桂林市酸雨变化特征及来源分析

对桂林市2008~2011年共396个降水样品p H值统计表明,桂林市酸雨具有明显的季节性差异,夏季酸雨污染程度较低,冬春两季最为严重;对其中44个降水样品做离子分析,通过计算中和因子(NF)分析2008年酸雨程度低主要是NH_4~+和Ca~(2+)等碱性离子中和所致,相对酸度FA达到0.006,表明有99.4%酸性离子被中和;通过富集因子(EF)分析降水中主要离子来源,CI~-和Na~+主要为海洋来源,Ca~(2+)主要为地壳来源,K~+、SO_4~(2-)、NO_3~-主要为人为来源;最后通过Hysplit后向轨迹模拟分季节对2010年强酸雨水汽来源进行追踪,聚类,分析桂林市酸雨受区域输送的影响,确定致酸物质的3个主要源地:1东北向的江西、安徽、湖南、湖北等省份的工业集中、人口密集地区,来源于这些地区的气团春季占到19%,夏季26%,秋季19%,冬季由于盛行东北风,占到36%;2东南方向的广东省尤其珠三角地区,来源于西太平洋的气流经过此地到达桂林,春季占到19%,秋季占到33%,冬季占到36%;3西南向的南宁、柳州等本省城市,春季所有的强酸雨水汽气团都汇合到桂林的西南侧,经南宁、柳州抵达桂林,夏季直接受西南季风的控制,来自印度洋的水汽径直抵达桂林占到75%,秋季途经该地的西南向气流占到14%,冬季63%.

Chemical Characteristics and Source of Acid Precipitation in Guilin

A total of 396 rainwater samples of Guilin from 2008 to 2011 were collected and analyzed for pH, 44 of which were analyzed for major ions. The analysis of pH values showed the obvious seasonal variation of acid rain in Guilin. The pollution level of summer was lower than those in other seasons, while the pollution levels in winter and spring were the highest. The investigation of fractional acidity(AF) and neutralization factors(NF) indicated that low acid rain pollution level in 2008 was caused by alkali neutralization, especially NH₄⁺ and Ca²⁺. Studies of the origins of major ions showed that CI^- and Na⁺ were mainly from sea, Ca²⁺ was mainly from the crustal dust while K⁺, SO₄^2- and NO₃^- were mainly originated from anthropogenic source. Finally, the effect of regional transportation on acid rain of Guilin was analyzed and 3 originatons of acid-causing substance were oriented by an air trajectory clustering methodology based on hysplit-4 and a clustering algorithm including 1Jiangxi, Anhui, Hunan and Hubei, with high population densities, these regions contributed 19% air mass in spring, 26% in summer, 19% in autumn and 36% in winter due to the northeast wind; 2Pearl River Delta, with airflow from west Pacific passing before arriving Guilin, contributing 19% in spring, 33% in autumn and 36% in winter; 3Nanning, Liuzhou. All strong acid rain vapor air mass converged in southwest Guilin in spring, and arrived in Guilin passing Naning and Liuzhou. In summer, under the direct control of southwest monsoon, the vapor from Indian Ocean directly arrived in Guilin, accounting for 75%. The southwest airflow passing these cities accounted for 14% in autumn and 63% in winter.