Collaborative Research: Field Investigation of Se Oxvanion Reduction and Se Sources in Wetlands: Application of Se Isotopes

本项目将应用硒（Se）稳定同位素比值作为了解硒在湿地迁移和化学转化的新工具。硒污染对美国西部许多湿地、飞灰处理区和世界其他地区的野生动物构成威胁。硒的复杂化学性质决定了该元素的流动性和生物利用度，而了解其在湿地中的长期循环和运输的努力取决于对湿地化学转化的准确理解。该小组先前的工作表明，硒同位素比值测量可以用作还原反应的指标，还原反应将硒氧阴离子转化为流动性和生物可利用性较低的形式。本研究将通过在蒙大拿州本顿湖国家野生动物保护区的硒污染湿地进行首次详细的硒同位素实地研究，解决该工作中出现的关键问题。主要目的是利用这种新技术确定硒的还原率，并限制细菌还原与植物和藻类同化的相对重要性。这项工作将包括对浓度、硒同位素比率和相关地球化学变量的详细测量，包括表层水、沉积物孔隙水、沉积物成分和微观实验。采样时间将根据水管理和生物地球化学的季节变化而定。如果可能的话，来自不同来源的硒将通过它们的同位素“特征”通过系统进行追踪。本研究为博士课题，研究生将接受环境地球化学、水文地质学、同位素地球化学和地球微生物学等方面的培训。

0003381JohnsonThis project will apply selenium (Se) stable isotope ratios as a new toolfor understanding the transport and chemical transformations of Se inwetlands. Se contamination poses a threat to wildlife in many wetlandareas of the western United States, in fly-ash disposal areas, and in othersettings worldwide. The complex chemistry of Se determines the element'smobility and bioavailability, and efforts to understand its long-termcycling and transport in wetlands depend on accurate understanding ofchemical transformations there.Previous work by this group suggests that Se isotope ratio measurements canbe used as indicators of reduction reactions, which transform Se oxyanionsinto forms that are less mobile and less bioavailable. The present studywill address critical questions arising from that work by performing thefirst detailed Se isotope field study, at a Se-contaminated wetland atBenton Lake National Wildlife Refuge, Montana. The primary objectives areto determine Se reduction rates using this new technique and constrain therelative importance of reduction by bacteria versus assimilation by plantsand algae. The work will involve detailed measurements of Seconcentrations, Se isotope ratios, and related geochemical variables insurface water, sediment pore waters, sediment components, and microcosmexperiments. Sampling will be timed according to seasonal variations inwater management and biogeochemistry. If possible, Se from the varioussources will be traced through the system via their isotopic "signatures".The study is designed as a Ph.D. project for a graduate student, who willbe trained in environmental geochemistry, hydrogeology, isotopegeochemistry and geomicrobiology.