Biogeochemical Framework to Evaluate Mercury Methylation Potential During in-situ

说明(申请人提供)：该项目将建立甲基汞生产的生物地球化学指标，用于提高汞污染沉积物就地修复的有效性。甲基汞(MeHg)是一种强烈的神经毒素，由厌氧微生物产生，并在水生食物网中进行生物放大。沉积物改良剂等就地修复方法尚未得到广泛实施，主要是因为对甲基汞生产的影响尚不清楚。此外，控制汞甲基化的过程在不同地点可能不同，这种不确定性是有效实施就地修复的障碍。该项目旨在通过建立汞甲基化潜力的指标，并利用这些指标来评估沉积物改良剂的补救效果，从而解决这一知识差距。这项研究将侧重于甲基汞生产的两个关键驱动因素：促进产生甲基汞的沉积物微生物生长的环境条件，以及影响这些微生物汞的生物利用率的过程。这两个驱动力之间的平衡将决定原位沉积物处理的成功。在这方面，这项工作的中心假设是，确定固定地点甲基汞生产的主要控制措施将提高沉积物处理的效果。为了验证这一假设，研究小组将应用有关汞生物地球化学的基本知识来改进沉积物中汞甲基化潜力的测定，并比较现场修复沉积物的技术。具体目标是：(1)发展沉积物中甲基化微生物的活动与甲基汞生产之间的关系；(2)改进量化沉积物中汞的生物有效性的方法；(3)确定控制甲基化潜力的因素，并制定地点特征的准则；以及(4)确定沉积物修正技术如何影响甲基汞生产潜力。这项工作将通过实验室沉积物微观实验来实施，这些实验将模拟与汞污染的超级基金地点相关的一系列条件。将使用各种分子生物学和地球化学工具来量化甲基化微生物的活性以及与生物吸收转化为厌氧微生物有关的汞的反应活性。这项工作的新奇之处在于，研究人员将应用最近的发现来开发新的工具来量化汞的甲基化潜力。这些发现包括微生物中汞甲基化的遗传基础和控制沉积物中汞形态的地球化学过程。研究人员将与超级基金地点的管理人员合作，实施研究，解释结果，并为具体外地地点的评估和补救战略的选择建立一个指导框架。

DESCRIPTION (provided by applicant): This project will establish biogeochemical indicators for methylmercury production that will be used to improve the effectiveness of in-situ remediation of mercury-contaminated sediments. Methylmercury (MeHg) is a potent neurotoxin that is produced by anaerobic microorganisms and biomagnifies in the aquatic food web. In-situ remediation methods such as sediment amendments have not been widely implemented, mainly because the effects on MeHg production are unknown. Moreover, the processes that control mercury methylation can differ between sites, and this uncertainty is a barrier for effective implementation of in-situ remediation. This project aims to address this knowledge gap by establishing indicators of mercury methylation potential and using them to assess the effectiveness of sediment amendments for remediation. The research will focus on two critical drivers of methylmercury production: the environmental conditions that promote the growth of sediment microorganisms that produce MeHg and the processes that influence the bioavailability of mercury for these microorganisms. The balance between these two drivers will determine the success of in-situ sediment treatments. In this respect, the central hypothesis of this work is that the identification of the primary controls to methylmercury production at the fied site will improve the efficacy of sediment treatments. To test this hypothesis, the research team will apply fundamental knowledge regarding mercury biogeochemistry to improve the determination of mercury methylation potential in sediments and compare in-situ techniques for sediment remediation. Specific aims are to: (1) Develop relationships between the activity of methylating microorganisms and MeHg production in sediments; (2) Refine methods to quantify mercury bioavailability in sediments; (3) Identify factors that control methylation potential and formulate guidelines for characterization of sites; and (4) Determine how sediment amendment techniques influence methylmercury production potential. This work will be implemented with laboratory sediment microcosm experiments that will simulate a range of conditions relevant to mercury-contaminated Superfund sites. A variety of molecular biological and geochemical tools will be used to quantify the activity of methylating microorganisms and the reactivity of mercury as related to biouptake into anaerobic microorganism. The novelty of this work is that the researchers will apply recent discoveries to develop new tools to quantify mercury methylation potential. These discoveries include the genetic basis of mercury methylation in microorganisms and the geochemical processes controlling mercury speciation in sediments. The researchers will work with managers of Superfund sites in the implementation of the research, interpretation of the results, and also in the establishment of a guiding framework for assessments at specific field sites and the selection of remediation strategies.