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This study reports for the first-time the ambient concentrations of HULIS mass (HULIS-OM, Humic-like substances) and HULIS-C (carbon) in PM10 (particulate matter with aerodynamic diameter ≤ 10 μm) from the Indo-Gangetic Plain (IGP at Kanpur, wintertime). HULIS extraction followed by purification and isolation protocol with methanol: acetonitrile (1:1 v/v) on HLB (Hydrophilic-Lipophilic Balanced) cartridge has been established. Quantification of HULIS-C was achieved on a total organic carbon (TOC) analyser whereas HULIS-OM was determined gravimetrically. Consistently high recovery (> 90%) of HULIS-C based on analysis of Humic standard (sodium salt of Humic acid) suggested suitability of our established analytical protocol involving solvent extraction, purification and accurate quantification of HULIS. HULIS-OM varied from 17.3-38 μg m−3 during daytime and from 19.8-40.6 μg m−3 during night in this study. During daytime the HULIS-OM constituted 20-30% mass fraction of OMTotal and 10-15% of PM10 mass. However, a relatively low contribution of HULIS-OM has been observed during the night. This observation has been attributed to higher concentrations of OM and PM10 in night owing to nighttime chemical reactivity and condensation of organics in conjunction with shallower planetary boundary layer height. Strong correlation of HULIS-C with K+BB (R2 > 0.80) and significant day-night variability of HULIS-C/WSOC ratio in conjunction with air-mass back trajectories (showing transport of pollutants from upwind IGP) suggest biomass burning emission and secondary transformations as important sources of HULIS over IGP. High-loading of atmospheric PM10 (as high as 440 μg m−3) with significant contribution of water-soluble organic aerosols (WSOC/OC: ~ 0.40-0.80) during wintertime highlights their plausible potential role in fog and haze formation and their impact on regional-scale atmospheric radiative forcing over the IGP. [ABSTRACT FROM AUTHOR]

Aerosol samples collected over a tropical location, Thumba, southernmost West Coast of India were analyzed for the abundance of homologous dicarboxylic acids (C to C), oxocarboxylic acids (ωC to ωC, pyruvic acid), α-dicarbonyls (glyoxal and methylglyoxal), organic and elemental carbon. Among the measured organics, oxalic acid was found to be the most abundant species followed by succinic and/or malonic acids. As oxoacid and α-carbonyl groups, glyoxylic acid and glyoxal, respectively, were observed to be dominant. On average, dicarboxylic acids accounted almost 2.1 ± 0.7 % of the aerosol total organic carbon. Among the aerosols over Thumba, two types of formation pathways were noticed for oxalic acid. During the post-monsoon and winter periods, the photo-oxidation of biogenic and anthropogenic volatile organic compounds lead to the formation of oxalic acid through a chain reaction involving glyoxal, methylglyoxal, pyruvic and glyoxylic acids. In contrast, during the pre-monsoon, the oxidative degradation of the biogenic unsaturated fatty acids give rise to succinic acid, which can be decomposed to malonic acid and then to oxalic acid. The observed seasonal variations in acid concentrations are consistent with photochemical production and the subsequent accumulation under favourable meteorological conditions prevailing over the region. [ABSTRACT FROM AUTHOR]

Residential cooking in China's urban areas could be a more significant contributor to organic aerosols when compared to restaurant cooking, yet no source profiles are available for Chinese residential cooking. In this study, a typical nine-floor residential apartment building in urban Guangzhou was selected to investigate the particulate mass emissions and chemical compositions of organic aerosols from Chinese residential cooking. During dinner cooking period, the average of total suspended particle (TSP) mass concentrations increased by a factor of 4.40 compared with that during non-cooking period. Organic matter (OM) was the major component of aerosols from cooking, and accounted for 66.9 % of the TSP mass. Over 90 organic species were identified and quantified, and could explain 14.5 % of OC in cooking emissions. Fatty acids alone shared 75.7 % of the total mass of quantified organic compounds, with palmitic acid as the predominant one. Sterols, monosaccharide anhydrides and polyols were also significant compositions and they together contributed 14.3 % in the total mass of the quantified organic compounds. While cholesterol was detected from western-style cooking, phytosterols were additionally observed from Chinese-style cooking, and campesterol and polyols were only reported in the present study. Chinese residential cooking emission showed small differences in composition patterns of organic compounds when compared to previously report Chinese restaurant cooking emissions, however, large differences existed when compared to western style cooking. Using cholesterol as a tracer for cooking emissions, in Guangzhou we found cooking emissions contributed 3.9-8.2 % of OC in PM. Spatial distributions of cooking emission contribution were consistent with the distributions of population. [ABSTRACT FROM AUTHOR]

The photooxidation of α-humulene in the presence of NOx, natural sunlight, and rural background air was investigated using a combination of gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). Identification and quantification of gas and particulate reaction products were reported over the course of the reaction. The daytime photooxidation was carried out in a large outdoor smog chamber (190 m3). A wide range of ring retaining and ring opening products in the gas and particle phase are reported. On average, measured gas and particle phase products accounted for ∼ 44% of the reacted α-humulene carbon. Measurements show that a number of reaction products with low vapor pressures (e.g. 3-seco-α-humulone aldehyde, 7-seco-α-humulone aldehyde, α-humulal aldehyde, α-humulene 3-oxide or α-humulene 7-oxide, α-humulaic/alic acid isomers, and 3-seco-α-14-hydroxyhumulone aldehyde) were found in the early stage of the reaction and may play an important role in the early formation of secondary organic aerosol. A detailed mechanism is proposed to account for most products observed in this investigation. [ABSTRACT FROM AUTHOR]

Gas and particulate reaction products from the ozonolysis of β -caryophyllene (I) in the presence of atmospheric air were investigated using a combination of gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). A Scanning Mobility Particle Sizer system (3936, TSI) and a Condensation Particle Counter (3025A, TSI) were used to study secondary organic aerosol formation. The nighttime oxidation was carried out in a large outdoor smog chamber (190 m3). A wide range of ring retaining and ring opening products in the gas and particle phase are reported over the course of the reaction. On average, measured gas and particle phase products accounted for ∼64% of the reacted β -caryophyllene (I) carbon. Measurements show that a number of reaction products with low vapor pressure (e.g., β-caryophyllone aldehyde (IV), β-norcaryophyllone aldehyde (V), β-caryophyllonic acid (VIII), β-14-hydroxycaryophyllonic acid (XIV)) were found in the sample taken during the first 20 min of the reaction and may play an important role in the early formation of secondary organic aerosol. A detailed mechanism is proposed to account for most products observed in this investigation. [ABSTRACT FROM AUTHOR]

The gas and particle phase products from the reaction of β-pinene with the atmospheric oxidants O3 and OH radicals in the presence of NOx were investigated using both gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC) for identification and quantification of reaction products. The nighttime oxidation of β-pinene in the presence of O3/air and the daytime oxidation of β-pinene in the presence of NOx/air and natural sunlight were carried out in the University of North Carolina large outdoor smog chamber (190 m3) located in Chatham County, North Carolina. A Scanning Mobility Particle Sizer system (3936, TSI) and a Condensation Particle Counter (3025A, TSI) were used to study the secondary organic aerosol (SOA) formation, and a filter pack/denuder sampling system was used for simultaneously collecting gas and particle phase products for analysis. A gas chromatograph coupled to a mass spectrometer (GC-EIMS or GC-CIMS) was used for the identification and quantification of gas and aerosol products. A HPLC method was used for the measurement of small carbonyl compounds (aldehydes and ketones) as their 2,4-dinitrophenylhydrazones (DNPH) derivatives. Mass balances for gaseous and aerosol reaction products were reported over the course of the reaction. More than sixteen products were identified and/or quantified in this study. On average, measured gas and particle phase products accounted for ∼57 to ∼71% of the reacted β-pinene carbon. Measurements showed that a number of reaction products were found in both O3 and NOx systems (pinic acid, pinalic-3-acid, 4-hydroxypinalic-3-acid, 4-oxonopinone, 1-hydroxynopinone, 3-hydroxynopinone, and nopinone). Pinic acid, pinalic-3-acid, and 4-hydroxypinalic-3-acid were observed in the early stage in the aerosol phase and may play an important role in the early formation of secondary aerosols. Detailed reaction schemes are presented to account for most of the observed reaction products. [ABSTRACT FROM AUTHOR]