2006—2007年南昌市城郊地带的酸雨特征

Characteristics of Acid Rain in the Suburb and Urban Areas of Nanchang During 2006 and 2007

为了解南昌地区酸雨现状,通过对南昌农区、郊区、市区布设观测点,根据有关监测数据资料,对2006—2007年酸雨pH值、酸雨频率、酸雨成分、空气污染状况进行了统计分析。结果表明,3个测点观测的南昌地区酸雨年均pH值处强酸性标准,3测点酸雨发生概率为88%～97%,9—4月酸雨较重、5—8月减弱,酸雨pH值与空气污染物浓度有极显著相关关系。酸雨呈硫酸性酸雨,主要阴离子为SO24-、NO3-、Cl-,阳离子为NH4+、Ca2+、K+,且SO24-/NO3-比值较小。农田保护区因处于城市及工业污染源下风向,降水总离子及SO24-浓度较高,酸雨强度不亚于城市。在新设工业园及迁出企业布局上,应考虑设于较小风频方位,以减轻南昌农田保护区及城市污染,建议选择城市西北、东南侧安排新设排放源。

Based on the statistical analysis for pH value, occurring frequency, constituents of acid rain, and air pollutants measured during 2006 and 2007 in the protected farmlands, suburb, and urban areas of Nanchang, the characteristics of acid rain in this region were studied. Measurements taken at three sites indicate that the annual mean pH values of acid rain in Nanchang are lower than the criteria of serous acid rain. The occurring frequency of acid rain was in the range from 88% to 97% at three sites. The acidity of rainfall was more serious during the period from September to April than during the period from May to August. The pH value of rainfall is significantly correlated with the concentration of atmospheric pollutants. Acid rain in this region is typically sulphuric acid, with SO4^2-, NO3^-and Cl^-as major anions and NH4＋, Ca^2＋ and K^＋ as major positive ions. The ratio of SO4^- to NO3^-is low. Since the protected farmlands are situated to the leeward of urban area and industrial pollution sources, the total ion and SO4^2- here are high. The seriousness of acid rain in the protected farmlands is compatible to that of acid rain in the urban area. In order to alleviate pollutions in the protected farmlands and urban area of Nanchang, industrial park to be set up and enterprises emigrated out from the urban area should be allocated at locations away from predominant wind directions. The northwest and southeast areas are the potential homes for the pollutant emission sources.