典型海水养殖底泥中汞形态的源解析研究

Source apportionment of mercury in surface sediments from mariculture areas has an important application to effectively control and block the mercury pollution of mariculture water, and to reduce and cut off the health hazards of mercury in aquatic products. What are the exogenous pollution sources of mercury in surface sediment? How much do the sources contribute? How does mercury migrate? The source apportionment methods usually used in present, such as multivariate statistical analysis, isotope signature analysis and GIS maping method, cannot achieve the above goals individually. Then, what are the endogenous release of mercury in surface sediments? How about the mobility and ecological effects of mercury from different sources? These methods cannot solve these problems either individually or integratedly. In this project, based on the reseach of sequential extraction procedure for mercury speciation in anoxic sediment, a new integrated source apportionment method is developed, that isotope signature analysis, GIS maping method and mercury speciation analysis are combined, to identify the sources of bound carriers of mercury speciation and then to discriminate the sources of mercury speciation, and to reveal the effects of mariculture on methylation of mercury in surface sediments. The integrated source apportionment method can assess the mobility and ecological risk of mercury from different sources while identify the type and contribution of the internal and external pollution sources and present the pollution route directly.

海水养殖底泥中汞的来源解析对有效控制和阻断养殖水体汞污染、降低和消除养殖水产品中汞的人体健康危害具有重要应用价值。养殖底泥中汞的外源污染有哪些？贡献大小如何？途径迁移如何？目前常用的多元统计法、GIS地图法和同位素分析等源解析法皆无法单独实现上述目标。养殖底泥中汞的内源释放有哪些？不同来源汞的迁移能力和生态效应如何？这些源解析法无论单独或联合应用皆无法解决上述问题。本项目拟在建立的养殖区缺氧沉积物底泥中汞形态连续萃取法的研究基础上，发展了一种新的底泥中汞形态的综合源解析方法：将同位素分析和GIS地图分析法与汞赋存形态分析相结合，通过汞形态结合载体的来源分析，对养殖底泥中汞形态进行源解析研究，并揭示海水养殖对底泥中汞甲基化的作用。综合源解析法可实现在判断内外污染源类型及贡献同时直观呈现污染途径，并评估底泥中来自不同污染源汞的迁移能力和生态危害风险。

在海水养殖区，养殖底泥中汞不断通过内源产生和外源输入进行富集，不同来源的迁移方式、贡献大小和富集汞的生态危害效应需要源解析进行揭示和评估。本项目首先建立了养殖海水中汞的快速分析方法，并进一步建立了养殖底泥中汞形态的分析方法，在此基础上建立了养殖区缺氧沉积物底泥中汞形态连续萃取法；发展了一种新的底泥中汞的源解析方法，通过汞形态结合载体的来源分析，对养殖底泥中汞形态进行源解析研究。通过研究建立了养殖底泥中汞可迁移态的单级提取法和薄膜扩散技术的评估方法，采用实验室模拟实验考察了不同形式外源汞的迁移能力，并根据典型海水养殖区采样位点汞的含量评估了其生态危害风险大小，汞的生态危害风险总体为轻微生态风险。通过向海水养殖底泥中添加无机汞，模拟外源汞输入，研究在海水养殖底泥中外源汞胁迫下，底栖生物（沙蚕）对汞的甲基化和甲基汞的富集，以及沙蚕的生物应激响应。底栖生物一方面自身具有将汞转化为甲基汞的能力，同时底栖生物活动对外源无机汞的甲基化有明显促进作用，底栖生物存在时汞甲基化能力提高1.93倍。养殖底泥中外源汞输入含量超过0.5 mg/kg，沙蚕抗氧化应激系统超过防御极限；与无机汞相比，甲基汞会对沙蚕造成更大的氧化压力，具有更强的生物毒性。不同形态的外源汞在底栖生物体内富集能力存在差异，DOM-Hg生物可利用性相比硝酸汞和硫化汞较高。项目研究对海水养殖底泥和养殖水体中汞来源和富集的有效阻断控制，从而降低和消除养殖水产品中汞的人体健康危害具有重要应用价值。