International Research Fellowship Program: The Influence of Sulfur Cycling on Mercury Methylation in Rice Paddies in the Mining Areas Guizhou Province, China

[0802014 .罗森伯格国际研究奖学金计划使美国科学家和工程师能够在国外进行9到24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持Sarah Rothenberg博士与中国贵阳环境地球化学国家重点实验室Feng Xinbin博士进行为期24个月的研究。贵州省位于中国西南部，由于历史上对朱砂的开采、工业径流、手工炼锌、城市垃圾的焚烧以及依赖燃煤电厂为经济增长提供燃料和为住宅供暖，贵州省受到了严重的汞污染。汞的径流和残留物污染了空气、水、土壤以及包括大米在内的农产品。尽管大多数人通过食用鱼类接触汞，但也可能通过摄入大米接触汞，这种接触途径在以大米为主食的国家可能很重要。与湿地一样，稻田是无机汞转化为有毒的单甲基汞（MMHg）的潜在热点。PI正在进行一项研究，以确定在哪种水文和生物地球化学制度下，稻田中MMHg浓度最高，可用于制定缓解战略。有两个研究组成部分。(1) PI表征了至少4个稻田内灌溉水、缺氧孔隙水和沉积物中硫循环和汞甲基化的特征，其中一半采用传统灌溉方法，一半采用节水方法。(2) PI还在相同的四个稻田中部署了一系列嵌入式传感器网络，分别在早春和夏末，以配合水稻生长季节的开始和结束。时间序列传感器测量的氧氧化还原电位和pH值将与孔隙水MMHG水平相关联，以确定在哪种条件下MMHG产量最高。本研究将回答以下问题：稻田是汞甲基化的热点吗？硫在表层土壤、缺氧块状土壤和根际的循环如何影响汞甲基化？淹水稻田和节水稻田有什么区别？孔隙水氧化还原电位（ORP）和pH值的时间/季节变化如何影响汞的形态？这个项目是中美研究人员之间的桥梁，也是一个合作项目，将环境科学家、工程师和计算机科学家聚集在一起，共同关注一个关键的环境问题。

0802014RothenbergThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four month research fellowship by Dr. Sarah Rothenberg to work with Dr. Xinbin Feng at State Key Laboratory of Environmental Geochemistry in Guiyang, China.Guizhou Province, located in southwestern China, is highly contaminated with mercury (Hg) due to historical mining of cinnabar, industrial runoff, artisinal zinc smelting, incineration of municipal wastes, and reliance on coal-burning power plants to fuel economic growth and heat residential homes. Hg runoff and residues have contaminated the air, water, soil, as well as agricultural products, including rice. Even though most human exposure to Hg occurs through the consumption of fish, Hg exposure may also occur through the ingestion of rice, and this exposure pathway may be important in countries where rice is a staple. Like wetlands, rice paddies are potential hot spots for the conversion of inorganic Hg to toxic mono-methylmercury (MMHg). The PI is conducting a study to determine under which hydrologic and biogeochemical regimes highest MMHg concentrations occur in rice paddies, which may be used to develop mitigation strategies. There are two research components. (1) The PI is characterizing sulfur cycling and Hg methylation within irrigation water, anoxic pore water and sediments within at least four rice paddies, half using traditional methods of irrigation and half using water saving methods. (2) The PI is also deploying a series of embedded sensor networks within the same four rice paddies in the early spring and in the late summer to coincide with the start and end of the rice growing season. Time series sensor measurements of oxygen redox potential and pH will be correlated with pore water MMHG levels to determine under which conditions MMHg production is highest. This study will answer the following questions: Are rice paddies hot spots for Hg methylation? How does sulfur cycling in the surface soil, anoxic bulk soil, and rhizosphere affect Hg methylation? Are there differences between flooded rice paddies and rice paddies that employ water-saving methods? How do temporal/seasonal changes in pore water oxidation-reduction potential (ORP) and pH affect Hg speciation?This project serves as a bridge between US and Chinese researchers, and is also collaborative, bringing together environmental scientists, engineers and computer scientists to focus on an critical environmental problem.