Statistical features of acid rain spatial distribution in Chongqing area

摘要

Based on the pH data of precipitation measured at 35 weather stations from 2004.12 to 2007.11, using spatial interpolation methods and cluster analysis, the spatial distribution features of acid rain during the recent three years in Chongqing area were analyzed. The results indicated that almost everywhere were endangered by the acid rain and some of them were very severe. In recent three years, the pH value in most areas of Chongqing had been lower than 4.5. The average pH of precipitation in Chongqing was 4.07. In Chongqing, the frequency of acid rain was high. In recent three years, the frequency of acid rain was 84.05%, the frequency of relatively strong acid rain was 27.42% in whole area of Chongqing. Cluster Analysis results indicated that when cluster distance was 19, the acid rain distribution of Chongqing could be combined into 2 kinds of areas. The kind mainly lay in the Ⅰ northeast, southeast and west-central where were the relatively weak acid rain areas in Chongqing. The Ⅱ kind mainly lay in the west and east-central where were the relatively strong acid rain areas in Chongqing. When cluster distance was 4, the acid rain distribution of Chongqing could be combined into 6 kinds of areas. The acid rain intensity changed in gradient among each kind of areas. The highest pH was in Wuxi. The lowest pH was in the southwest and southeast-central. Cluster analysis could divide strong acid rain areas and weak areas and have the property of geographic distribution of each kinds of acid rain areas centralized, acid rain intensity changed in gradient among each kind of areas. Cluster analysis can be used in the statistical analysis of acid rain spatial distribution.