Collaborative Proposal: "SG" Identifying Sources and Degradation Mechanisms of Methylmercury in Temperate Forest Ecosystems

该项目旨在了解汞的循环，包括其在陆地系统中转化为剧毒形式甲基汞的机制。汞自然存在于生态系统中，但也来自人类来源。甲基汞生物积累在食物网中，并可能威胁到鸣禽等森林生物。这项研究将使用森林食物网的汞稳定同位素分析来检查美国四个不同温带森林中的汞循环。这项技术可以对森林生物中的甲基汞进行指纹识别，并帮助确定包括雨水、土壤和树叶在内的路径和来源。在获得所有样本的同位素指纹后，将使用统计模型估计每个来源(降水、土壤和树叶)对森林食物网中甲基汞积累的相对贡献。研究人员基于两个令人惊讶的发现进行了这项研究：1)土壤中的甲基汞含量很高(令人惊讶的是，森林土壤不缺氧)；2)土壤中的甲基汞正在被降解，因此汞的负载量比之前预测的要高得多。拟议的工作将为北卡罗来纳大学格林斯伯勒分校和密歇根大学不同学术背景的本科生和研究生提供独特的培训机会。首席调查员将把这项研究纳入两个机构的课堂，包括实地考察和个案研究。首席调查员还将以网站的形式开展公众宣传，旨在向非科学受众突出汞对野生动物的调查结果和影响。

This project is aimed at understanding the cycling of mercury, including the mechanisms of its transformation into the highly-toxic form, methylmercury, in terrestrial systems. Mercury is naturally present in ecosystems, but also comes from human sources. Methylmercury bio-accumulates in food webs and can threaten forest organisms such as songbirds. This research will examine mercury cycling in four different temperate forests across the United States using mercury stable isotope analysis of forest food webs. This technique can fingerprint the methylmercury in forest organisms and help determine the pathways and sources including rain, soil and tree leaves. After obtaining the isotope fingerprint of all samples, statistical models will be used to estimate the relative contribution of each source (precipitation, soil and tree leaves) to methylmercury accumulation in forest food webs. The investigators are basing this research on two surprising findings: 1) that methylmercury is high in soils (surprising because forest soils are not anoxic); and 2) that methylmercury is being degraded in soils, and thus the mercury loading is much higher than previously predicted. The proposed work will provide unique training opportunities for undergraduate and graduate students of different academic backgrounds from both the University of North Carolina at Greensboro and the University of Michigan. The principal investigators will integrate this research into classes at both institutions, including field visits and case studies. The principal investigators will also carry out public outreach in the form of a website intended to highlight the findings and impacts of mercury on wildlife to non-scientific audiences.