The pH variation and ionic composition of precipitation at Wuzhi Mountain in Hainan Province and Wuyi Mountain in Fujian Province were analyzed from January 2008 to December 2009. The ionic sources were simultaneously investigated. The results showed that the precipitation at Wuzhi Mountain was neutral with an annual mean pH of 5. 64, while that at Wuyi Mountain was weak-acidic with an annual mean pH of S. 30. The sum concentration of S042' , NO," and NH4 * in the precipitation accounted for about 59% of the total ionic composition at the two sites, indicating the impact of human activities. In spite of SO42~ and NO, ~ , the acidity of the precipitation was also affected by alkaline substances such as NH4 * , Ca , Mg * , etc. Calculation through fractional acidity and neutralizing factors showed that nearly 85% and 76% of the acidity in the precipitation at Wuzhi Mountain and Wuyi Mountain, respectively, were neutralized by the main alkaline cations NH4 * and Ca2 *. Source identification by enrichment factor analysis and quantification of the major ions from different sources indicated that the two sites have been affected by anthropogenic sources, and the influence of human activities was greater than those from the marine and crustalsources. At Wuyi Mountain, about 88% of Ca and 56% ofK* were from anthropogenic sources through long distance transport and biomass burning.%分析海南五指山及福建武夷山大气背景点2008年1月-2009年12月的降水pH及离子组成,并探讨离子来源.结果表明:海南五指山监测点降水年均pH约为5.64,呈中性;武夷山监测点降水的年均pH约为5.30,呈弱酸性.2个监测点降水中的SO42-、NO3-和NH4+的浓度和占总离子浓度的59％左右,表现出与城市相似的组成特征,表明这2个监测点的降水已经受到人类活动的影响.降水酸度除受SO42-和NO3-的影响外,还受到NH4+、Ca2和Mg2等碱性物质的中和作用.相对酸度和中和因子的计算表明,五指山和武夷山监测点降水酸度分别有85％和76％被碱性物质NH4+和Ca2+中和.富集因子计算及来源定量分析表明,这2个监测点已受到人为源的影响,人为源的贡献大于海洋源及地壳源.武夷山监测点88％的Ca2+和56％的K+均来自人为源,主要是受人为污染物长距离传输及生物质燃烧的影响.
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