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

利用这项探索性研究小额赠款（SGER）的资金，康涅狄格大学和哈佛公共卫生学院的研究人员将调查卡特里娜飓风和丽塔飓风对墨西哥湾（GOM）汞（Hg）地球化学和甲基汞（MeHg）形成的影响。 甲基汞是一种神经毒素，在水生食物链中会产生生物放大作用，对人类健康产生影响。 食用海鲜是一个重要的接触途径。 然而，人们对影响甲基汞（甲基化）产生的地点和因素知之甚少，甲基汞主要是在沉积物中由硫酸盐还原菌（SRB）产生的。沿海地区是甲基化的一个重要场所。汞甲基化速率取决于SRB的活性和SRB吸收Hg（II）的可用性。任何环境扰动，如风暴扰动，改变SRB活动或汞（II）的可用性有可能影响汞甲基化率。本文将探讨以下假设：（1）？卡特里娜飓风和丽塔飓风破坏了沉积物的混合和再沉积的上层沉积物，这将导致氧化还原条件的重要变化，并在汞的形态和不稳定性已经存在于这些沉积物;（2）？飓风径流导致大量Hg（II）脉冲流经密西西比河。和Atchafalaya R.（3）密西西比河和阿查法拉亚河也将新鲜的陆地有机碳输送到墨西哥湾，沿着的营养物质脉冲将导致海洋有机碳的增加。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，因此，导致汞甲基化的增强。? 4)增加有机碳的投入和提高生产力将促进水体缺氧，这反过来又会提高甲基化和/或甲基汞的水平。这些假设将通过收集沉积物岩心和水样在2005年秋季和2006年春季从多个地点沿着路易斯安那州海岸地区已受到卡特里娜飓风或丽塔的影响进行测试。汞甲基化和去甲基化率将在沉积物芯中确定，沿着还有总汞和甲基汞。将测量短寿命（234 Th，7 Be）和长寿命（210 Pb）放射性同位素，以表征沉积物沉积历史。就更广泛的影响而言，这项研究将有助于确定飓风（和其他重大风暴事件）对汞地球化学的影响程度，并评估将飓风/风暴影响纳入年度甲基汞生产预算的必要性。 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.