城市内湖疏浚前重金属的沉积与污染特征研究

Study of Heavy Metals Deposition and Pollution Characteristics in Urban Lake before Dredging

象湖作为南昌市重要的内湖,汇聚南江、北江、东江、西江及青山湖的水流,经由抚河流入赣江,最终汇入鄱阳湖,其水质安全对鄱阳湖的保护意义重大。为了解象湖的重金属分布、沉积特征与污染状况,该研究利用南昌市对象湖整治之际,采集了25个表层沉积物、2个柱状沉积物样品,对重金属Cu、Zn、Pb、Cr、Ni、p H值及有机质进行了测定,并采用地质累积指数法评价了象湖沉积物中重金属的污染现状,探讨分析了各元素的相互作用、来源以及环境因素对重金属的影响。结果表明:(1)象湖表层沉积物中Cu、Zn、Pb、Cr、Ni的平均值分别为53.16、1 988.13、205.32、49.00、32.67 mg/kg,其中Zn变异系数最大,受人为影响较大;柱状沉积物的分布图表明象湖长期受到污染,且重金属含量在湖心处较小,排污口较大;(2)评价结果显示象湖表层沉积物污染程度为Zn(中度污染)>Pb(轻度污染)>Cu(轻微污染)>Ni(无污染)>Cr(无污染),与国内其他湖泊相比,象湖Zn、Pb污染严重,应当受到重视;(3)统计分析显示Cr、Cu、Ni和有机质呈显著的相关性,可能被腐殖酸吸附或络合而富集于有机质中,Cr、Ni相关性显著,二者可能具有相同的来源以及相似的地球化学行为,Zn和Pb与其他物质相关性均较差。

Xianghu Lake,gathering the flow of Nanjiang,Beijiang,Xijiang,Dongjiang and Qingshanhu River,through Fuhe River stroking into Ganjing River,ultimately into Poyang Lake,is an important urban lake in Nanchang City. Xianghu Lake＇s water safety is of great significance for Poyang Lake protection. To explore the heavy metal＇s distribution and contamination in the Lake,25 surface sediments and 2 core sediments were collected during the harnessing of Xianghu Lake,and the concentrations of Cu,Zn,Pb,Cr,Ni,p H and organic matter were determined. The contamination status of heavy metals was comprehensively evaluated by geo-accumulation index. The function and sources of different elements were discriminated by statistical analysis. The results indicated that average contents of Cu,Zn,Pb,Cr,and Ni were 53.16,1988.13,205.32,49.00,32.67 mg/kg,respectively. The variation coefficient of Zn was the largest in all elements,which was greatly influenced by human activities. Columnar sediment distribution showed that the Lake has been polluted for a long time,and heavy metals content in the middle was much smaller than the lakeside. The assessment result indicated the pollution order of heavy metals as ZnPbCuNi. Compared with other domestic urban lakes,the contamination of Zn and Pb in the Lake is more serious,which need attention. The statistical analysis showed that there were positive correlations between organic matter and Cu,Cr,Ni,maybe on account of the humic acid＇s adsorption and complexation. Furthermore,Cr was significantly correlated with Ni,suggesting the two elements had the same source and similar geochemical behavior.Zn and Pb had poor relation with other elements.