降水对颗粒物的冲刷作用及其对雨水化学的影响

为研究湿沉降冲刷过程中大气颗粒物对雨水化学组成和酸度的影响,2008年6月至2009年6月,在中国酸雨污染最严重地区之一的杭州市进行了降水前、中、后的大气颗粒物样品采集,同时采集了降水样品,分析了颗粒物样品和雨水样品中的主要水溶性离子组分,使用统计学方法探讨了大气颗粒物的浓度及化学特征在雨水冲刷过程中的变化规律,并使用主成分分析方法分析了雨水中主要离子成分的来源.结果表明:杭州市TSP和PM10的酸缓冲能力分别为1.95和1.02,具有一定的酸缓冲能力;从颗粒物浓度、酸缓冲能力A值以及颗粒物化学组成在降水前、中、后过程中的变化看,雨水对颗粒物中的碱性组分具有显著冲刷作用;结合雨水主成分分析,颗粒物对雨水中Ca2+、Na+的贡献较为显著,对Mg2+、K+的贡献有待进一步验证,对NH4+、SO42-和NO3-的贡献较小,而F-和部分Cl-则可能主要来自云内雨除过程或者对气态化合物的云下冲刷作用.

Changes of particulate matters during rain process and influence of that on chemical composition of precipitation in Hangzhou, China

Rainwater and atmospheric particle samples were collected from June, 2008 to June, 2009 in Hangzhou, which is located in the most serious acid rain pollution areas of China. To research the effect of atmospheric particles on the chemical composition and acidity of precipitation during washout process under cloud, particle sampling was carried out before, during and after rain processes. The variations of TSP and PM10 before, during and after rain processes were analyzed to explore the scavenging effect on particles by rain. Principle component analysis was used to analyze the origin of main ions in precipitation. TSP and PM10 showed certain acid buffer capacity with A-value of 1.95 and 1.02, respectively. According to the variations of particles’ concentration, acid buffer capacity and chemical compositions in three (before, during and after) rain processes, it can be concluded that rain has significant washout effect on the alkaline components in particles. Combine with the rain principal component analysis, particulate matters made a significant contribution to Ca2+ and Na+, and little contribution to NH4+, SO42- and NO3-, its contribution to Mg2+ and K+ needed to be further validated, F- and part of Cl- were mainly originated from rainout process and washout of gaseous pollutants.