel – 80/15/5%, diesel/ethanol/soybean oil – 90/7/3%, and diesel/ethanol/castor oil – 90/7/3%. The diesel/ethanol fuel showed higher reduction of NO x emission at a lower load (2 kW) when compared with pure diesel. The other fuels showed a decrease of NO x emissions in the ranges of 6.9–75% and 4–85% at 1800 rpm and 2000 rpm, respectively. The combustion efficiencies of the diesel can be enhanced by the addition of the oxygenate fuels, like ethanol and biodiesel/vegetable oil, resulting in a more complete combustion in terms of NO x emission. In the case of CO2 the decreases were in the ranges of 5–24% and 4–6% at 1800 rpm and 2000 rpm, respectively. Meanwhile, no differences were observed in CO emission. The carbonyl compounds (CC) studied were formaldehyde, acetaldehyde, propionaldehyde, acrolein, acetone, crotonaldehyde, butyraldehyde, butanone, benzaldehyde, isovaleraldehyde, valeraldehyde, o-toluenaldehyde, m-toluenaldehyde, p-toluenaldehyde, hexaldehyde, octaldehyde, 2,5-dimethylbenzaldehyde, and decaldehyde. Among them, formaldehyde, acetaldehyde, acetone, and propionaldehyde showed the highest emission concentrations. When ternary blend contains vegetable oil, there is a strong tendency to increase the emissions of the high weight CC and decrease the emissions of the low weight CC. The highest concentration of acrolein was observed when the fuel contains diesel, ethanol and biodiesel. With the exception of NO x , the use of ternary blended fuels resulted on the increase in the emission rates of the studied compounds.
Keywords: Biodiesel; Ethanol; Diesel; Carbonyl compounds; Vehicular emissions;

Nitric oxide emissions from conventional vegetable fields in southeastern China by Baoling Mei; Xunhua Zheng; Baohua Xie; Haibo Dong; Zaixing Zhou; Rui Wang; Jia Deng; Feng Cui; Huajun Tong; Jianguo Zhu (2762-2769).
We conducted multi-year observations of nitric oxide (NO) fluxes from typical vegetable fields in the Yangtze River delta, which is located in southeastern China. Flux measurements were performed manually twice per week at intervals of 2–3 days, in both fertilized and unfertilized fields, over an investigation period of 1448 days (September 2004–August 2008). In total, twelve vegetable-growing periods and a short fallow period were investigated. On average, the NO fluxes from the fertilized plots were 21 times higher than fluxes from the unfertilized plots (p < 0.001). Peak NO emissions usually occurred soon after the addition of nitrogenous fertilizer. Peak emissions took place during about 15% of the whole investigation time, but contributed to approximately 89% of the total NO release. The annual background NO emissions (from fields without nitrogen amendment) were observed at 0.290 ± 0.019 (standard deviation of 3 observations) kg N ha−1. The total amounts of NO emitted during the individual vegetable-growing periods correlated positively and exponentially with the products of seasonal mean soil temperatures and nitrogen addition rates (R 2 = 0.87, p < 0.001). The mean direct NO emission factor (EFd, the loss rate of fertilizer nitrogen via NO emissions) for the four-year period was determined to be 0.51% ± 0.11% (standard error of 3 observations). The EFds of individual vegetable-growing seasons ranged from 0.05% to 1.24%, varying linearly and positively with the products of seasonal mean soil temperatures and nitrogen addition rates (R 2 = 0.58, p < 0.01). The observed interaction of soil temperature and nitrogen addition on NO emission in seasonal totals and EFds occurred in soils with moisture contents ranging from 55% to 100% water-filled pore space (mean: 79%; standard deviation: 9%). The results of this study indicate that when other conditions remain relatively stable, the direct emission factor, a key parameter for compiling an inventory of NO emissions from vegetable fields, may vary with not only soil temperature but also nitrogen addition.
Keywords: Nitric oxide; Vegetable; Soil temperature; Nitrogen fertilizer; Direct emission factor; Background emission;

Quantifying road dust resuspension in urban environment by Multilinear Engine: A comparison with PMF2 by F. Amato; M. Pandolfi; A. Escrig; X. Querol; A. Alastuey; J. Pey; N. Perez; P.K. Hopke (2770-2780).
Atmospheric PM pollution from traffic comprises not only direct emissions but also non-exhaust emissions because resuspension of road dust that can produce high human exposure to heavy metals, metalloids, and mineral matter. A key task for establishing mitigation or preventive measures is estimating the contribution of road dust resuspension to the atmospheric PM mixture. Several source apportionment studies, applying receptor modeling at urban background sites, have shown the difficulty in identifying a road dust source separately from other mineral sources or vehicular exhausts. The Multilinear Engine (ME-2) is a computer program that can solve the Positive Matrix Factorization (PMF) problem. ME-2 uses a programming language permitting the solution to be guided toward some possible targets that can be derived from a priori knowledge of sources (chemical profile, ratios, etc.). This feature makes it especially suitable for source apportionment studies where partial knowledge of the sources is available.In the present study ME-2 was applied to data from an urban background site of Barcelona (Spain) to quantify the contribution of road dust resuspension to PM10 and PM2.5 concentrations. Given that recently the emission profile of local resuspended road dust was obtained (Amato, F., Pandolfi, M., Viana, M., Querol, X., Alastuey, A., Moreno, T., 2009. Spatial and chemical patterns of PM10 in road dust deposited in urban environment. Atmospheric Environment 43 (9), 1650–1659), such a priori information was introduced in the model as auxiliary terms of the object function to be minimized by the implementation of the so-called “pulling equations”.ME-2 permitted to enhance the basic PMF solution (obtained by PMF2) identifying, beside the seven sources of PMF2, the road dust source which accounted for 6.9 μg m−3 (17%) in PM10, 2.2 μg m−3 (8%) of PM2.5 and 0.3 μg m−3 (2%) of PM1. This reveals that resuspension was responsible of the 37%, 15% and 3% of total traffic emissions respectively in PM10, PM2.5 and PM1. Therefore the overall traffic contribution resulted in 18 μg m−3 (46%) in PM10, 14 μg m−3 (51%) in PM2.5 and 8 μg m−3 (48%) in PM1. In PMF2 this mass explained by road dust resuspension was redistributed among the rest of sources, increasing mostly the mineral, secondary nitrate and aged sea salt contributions.
Keywords: Source apportionment; Receptor models; Positive Matrix Factorization; Emission profile; Non-exhaust emissions;

Interest in the role and contribution of fungi to atmospheric aerosols and processes grows in the past decade. Substantial data or information such as fungal mass or carbon loading to ambient aerosols is however still lacking. This study aimed to quantify the specific organic carbon content (OC per spore) of eleven fungal species commonly found airborne in the subtropics, and estimated their contribution to organic carbon in aerosols. The specific OC contents showed a size-dependent relationship (r = 0.64, p < 0.05) and ranged from 3.6 to 201.0 pg carbon per spore or yeast cell, giving an average of 6.0 pg carbon per spore (RSD 51%) for spore or cell size less than 10 μm. In accounting for natural variations in the composition and abundance of fungal population, weighted-average carbon content for field samples was adopted using the laboratory determined specific OC values. An average of 5.97 pg carbon per spore (RSD 3.8%) was enumerated from 28 field samples collected at the university campus. The mean fungal OC concentration was 3.7, 6.0 and 9.7 ng m−3 in PM2.5, PM2.5–10 and PM10, respectively. These corresponded to 0.1%, 1.2% and 0.2% of the total OC in PM2.5, PM2.5–10 and PM10, respectively. In the study period, rain provided periods with low total OC but high fungal prevalence and fungi contributed 7–32% OC in PM2.5–10 or 2.4–7.1% OC in PM10. More extensive studies are deserved to better understand the spatial-, temporal- and episodic dependency on the fungal OC contribution to the atmospheric aerosols.
Keywords: Fungal carbon; Organic carbon; Fungal contribution; Weighted-average carbon content; Subtropics;

Household wood heater usage and indoor leakage of BTEX in Launceston, Australia: A null result by Ian E. Galbally; Robert W. Gillett; Jennifer C. Powell; Sarah J. Lawson; Simon T. Bentley; Ian A. Weeks (2788-2795).
A study has been conducted in Launceston, Australia, to determine within households with wood heaters the effect of leakage from the heater and flue on the indoor air concentrations of the pollutants: benzene, toluene, ethylbenzene and xylene (BTEX). The study involved three classes: 28 households without wood heaters, 19 households with wood heaters compliant with the relevant Australian Standard and 30 households with non-compliant wood heaters. Outdoor and indoor BTEX concentrations were measured in each household for 7 days during summer when there was little or no wood heater usage, and for 7 days during winter when there was widespread wood heater usage. Each participant kept a household activity diary throughout their sampling periods. For wintertime, there were no significant differences of the indoor BTEX concentrations between the three classes of households. Also there were no significant relationships between BTEX indoor concentrations within houses and several measures of the amount of wood heater use within these houses. For the households sampled in this study, the use of a wood heater within a house did not lead to BTEX release within that house and had no direct detectable influence on the concentrations of BTEX within the house. We propose that the pressure differences associated with the both the leakiness or permeability of the building envelope and the draught of the wood heater have key roles in determining whether there will be backflow of smoke from the wood heater into the house. For a leaky house with a well maintained wood heater there should be no backflow of smoke from the wood heater into the house. However backflow of smoke may occur in well sealed houses.The study also found that wood heater emissions raise the outdoor concentrations of BTEX in winter in Launceston and through the mixing of outdoor air through the building envelopes into the houses, these emissions contribute to increases in the indoor concentrations of BTEX in winter in all houses in Launceston.
Keywords: BTEX; Indoor air pollution; Wood smoke; Wood heater; Smoke leakage;

Characterization and sources assignation of PM2.5 organic aerosol in a rural area of Spain by Oscar Pindado; Rosa Ma Pérez; Susana García; Miguel Sánchez; Pilar Galán; Marta Fernández (2796-2803).
The results from a year-long study of the organic composition of PM2.5 aerosol collected in a rural area influenced by a highway of Spain are reported. The lack of prior information related to the organic composition of PM2.5 aerosol in Spain, concretely in rural areas, led definition of the goals of this study. As a result, this work has been able to characterize the main organic components of atmospheric aerosols, including several compounds of SOA, and has conducted a multivariate analysis in order to assign sources of particulate matter. A total of 89 samples were taken between April 2004 and April 2005 using a high-volume sampler. Features and abundance of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), alcohols and acids were separately determined using gas chromatography/mass spectrometry and high performance liquid chromatography analysis. The Σn-alkane and ΣPAHs ranged from 3 to 81 ng m−3 and 0.1 to 6 ng m−3 respectively, with higher concentrations during colder months. Ambient concentrations of Σalcohols and Σacids ranged from 21 to 184 ng m−3 and 39 to 733 ng m−3, respectively. Also, several components of secondary organic aerosol have been quantified, confirming the biogenic contribution to ambient aerosol. In addition, factor analysis was used to reveal origin of organic compounds associated to particulate matter. Eight factors were extracted accounting more than 83% of the variability in the original data. These factors were assigned to a typical high pollution episode by anthropogenic particles, crustal material, plant waxes, fossil fuel combustion, temperature, microbiological emissions, SOA and dispersion of pollutants by wind action. Finally, a cluster analysis was used to compare the organic composition between the four seasons.
Keywords: PM2.5; Organic composition; Rural aerosol; Source attribution; Cluster analysis;

Atmospheric degradation of alkylfurans with chlorine atoms: Product and mechanistic study by F. Villanueva; B. Cabañas; E. Monedero; S. Salgado; I. Bejan; P. Martin (2804-2813).
As part of a study on the oxidation mechanism of heterocyclic aromatic compounds, some aspects of the atmospheric chemistry of several alkyl derivatives of furan have been investigated. The aim of this work was to identify the products of the reactions of chlorine atoms with 2-methylfuran, 2-ethylfuran and 2,5-dimethylfuran. Experiments were performed in two different smog chambers at 296 ± 2 K and 1000 ± 20 mbar of synthetic air. The experimental investigation was carried out using in situ long-path FTIR absorption spectroscopy and both SPME-GC/FID-ECD and SPME-GC/MS as sampling and detection techniques. The major primary products from the addition reaction channel were 4-oxo-2-pentenoyl chloride and formaldehyde for the reactions of 2-methylfuran and 2,5-dimethylfuran; 4-oxo-2-hexenoyl chloride and acetaldehyde for the reaction of 2-ethylfuran and 5-chloro-2(5H)-furanone for the reactions of both 2-methylfuran and 2-ethylfuran. Other minor products were 4-oxo-2-pentenal, 4-oxo-2-hexenal and 3-hexene-2,5-dione for the 2-methylfuran, 2-ethylfuran and 2,5-dimethylfuran reactions, respectively. From the abstraction pathway, HCl, furfural, 2-acetylfuran, 5-methylfurfural, maleic anhydride and 5-hydroxy-2(5H)-furanone were detected. The formation of furfural, 2-acetylfuran and 5-methylfurfural confirmed the H-atom abstraction from the alkyl group of 2-methylfuran, 2-ethylfuran and 2,5-dimethylfuran, respectively. This mechanism was not observed in previous studies with OH and NO3 radicals. A mechanism is proposed to explain the main reaction products observed. The observed products confirm that addition of Cl atoms to the double bond of the alkylfuran is the dominant reaction pathway.
Keywords: Gas phase mechanism; Reaction products; Alkylfuran; Chlorine atoms; 4-Oxo-2-pentenoyl chloride; 4-Oxo-2-hexenoyl chloride; 5-Chloro-2(5H)-furanone;

Aerosols are harmful to human health and have both direct and indirect effects on climate. China is a major contributor to global emissions of sulfur dioxide (SO2), a sulfate (SO4 2−) precursor, organic carbon (OC), and black carbon (BC) aerosols. Although increasingly examined, the effect of present and potential future levels of these emissions on global premature mortality and climate change has not been well quantified. Through both direct radiative effects and indirect effects on clouds, SO4 2− and OC exert negative radiative forcing (cooling) while BC exerts positive forcing (warming). We analyze the effect of China's emissions of SO2, SO4 2−, OC and BC in 2000 and for three emission scenarios in 2030 on global surface aerosol concentrations, premature mortality, and radiative forcing (RF). Using global models of chemical transport (MOZART-2) and radiative transfer (GFDL RTM), and combining simulation results with gridded population data, mortality rates, and concentration–response relationships from the epidemiological literature, we estimate the contribution of Chinese aerosols to global annual premature mortality and to RF in 2000 and 2030. In 2000, we estimate these aerosols cause approximately 470 000 premature deaths in China and an additional 30 000 deaths globally. In 2030, aggressive emission controls lead to a 50% reduction in premature deaths from the 2000 level to 240 000 in China and 10 000 elsewhere, while under a high emissions scenario premature deaths increase 50% from the 2000 level to 720 000 in China and to 40 000 elsewhere. Because the negative RF from SO4 2− and OC is larger than the positive forcing from BC, Chinese aerosols lead to global net direct RF of −74 mW m−2 in 2000 and between −15 and −97 mW m−2 in 2030 depending on the emissions scenario. Our analysis indicates that increased effort to reduce greenhouse gases is essential to address climate change as China's anticipated reduction of aerosols will result in the loss of net negative radiative forcing.
Keywords: Aerosols; China; Air pollution; Premature mortality; Health; Radiative forcing;

A study on variations of concentrations of particulate matter with different sizes in Lanzhou, China by Shigong Wang; Xinyuan Feng; Xiaoqing Zeng; Yuxia Ma; Kezheng Shang (2823-2828).
Lanzhou is one of the most air-polluted cities in China and in the world, and its primary air pollutant is particulate matter (PM). Different size particulate matter (TSP, PM10, PM2.5 and PM1.0) have different sources and affect the environment and human health differently, so it is very important to study the pollutant characteristics of different particles in order to deeply understand the pollution situation of Lanzhou city and establish reasonable preventive countermeasures. TSP, PM10, PM2.5 and PM1.0 concentrations were simultaneously measured in Lanzhou to detect the annual and diurnal variations of concentrations of PM with different sizes and possible causes. The main results are as follows: (1) The annual distribution of monthly average concentrations for coarse particles (TSP and PM10) is bimodal with the highest peak in April, which is different from the situation in other cities not affected by sand-dust events. However, the annual distribution for fine particles (PM2.5 and PM1.0) is unimodal with the peak in December. This difference between coarse and fine particles indicates that sand-dust events in spring carry much more coarse than fine particles to Lanzhou. This result is supported by the correlation between springtime wind speed and concentrations of PM with different sizes. (2) Under normal conditions (without dust intrusions), the diurnal distribution of coarse particle concentration in Lanzhou is bimodal. However, the distribution is trimodal during dust intrusions in April, with an extra peak in the afternoon. (3) In general, the highest concentration peaks of the diurnal variations for TSP, PM10, PM2.5 and PM1.0 occur at about the same time. However, there are obvious differences in the occurrence time of the minimum concentrations among different kinds of PM. The differences in the occurrence time of minima between coarse and fine particles are due to their different diffusion behaviors in the atmospheric boundary layer.
Keywords: Particulate matter with different sizes (TSP, PM10, PM2.5 and PM1.0); Particulate concentration; Annual variation; Diurnal variation; Lanzhou;

Current regional models for predicting atmospheric organic particulate matter (OPM) levels rely heavily on the computationally simple, lumped “two-product” (2p) approach for parameterizing the formation of secondary organic aerosol (SOA). At the other extreme, molecular kinetic models of SOA formation are available that use numerous complex reaction pathways to produce large numbers of potentially condensable organic oxidation products, but the complexities of those models currently limit implementation in large-scale air quality models. This study proposes use of a carbon number (n C) vs. polarity grid (with concentration bins) for tracking the various OPM-relevant compounds and their time-dependent concentrations T i (μg m−3). The grid can be used when adding complexity to the 2p approach, or for managing and limiting the complexity of molecular kinetic models. For the former, an expanded n p + m P approach is proposed with n products and m possible types of very low volatility polymer ( P ) materials. For the latter, the grid limits system complexity by allowing compounds with similar structures to be lumped together in the same grid bin even when they are formed by different routes. With either an n p + m P approach or a molecular kinetic approach, the n C vs. polarity grid will allow consideration of the effects of variation in the activity coefficients ζi of the partitioning compounds, variation in the mean molecular weight of the absorbing OPM phase, water uptake, and the possibility of phase separation in the OPM phase.
Keywords: Organic particulate matter (OPM); Secondary organic aerosol (SOA); Absorption model; Two-product; Modeling; Volatility; Polarity;

Contamination from electrically conductive silicone tubing during aerosol chemical analysis by Yong Yu; M. Liz Alexander; Veronique Perraud; Emily A. Bruns; Stanley N. Johnson; Michael J. Ezell; Barbara J. Finlayson-Pitts (2836-2839).
Electrically conductive silicone tubing is used to minimize losses in sampling lines during the analysis of airborne particle size distributions and number concentrations. We report contamination from this tubing using gas chromatography–mass spectrometry (GC–MS) of filter-collected samples as well as by particle mass spectrometry. Comparison of electrically conductive silicone and stainless steel tubing showed elevated siloxanes only for the silicone tubing. The extent of contamination increased with length of tubing to which the sample was exposed, and decreased with increasing relative humidity.
Keywords: Aerosol chemical analysis; Electrically conductive silicone tubing; Siloxanes; Contamination;