[Low molecular weight carboxylic acids in precipitation during the rainy season in the rural area of Anshun, West Guizhou Province].
40 rainwater samples were collected at Anshun from June 2007 to October 2007 and analysed in terms of pH values, electrical conductivity, major inorganic anions and soluble low molecular weight carboxylic acids. The results showed that pH of individual precipitation events ranged from 3.57-7.09 and the volume weight mean pH value was 4.57. The most abundant carboxylic acids were acetic (volume weight mean concentration 6.75 micromol x L(-1)) and formic (4.61 micromol x L(-1)) followed by oxalic (2.05 micromol x L(-1)). The concentration levels for these three species during summer especially June and July were comparatively high; it implied that organic acids in Anshun may came primarily from emissions from growing vegetations or products of the photochemical reactions of unsaturated hydrocarbons. Carboxylic acids were estimated to account for 32.2% to the free acidity in precipitation. The contribution was higher than in Guiyang rainwater, which indicated contamination by industry in Guiyang was more than in Anshun. The remarkable correlation(p = 0.01) between formic acid and acetic acid suggest that they have similar sources or similar intensity but different sources. And the remarkable correlation (p = 0.01) between and formic acid and oxalic acid showed that the precursors of oxalic acid and formic acid had similar sources. During this period, the overall wet deposition of carboxylic acids were 2.10 mmol/m2. And it appeared mainly in the summer, during which both concentration and contribution to free acidity were also relatively high. Consequently, it was necessary to control emission of organic acids in the summer to reduce frequence of acid rain in Anshun.
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China. zhangyanlin@mails.gyig.ac.cn
Yan-Lin
YL
Zhang
Xin-Qing
XQ
Lee
Dai-Kuan
DK
Huang
Rong-Sheng
RS
Huang
Wei
W
Jiang
D019342:Acetic Acid / Q000032:analysis*; D015258:Acid Rain / Q000032:analysis*; D002264:Carboxylic Acids / Q000032:analysis*; D011232:Chemical Precipitation; D002681:China; D004784:Environmental Monitoring; D005561:Formates / Q000032:analysis; D019815:Oxalic Acid / Q000032:analysis; D011891:Rain / Q000737:chemistry*; D012423:Rural Health; D012621:Seasons
D015258:Acid Rain; D002264:Carboxylic Acids; D005561:Formates; C030544:formic acid; D019815:Oxalic Acid; D019342:Acetic Acid