Linking hydrology with biogeochemistry using stable isotopes to understand the consequences of ecosystem disturbance

了解污染物如何在环境中移动和转化，对于制定减轻污染物影响的计划非常重要。 一些污染物，包括重金属，与土壤和环境中的其他固体强烈结合。 尽管有这种亲和力，但当土壤被暴雨或融雪冲刷时，这些污染物继续进入水生生态系统。 在适当的空间和时间尺度上将水的流动和环境中的化学反应联系起来是困难的，但对于提供处理不断变化的污染程度和可能的环境改变（气候变化、伐木）所需的过程信息至关重要。 最近在涉及浓缩稳定（非放射性）同位素的技术方面取得的进展应能为将这些过程联系起来提供一种手段。 这项研究计划中要研究的污染物是汞，一种有毒金属。 汞是特别危险的，因为它可以在环境中发生化学转化，形成甲基汞，一种在鱼类和野生动物中积累的强效神经毒素。 食用鱼类是人类接触的主要途径。 通过使用稳定同位素进行的一系列受控实验室和实地实验，这项研究将首先调查和开发汞如何在森林和湿地等生态系统分区之间移动的模型。 然后将调查这种移动的空间和时间变异性及其对甲基汞生产的影响。 这一信息将用于直接测试伐木如何影响汞在流域中的移动和转化。 总之，这些知识将使模型有更多的预测可能性，更好地了解土地使用变化如何影响汞循环，并有机会制定有效的战略，防止流域进一步的甲基汞污染。

Understanding how pollutants move through the environment and are transformed within it is important to developing plans for mitigating pollutant effects. Some pollutants, including heavy metals, strongly bind to soil and other solids in the environment. Despite this affinity, these pollutants continue to move into aquatic ecosystems when soils are flushed by rainstorms or melting snow. Linking the movement of water and chemical reactions in the environment together at appropriate spatial and temporal scales is difficult, but critical to providing the process information necessary to deal with changing levels of pollution and possible alterations to the environment (climate change, logging). Recent advances in techniques involving enriched stable (non-radioactive) isotopes should provide a means for linking these processes. The pollutant to be studied in this research program is mercury, a toxic metal. Mercury is particularly dangerous because it can undergo biogeochemical transformations in the environment that form methylmercury, a potent neurotoxin that accumulates in fish and wildlife. The consumption of fish is the primary pathway for human exposure. Through a number of controlled laboratory and field experiments using stable isotopes, this research will first investigate and develop a model of how mercury moves between ecosystem compartments such as forests and wetlands. It will then investigate the spatial and temporal variability of this movement and its effects on the production of methylmercury. This information will be used to directly test how logging affects the movement and transformation of mercury in watersheds. Together, this knowledge will lead to more predictive possibilities from models, an improved understanding of how land-use changes affect mercury cycling, and an opportunity to develop effective strategies for preventing further methylmercury pollution in watersheds.