北京市湿沉降特征分析

通过分析北京市降水中水溶性离子组分的浓度,研究了2005～2009北京市降水酸化程度及水质变化特征.北京市5 a年均pH为5.19,总体变化趋势平稳.5 a间,降水中各离子组分含量均有下降趋势,北京市的环境质量逐步改善;NH 4^＋和NO 3^-在降水中所占比例明显增加,北京市降水受含N污染物排放的影响较大.季节变化显...

Characteristics of Chemical Compositions of Precipitation in Beijing

Characteristics of chemical compositions of precipitation in Beijing were analyzed. The average value of pH was 5.19 from 2005 to 2009, showing stable characteristics of acidification with precipitation. The lowest annual average pH was 4.87 in 2008 with the highest acidification frequency of 42% and 23% in Chegongzhuang and Daxing districts respectively. The inorganic ion concentrations declined in 5a, indicating an increasing improvement of air quality in Beijing. The concentrations of NH⁺₄ and NO^-₃ were found to increase and contributed to the high nitrogen amount in precipitation. Different seasons have influence on composition concentrations. Generally speaking, the ion concentrations in winter were higher that that in summer. SO^2-₄ was the main factor responsible for the acidification of snow in winter, SO^2-₄ and NO^-₃ had similar contributions to the acidification of precipitation in summer. It was also found that the local pollutants of SO₂,NO_x and NH₃ were major contributors to the acidification of precipitation in Beijing area, local geological conditions and long-distance transfers have important effects on the neutralization of the precipitation.