| 1 | Seasonal variations of carboxylic acids and their contributions to the rainwater acidity: A case study of Guiyang and Shangzhong,China显示文摘Low molecule weight carboxylic acids are ubiquitous and important chemical constituents in the troposphere.Seven carboxylic acids in the rainwater of Guiyang and Shangzhong were simultaneously determined by ion chromatography from April 2006 to April 2007.Formic, acetic and oxalic acids were found to be the predominant carboxylic acids.Their volume weighted average concentration (VWA) in the rainwater of Guiyang were 14.24 μmol/L, 9.35 μmol/L and 2.79 μmol/L, respectively;as compared to 4.95 μmol/L, 1.35 μmol/L and 2.31 μmol/L in the rainwater of Shangzhong.In Shangzhong it is witnessed that the concentra-tions of these acids were higher in the summer than in the winter and direct emissions from vegetations or soils may account for the main provenance of the acids.This is, however, not the case in Guiyang, where the concentrations of the carboxylic acids were higher during the non-growing season than during the growing season.The relatively weak scavenging affected by scarce and little rainwater as well as the particles accompanied with the rainfall may have some effect on the carboxylic acids during the wintertime in Guiyang.Carboxylic acids in the rainwater of Guiyang were estimated to account for 18.7% to the free acidity, where formic, acetic and oxalic acids accounted for 7.9%, 4.7%, 6.1%, respectively.In Shangzhong, the 3 primary carboxylic acids represented 58.1% to the free acidity where formic, acetic and oxalic acids represented 25.1%, 7.5%, 25.5%, respectively.Carboxylic anions accounted for 6.6% (1.7%–19.2%) to the total anions in the rainwater of Guiyang.Carboxylic anions repre-sented 13.2% (0.5%–92.2%) to the total anions in the rainwater of Shangzhong.These results indicated that carboxylic acids were the important contributors to the rainwater acidity, especially in remote regions. | XU Gang LEE XinQing LU YingChun CHEN YingJun HUANG DaiKuan | 2010 | Chinese Science Bulletin2010，55，16： | 5 |
| 2 | Seasonal variation and sources of low molecular weight organic acids in precipitation in the rural area of Anshun显示文摘Low molecular weight (LMW) organic acids are important and ubiquitous chemical constituents in the atmosphere.A comprehensive study of the chemical composition of precipitation was carried out from June 2007 to June 2008 at a rural site in Anshun,in the west of Guizhou Province,China.During this period,118 rainwater samples were collected and the main LMW carboxylic acids were determined using ion chromatography.The average pH of rainwater was 4.89 which is a typical acidic value.The most abundant carboxylic acids were formic acid (volume weight mean concentration:8.77 μmol L-1) and acetic acid (6.90 μmol L-1),followed by oxalic acid (2.05 μmol L-1).The seasonal variation of concentrations and wet deposition fluxes of organic acids indicated that direct vegetation emissions were the main sources of the organic acids.Highest concentrations were observed in winter and were ascribed to the low winter rainfall and the contribution of other air pollution sources northeast of the study area.The ratio of formic and acetic acids in the precipitation ([F/A] T) was proposed as an indicator of pollution source.This suggested that the pollution resulted from direct emissions from natural or anthropogenic sources.Comparison with acid precipitation in other urban and rural areas in Guizhou showed that there was a decreasing contribution of LMW organic acids to free acidity and all anions in rainwater from urban to remote rural areas.Consequently,it is necessary to control emissions of organic acids to reduce the frequency of acid rain,especially in rural and remote areas. | ZHANG YanLin LEE XinQing CAO Fang HUANG DaiKuan | 2011 | Chinese Science Bulletin2011，56，10： | 2 |
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