Collaborative Research: Isotopic insights to mercury in marine food webs and how it varies with ocean biogeochemistry

合作研究：海洋食物网中汞的同位素见解及其如何随海洋生物地球化学变化

• 批准号: 1433313
• 负责人: Claudia Benitez-Nelson
• 金额: $ 36.22万
• 依托单位: University of South Carolina at Columbia
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1433313&HistoricalAwards=false
• 关键词: Collaborative; Research; Isotopic; insights; mercury

Mercury is a pervasive trace element that exists in several states in the marine environment, including monomethylmercury (MMHg), a neurotoxin that bioaccumulates in marine organisms and poses a human health threat. Understanding the fate of mercury in the ocean and resulting impacts on ocean food webs requires understanding the mechanisms controlling the depths at which mercury chemical transformations occur. Preliminary mercury analyses on nine species of marine fish from the North Pacific Ocean indicated that intermediate waters are an important entry point for MMHg into open ocean food webs. To elucidate the process controlling this, researchers will examine mercury dynamics in regions with differing vertical dissolved oxygen profiles, which should influence depths of mercury transformation. Results of the study will aid in a better understanding of the pathways by which mercury enters the marine food chain and can ultimately impact humans. This project will provide training for graduate and undergraduate students, and spread awareness on oceanic mercury through public outreach and informal science programs. Mercury isotopic variations can provide insight into a wide variety of environmental processes. Isotopic compositions of mercury display mass-dependent fractionation (MDF) during most biotic and abiotic chemical reactions and mass-independent fractionation (MIF) during photochemical radical pair reactions. The unusual combination of MDF and MIF can provide information on reaction pathways and the biogeochemical history of mercury. Results from preliminary research provide strong evidence that net MMHg formation occurred below the surface mixed layer in the pycnocline and suggested that MMHg in low oxygen intermediate waters is an important entry point for mercury into open ocean food webs. These findings highlight the critical need to understand how MMHg levels in marine biota will respond to changes in atmospheric mercury emissions, deposition of inorganic mercury to the surface ocean, and hypothesized future expansion of oxygen minimum zones. Using field collections across ecosystems with contrasting biogeochemistry and mercury isotope fractionation experiments researchers will fill key knowledge gaps in mercury biogeochemistry. Results of the proposed research will enable scientists to assess the biogeochemical controls on where in the water column mercury methylation and demethylation likely occur.

汞是一种普遍存在的微量元素，存在于海洋环境的多个州，其中包括一甲基汞（MMHg），这是一种神经毒素，在海洋生物中生物累积并对人类健康构成威胁。要了解汞在海洋中的命运及其对海洋食物网的影响，就需要了解控制汞化学转化发生深度的机制。对北太平洋9种海洋鱼类的初步汞分析表明，中间沃茨是MMHg进入公海食物网的重要入口。为了阐明控制这一过程，研究人员将研究具有不同垂直溶解氧分布的区域中的汞动态，这应该会影响汞转化的深度。研究结果将有助于更好地了解汞进入海洋食物链并最终影响人类的途径。该项目将为研究生和本科生提供培训，并通过公共宣传和非正式科学方案传播对海洋汞的认识。汞同位素的变化可以提供对各种环境过程的洞察。汞的同位素组成在大多数生物和非生物化学反应中表现为质量相关分馏（mass dependent fractionation，简称QF），而在光化学自由基对反应中表现为质量无关分馏（mass independent fractionation，简称MIF）。这种不寻常的结合，可提供汞的反应途径和地球化学史的信息。初步研究结果提供了强有力的证据，净MMHg的形成发生在密度跃层的表面混合层以下，并建议MMHg在低氧中间沃茨是一个重要的入口点汞进入开放的海洋食物网。这些研究结果强调，迫切需要了解海洋生物群中的MMHg水平将如何应对大气汞排放的变化，无机汞沉积到海洋表面，以及假设未来氧气最小区的扩张。研究人员将通过生态系统的实地收集与对比汞地球化学和汞同位素分馏实验相结合，填补汞地球化学领域的关键知识空白。拟议的研究结果将使科学家能够评估汞甲基化和去甲基化可能发生在水柱中的位置的生物化学控制。