Interactions of Mercury With Organic Matter in Water and Soils

ryan：汞与有机物的相互作用在确定水和沉积物中汞的环境风险和毒性方面起着重要作用。我们对水和沉积物中汞形态的了解大多来自于对高浓度汞的研究。这些研究可能与严重汞污染的地点有关，但即使在汞浓度仅略高于检测限度的地区，汞毒性也是一个问题。汞的有毒形式，甲基汞，是由汞（II）物种的甲基化形成的，并在高等生物体中积累。强配体络合Hg（II）可以阻止Hg（II）的甲基化。越来越多的证据表明，有机物质有效地结合Hg(II)，阻止Hg（II）的甲基化，并控制Hg（II）在水和沉积物中的运输。然而，我们对有机物质与汞的相互作用的理解在几个关键领域是缺乏的：为什么有机物与汞的结合如此强烈？在相对原始的沉积物中汞的形式是什么？汞从汞固体中释放的速度有多快，通过什么机制释放？本研究的目标是通过三个主要任务来提供这些问题的答案：(1)分离和表征负责Hg（II）结合的有机质组分，(2)开发顺序提取以确定相对原始沉积物中汞的形态，以及(3)检查有机质在汞固体中汞（II）释放中的作用。这些任务将由Joe Ryan（科罗拉多大学）、George Aiken（美国地质调查局）和Kathy Nagy（科罗拉多大学）组成的研究小组完成，Joe Ryan是一位具有表面化学和顺序萃取经验的环境工程师，George Aiken是一位具有分离和表征有机物质经验的有机地球化学家，Kathy Nagy是一位具有矿泉水相互作用经验的水地球化学家。第一项任务是通过亲和色谱法鉴定负责汞结合的天然有机物质的关键成分。这项任务，结合完整的有机物质表征方法，将帮助我们验证一个假设，即减少的硫官能团是汞与有机物质结合强度的关键因素。在布鲁克海文国家实验室的Murthy Vairavamuthy提供的分析技术的帮助下，George Aiken将领导这项工作。第二项任务是利用精细的顺序提取程序表征沉积物中汞的形态。这项任务将研究沉积物中汞隔离的新可能性，并检验有机质主导沉积物中汞形态的假设。科罗拉多大学土木、环境和建筑工程系的乔·瑞安将在一名研究生研究助理的协助下领导这项工作。第四项任务是考察天然有机物质在朱砂溶解过程中释放汞的速率和机制，以评估沉积物中汞的动员。这项任务将提供有关汞从硫化汞固体中释放的基本数据，并验证一个新的假设，即有机物质既作为强配体又作为电子受体，以增强硫化汞固体的溶解。凯西·纳吉（Kathy Nagy）将在一名研究生助理的协助下指导这项工作。该提案已提交给EGB项目，并由CTS部门（Roger Arndt）共同资助。

9807735RyanThe interactions of mercury with organic matter play an important role in determining the environmental risk and toxicity of mercury in water and sediments. Most of our understanding of mercury speciation in water and sediments comes from studies of mercury at high concentrations. These studies may be relevant for sites of substantial mercury contamination, but mercury toxicity is a problem even in areas where mercury concentrations are barely above detection limits. The toxic forms of mercury, methylmercury,is formed by the methylation of Hg(II) species and accumulated in higher organisms. The methylation of Hg(II) may be prevented by complexation of Hg(II) by strong ligands. Increasing evidence suggests that organic matter effectively binds Hg(II), prevents methylation of Hg(II), and controls the transport of Hg(II) in water and sediments. However, our understanding of the interactions of organic matter with mercury is lacking in several crucial areas:1. Why does organic matter bind mercury so strongly?2. What is the form of mercury in relatively pristine sediments?3. How rapidly and by what mechanism is mercury released from mercury solids? It is the goal of this study to provide answers to these questions by pursuing three major tasks:(1) isolation and characterization of organic matter fractions responsible for Hg(II) binding, (2) development of sequential extractions for determination of mercury speciation in relatively pristine sediments, and (3) examination of the role of organic matter in the release of Hg(II) from mercury solids. These tasks will accomplished by a research team of Joe Ryan (University of Colorado), an environmental engineer with experience in surface chemistry and sequential extractions, George Aiken (U.S. Geological Survey), an organic geochemist with experience in the isolation and characterization of organic matter, and Kathy Nagy (University of Colorado), an aqueous geochemist with experience in mineral-water interactions. The first task is the identification of key components of natural organic matter responsible for mercury binding through affinity chromatography. This task, combined with a full arsenal of organic matter characterization methods, will help us test the hypothesis that reduced sulfur functional groups are the key factor in strength of mercury binding by organic matter. George Aiken will lead this effort with the assistance of analytical techniques provided by Murthy Vairavamuthy of Brookhaven National Laboratory. The second task is the characterization of the speciation of mercury in sediments using refined sequential extraction procedures. This task will examine new possibilities for the sequestration of mercury in sediments and test the hypothesis that organic matter dominates the speciation of mercury in sediments. Joe Ryan of the Department of Civil, Environmental, and Architectural Engineering, University of Colorado, will lead this effort, assisted by a graduate research assistant. The fourth task is an examination of the rate and mechanism of mercury released by natural organic matter during cinnabar dissolution to assess the mobilization of mercury from sediments. This task will provide basic data on the release of mercury from mercuric sulfide solids and test a novel hypothesis that organic matter is acting both as a strong ligand and an electron acceptor in enhancing the dissolution of mercuric sulfide solids. Kathy Nagy, assisted by a graduate research associate, will direct this effort.This proposal was submitted to the EGB Program and is being jointly funded by:Division of CTS (Roger Arndt)