长江中游不同类型湖泊重金属污染历史过程、来源及其影响因素研究

Heavy metal pollution in lake sediments has become one of the hottest research areas in the world. A number of studies have revealed that the status of heavy metal pollution in lake sediments got increasingly serious in China. This project aims to investigate the level of heavy metal pollution in lake sediments as well as discuss the mechanism and distinguish possible sources of pollutants in the middle reaches of Yangtze River. The lakes in this region have undergone dramatic changes over the past century under the interaction of climate change and human activities. Three different types of lakes ---- Lake Dayehu, Lake Liangzihu and Lake Wanghu, located in the smelting and mining city Huangshi, were selected to conduct this research. Through high-precision dating sediment cores, heavy metal content, high resolution multi-proxies, the history of heavy metal pollution in lake sediments could be obtained over the past century. Furthermore, the anthropogenic heavy metal accumulation fluxes were estimated based on the results of lead isotope and reference element combined with the changes in sediment fluxes caused by the different patterns and intensities of human activities. The comparison of heavy metal content in lake sediment and soil, plants and aquatic plants would help to assess the dominant impact on the heavy metal pollution in lake sediment. Compared with the results from other lakes in the middle and lower reaches of Yangtze River, it is possible to understand the underline mechanism as well as the patterns and regional differences of heavy metal pollution in the region. In addition, based on the heavy metal contents in surface sediments, the level of heavy metal pollution and pollution risk were accurately assessed using the multi-methods such as sediment quality guidelines(SQG)、enrichment factor(EF) and geo-accumulation index(Igeo), for the purpose of lake environmental protection and management.

湖泊沉积物重金属污染是当前研究的热点。许多研究表明我国湖泊沉积物重金属污染日趋严重。本项目拟通过长江中游地区著名矿冶城市黄石市的三个不同类型湖泊----大冶湖、梁子湖和网湖为研究对象来开展湖泊重金属污染研究。通过沉积岩芯高精度测年、重金属含量、高分辨率多环境代用指标，建立百年来湖泊重金属污染历史；基于铅同位素结果和参考元素方法，结合多环境代用指标和文献资料所揭示人类活动强度、方式差异引起的入湖及沉积通量的变化，定量分析人类活动对湖泊重金属污染的贡献，并在对比流域土壤、植物及水生植物中重金属元素含量结果上探讨湖泊重金属污染的主要影响因素。同时，与长江中下游其他湖泊研究结果进行对比，探讨湖泊重金属污染的模式及区域差异。此外，利用各湖泊表层沉积物重金属元素含量借助沉积物质量标准、富集系数和地累计指数多方法对上述湖泊进行准确的湖泊重金属污染程度和污染风险等级评价，为湖泊环境保护与管理决策服务。

湖泊沉积物重金属污染是当前研究的热点。长江中游湖泊众多,近年来该区湖泊环境变化剧烈，尤其湖泊重金属污染。本研究为揭示长江中游不同类型湖泊重金属污染历史过程、来源及其影响因素，选择该区大冶湖、磁湖、梁子湖和网湖为研究对象来开展湖泊重金属污染研究。基于沉积岩芯高精度测年结果四个湖泊沉积速率分别为0.02-0.35g/cm2.yr、0.03-0.27g/cm2.yr、0.034 g/cm2.yr、0.56 cm/yr，该区花马湖和保安湖沉积速率为0.04-0.45g/cm2.yr和0.03-0.65g/cm2.yr。同时湖泊重金属自1960s以来呈现快速增加趋势，明显不同于其他区域湖泊如巢湖和太湖，这可能与工业化进程有关。湖泊重金属污染来源分析表明Cr、Ni多与自然来源有关，Cu、Pb和Zn则和工业活动和交通有关，Cd属于双重来源。基于多种方法重金属污染评价表明该区Cd污染严重，Cu、Pb和Zn中等程度污染，与以往研究相比湖泊重金属含量有所降低，但是Cu、Cd和Zn仍较为严重。此外，该区湖泊重金属含量显著高于与其他区域湖泊，这表明该区湖泊重金属Cu、Pb、Zn、Cd 的污染问题不容忽视。最后多种沉积物质量基准比较显示差异较大，选择合适沉积物质量基准对评价结果尤为重要。本研究揭示了该区湖泊污染历程和湖泊所面临的重金属风险，同时为该区湖泊生态环境保护提供了重要背景资料。