Analysis of Chemical Characteristics of Meteoric Precipitation Based on the Data of a Series of Rainwater——A Case Study of Southwest University,Beibei District,Chongqing

An investigation of the concentrations of Cl-,NO-3 and SO2-4,and on the monitored values of pH and electrical conductivity(EC) from the rainwater collected in 48 precipitation events during the period from October,2009 to August,2010 in Beibei district,Chongqing showed that the variation range of rainwater pH and EC were from 4 to 7.33 and from 14 to 379 μs/cm respectively.Acid rain occurred in various seasons of the year with a total frequency of 46%.The changes in pH and EC of the rainwater were determined by the difference in ion concentrations and the interactions among the ions in rainwater during every precipitation.However,there was no significant relevance between the pH and EC proxies.The summations(Σ) of the concentration of Cl-,NO-3 and SO2-4 anions in rainwater changed from 4.61 to 178.84 mg/L,and there were significant correlations among these anions.Σ was significantly correlated with EC of rainwater and characterized by higher values during the summer months and lower values during the winter months,which might be attributed to the dilution effect of rainwater during rainy summer and the accumulation of atmospheric impurity during winter.SO2-4 proved to be the dominant acid-inducing anion for the rainwater in Chongqing area,which was consistent with the local coal-dominated energy composition structure.