[Concentrations and acidity contributions of acetate and formate in precipitation at 14 stations of China].
To investigate the concentrations of organic acids in precipitation in China and their contributions to the total acidity of precipitation, samples were taken at 14 stations of regional representativeness in 2007 and analyzed for acetate and formate using ion chromatography. In this paper, data of acetate and formate in precipitation at 14 stations are presented, wet depositions of these organic acids are calculated, and contributions of them to the total free acidity (TFA) of precipitation are estimated. Based on the measurements, the mean concentrations of formate at different stations were in the range of 0.96-3.43 micromol/L, and those of acetate in the range of 0-5.13 micromol/L, close to the levels at remote sites in other countries and at the lower ends of concentration ranges from previous measurements in China. Comparisons indicate that the concentrations of the organic acids at remote sites are lower than those at sites in the vicinity of urban areas. The annual wet depositions of formate and acetate were estimated to be in the ranges of 0.38-4.18 mmol/(m2 x a) and 0.06-5.87 mmol/(m2 x a), respectively, with larger depositions in southern China and smaller depositions in northern China. The relative contributions of the two organic acids to the TFA of precipitation were estimated to be in the range of 0.02%-51.6%, with an overall average of 2.95%. This suggests that although acid rain in China is mainly caused by emissions of sulfur and nitrogen oxides, organic acids can significantly contribute to the acidification of precipitation in some regions and during some periods, hence need to be included in observational studies of acid rain.
Key Laboratory for Atmospheric Chemistry, China Meteorological Administration, Centre for Atmosphere Watch and Services, Chinese Academy of Meteorological Sciences, Beijing 100081, China. he_xiaohuan@126.com
Xiao-huan
XH
He
Xiao-bin
XB
Xu
Xiao-lan
XL
Yu
Jie
J
Tang
D000085:Acetates / Q000032:analysis*; D015258:Acid Rain / Q000009:adverse effects*; D002681:China; D004784:Environmental Monitoring / Q000379:methods; D004787:Environmental Pollution / Q000032:analysis*; D005561:Formates / Q000032:analysis*; D006863:Hydrogen-Ion Concentration
D000085:Acetates; D015258:Acid Rain; D005561:Formates; C030544:formic acid