无锡梅雨期湿沉降综合分析

Comprehensive analysis of wet deposition during the Meiyu period in Wuxi

利用2008—2014年梅雨期间酸雨观测资料及2014年6月16—27日降水个例加密采样资料,结合大气污染物资料分析了近7 a无锡梅雨期酸雨特征,研究降水过程中空气污染物、p H值、电导率的变化及降水对污染物的清除作用。结果表明：无锡市梅雨期酸雨年平均p H值呈现逐年递增趋势。降水过程中,颗粒物质量浓度显著降低;气体浓度变化受其自身日变化及排放源影响大于雨水的清除作用;样品的p H值、K值每个过程变化并不一致,K值变化与颗粒物质量浓度变化大致保持一致。降水、风对颗粒物质量浓度影响大于对气体浓度的影响。长时间连续降水时,降水对颗粒污染物的清除存在极限。小时雨量在0～0.5 mm时,降水对颗粒物浓度做负清除,其值反而略有增加;小时雨量在0.6～5.0 mm时,降水对颗粒物质量浓度做正清除;小时雨量达到5.1 mm及以上时,对PM_（2.5）和PM_（2.5-10）做正清除,对PM_（10）做负清除。降水对SO_2有稀释清除作用;对NO_2的稀释作用取决于其开始浓度值;对CO、O_3的清除作用不显著。

By using the acid rain observation data during the Meiyu period from 2008 to 2014, the precipitation and the air pollutant data during 16-27 June 2014, the characteristics of the acid rain in re- cent 7 years and the scavenging effect of the changes of the air pollutant, pH value, K value and the ore- cipitation on the pollutant were analyzed. Results show that the average pH value of acid rain during the Meiyu period increased yearly in Wuxi. The concentration of air pollutants in the precipitation process sig- nificantly decreased, which was affected more by its durnal variation and emission source than by rainfall. The pH and K value were inconsistent during each precipitation. The K value was consistent with the par- ticulate concentration. The effects of precipitation and wind on the particulate matter concentration was greater than that on gas. There is a limit of removal effect on particulate matter for long-time precipitati- on. When the hourly precipitation was between 0 mm and 0.5 mm, the scavenging effect was negative. When the hourly precipitation was between 0.6 mm and 5.0 mm, the scavenging effect was positive. When the hourly precipitation was more than 5.0 mm, the scavenging effect on PM2. 5 and PM2.5-10 was positive, but for PM10, it was negative. Precipitation has a dilution effect on SO2. The dilution effect on NO, depends on its starting concentration, and the removal effect is not significant on CO and O3.