西太湖沉积物污染的地球化学记录及对比研究

通过对西太湖Ms、DLs沉积短岩芯中金属元素、营养指标的对比分析，讨论了西太湖近80年来的元素地球化学演化特征。结果表明，20世纪40年代以前，西太湖沉积物中元素为自然来源；40～70年代末期，除北部Hg、TP受到人为污染之外，其余元素仍主要为自然来源；70年代末期以来，重金属元素人为污染逐渐加重，湖泊营养程度升高。西太湖北部沉积物中Pb、Zn、Mn、Ni、As污染开始于20世纪70年代末期，Hg污染开始于40年代初期；与北部相比，南部沉积物重金属污染历史较短，Pb、Zn污染开始于70年代末期，灿、Mn、Ni、Hg污染开始于80年代中期～末期。西太湖北部、南部沉积物中TN、TOC含量70年代末期以来开始增加，C／N比值增大，有机质外源输入比例增加。西太湖北部沉积物中11P含量自40年代初期以来逐渐增加，受到人为污染；南部11P含量在40～70年代略高，但无明显的人为污染特征。

Geochemical Records and Comparative Study of the Sediments in the Western Taihu Lake

Sedimentation rates,element concentrations and grain size distribution of cores MS and DLS sediments from western Taihu Lake are investigated,which represent the sediment characters of north and south western Taihu Lake.According to ~(137)Cs dating,the average modern sedimentation rates of cores MS and DLS are 1.7 mm/a and 0.9 mm/a respectively.The geochemistry evolutional history of western Taihu Lake since 1920s' is studied on the basis of analyzing geochemical characteristics of sediments from core MS and DLS. The chemical elements in the sediments were from natural sources before 1940s' and some heavy metals and nutrients have been polluted due to human activities ever since.Pb,Zn,Mn,Ni,As and Hg are the main pollution heavy metals,which have different pollution history and pollution degree. Hg pollution began in the early 1940s' in north western Taihu Lake sediments,while in the south western Taihu Lake,it didn't begin to accumulate until the late 1980s' along with Mn,Ni and As.Pb,Zn,Ni,Mn and As pollution began in late 1970s' in north western Taihu Lake sediments and in the south western Taihu Lake Pb,Zn pollution also began.The concentration of TP in the north western Taihu Lake increased since early 1940s' because of the domestic wastewater,while that high concentration during 1940s' to 1970s' in the south western Taihu Lake might have a correlation with the chemical properties of phosphorous.The concentration of TN and TOC increased since late 1970s' both in north and south of the western Taihu Lake indicated the input of outsource organic matters,and the increased TN also related to the increased use of agricultural chemical fertilizer since late 1970s'. The higher concentration of TN and TP have close correlations with eutrophication of Taihu Lake.The pollution history recorded by sediments' geochemical proxies is correspondent with the economy development of Taihu Lake drainage basin.