【作者】 林碧娜；

【导师】 肖化云；

【作者基本信息】 南昌大学 ， 环境工程， 2008， 硕士

【摘要】 酸性降水使环境酸化,带来了一系列的生态破坏和经济损失,引起人们的高度重视。为了探讨重酸雨区南昌市大气降水的区域污染特征,本课题对南昌市2007年4月至2008年3月市区（南昌大学北区）、市郊（南昌大学前湖校区）大气降水的化学成份进行测定。采用了化学成份的离子平衡分析、扣除海盐和地壳源计算人为活动源对大气降水的影响,同时结合化学离子的相关性分析、聚类分析和主成分分析等数理统计方法,探讨了市区市郊大气降水化学特征、痕量有毒金属的组成特征差异以及污染来源,并在此基础上利用稳定硫同位素组成的“指纹”值的特征来进一步解析南昌市降水中硫污染的来源。研究结果表明:（1）南昌市大气降水的降雨量加权pH值小于5.00,达到了“逢雨必酸”,与已往研究相比酸度有所提高。前湖和北区的雨量加权平均pH值低分别为3.96和4.16,市区大气中有较高浓度的碱性物质加入,降水比市郊电导率大pH值高;SO₄^2-/NO₃^-值均在0.5-3.0间,属于硫酸和硝酸混合型酸雨;前湖和北区的∑+/∑-的值为1.195和1.154,达到离子平衡;降水的pH值、电导率和各种阴阳离子存在明显的季节变化;Ca²⁺、K⁺、SO₄^2-和NO₃^-海盐富集因子都大于10,相对于海盐已被富集;人为活动对降水贡献最大,前湖主要受人为活动和地壳影响,北区主要受人为活动和海盐影响。陆源离子、海盐离子和NO₃^-与SO₄^2-之间存在显著的相关性。主成分分析和聚类分析结果表明市郊前湖校区降水主要受地壳和人为活动来源影响;市区北校区主要受人为活动和海盐源影响。（2）南昌市大气降水中痕量金属浓度远远大于许多地方,与重酸雨区贵阳比较接近,同时表现出明显的冬高夏低的季节性波动。对Cu、Hg和Pb来说,降水是地表水中的一个污染因子。降水中的金属浓度与pH值之间不存在线性相关,但当pH小于4时,金属浓度急剧增大。前湖校区的降水受海盐源影响较北区小,受地壳源较北区大。三种来源的对大气降水金属浓度影响大小为:人为＞地壳＞海盐,人为活动对两个校区的影响分别95.428%和96.60%。降水中Cd、Cr、Cu、Mn、Pb和Zn都表现出良好的相关性,主成分分析与聚类分析结果一致,降水中痕量有毒金属的主要来自冶炼工业、燃油熔炉废气、汽车轮胎磨损和汽车尾气等人为活动的释放。（3）市郊前湖校区和市区北区春夏季降水的δ³⁴S值变化范围分别为-3.55-+3.91‰和-3.88-+7.24‰,均在世界大气降水的δ³⁴S值范围内,市区的范围较大,表明了相对于市郊有多种硫来源。两个校区的雨水样品中罩SO₄^2-浓度和δ³⁴S值明显小于前湖和青山湖湖水中δ³⁴S值,降水不是南昌市地表水中硫酸盐主要来源。梅雨期,暴雨时大气中硫受海盐气溶胶影响大,出现较大的δ³⁴S;小雨时,大气中硫受当地轻硫同位素组成的陆源（人为成因硫和生物成因硫）影响较大,δ³⁴S值较小。市郊地区春夏季降水中硫主要来自生物成因硫:市区春夏季降水的硫主要来自人为成因硫和生物成因硫。海盐成因硫对市区市郊影响均较小。更多还原

【Abstract】 Great attention has been played on sulfur pollution after a series of ecological damage and economic losses caused by environmental acidification. The chemical composition of precipitation was analyzed on the basis of the result of precipitation collected at two sites in Nanchang during the period from 2007 to 2008, and discussed the chemical feature and pollutant sources. The tow sites located at Qianhu campus and the North campus of Nanchang University, standing for the urban and suburban. To discussed the pollutant characteristics and sources of chemical composition and differences of the toxic trace metal in precipitation at two sites, this study take the method of discounting the effect of sea salt and crust to work out the proportion of anthropogenic activity , combined with mathematical statistics such like the relevance analysis, cluster analysis and principal component analysis. Further more, for the stable sulfur isotopic composition can effectively judge the difference sources of sulfur in the atmospHeric pollution by its "fingerprint" of the characteristics, theδ³⁴S value was taken to analysis the sulfur source of precipitation in Nanchang. Results show that:（1） The weighted rainfall pH value of precipitation in Nanchang less than 5.00, and every precipitation is acid rain, it is lower than previous studies. The volume weighted mean pH value of Qianhu and the north campus are 3.96 and 4.16, respectively. The pH of precipitation at the north campus is higher than it at Qianhu campus while the conductivity is larger, for there are more strong acid buffered by alkaline substances in the atmospHeric environment of the urban area than at suburban. Precipitation is a kind of sulfuric acid and nitric acid mixed acid rain with the value of SO₄^2-/NO₃^- ranging from 0.5 to 3.0∑+/∑- of Qianhu and the north campus are 1.195 and 1.154, shows that it is essential balance between the cation and anion. The pH, conductivity and ions showed a significant seasonal variation. Anthropogenic activity had the greatest impact on the precipitation, Qianhu site was mostly influenced by anthropogenic activity and crust while the north site was mostly influenced by anthropogenic activity and sea salt. A significant correlation between ions of land-based sources, sea salt ions and NO₃^- with SO₄^2-. Principal components analysis and cluster analysis has the same result, shows that the major sources of precipitation are the crust and human activities in Qianhu campus, and human activities and sea salt in the North campus.（2） The concentrations of toxic trace metal elements are much high than other place while close with the concentrations in Guiyang, and show a seasonal fluctuation of high in summer and low in winter. To Cu, Hg and Pb, precipitation is a pollution factor of surface water. There are no correlations between metal elements and pH in the precipitation, but when the pH is less than 4.00, metal concentration increases rapidly. Qianhu site is more influenced by crust and less by sea salt than the north campus. The effect of three sources to the metal concentration is: human＞crust＞sea salt, the impact of human activities to the two campuses is 95.43% and 96.60%, respectively. Cd, Cr, Cu, Mn, Pb and Zn show a good correlation for come from the same sources. The results of principal component analysis are consisted with the cluster analysis. The pollution of trace toxic metals in rainwater is mainly released from human activities, like large smelting, oil-fire furnaces, the wearing tire and automobile exhaust, and so on.（3） Theδ³⁴S in precipitation of Qianhu campus and the North campus in spring and summer precipitation ranged from -3.55 to +3.91‰and from -3.88 to +7.24‰, respectively, which were both in the scope ofδ³⁴S value in precipitation all over the world. There were several sources of sulfur in urban areas, compare with the suburbs areas. It was significantly that the SO₄^2- concentration andδ³⁴S at two sites smaller than the Qianhu and Qingshan Lake, which indicated that the precipitation was not the main source of sulfate in surface water. During the rainy season, the sea salt aerosol was the major source of precipitation with a greaterδ³⁴S value in the rainstorm, while the local land-based sources （anthropogenic and biological sulfur） were the major source of precipitation with a lowerδ³⁴S value. The biological sulfur was the major factor in rainwater of suburban in the spring and summer, and both the anthropogenic and biological sulfur of urban, whereas the sea salt sulfur had less effect to suburban and urban.更多还原