Collaborative Research: Mercury Biogeochemistry in a Semi-Arid Aquatic Ecosystem: Processes Controlling Methylation and Demethylation

9523894 Hines汞的生物地球化学很重要，因为甲基汞的毒性、其在生物群中的积累以及其在食物链中的生物放大作用。需要了解甲基汞的浓度、迁移和动态，以预测其对人类和水生生物的潜在影响。该计划将甲基汞的形成和降解的生物地球化学、微生物学和分子研究与某些非生物因素结合起来，并进行稳健的建模工作，以描述内华达州卡森河/拉洪坦水库系统中控制甲基汞动态的因素。卡森系统在19世纪接收了7000吨元素汞用于金汞齐，现在提供了一个很强的汞浓度梯度。具体目标是：1)确定甲基汞的来源和汇；2)检查细菌过程，包括遗传控制和最终分解的作用；3)调查硫和汞循环之间的关系，以及4)开发模拟模型。该项目将由两项重叠的主要活动组成。首先，调查：1)汞转化率；2)引起汞抗性的细菌基因的表达；3)模型的速率将被开发和验证，并用于微调未来的采样计划。其次，该计划将解决以下假设：1)汞浓度和形态形成之间的相互作用；2)细菌作为甲基汞的生产者和消费者的作用；3)遗传和甲基汞浓度的变化；4)悬浮颗粒的作用；以及5)沉积物中甲基汞的通量。模拟模型将使用生物地球化学数据进行改进，并用于预测目的。该项目将提供必要的数据，用于确定控制半干旱生态系统中鱼类和其他高等生物体内甲基汞的积累，并将有助于与潮湿和北方环境进行比较。总体而言，这项研究将区分对甲基汞的生产、降解和运输影响最大的水生系统的各个方面，甲基汞是地球上最危险的污染物之一。

9523894 Hines The biogeochemistry of mercury is important because of the toxicity of methylmercury, its accumulation in biota, and its biomagnification in food chains. A knowledge of the concentration, transport, and dynamics of methylmercury is needed to predict its potential impact on human and aquatic life. The proposed program combines biogeochemical, microbiological, and molecular investigations of the formation and degradation of methylmercury with certain abiotic factors, and a robust modeling effort, to depict factors controlling methylmercury dynamics in the Carson River/Lahontan Reservoir System in Nevada. The Carson System received 7000 tons of elemental mercury during the 19th century for gold amalgamation, and now provides a strong gradient in mercury concentrations. Specific goals are to: 1) locate sources and sinks of methylmercury; 2) examine bacterial processes including genetic controls and the role of terminal decomposition; 3) investigate the relationship between the sulfur and mercury cycles, and 4) develop simulation models. The project will consist of two major overlapping activities. First, surveys of : 1) rates of mercury transformation; 2) expression of bacterial genes incurring mercury resistance; 3) rates of model will be developed and validated, and used to fine tune future sampling programs. Second, the program will address hypotheses encompassing: 1) interactions among mercury concentration and speciation; 2) the role of bacteria as producers and consumers of methylmercury; 3) changes in genetics and methylmercury concentrations; 4) the role of suspended particles, and; 5) fluxes of methylmercury from sediments. The simulation model will be refined using biogeochemical data and used for predictive purposes. The project will provide data essential for determining controls on the accumulation of methylmercury in fish and other higher forms of life in semi-arid ecosystems, and will be useful for comparison to wet and northern environments. In general, the research will distinguish aspects of aquatic systems that most influence the production, degradation, and transport of methylmercury, one of the Earth's most insidious pollutants.