Collaborative Research: Mercury Cycling in Soils: Dynamic Sources for Aquatic Environments

由于甲基汞的毒性和生物放大作用，水生系统中汞的生物地球化学已受到相当大的关注。然而，进入水体的甲基汞大部分来自土壤。该计划将利用多学科方法，以内华达州卡森河为试验点，调查土壤中汞甲基化的控制因素及其向水生系统的迁移。现场和实验室调查将包括分析汞的形态，测量汞的甲基化、去甲基化和还原，负责汞转化的细菌基因的分布和表达，以及汞生物传感器在调查汞的生物有效性方面的应用。将进行操纵性实验，以确定湿、干循环和氧气可用性对汞循环途径的影响。生物地球化学/分子结果将被用来极大地改进汞的传输模型，该模型将在低流量和高流量条件下进行经验测试。研究结果将描述对污染场地中甲基汞净形成和最终迁移的控制，并将有助于了解土壤在总体上控制甲基汞污染的作用。这项建议是应环境地球化学和生物地球化学征集NSF 99-9的要求提交的，由化学部、地球科学部和海洋科学部联合资助。

Lyons9975414The biogeochemistry of mercury in aquatic systems has received considerable attention because of the toxicity and biomagnification of methylmercury. However, much of the methylmercury entering water bodies is derived from soils. This program will utilize a multidisciplinary approach to investigate factors controlling mercury methylation in soils and its transport into aquatic systems using the Carson River, Nevada as the test site. Field and laboratory investigations will include analysis of mercury speciation, measurements of methylation, demethylation, and reduction of mercury, the distribution and expression of bacterial genes responsible for mercury transformations, and application of a mercury biosensor for investigating mercury bioavailability. Manipulative experiments will be conducted to determine effects of wetting and drying cycles and oxygen availability on pathways of mercury cycling. The biogeochemical/molecular results will be used to greatly improve a mercury transport model, which will be tested empirically during low and high flow conditions. The results will delineate controls on net methylmercury formation and eventual transport in a contaminated site, and will be useful for understanding the role of soils in controlling methylmercury pollution in general.This proposal was submitted in response to the Environmental Geochemistry and Biogeochemistry solicitation NSF 99-9, and is being funded jointly by the Divisions of Chemistry, Earth Sciences, and Ocean Sciences.