METAALICUS Part II: The Fate of Mercury in Watersheds and the Recovery of Lake 658 from Elevated Mercury Deposition

该项目建立在正在进行的大规模实验的基础上，六年来，汞一直被添加到包括旱地森林、湿地及其相关湖泊在内的整个流域。其目标是了解痕量金属的循环，并评估新沉积的物质如何通过分水岭进入湿地和湖泊。在这项实验中，最初使用不同的富集型稳定同位素对高地、湿地和湖泊进行了添加，因此现在可以确定这些生态系统内部和之间的生物地球化学循环的途径。鱼类中的甲基汞水平对直接添加到湖中的汞做出了快速反应。但到目前为止，几乎所有应用于分水岭的汞都留在了那里，这是通过内部生态系统循环和保留的生物地球化学机制实现的，这些机制尚不清楚。研究人员有一个独特的机会来确定导致高度滞留的生物地球化学机制。将确定对汞在植被、矿物土壤、土壤和沉积物有机成分之间的吸收、储存、转化和移动的控制。结果将揭示痕量金属在不同类型的生态系统中循环的时间尺度，这是一个对模拟未来动态至关重要的主要未知变量。了解湖泊对沉积物增加作出反应的时间尺度对于制定环境政策尤为重要。这一跨学科项目将通过对研究生和博士后助理的支持产生教育影响。

This project builds on ongoing, large-scale experiments where for six years mercury has been added to whole watersheds including upland forests, wetlands and their associated lakes. The goal is to understand trace metals cycling and to assess how newly deposited substances move through the watershed into wetlands and lakes. In this experiment, additions were originally made to the uplands, wetlands and lakes using different enriched stable isotopes, so that now the pathways of biogeochemical cycling within and among these ecosystems can be determined. Methylmercury levels in fish responded rapidly to the mercury added directly to the lake. But almost all of the mercury applied to the watershed has thus far remained there, through biogeochemical mechanisms of internal ecosystem recycling and retention that remain unknown. Researchers have a unique opportunity to determine the biogeochemical mechanisms responsible for the high degree of retention. Controls over the uptake, storage, transformation and movement of mercury among the vegetation, mineral soil, and soil and sediment organic components will be determined. The results will reveal the time scales at which trace metals are cycled in different types of ecosystems, a major unknown variable critical to modeling future dynamics. Knowing the time scale at which lakes respond to increases in deposition is especially important for the formulation of environmental policy. This interdisciplinary project will have educational impacts through support of graduate students and post-doctoral associates.