Acids In PM2 Research Articles

Seasonal distributions and possible sources of low molecular weight organic acids in PM2.5 from a typical mining city after decade green mining developing in Southeastern Hubei, Central China

Low molecular weight (LMW) organic compounds are prevalent in the atmospheric aerosols. Human activities and natural sources could significantly influence aerosol compositions and concentrations, particularly in a typical mining and metallurgy city. In this study, we measured dicarboxylic acids, ω-oxocarboxylic acids, pyruvic acid, α-dicarbonyls, and fatty acids in PM2.5 from Huangshi, China throughout one year. The results indicated that oxalic acid and glyoxylic acid were the most abundant dicarboxylic acid and ω-oxocarboxylic acid, respectively, across all seasons. Following nearly a decade of environmentally conscious economic development in Huangshi, it is observed that organic compounds primarily accumulated in PM2.5 due to the combustion of fossil fuels for mining-related activities and biogenic emissions. Furthermore, anthropogenic activities, including emissions related to traffic, biomass burning, and plastic incineration, significantly influence the composition of organic aerosols. Natural processes, such as atmospheric oxidation during long-distance transport, predominantly from North China, Mongolia, Russia, and Kazakhstan, also play a substantial role. The findings underscore the transitioning energy structures, modes of transport, and oxidation processes during long-distance transport have already begun to influence the composition of LMW organic compounds. The insights gained from this study offer valuable information for researchers and governmental authorities to understand the molecular composition and potential sources of LMW organic acids in the context of green mining development. This knowledge can aid in the formulation of targeted policies for the prevention and control of carbonaceous pollution in similar mining regions globally.

Pollution Characteristics，Sources，and Secondary Generation of Organic Acids in PM2.5 in Zhengzhou

Organic acids in atmospheric particulate matter are widely involved in various physical and chemical reactions in the atmosphere and contribute greatly to the formation of secondary organic aerosols and haze pollutions. Therefore， the concentration distribution characteristics， sources， and secondary formation of organic acids in particulate matter are of great significance for further investigation of organic aerosols and their secondary transformation. Fine particulate matter （PM2.5） samples were collected in Zhengzhou， and three types of organic acids， including dicarboxylic acids， fatty acids， and resin acids， were analyzed to explore their species distribution， seasonal variations， source contribution， and secondary generation. Malonic acid （di-C3） and succinate acid （di-C4） were the most abundant in the identified dicarboxylic acids， which showed obvious seasonal variations in the order of summer > autumn > winter > spring. Fatty acids had the highest concentration in winter and the lowest concentration in spring， showing obvious bimodal advantages， with the most abundant compounds being palmitic acid and stearic acid （C18）. Principal component analysis and multiple linear regression （MLR） were used to analyze the source of organic acids in PM2.5 in Zhengzhou； the results showed that 35% of the organic acids came from combustion and traffic sources， 24% from cooking sources， 23% from secondary formation， and 17% from natural sources. The ratios of the selected marker species （i.e.， di-C3 / di-C4， F/M， and C18：1 / C18） were used as tracers for the secondary formation of the organic aerosol and its aging process. The results showed that the photochemical reaction was intense in summer， and the proportion of organic aerosol aging or secondary production was high， whereas the photochemical reaction was weak in winter， and the aging degree of organic aerosol was low. Correlation analysis and MLR were used in combination to quantify the relative contribution of gas-phase oxidation and liquid-phase oxidation to dicarboxylic acid formation， and the results showed that gas-phase oxidation played a dominant role in the sampling period （accounting for 58%）， especially in summer （61%）.

Enrichment of Organic Acids in Fine Particles Over a Megacity in South China

AbstractOrganic acids are abundant aerosol components that impact the hygroscopicity and multiphase processes of particulate matter, yet their changing compositions and sources are poorly understood. In this study, filter‐based PM2.5 samples were collected concurrently at three sites (urban, rural, and coastal) during the summer and winter of 2018 in the megacity Guangzhou, south China, to determine organic acids including C9–C32 fatty acids, C4–C10 dicarboxylic acids, and aromatic acids. On average, the total concentrations of the speciated organic acids were higher in winter than in summer, and were the highest at the urban site. Compared to observations at the same sites in winter 2009, average concentrations of organic acids in winter 2018 increased by 35.0%, 66.0%, and −3.2% at the urban, rural and coastal sites, while their fractions in organic matter (OM) increased by approximately 261.5%, 266.7%, and 61.1%, and their fractions in PM2.5 increased by approximately 318.2%, 308.7%, and 221.1%, respectively. Source apportionment of organic acids revealed that cooking emission and vehicle exhaust were the major sources at the urban site, plant wax and vehicle exhaust were the two largest sources at the rural site with substantial contributions from biomass burning in winter, while vehicle exhaust and ship emission were the two major sources at the coastal site. Less contributions from secondary production were retrieved in winter 2018 than in winter 2009, and the enrichment of organic acids in PM2.5 or OM was attributed to their elevated primary emissions from vehicles and ships, cooking, and plant wax.

Spatio-temporal characteristics and source apportionment of water-soluble organic acids in PM2.5 in the North China Plain

Water-soluble organic acids (WSOAs) are important chemical components of fine particulate matter (PM2.5). WSOAs can aggravate PM2.5 pollution and contribute to the acidity of aerosol and rain. PM2.5 pollution in the North China Plain (NCP) has been extensively researched. However, with the decrease in PM2.5 and enhancement of atmospheric oxidation in the NCP, it is unclear how the amount and source of WSOAs in ambient PM2.5 change. In this study, we investigated WSOAs in PM2.5 from 2018 to 2019 at urban and rural sites in the NCP. Our results showed that WSOAs accounted for 0.8% of the PM2.5 mass with a dominance of oxalic acid (OA), followed by formic acid (FA) and methanesulfonic acid (MSA). High MSA concentrations at inland sites, such as Yucheng, indicated that MSA in PM2.5 primarily originated from anthropogenic activities rather than marine sources, as previously inferred. WSOAs in ambient PM2.5 were comparable at rural and urban sites with 0.73 ± 0.46 μg/m³ and 0.66 ± 0.40 μg/m³, respectively. The secondary transformation of pollutants from coal combustion and vehicle exhaust emissions was the major WSOAs source, with an average contribution of 70% at all sites. Photochemical oxidation played a stronger role in WSOAs transformation than aqueous oxidation. The potential source contribution function analysis revealed that southern Hebei and central Shandong provinces were potential source areas for WSOAs in the NCP. In the future, the integrated regional control of precursor and oxidant emissions will be important in the NCP.

Diurnal Variation of Chemical Characteristics and Source Identification of Fine Particles in the Kaohsiung Harbor

This study investigated the diurnal and monthly variation of fine particle (PM2.5) concentrations and its chemical characteristics and source identification in the Kaohsiung Harbor. Three sites located in the harbor areas were selected for simultaneously sampling 12-h PM2.5 in four months with consecutive seven days in each month. Water-soluble ions (WSIs), metallic elements, carbons, anhydrosugars, and organic acids in PM2.5 were analyzed to characterize their chemical fingerprints and monthly variation. Field sampling and chemical analysis of PM2.5 showed that significant diurnal and monthly variations of PM2.5’s mass concentration and chemical composition were observed in the Kaohsiung Harbor. Prevailing wind direction highly influences the mass concentrations and chemical characteristics of PM2.5 in the port areas. PM2.5 was dominated by WSIs with the abundance of secondary inorganic aerosols (SIAs). Crustal elements dominated the metallic content of PM2.5, but trace elements mainly originated from anthropogenic sources. The V/Ni ratios of PM2.5 in the Kaohsiung Harbor were generally higher than 2.0. Organic carbon (OC) was superior to elemental carbon (EC) in PM2.5 with the dominance of secondary OC (SOC). High concentration of levoglucosan (levo) was observed in spring due to nearby biomass burning. Additionally, high mass ratios of malonic and succinic acids (M/S) in PM2.5 indicated the potential formation of SOAs. Results obtained from chemical mass balanced (CMB) receptor modeling showed that the major sources of PM2.5 resolved in the Kaohsiung Harbor were mobile sources, ship emissions and oil-fired boilers, steel plants, secondary aerosols, sea salt spray, and fugitive dust. Primary PM2.5 emitted from ship traffics accounted for 20.8% of PM2.5.

Inter-comparison of chemical characteristics and source apportionment of PM2.5 at two harbors in the Philippines and Taiwan

This study inter-compared the concentration and chemical characteristics of PM2.5 at two harbors in East Asia, and identified the potential sources of PM2.5 and their contribution. Two sites located at the Kaohsiung (Taiwan) and Manila (the Philippines) Harbors were selected for simultaneous sampling of PM2.5 in four seasons. The sampling of 24-h PM2.5 was conducted for continuous seven days in each season. Water-soluble ions, metallic elements, carbonaceous content, anhydrosugars, and organic acids in PM2.5 were analyzed to characterize their chemical fingerprints. Receptor modeling and trajectory simulation were further applied to resolve the source apportionment of PM2.5. The results indicated that the Kaohsiung Harbor was highly influenced by long-range transport (LRT) of polluted air masses from Northeast Asia, while the Manila Harbor was mainly influenced by local emissions. Secondary inorganic aerosols were the most abundant ions in PM2.5. Crustal elements dominated the metallic content of PM2.5, but trace elements were mainly originated from anthropogenic sources. Higher concentrations of organic carbon (OC) than elemental carbon (EC) was found in PM2.5, with secondary OC (SOC) dominant to the former. Levoglucosan in PM2.5 at the Manila Harbor were superior to those at the Kaohsiung Harbor due to biomass burning surrounding the Manila Harbor. Additionally, high mass ratios of malonic and succinic acids (M/S) in PM2.5 indicated the formation of SOAs. Overall, the ambient air quality of Manila Harbor was more polluted than Kaohsiung Harbor. The Kaohsiung Harbor was more severely affected by LRT of polluted air masses from Northeast Asia, while those toward the Manila Harbor came from the oceans. The major sources resolved by CMB and PMF models at the Kaohsiung Harbor were secondary aerosols, ironworks, incinerators, oceanic spray, and ship emissions, while those at the Manila Harbor were secondary aerosols, soil dust, biomass burning, ship emissions, and oceanic spray.

Seasonal variation of dicarboxylic acids in PM2.5 in Beijing: Implications for the formation and aging processes of secondary organic aerosols

Dicarboxylic acids are a group of highly oxidized components, which can provide insights into the formation mechanism and aging process of secondary organic aerosols (SOA). Based on the 12-h day and night PM2.5 samples collected in downtown Beijing in January, April, July and October of 2017, dicarboxylic acids and relevant components were measured to investigate their seasonal variation pattern and sources. High concentrations of the identified organic acids were observed, following the decreasing order of July > January > October > April. The high fractions of phthalic acid and maleic acid in January indicated severe aromatic SOA pollution during the sampling period in winter, and the high malonic acid to succinic acid and malic acid to succinic acid ratios in July suggested strong photochemical formation over the sampling period in summer. Based on the calculation of principle component analysis and multiple linear regression, water-soluble organic acids were mainly formed from the aerosol aging process during the sampling periods except for January, while water-soluble organic carbon (WSOC) mostly originated from combustion sources. Correlation analysis was conducted between the CO-normalized concentrations of organic acids and PM2.5, O3, as well as the meteorological parameters. The results suggested that gas-phase photooxidation contributed significantly to the formation of these organic acids during the entire sampling period, and the aqueous-phase process played an important role over the severe haze event in January. Our results also suggested that the intensity of photooxidation and the aging degree of SOA were enhanced along with the reduction of PM2.5 in Beijing in recent years.

Sources and Transformation Processes of Proteinaceous Matter and Free Amino Acids in PM2.5

AbstractAmino acids is an important organic nitrogen compound class in aerosol. Its origins and transformation in the atmosphere remain poorly understood. The concentrations of free amino acids (FAAs) and combined amino acids (CAAs) and δ15N values of free and combined Glycine (Gly) in PM2.5 and main emission sources (plant, soil, and aerosol from biomass burning) were investigated from five sampling sites in Nanchang area (Jiangxi Province, China). Our results showed that the composition profiles of CAAs and FAAs were quite different from each other in PM2.5. For CAAs, percentages of individual combined amino acids were different between biomass burning sources and plant or soil sources, and we found that the composition profiles of aerosol CAAs could reflect the contribution of the main emission sources. For FAAs, a predominance of free Gly was observed in aerosol FAAs pool because atmospheric photooxidative processes could increase free Gly and decrease other reactive FAAs. This implied that the composition of aerosol FAAs could not reflect their origins. A strong correlation between δ15NF‐Gly values in aerosols or sources and the δ15NC‐Gly values in their parent CAAs was observed, indicating that the isotope effect associated with Gly transformation in aerosols may be small. Additionally, we found more positive δ15NGly in aerosols emitted by biomass burning, which was likely due to 15N‐depleted amino‐N loss from Gly molecule. The results suggested that δ15NGly values in aerosols might be used to identify biomass burning sources.

Characteristics of water-soluble organic acids in PM2.5 during haze and Chinese Spring Festival in winter of Jinan, China: concentrations, formations, and source apportionments.

PM2.5 aerosols from Jinan (36°256'N, 117°106'E) in the North China Plain region were investigated for water-soluble organic acids (WSOAs, i.e., oxalic acid, formic acid, acetic acid, methanesulfonic acid (MSA), and lactic acid) during 30 December 2016 to 21 February 2017. The average PM2.5 concentration was 168.77μg/m3 with about 90.74% samples beyond the National Ambient Air Quality (NAAQ) standards (Grade II). The total concentration of the measured WSOAs averaged at 1.34μg/m3, contributing to 0.80% of PM2.5 mass. In the observation, acetic acid was the most abundant WSOA, followed by oxalic acid, lactic acid, formic acid, and MSA. During the period, serious haze events frequently happened. The average concentrations of PM2.5 and every WSOA species were higher in haze than those in non-haze. The correlations among species suggested that WSOAs in haze had complicated sources and secondary pathways, especially aqueous-phase reactions which played an important role on WSOAs. The concentrations of WSOAs declined in the Spring Festival compared with those in the non-Spring Festival due to holiday effect. Fireworks burning during the Spring Festival had different influences on WSOAs with slight increases for acetic acid and lactic acid. Five source factors were identified by positive matrix factorization (PMF) model for five WSOAs, respectively, and the results revealed that secondary reactions were the main sources of WSOAs in haze.

Molecular Compositions and Sources of Organic Aerosols from Urban Atmosphere in the North China Plain during the Wintertime of 2017

ABSTRACT PM2.5 samples were collected from Liaocheng, a typical city in the North China Plain, during a winter haze episode around 2017 Chinese Spring Festival (Lunar New Year, LNY) to investigate the impact of firework on organic aerosols. A comparison of PM2.5 concentrations during different periods, with different air mass origins, and under different pollution situations was done. Organic compounds including normal alkanes (n-alkanes), polycylic aromatic hydrocarbons (PAHs), saccharides, and organic acids in PM2.5 aerosols were determined by GC/MS. Sources were analyzed by diagnostics ratios and principal component analysis/multiple linear regression (PCA/MLR) model. The results showed that fireworks burning has significant impacts on fine particle pollution. During the haze period, a sharp increase in n-alkanes, PAHs, saccharides, and fatty acids were observed, but the influence of fireworks burning on n-alkanes concentration is minor. The concentrations of carcinogenic PAHs during haze and LNY periods were more than three times higher than those in the clean period, indicating that PAHs were more carcinogenic during the two periods. In addition, the estimated ILCR for children and adults were both about three times higher than those in the clean periods, suggesting a moderate potential carcinogenic risk in Liaocheng. The higher concentration and the dominance of levoglucoan in the total saccharides suggested that the biomass burning is the predominance source of saccharides. Both the ratios of C18:1/C18:0 and BaP/BeP were the highest during the haze period, indicating that aerosols in the haze period were more oxidized. According to the source precise molecular tracers and the PCA-MLR model, coal combustion, biomass burning, and vehicle emissions were the major sources of organic compounds in PM2.5 aerosols during the winter in Liaocheng, cooking activity and firework burning had impact on organic aerosols obviously during LNY. Our data provided first analysis of the molecular distributions and sources of organic aerosols during Chinese Spring Festival in Liaocheng and their potential effects on human health.

Low Molecular Weight Monocarboxylic Acids in PM2.5 and PM10: Quantification, Seasonal Variation and Source Apportionment

ABSTRACTPM2.5 and PM10 aerosols from a semi-urban site of Agra (27°10′N, 78°05′E) in North-Central India were analyzed for carbonaceous aerosols (Organic and Elemental carbon), low molecular weight monocarboxylic acids (Acetic and Formic acid) along with inorganic ions (Cl–, NO3–, SO42–, K+ and Ca2+) during April 2014 to August 2015. The average PM2.5 and PM10 mass concentrations were 86.3 ± 71.3 and 169.7 ± 100.5 µg m–3, respectively; about 45% of PM2.5 and 67% of PM10 samples were above NAAQ (National Ambient Air Quality) standards. The average organic carbon (OC) and elemental carbon (EC) concentrations were 18.2 ± 12.3 and 6.7 ± 4.5 µg m–3, respectively in PM2.5 and 25.2 ± 14.1 and 8.1 ± 5.9 µg m–3 respectively in PM10. The average concentration of acetic acid (AA) in PM2.5 and PM10 were 330 ± 211 and 392 ± 224 ng m–3 respectively. The average concentration of formic acid (FA) in PM2.5 and PM10 were 348 ± 193 and 336 ± 175 ng m–3 respectively. Formic acid concentration was higher in PM2.5 than PM10 but the difference is not statistically significant. Both AA and FA showed similar seasonal variation: winter > post-monsoon > summer > monsoon. Low temperature and high relative humidity in winter season favours gas to particle conversion resulting in high concentrations. The average FA to AA (F/A) ratio was 0.69 indicating dominance of primary sources at the study site. Correlation analysis of AA and FA with major ions (Cl–, NO3–, SO42–, K+ and Ca2+), EC, secondary organic carbon and trace gases (O3 and CO) was performed to identify their primary or secondary origin. The results of correlation analysis suggest that AA is mainly contributed by primary sources while FA originates from secondary sources.

Determination and Source Apportionment of Aromatic Acids in PM2.5 from the Northern Suburb of Nanjing in Winter

Atmospheric particulate samples of PM2.5 were collected from the northern suburb of Nanjing in December, 2014, and a LC-MS method was optimized for the determination of aromatic acids in PM2.5; The concentrations of major water-soluble ions, organic carbon and elemental carbon were also determined. The quantification results showed that the average total concentration of five aromatic acids we have determined was (50.01±16.05) ng·m-3, and the average concentrations of terephthalic acid, phthalic acid, trimellitic acid, 4-methylphthalic acid and iso-phthalic acid were (34.54±12.79)、(8.14±3.34)、(2.27±1.39)、(1.68±0.77) and (1.08±0.43) ng·m-3, respectively. The different source apportionments of atmospheric particulate were analyzed by principal component analysis/absolute principal component scores (PCA/APCS) receptor model. The results of source apportionment showed that the main sources of Phthalic acid, Trimellitic acid and 4-methylphthalic acid were mainly secondary transformation, and primary emissions such as vehicle exhaust contributed less to Trimellitic acid; Secondary transformation and biomass burning made the most significant contributions to iso-Phthalic acid and vehicle exhaust contributed less; The sources of Terephthalic acid were primary emissions such as biomass burning and vehicle exhaust.

Volatile and semivolatile organic compounds in laboratory peat fire emissions

In this study, volatile and semi-volatile organic compound (VOCs and SVOCs) mass emission factors were determined from laboratory peat fire experiments. The peat samples originated from two National Wildlife Refuges on the coastal plain of North Carolina, U.S.A. Gas- and particle-phase organic compounds were quantified by gas chromatography-mass spectrometry and by high pressure liquid chromatography. Hazardous air pollutants (HAPs) accounted for a large fraction (∼60%) of the speciated VOC emissions from peat burning, including large contributions of acetaldehyde, formaldehyde, benzene, toluene, and chloromethane. In the fine particle mass (PM2.5), the following organic compound classes were dominant: organic acids, levoglucosan, n-alkanes, and n-alkenes. Emission factors for the organic acids in PM2.5 including n-alkanoic acids, n-alkenoic acids, n-alkanedioic acids, and aromatic acids were reported for the first time for peat burning, representing the largest fraction of organic carbon (OC) mass (11–12%) of all speciated compound classes measured in this work. Levoglucosan contributed to 2–3% of the OC mass, while methoxyphenols represented 0.2–0.3% of the OC mass on a carbon mass basis. Retene was the most abundant particulate phase polycyclic aromatic hydrocarbon (PAH). Total HAP VOC and particulate PAH emissions from a 2008 peat wildfire in North Carolina were estimated, suggesting that peat fires can contribute a large fraction of state-wide HAP emissions.

Seasonal Variations and Sources of Carboxylic Acids in PM2.5 in Wuhan, China

ABSTRACTAerosol PM2.5 samples collected from three sites in Wuhan, China, during 2011–2012 were analyzed by gas chromatography-mass spectrometry to better understand the molecular composition and sources of carboxylic acids. The concentrations of total monocarboxylic acids did not show apparent seasonal variations in Wuhan. Palmitic acid and stearic acid were the most abundant species, accounting for 32.4%–62.4% (average 51.8%) of all quantified monocarboxylic acids. Oxalic acid was found as the most dominant dicarboxylic acid, followed by succinic acid at the three sampling sites. The total concentration of dicarboxylic acids displayed obvious seasonal variation, with the highest in summer (1036.7–1546.4 ng/m3) and the lowest in winter (126.8–211.0 ng/m3). Positive matrix factorization (PMF) revealed that coal combustion, traffic-related emissions and biomass burning are the most important contributors to carboxylic acids at industrial site, downtown site and botanical garden, respectively. Plant waxes and secondary photochemical products are also significant sources of carboxylic acids at the three sampling sites.

Compositions and sources of organic acids in fine particles (PM2.5) over the Pearl River Delta region, south China

Organic acids as important constituents of organic aerosols not only influence the aerosols' hygroscopic property, but also enhance the formation of new particles and secondary organic aerosols. This study reported organic acids including C14–C32 fatty acids, C4–C9 dicarboxylic acids and aromatic acids in PM2.5 collected during winter 2009 at six typical urban, suburban and rural sites in the Pearl River Delta region. Averaged concentrations of C14–C32 fatty acids, aromatic acids and C4– C9 dicarboxylic acids were 157, 72.5 and 50.7 ng/m3 respectively. They totally accounted for 1.7% of measured organic carbon. C20–C32 fatty acids mainly deriving from higher plant wax showed the highest concentration at the upwind rural site with more vegetation around, while C14–C18 fatty acids were more abundant at urban and suburban sites, and dicarboxylic acids and aromatic acids except 1,4-phthalic acid peaked at the downwind rural site. Succinic and azelaic acid were the most abundant among C4–C9 dicarboxylic acids, and 1,2-phthalic and 1,4-phthalic acid were dominant aromatic acids. Dicarboxylic acids and aromatic acids exhibited significant mutual correlations except for 1,4-phthalic acid, which was probably primarily emitted from combustion of solid wastes containing polyethylene terephthalate plastics. Spatial patterns and correlations with typical source tracers suggested that C14–C32 fatty acids were mainly primary while dicarboxylic and aromatic acids were largely secondary. Principal component analysis resolved six sources including biomass burning, natural higher plant wax, two mixed anthropogenic and two secondary sources; further multiple linear regression revealed their contributions to individual organic acids. It turned out that more than 70% of C14–C18 fatty acids were attributed to anthropogenic sources, about 50%–85% of the C20–C32 fatty acids were attributed to natural sources, 80%–95% of dicarboxylic acids and 1,2-phthalic acid were secondary in contrast with that 81% of 1,4-phthalic acid was primary.

Carboxylic acids in PM2.5 over Pinus morrisonicola forest and related photoreaction mechanisms identified via Raman spectroscopy

Abstract The PM 2.5 aerosol from within an area of Pinus morrisonicola Hayata in Taiwan was collected and analyzed for its low molecular weight carboxylic acid (LMWCAs) content. Oxalic acid was the major LMWCA in the aerosol, followed by acetic, tartaric and maleic acids. This differs significantly from the LMWCA composition of PM 2.5 aerosol reported for a southern Taiwan suburban region (oxalic > succinic > malonic) [Atmospheric Environment 42, 6836–6850 (2008)]. P. morrisonicola Hayata emits oxalic, malic and formic acids and yet there was an abundance of maleic and tartaric acids in the PM 2.5 forest aerosol, indicating that tartaric acid is derived from the transformation of other P. morrisonicola Hayata emissions. Raman spectroscopy was applied and 28 species of LMWCAs and inorganic species were identified. The photochemical mechanisms of maleic and tartaric acids were studied and it was found that the abundant tartaric acid in forest aerosol is most probably the photochemical product from reactions of maleic acid. Furthermore, tartaric acid is photochemically transformed into formic acid and ultimately into CO 2 .

Distribution and sources of solvent extractable organic compounds in PM2.5 during 2007 Chinese Spring Festival in Beijing

The solvent extractable organic compounds (SEOC), including n-alkanes, polycylic aromatic hydrocarbons, fatty acids, and dicarboxylic acids in PM2.5 during the 2007 Chinese Spring Festival in Beijing, were measured via gas chromatography-mass spectrometry for determining the characteristics and sources of these organic pollutants. The concentrations of total n-alkanes, PAHs, and organic acids before Chinese Spring Festival Eve (1025.5, 95.9, and 543.3 ng/m3, respectively) were higher than those after (536.6, 58.9, and 331.8 ng/m3, respectively). n-Aalkanes and PAHs had much higher concentration in nighttime than those in daytime because of high relative humidity and low wind speed during the night. Combustion of coal and exhaust emission were major sources of n-alkanes. It could be concluded by the characteristic ratios that the primary source of PAHs in fine particles was the combustion of coal, but the combustion of gasoline was in the next place. The ratios of C18:0/C16 indicated the contribution of vehicular emissions to the fatty acids. Dicarboxylic and aromatic acids were abundant in daytime than in nighttime because these acids were secondary organic acid and the photochemical degradation of aromatic hydrocarbons was the main source.

Nonderivatization Analytical Method of Fatty Acids andcis-Pinonic Acid and Its Application in Ambient PM2.5Aerosols in the Greater Vancouver Area in Canada

A nonderivatization analytical method has been developed to analyze C6-C20 fatty acids and cis-pinonic acid on a GC/ FID and a GC/MSD using a polar DB-FFAP capillary column. On the GC/FID, the response was highly linear over concentration ranges >2 orders of magnitude (R2 = 1.00). Using a mixed solvent of dichloromethane (DCM): methanol (3:1, v/v) and an extraction temperature of 40 degrees C, the method recoveries of the acids from spiked filters were 81-115% based on deuterated surrogates, and the relative standard deviations were <12%. The recoveries were mainly controlled by the extraction temperature. At 40 degrees C the acids in sample extracts were stable for at least 12 months, while at 80 degrees C, unintended esterization of the acids by methanol was found that reduces their stability in the sample extracts. The analysis of the acids in PM2.5 samples from NIST using this nonderivatization method showed that the efficiency and accuracy were comparable to the derivatization method. Compared with existing derivatization methods, the method is accurate and sensitive, yet simple to use. This method was applied to PM2.5 ambient aerosols collected from a forest site and at a traffic tunnel outlet in the greater Vancouver area in Canada. Total fatty acids (sum of C6-C20) in the aerosols were measured as 20.2-138.7 ng/m3 at the forest site and 100.2-264.6 ng/m3 at the tunnel site. The cis-pinonic acid concentrations were 1.6-44.2 ng/m3 in the forest and from below detection to 6.5 ng/m3 at the tunnel outlet.

Characterization of dicarboxylic acids in PM2.5 in Hong Kong

Abstract Dicarboxylic acids in atmospheric aerosols have received much attention because of their potential roles in affecting the global climate. The composition and the sources of dicarboxylic acids in PM2.5 were studied at one remote and two urban sites in Hong Kong in the winter of 2000 and in the summer of 2001. Oxalate was the dominant dicarboxylic acid in all samples. The winter oxalate concentrations were high and spatially uniform, with an average value of 0.36 μg m −3 , but the summer oxalate concentrations were low and had a large spatial variation. The influence of meteorological factors on the concentrations of dicarboxylic acids was also studied. The ratio of malonate to succinate was used to distinguish primary sources from secondary sources of these acids. This ratio at all three sites was close to that from direct vehicular exhaust in the winter, but it was close to that of secondary reactions in the summer. Hence, the acids were attributed to vehicular emissions in the winter and secondary sources in the summer. This hypothesis is also supported by a good correlation of oxalate with sulfate in the summer but a poor one in the winter. The correlations of oxalate with malonate, succinate, sulfate and K + were also studied in terms of the routes of secondary formation of these dicarboxylic acids.

Identification of dicarboxylic acids and aldehydes of PM10 and PM2.5 aerosols in Nanjing, China

In this study aerosol samples of PM10 and PM2.5 collected from 18 February 2001 to 1 May 2001 in Nanjing, China were analyzed for their water-soluble organic compounds. A series of homologous dicarboxylic acids (C 2–10) and two kinds of aldehydes (methylglyoxal and 2-oxo-malonaldehyde) were detected by GC and GC/MS. Among the identified compounds, the concentration of oxalic acid was the highest at all the five sites, which ranged from 178 to 1423 ng/m 3. The second highest concentration of dicarboxylic acids were malonic and succinic acids, which ranged from 26.9 to 243 ng/m 3. Higher level of azelaic acid was also observed, of which the maximum was 301 ng/m 3. As the highest fraction of dicarboxylic acids, oxalic acid comprised from 28% to 86% of total dicarboxylic acids in PM10 and from 41% to 65% of total dicarboxylic acids in PM2.5. The dicarboxylic acids (C 2, C 3, C 4) together accounted for 38–95% of total dicarboxylic acids in PM10 and 59–87% of dicarboxylic acids in PM2.5. In this study, the total dicarboxylic acids accounted for 2.8–7.9% of total organic carbon (TOC) of water-soluble matters for PM10 and 3.4–11.8% of TOC for PM2.5. All dicarboxylic acids detected in this study together accounted for about 1% of particle mass. The concentration of azelaic acid was higher at one site than others, which may be resulted from higher level of volatile fat used for cooking. The amounts of dicarboxyic acids (C 2,3,4,9) and 2-oxo-malonaldehyde of PM2.5 were higher in winter and lower in spring. Compared with other major metropolitans in the world, the level of oxalic acid concentration of Nanjing is much higher, which may be contributed to higher level of particle loadings, especially for fine particles.