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

0003381约翰逊本项目将应用硒（Se）稳定同位素比值作为一种新的工具，了解硒在湿地中的运输和化学转化。 硒污染对美国西部许多湿地地区、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元素的流动性和生物有效性，而要理解其在湿地中的长期循环和迁移，则取决于对湿地中化学转化的准确理解。该研究小组先前的工作表明，硒同位素比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移动的和生物有效性较低的形式。 目前的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第一次详细的硒同位素实地研究来解决这项工作中出现的关键问题。 主要目的是确定硒的减少率，使用这种新技术，并限制相对重要性的减少细菌与同化植物和藻类。 这项工作将包括地表水、沉积物孔隙沃茨、沉积物成分和微观实验中的硒浓度、硒同位素比值和相关地球化学变量的详细测量。 根据水管理和地球化学的季节性变化来安排取样时间。 如果可能的话，来自不同来源的硒将通过它们的同位素“签名”通过系统进行追踪。该项目是一个研究生项目，将在环境地球化学、水文地质学、同位素地球化学和地球微生物学方面进行培训。

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.