天津市酸雨变化特征及其影响因素

Variational Characteristics of Acid Rain and Its Affecting Factors in Tianjin

通过对天津市1993-2004年酸雨观测资料的分析,结果表明:天津属于弱酸雨区,总体pH值为5.4,酸雨率为28%。虽然天津酸雨较少,酸雨酸度较弱,但仍然会出现pH值小于4.5的强酸性降雨。天津市酸雨有如下特征:冬季、夏末和秋季降水的pH值呈酸性,春季和初夏基本没有酸雨出现。天津酸雨另一个特征是大雨呈酸性,小雨偏碱性,在天津地区中雨以上的降水出现酸雨的频率较大,主要出现在夏秋两季。小雨以下的降水过程出现酸雨的频率仅为20%左右,多数出现在冬季。这些特征与天津的降水量、风向风速具有密切的关系,与SO2、氮氧化物等污染物的排放量相关系数较小。

Analyzing the observation data of acid rain in Tianjin from 1993 to 2004,the results were summarized as follows:Tianjin was a weak acid rain area,the general pH in the rain was 5.4 and the acid rain rate was 28%.The strong acid rain which pH was less than 4.5 may also occur although the acid rain was less and the acidity was weak.The characteristic of acid rain in Tianjin was that the pH value was acidic in winter and autumn while there was no acid rain in spring and early summer.Another characteristic was that heavy rain was acidic while light rain was alkalic.The frequency of acid rain was high when precipitation at moderate and above levels occurred,which mainly happened in summer and fall.On the contrary,the frequency of acid rain was only 20% in the process of light rainfall,which mainly happened in winter.All the features were closely related with the precipitation,wind direction and wind velocity in Tianjin and less related with the discharge amount of SO2 and nitrogen oxide.