• 关键词：酸雨  降水化学  长期观测  趋势分析  侯马市

• 基金项目：国家重点基础研究发展计划项目(No.2005CB422202)

• 张红安
• 1. 中国气象科学研究院 大气成分观测与服务中心 中国气象局大气化学重点开放实验室, 北京 100081; 2. 山西省侯马市气象局, 侯马 043010

• 汤洁
• 中国气象科学研究院 大气成分观测与服务中心 中国气象局大气化学重点开放实验室, 北京 100081

• 于晓岚
• 中国气象科学研究院 大气成分观测与服务中心 中国气象局大气化学重点开放实验室, 北京 100081

• 程红兵
• 中国气象科学研究院 大气成分观测与服务中心 中国气象局大气化学重点开放实验室, 北京 100081

• 朱新民
• 山西省侯马市气象局, 侯马 043010

• 李亚军
• 山西省侯马市气象局, 侯马 043010

• 徐晓斌
• 中国气象科学研究院 大气成分观测与服务中心 中国气象局大气化学重点开放实验室, 北京 100081

• 摘要：根据1992年至2008年的酸雨观测记录,对侯马市的酸雨变化特征及其长期趋势进行了统计分析.结果表明,17年间,除个别年份外,侯马地区的降水pH值长期低于5.6,2006年以来甚至低于4.5,多年平均pH值为4.88,是我国长江以北地区酸雨污染最严重的地区.降水pH值的平均月际变化幅度为0.8pH单位,呈不规则起伏变化.在降水集中的7、8、9月间,酸沉降量约占全年的60%.作为出现在我国北方的区域性酸雨地区,侯马地区降水酸度2002年前后呈现不同的变化趋势,2002年前,降水pH值平均年变率约为0.10a^-1,酸雨污染呈现减弱趋势,而之后的pH值平均年变率约为-0.28a^-1,呈现酸雨污染快速加重的变化趋势.该地区降水量的变化不仅对单次降水的酸性有较明显的影响,而且对降水酸度的季节变化和年际变化也有明显影响,显示当地的大气颗粒物具有显著的碱性中和能力.2007年对降水离子成分的加强观测分析结果显示,SO₄^2-、NO₃^-、Ca²⁺、NH₄⁺是降水中最主要的离子;[1/2]SO₄^2-与NO₃^-的比值约为6.9,说明当地的酸雨为较明显的硫酸型污染;降水中NH₄⁺含量较高,大约与[1/2]Ca²⁺的离子含量相当;主成分因子分析显示,[1/2]SO₄^2-、NO₃^-、[1/2]Ca²⁺、NH₄⁺4种离子含量的变化存在显著相关,当地的焦煤、煤化工等高污染排放可能是其重要的共同来源.

• Abstract：This paper presents long-term trend analysis of precipitation acidity at Houma city,in southern Shanxi Province,based on monitoring data from 1992 to 2008. As a severe acid rain area north of the Yangtze River,the annual precipitation pHvalues during the period of 1992～2008 are below 5.6 with only one exception in 2002. Since 2006,the annual pHvalues of precipitation at Houma are even below 4.5. The overall average pHvalue for the 17 years is 4.88. The seasonal variation of monthly average precipitation pHdoes not show a clear pattern,but has a range of 0.8. During the rainy season,the wet deposition of H⁺ from July to September accounts for 60% of the annual total. The trends of precipitation acidity at Houma,for the period before 2002 and for the period after 2002,are obviously different. The averaged annual rate of precipitation pHin the period 1992～2002 is 0.10 a^-1,showing an ameliorating trend of the acid rain situation. However,the averaged annual rate of precipitation pHin the period of 2002～2008 is -0.28 a^-1,showing a rapid development of acid rain in the area. Rainfall amount shows clear effects on the acidity of single precipitation events,and seasonal and interannual variation,implying high neutralizing capacity of airborne particles in the atmosphere. The measurement of soluble ions in the precipitation was made with 56 samples collected in_2007. The analysis results show that SO₄^2-,NO₃^-,Ca²⁺,and NH₄⁺ are the major ions. The mole ratio of [1/2]SO₄^2- over NO₃^- is 6.9,showing a sulfate type acid rain in the area. The concentration of NH₄⁺ ion is relatively high,close to that of [1/2]Ca²⁺ ion. The result of principal component analysis shows that there are good correlations between the concentrations of [1/2]SO₄^2-,NO₃^-,[1/2]Ca²⁺,NH₄⁺ ions,indicating that the regional dominant industrial emissions from coking and coal chemical plants are possible common sources for these ions.

• Key words：acid rain  precipitation chemistry  long-term observation  trend analysis  Houma

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