太湖流域水体和沉积物重金属时空分布特征及潜在生态风险评价

doi:10.11934/j.issn.1673-4831.2017.03.004

摘要/Abstract

摘要：

为了研究太湖流域重金属含量分布特征及污染现状，采用ICP-MS和直接汞分析仪对2012年11月至2013年8月期间太湖流域98个点位水体和沉积物中Cr、Cu、Zn、As、Cd、Pb和Hg进行监测。结果表明：水体中ρ（Cr）、ρ（Cu）、ρ（Zn）、ρ（Cd）、ρ（Pb）、ρ（As）和ρ（Hg）年平均值分别为0.88、3.21、10.96、3.29、0.019、0.07和0.021 μg·L^-1，均没有超过GB 3838-2002《地表水环境质量标准》，而沉积物中w（Cr）、w（Cu）、w（Zn）、w（Cd）和w（Pb）年平均值分别为102.32、65.24、185.64、0.93、45.88 mg·kg^-1，这5种重金属含量均超过GB 15618-2008《土壤环境质量标准》，其中Cd含量为标准值的4.7倍。而w（As）和w（Hg）年平均值为9.87和0.107 mg·kg^-1，只有标准值的65.8%和71.3%。水体和沉积物中重金属含量的时空分布存在显著差异。平水期水体Cr和Cu浓度高于枯水期和丰水期，丰水期Zn和As浓度最大，Cd、Pb和Hg浓度在枯水期、平水期、丰水期稳定，无显著变化。Cr、Cu、Zn、As、Cd、Hg 这6种重金属浓度在运河水系中最高，苕溪水体中最低，太湖水体中处于中等值，平水期沉积物中Cr和Cu浓度高于枯水期和丰水期。沉积物中Zn、Cd和Hg含量则以丰水期为最高，枯水期最低；As和Hg含量以枯水期为最高。运河水系和出湖水系沉积物中Cr、Cu和Pb含量明显超出标准值，而其他水系低于或者接近标准值。沉积物中Zn含量最高的为出湖水系和运河水系，而Cd含量最高的为宜溧河水系和太湖。太湖流域沉积物中7种重金属的潜在生态风险因子从大到小依次为Cd、Hg、Cu、As、Pb、Cr和 Zn。Cd是最主要的生态风险贡献因子，其生态危害程度为强水平。宜溧河水系生态风险指数为278.13，属于重生态危害，而其他水系处于中等生态危害水平。

关键词: 太湖流域, 重金属, 水体, 沉积物, 时空分布, 生态风险

Abstract:

A total of 98 monitoring sites were set up in the Lake Taihu Basin and water and sediment samples were collected routinely from these sites during the period from November 2012 to August 2013 for analysis of heavy metals (Cr, Cu, Zn, As, Cd, Pb and Hg) with the Inductively Coupled Plasma-Mass Spectromtry (ICP-MS) and a Direct Mercury Analyzer, to explore content distribution characteristics of the heavy metals and status quo of heavy metals pollution of the region. Results show that: the seven heavy metals (Cr, Cu, Zn, As, Cd, Pb and Hg) in the surface water did not exceed the criteria set in the National Environmental Quality Standards for Surface Water in content, being 0.88, 3.21, 10.96, 3.29, 0.019, 0.07 and 0.021 μg·L^-1, on average, while the content of Cr, Cu, Zn, Cd and Pb in the sediment was 102.32, 65.24, 185.64, 0.93 and 45.88 mg·kg^-1, on average, all exceeding the criteria set in the standard, especially the content of Cd, being 4.7 times as high as the criterion in the standard. However, the content of As and Hg was only 9.87 and 0.107 mg·kg^-1 on average, respectively, or 65.8% and 71.3% of their respective criterion in the standard. Contents of the seven heavy metals in the surface water and sediment varied significantly in temporal and spatial distribution. The concentrations of Cr and Cu in the surface water were higher during the normal water seasons than during the high or low water seasons, and the concentrations of Zn and As the highest during the high water season, whereas the concentrations of Cd, Pb and Hg relatively unchanged throughout all the three seasons. Cr, Cu, Zn, As, Cd and Hg were the highest in concentration in the Canal water system area, the lowest in the water body of Shaoxi and moderate in the water body of Lake Taihu. In the sediments, the concentrations of Cr and Cu were higher during the normal water season than during the high or low water seasons; the concentrations of Zn, Cd and Hg were the highest during the high water seasons and the lowest during the low water season; and the concentrations of As and Hg were the highest during the low water seasons in the sediments of the Canal water system and the effluent system, the concentrations of Cr, Cu and Pb were significantly higher than the criteria in the standard, while in the sediments of the other water system, their concentrations were lower or approximate to the criteria in the standard. Zn content in the sediments was the highest in the effluent water system and the Canal water system, while Cd content was in the Yili water system and the Taihu Lake water system. In the sediments of the Taihu Lake Basin, the 7 heavy metals followed a decreasing order of Cd > Hg > Cu > As > Pb > Cr > Zn as potential ecological risk factor, among which Cd was the paramount one, reaching the heavy level in ecological hazard degree. Of the heavy metals, the ecological risk index in the Yixi River water system was rated as heavy ecological hazard, being 278.13, while the indices in the other areas as moderate ecological hazard.

Key words: Lake Taihu Basin, heavy metal, water body, sediment, spatial and temporal distribution, ecological risk

中图分类号:

方斌斌, 于洋, 姜伟立, 常闻捷, 杜明勇, 张民. 太湖流域水体和沉积物重金属时空分布特征及潜在生态风险评价[J]. 生态与农村环境学报, 2017, 33(3): 215-224.

FANG Bin-bin, YU Yang, JIANG Wei-li, CHANG Wen-jie, DU Ming-yong, ZHANG Min. Spatio-Temporal Distribution of Heavy Metals in the Surface Water and Sediment of the Lake Taihu Basin and Assessment of Their Potential Ecological Risks[J]. Journal of Ecology and Rural Environment, 2017, 33(3): 215-224.

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