成都经济区大气降尘中铅、镉的环境化学行为研究

【作者】 周琳；

【导师】 曾英；

【作者基本信息】 成都理工大学 ， 分析化学， 2006， 硕士

【摘要】 大气降尘中所含的镉和铅都对环境和人体健康造成危害。对大气降尘中所含镉和铅的环境化学行为研究，有助于我们防治或减轻这种危害的发生。 本文以成都经济区为研究区域，开展大气降尘中重金属镉和铅的环境化学行为研究。主要研究内容有：成都大气降尘的镉和铅的污染状况调查；大气降尘中的镉和铅的化学形态的研究、降尘性状同镉和铅赋存形态的关系研究；降尘的淋滤实验研究。 研究结果表明：成都经济区大气降尘含镉和铅的量分别为1.64～7.80μg·g^-1和167～777μg·g^-1，镉和铅的综合污染水平均为轻度污染，综合污染指数分别为1.72和1.84。 采用Tessier连续提取分离法对成都经经济区大气降尘中的铅和镉的赋存化学形态进行了提取分离。成都经济大气降尘中镉和铅的主要赋存化学形态可分为可交换态、碳酸盐结合态、铁锰氧化物结合态、有机结合态和残留态。研究表明，该研究区大气降尘中的镉和铅主要是以残留态存在；各形态镉和铅在总镉、铅中所占百分比含量的大小排列顺序依次是：残留态＞碳酸盐结合态＞交换态＞铁锰结合态＞有机结合态。其中，交换态镉、碳酸盐结合态镉这2种具有较高生物有效性的形态镉在总镉中所占的平均百分比含量分别是6.42％和8.92％，铁锰氧化物结合态、有机结合态、残留态镉在总镉中所占的平均百分比含量分别是3.42％、2.37％和78.91％；交换态铅、碳酸盐结合态铅这2种具有较高生物有效性的形态铅在总铅中所占的平均百分比含量分别是8.88％和9.15％，铁锰氧化物结合态、有机结合态、残留态铅在总铅中所占的平均百分比含量分别是7.05％、2.00％和74.14％。 大气降尘中镉和铅的赋存形态可能要受降尘自身的pH值、腐殖质和铁含量等因素的影响。成都经济区大气降尘中的腐殖质与铁锰氧化物结合态、有机结合态、残留态镉和铅有一定的相关性，与可交换态、碳酸盐结合态镉和铅的相关性不显著；各形态镉和铅与大气降尘的pH值和全铁的存在无明显的相关性。 以pH=2.0、pH=3.5、pH=5.0、pH=5.6的淋滤液对24份大气降尘样品进行淋滤实验的结果表明：随着pH值的升高，降尘样的镉和铅的淋出量下降，在pH=2.0时，镉和铅的淋出量最高。镉和铅的淋出量均随时间的增加而增加，0～更多还原

【Abstract】 Cadmium and Lead in dustfall is harmful to environment and human health. Study on environmental chemical behaviour of Cadmium and Lead in dustfall is helpful to precaute and eliminate the harmness.In this paper, enviromental chemical behaviour of Cadmium and Lead in dustfall in economical region of Chengdu has been studied, including the investigation of pollution state of Cadmium and Lead in dustfall in economical region of Chengdu, the chemical speciation of Cadmium and Lead in dustfall, the correlationship between dustfall character and chemical speciation of Cadmium and Lead , and eluviating experiment on dustfall.The reasearch show that the concentration of Cadmium and Lead in the dustfall was 1.64⁷.80 μg.g^-1 The dustfall was slightly polluted by Cadmium and Lead, whose synthesis pollution index is 1.72 and 1.84.The speciation of Cd and Lead in dustfall samples from Chengdu economic region was studied by Tessier extraction method. Results indicated that the main speciation of Cd and Pb residual form. The distribution sequerce of speciation for Cd and Lead in dustfall is residual > carbonates-bound > exchangeable > Fe-Mn oxides-bound > organic-bound. The bioactivity of exchangeable Cd and carbonates-bound Cd are much higher than that of the other three speciation. The percentage of exchangeable Cd and carbonates-bound Cd is 6.42 % and 8.92 %, respectively. The percentage of Fe-Mn oxides-bound Cd, organic -bound Cd and residual Cd is 3.42 %, 2.37 % and 78.91 % respectively. The percentage of exchangeable Pb and carbonates-bound Pb is 8.88 % and 9.15 %, respectively. The percentage of Fe-Mn oxides-bound Pb, organic -bound Pb and residual Pb is 7.05 % 2.00 % and 74.14 % respectively.The factor of Cd and Pb speciation in dustfall may be affected by the hunmus ,pH values and the concention of Fe and Mn. The result indicated that humus has certain correlation with Fe-Mn oxide-bound Cd and Pb, organic-bound更多还原