RAPID: Transformation of Elemental Mercury Dispersed by Flooding During Hurricane Harvey

2017年8月，飓风哈维在德克萨斯州东南部造成灾难性洪水，并将液态元素汞[Hg（0）]从未知来源分散到休斯顿以东地区。 飓风过后几天进行的初步测量显示，圣哈辛托河洪泛区沉积物中的汞浓度超过2500毫克/千克。由于汞是一种剧毒元素，飓风引起的污染可能对公众健康构成重大威胁。 本项目旨在阐明圣哈辛托河沉积物中元素汞[Hg（0）]甲基化的地球化学控制。将收集洪泛区和河流沉积物样本，并分析汞甲基化活性。国家科学基金会的资金将用于培训罗格斯大学的研究生和本科生开展实地工作和实验室汞分析。考察被哈维飓风驱散的圣哈辛托河沉积物中元素汞的转化是研究元素汞释放后不久在沉积物中的命运的一个独特机会，并将为开发精确的污染物传输模型和未来的修复工作提供关键信息。并将细胞内的汞转化为甲基汞。然而，这一微生物过程在污染沉积物中的发生情况尚未得到调查，微生物群落对液态Hg（0）的厌氧甲基化作用仍然知之甚少。 在本项目中，将利用沿着圣哈辛托河采集的河漫滩和河流沉积物样品来检验两个假设：1）受污染沉积物中的元素汞在缺氧、水饱和条件下转化为甲基汞;在好氧条件下，元素汞被氧化，但不被甲基化; 2）沉积物中汞浓度升高会由于对微生物群落的毒性影响而抑制汞甲基化。罗格斯大学的研究小组和学生将进行实验室实验，以检验这些假设，目的是获得对污染沉积物中Hg（0）氧化和甲基化的地球化学控制的新见解。 NSF基金将用于培养2名博士。学生和2名本科生。学生将获得跨学科的经验，在地球化学和微生物学作为国家？环境地球科学的最新学科。这一项目的成果将通过同行审查的出版物和在国家会议上的介绍加以传播。通过阐明促进甲基汞生产的地球化学条件，调查人员旨在更好地告知当地公共卫生官员和环境管理人员与此污染事件相关的可能危险。

In August 2017, Hurricane Harvey caused catastrophic flooding in southeastern Texas and dispersed liquid elemental mercury [Hg(0)] from an unknown source to an area east of Houston. Preliminary measurements performed days after the hurricane showed mercury concentrations exceeding 2500 mg/kg in floodplain sediments of the San Jacinto River. Because mercury is a highly toxic element, the hurricane-induced contamination may pose a significant threat to public health. This project aims to elucidate the geochemical controls on the methylation of elemental mercury [Hg(0)] in San Jacinto River sediments. Floodplain and river sediment samples will be collected and analyzed for mercury methylation activity. NSF funds will be used to train graduate and undergraduate students at Rutgers University to carry out field work and laboratory mercury analyses. An examination of the transformations of elemental mercury in San Jacinto River sediments dispersed by Hurricane Harvey is a unique opportunity to investigate the fate of elemental mercury in sediments shortly after release and will provide critical information for the development of accurate contaminant transport models and future remediation efforts.Recent laboratory experiments have shown that certain anaerobic bacteria can take up dissolved Hg(0) and transform intracellular Hg to methylmercury. However, the occurrence of this microbial process in contaminated sediments has not been investigated, and anaerobic methylation of liquid Hg(0) by microbial communities remains poorly understood. In this project, floodplain and river sediment samples collected along the San Jacinto River will be used to test two hypotheses: 1) Elemental mercury in contaminated sediments is converted to methylmercury under anoxic, water-saturated condition; under oxic conditions, elemental mercury is oxidized, but not methylated; and 2) Elevated mercury concentrations in sediments inhibits mercury methylation due to toxicity effects on the microbial community. Laboratory experiments carried out by the research team and students at Rutgers University will test these hypotheses with the goal of obtaining new insights into the geochemical controls on Hg(0) oxidation and methylation in contaminated sediments. NSF funds will be used to train 2 Ph.D. students and 2 undergraduate students. The students will gain interdisciplinary experiences in geochemistry and microbiology as state-of?the-art disciplines in environmental geosciences. The results of this project will be disseminated through peer-reviewed publications and presentations at national conferences. By elucidating the geochemical conditions that promote methylmercury production, the investigators aim to better inform local public health officials and environmental managers about the possible dangers associated with this contamination event.