深圳降水中低分子量有机酸对降雨酸性的贡献

Wet Deposition of Low Molecular Weight Carboxylic Acids in Shenzhen

有机酸可能对降水酸性具有重要贡献,尤其是深圳处于亚热带地区太阳辐射强烈、光化学过程活跃,有利于有机酸的生成.对深圳市2004─2005年降雨中有机酸进行研究,结果表明:含量最高的有机酸依次为甲酸、乙二酸和乙酸,三者之和超过总有机酸浓度的98%;有机酸对阴离子总浓度的贡献约7%,对降水总自由酸度(TFA)的贡献约5%,上述各值均高于北京,深圳有机酸对降水的酸度有一定的贡献;深圳有机酸的湿沉降主要集中在夏季,此时酸性物质沉降量大,因此有必要减少夏季深圳有机酸的排放.

Carboxylic acids possibly made significant contributions to acid rain, especially in Shenzhen, which is located at subtropical zone with strong solar radiation and active photochemical process, favorable to carboxylic acid formation. Rainwater samples were collected at Shenzhen from 2004 to 2005 and analyzed for low molecular weight monocarboxylic acids and dicarboxylic acids. Distributions of carboxylic acids showed a predominance of formic and oxalic acid followed by acetic acids and they were found to comprise over 98% of total carboxylic acids. Carboxylic acids accounted for 7 % of total anions and 5 % of total free acidity, respectively. The concentrations and contributions to anions and TFA of carboxylic acids in Shenzhen rainwater were higher than in Beijing rainwater. Carboxylic acids made certain contributions to acid rain in Shenzhen. Wet depositions of organic acids were mainly in the summer. This suggests that it is necessary to control emission of organic acids in Shenzhen in the summer.