The effects of solar radiation and dissolved organic matter on contaminant fate in freshwater ecosystems

目前还不清楚为什么加拿大的一些湖泊有高污染水平的鱼类和动物，而其他类似的湖泊没有。已知污染物的形态（或化学形式）是控制其在生态系统中移动和被生物体吸收的关键因素。物种形成又受到光化学反应的控制，光化学反应以不同的方式对太阳辐射的变化作出反应，并与溶解的有机物（DOM）（植物和动物物质的腐烂产物）相互作用。然而，这些变量之间的确切关系知之甚少。我的研究计划的总体目标是确定太阳辐射和DOM对淡水污染物命运的影响。更具体地说，我将从一系列湖泊中收集水样，并描述DOM结构的差异。然后，我将使用受控实验室实验来测试DOM结构和不同波段的辐射对控制污染物命运和物种形成的光化学反应的影响。最初的重点将放在汞上，汞具有广泛的有机和无机特性，因此可用作其他污染物的模型系统。汞也是一种剧毒污染物，由于其广泛的分散性，它既是一个区域性问题，也是一个全球性问题。我预计，这项研究将导致预测模型，描述控制污染物的物种形成和生态系统的命运的关键因素。这将提高我们预测哪些淡水生态系统最有可能在生物体中积累大量污染物的能力。这反过来将有利于加拿大，因为它支持有效的监管政策和缓解措施，以保护敏感的淡水生态系统及其所维持的人类和野生动物种群的健康。

It is currently unclear why some lakes in Canada have fish and animals with high levels of contaminants while other similar lakes do not. The speciation of contaminants (or chemical form) is known to be a key factor controlling their movement in ecosystems and uptake by organisms. Speciation in turn is controlled by photochemical reactions which respond in different ways to changes in solar radiation, and interactions with dissolved organic matter (DOM) (the decay products of plant and animal matter). However, the exact relationships between these variables are poorly understood. The general goal of my research program is to determine the effects of solar radiation and DOM on contaminant fate in freshwaters. More specifically, I will collect water samples from a range of lakes and characterize differences in DOM structure. I will then use controlled laboratory experiments to test the effects of DOM structure and different wavebands of radiation on the photochemical reactions that control the fate and speciation of contaminants. The initial focus will be on mercury, which has a wide range of organic and inorganic properties, and is therefore useful as a model system for other contaminants. Mercury is also a highly toxic contaminant and due to its wide dispersion it is both a regional and a global concern. I anticipate that this research will result in predictive models that describe key factors controlling contaminant speciation and fate in ecosystems. This will increase our ability to predict which freshwater ecosystems are most likely to have significant contaminant accumulations in organisms. This in turn will benefit Canada by supporting effective regulatory policies and mitigative measures to protect the health of sensitive freshwater ecosystems and the human and wildlife populations that they sustain.