2001～2003年间北京大气降水的化学特征

Chemical characters of atmospheric precipitation in Beijing in years of 2001～2003

为了了解北京大气降水的化学组成与时间变化特征,连续进行了2年的降雨采样与分析.在65个降雨样品中,12%的降水呈酸性;全年降水的酸度主要取决于夏季的降水.SO42-、NH4+与Ca2+是含量最丰富的组分,其平均浓度均接近或超过200礶q/L.比较分析表明,在近几年,SO42-对降水酸度的贡献显著降低,降水的硫污染特征减弱,而NO3-的贡献显著增加.人为污染元素和地壳元素的浓度均在冬春季较高,在夏季最低.

To understand the chemical composition and temporal variations of atmospheric precipitation in Beijing, the precipitation samples were collected and analyzed continuously for two years. In 65 precipitation samples, 12% were acidic; annual precipitation acidity was mainly determined by summer precipitation. SO42-, NH4+, and Ca2+ were the most abundant components with their average concentrations all near or above 200礶q/L. Comparison analysis showed that in late years, the SO42- contribution to precipitation acidity was reduced markedly and its sulfur-pollution character was weaken, while that of NO3- was enhanced markedly. The concentrations of anthropogenic and crustal-elements were all higher in winter and spring while lowest in summer.