中文摘要：

以淮河中下游洪泽湖湖底沉积物为研究载体，将放射性核素计年与沉积物重金属元素含量变化分析相结合，初步探讨了近百年来洪泽湖湖底重金属元素变化特征及人类活动对湖泊环境的影响。结果表明：20世纪50年代初以前，洪泽湖沉积物中重金属元素主要为自然沉积，元素含量具有一致的变化趋势；1950-1978年，特别是1952年后各元素含量开始小幅度上升，Pb，Zn，As等元素均出现较为明显的累积峰值。原因在于1953年洪泽湖下游三河闸水利工程的修建，使部分重金属重新溶出吸附，导致沉积物中重金属元素含量发生波动，另一方面也反映出当时洪泽湖已经受到流域重金属的污染；1979-1989年间，Hg元素含量开始逐渐增加上升，系自然来源、人类污染及生物累积效应的影响；1990-2001年，大规模城乡开发活动对环境污染影响加剧，所有重金属元素均呈现逐渐增加的趋势，尤其在表层达到最高值，此阶段Hg和Cd的上升幅度较大，Hg元素平均含量为0.21ppm，Cd元素平均含量2.36ppm，超过土壤环境质量重金属评价三级标准。洪泽湖水体中Hg元素含量的上升，Cd元素含量的严重超标及其引起的生态效应问题应引起高度重视。

英文摘要：

The Lake Hongze, a typical large-shallow freshwater lake in China is located on the northwest of Jiangsu Province, 33°06′ - 33°40′ N, 118°10′ - 118°52′ E. The environmental implications of heavy metals from core sediment from the lake（ core HLC1 ）was studied with 210^pb and317^Cs isotope dating method, for the main purpose of discussing the characteristic changes of heavy metals and the influence of human activities. Four stages of the heavy metal concentrations are recognized： （ 1 ） From 1901 to 1950, all heavy metal concentrations have the same changing tendency reflecting that human activity at this stage has little influence on basin environment, the heavy metals of the sediment were from natural sources. （2）From 1950 to 1978, particularly after 1952, contents of all heavy metals increased slowly, with Pb, Zn, and As having obvious accumulation peak values. One possible reason is that with the Sanhe Sluice building up in 1953, the Lake Hongze was dredged up which caused heavy metals of the sediment to be re-dissolved and re-deposited. Another possible reason is that the Hongze Lake has been polluted by heavy metals at this stage, along with the development of industry, agriculture, and aquaculture around the Huaihe River and the Hongze Lake in the late 1970s. （3）From 1978 to 1990, most heavy metals have low accumulation except As, Hg, and Cr. Hg concentration showed an ascending trend which was affected by many factors including natural sources, human activity, and biological accumulation. The content of Sr and Cr is also increased quickly which could be attributed to coal combustion and use of pesticide. （4）From 1990 to 2001, content of all heavy metals increased and reached their maximum values at the surface, which is the result of the fast development of local economy and the deterioration of water quality of the Hongze Lake and the Huaihe River. Hg concentration and Cd concentration increased abruptly at this stage, with their average contents 0.21ppm and 2.36ppm respec