上海市“十一五”期间酸雨状况与成因分析

分析“十一五”期间上海市酸雨污染变化趋势和特征，简析酸雨污染形成的原因。结果表明，“十一五”期间，降水pH低值区和酸雨频率高值区范围明显扩大。降水中化学组分的变化印证了上海市脱硫措施和扬尘防治措施的成效。但是，全市降水的酸化仍在持续，主要原因在于大气中强碱钙离子和人类活动产生的弱碱铵离子的相对变化，导致现有的碱性离子无法完全中和降水中比例最高的硫酸根和贡献日益显著的硝酸根。

The Reason Analysis of Acid Rain Characteristics during ＂Eleventh Five-Year＂ Period in Shanghai

The acid rain data during ＂Eleventh Five-Year＂ period was used to analyse the trend, characteristics and reasons of acid rain in Shanghai. The results showed that the low-value area of pH and high-value area of acid rain frequency expanded signifi- cantly. The changes of the chemical composition confirm the effectiveness of the measures for desulphurization and dust control in Shanghai. But the precipitation acidification of Shanghai continues. The main reason is that the relative change of the strong alkaline calcium and the weak alkaline ammonium causes that alkaline ions can＇ t completely neutralize the sulfate which had the highest rati- o and the increasing nitrate in precipitation.