大气降水中离子化学特征及来源分析

通过研究2006-2010年上海市闸北区大气降水中离子的组成特征和变化,分析了离子可能的来源和酸雨的成因。结果表明,近年来酸雨污染有所改善,酸雨成因也有所改变。阴阳离子当量浓度之比小于1,可能缺少对某些低分子弱有机酸离子的监测。降水化学组份中浓度最高的四种离子分别是SO42-、NH4+、Ca2+和NO3-,SO42-浓度是NO3-的3.14倍,NH4+是Ca2+的2.76倍,降水的主要致酸物质是硫酸盐,主要中和物质是铵盐。大多数离子间有较好的相关性,NO3-和SO42-绝大部分来自人为源的贡献。降水中SO42-的致酸作用和Ca2+的中和作用逐渐下降,Cl-的致酸作用在逐渐增大。

Chemical Characteristics of Ions in Atmospheric Precipitation and Their Source Analysis

The ionic compositions and variation of atmospheric precipitation in Shanghai Zhabei District from 2006 to 2010 are analyzed and the sources of ions and cause of acid rain are studied.Results indicate that acid rain pollution is improving and cause of acid rain is changing slightly.The equivalent concentration ratio of anions over cations is lower than 1,indicating the lack of monitoring to some low-molecule weak organic acid ions.Four ions including sulfate,ammonia,calcium and nitrate have higher concentration and sulfate is 3.14 times larger than nitrate while ammonia is 2.76 times higher than calcium ion.Therefore,the main acidic compound is sulfate,while the main neutralization compound is ammonia in precipitation.Most ions have good correlation between each other.Sulfate and nitrate mainly result from anthropogenic sources.It is also found that the acidic contribution of sulfate and neutralization of calcium is decreasing while the contribution to acidity of chloride increases gradually.