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并在环境中转化，对于制定减轻污染物影响的计划非常重要。包括重金属在内的一些污染物与环境中的土壤和其他固体紧密结合。尽管有这种亲和力，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把水的运动和环境中的化学反应联系起来是困难的，但对于提供处理污染程度变化和环境可能改变（气候变化、伐木）所必需的过程资料是至关重要的。涉及浓缩稳定（非放射性）同位素的技术的最新进展应提供一种将这些过程联系起来的手段。这个研究项目要研究的污染物是汞，一种有毒金属。汞特别危险，因为它可以在环境中发生生物地球化学转变，形成甲基汞，甲基汞是一种在鱼类和野生动物中积累的强毒性神经毒素。食用鱼类是人类接触的主要途径。通过一些使用稳定同位素的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隔间之间移动的模型。然后，它将调查这一移动的空间和时间变异性及其对甲基汞产生的影响。这些信息将用于直接测试测井如何影响流域中汞的移动和转化。总之，这些知识将提高模型的预测可能性，提高对土地利用变化如何影响汞循环的理解，并有机会制定有效战略，防止流域进一步受到甲基汞污染。

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.