SGER:Collaborative Research: Assessing the Impact of Hurricanes on Mercury Biogeochemistry and Methylation in the Gulf of Mexico

康涅狄格大学和哈佛大学公共卫生学院的研究人员将利用这一探索性研究小额赠款提供的资金，调查飓风卡特里娜和丽塔对墨西哥湾汞生物地球化学和甲基汞形成的影响。汞以甲基汞的形式存在，是一种神经毒素，在水生食物链中生物放大，对人类健康有影响。食用海鲜是接触的重要途径。然而，人们对甲基汞(甲基化)产生的地点和影响因素知之甚少，甲基汞主要是由硫酸盐还原细菌(SRB)在沉积物中进行的。海岸带是甲基化的重要场所之一。汞的甲基化速率取决于SRB的活性和可供SRB吸收的汞(II)。任何环境扰动，如风暴干扰，改变了SRB的活动或汞(II)的可获得性，都有可能影响汞的甲基化速率。将探讨以下假设：(1)飓风卡特里娜和丽塔通过混合和重新沉积上层沉积物扰乱了沉积物，这将导致这些沉积物中氧化还原条件的重要变化，以及这些沉积物中已经存在的汞的形态和不稳定；(2)飓风产生的径流导致汞(Ii)通过密西西比河和阿查法拉亚R进入GOM，当沉积时，可能比海湾沉积物中的当前汞更可用于甲基化；(3)密西西比河和阿查法拉亚河还向GOM输送了新鲜的陆地有机碳，以及一系列营养物质，这将导致海洋有机碳产量的增加。这种有机碳的很大一部分将最终进入沉积物，并增强SRB的活性，结果是导致汞甲基化增强。？4)有机碳投入的增加和生产力的提高将促进水柱缺氧，进而提高甲基化和/或甲基汞水平。2005年秋季和2006年春季，将从路易斯安那州海岸受卡特里娜飓风或丽塔飓风影响的地区的多个地点收集沉积物岩芯和水样，以检验这些假设。将测定沉积物岩心中汞的甲基化和去甲基化速率，以及总汞和甲基汞。将测量短寿命(234，7Be)和长寿命(210Pb)放射性同位素，以表征沉积物沉积历史。在更广泛的影响方面，这项研究将有助于确定飓风(和其他主要风暴事件)对汞生物地球化学的影响程度，并评估将飓风/风暴影响纳入甲基汞年度生产预算的必要性。它还将为研究生和博士后提供研究机会，并将提供科学家、管理人员和普通公众感兴趣的信息。

ABSTRACTOCE-0601098 / OCE-0600624With funding from this Small Grant for Exploratory Research (SGER), investigators at the University of Connecticut and the Harvard School of Public Health will investigate the impacts of Hurricanes Katrina and Rita on mercury (Hg) biogeochemistry and the formation of methylmercury (MeHg) in the Gulf of Mexico (GOM). Mercury in the form of MeHg is a neurotoxin that biomagnifies in aquatic food chains and has human health impacts. Seafood consumption is an important route of exposure. Little is known, however, about the locations and factors influencing the production of MeHg (methylation), which is carried out primarily in sediments by sulfate reducing bacteria (SRB). Coastal zones are one important location for methylation. Hg methylation rates depend on both the activity of SRB and availability of Hg(II) for uptake by SRB. Any environmental perturbation, such as storm disturbance, that alters SRB activity or the availability of Hg(II) has the potential to impact Hg methylation rates. The following hypotheses will be explored: (1)?Hurricanes Katrina and Rita have disrupted sediments by mixing and redepositing the upper layer of sediments, which will have resulted in important changes in redox conditions, and in the speciation and lability of Hg already present in these sediments; (2)?hurricane-derived runoff has resulted in a substantial pulse of Hg(II) via the Mississippi R. and Atchafalaya R. into the GOM, which, when deposited, is likely more available for methylation than the current Hg in Gulf sediment; (3) the Mississippi and Atchafalaya Rivers have also transported fresh terrestrial organic carbon into the GOM, along with a pulse of nutrients that will lead to enhanced production of marine organic carbon. A large fraction of this organic carbon will end up in the sediments and enhance SRB activity, and, as a result, lead to enhanced mercury methylation. ?4) increased inputs of organic carbon and the enhanced productivity will promote water column hypoxia, which in turn will enhance methylation and/or methylmercury levels.These hypotheses will be tested by collecting sediment cores and water samples during Fall 2005 and Spring 2006 from multiple locations along the Louisiana coast in areas that have been impacted by Hurricane Katrina or Rita. Hg methylation and demethylation rates will be determined in sediment cores, along with total Hg and MeHg. Short-lived (234Th, 7Be) and longer-lived (210Pb) radioisotopes will be measured to characterize sediment deposition history. Indicators of sediment redox conditions will also be measured.In terms of broader impacts, this research will help determine the degree to which hurricanes (and other major storm events) impact Hg biogeochemistry and assess the need for incorporating hurricane/storm impacts into annual MeHg production budgets. It will also provide research opportunities for graduate students and post-docs, and will provide information of interest to scientists, managers and the general public.