Environmental Geochemistry of Chromium and Selenium: Spectroscopy, Solution Chemistry, Electrochemistry, and Collaborative Field Studies

该项目重点研究控制土壤、沉积物和自然水体中铬和硒的地球化学行为的因素，特别是那些影响它们在普通氧化物和粘土矿物表面吸附的因素。它整合了磁铁矿、高岭石和蒙脱石的表面地球化学的实验室研究，以及硒在这些矿物上的吸附和氧化还原行为，铬在磁铁矿上的吸附和氧化还原行为，以及由USGS和LBL的助理研究员进行的磁铁矿和粘土沉积物中铬和硒的环境地球化学的几个正在进行的现场调查。本研究的目标是：(1)定量定义吸附在磁铁矿上的Cr（III）和Cr（VI）配合物以及吸附在磁铁矿、高岭石和蒙脱石上的Se（IV）和Se（VI）配合物的化学计量学、几何形状和组成；(2)利用各种光谱和散射技术对吸附前后的磁铁矿表面进行表征；(3)利用我们的光谱测量结果来开发预测铬和硒离子的吸附行为和流固分配的宏观模型；(4)研究了自然沉积物和土壤中铬和硒的形态。提议的研究建立在nsf资助的无机溶质在矿泉水界面的吸附过程研究的基础上，是对氧化还原敏感的无机溶质系统的自然延伸。

9406490 Brown This project focuses on factors that control the geochemical behavior of Cr and Se in soils, sediments, and natural waters particularly those affecting their sorption on the surfaces of common oxide and clay minerals. It integrates laboratory studies of the surface geochemistry of magnetite, kaolinite, and smectite and the sorption and redox behavior of Se on these minerals and Cr on magnetite with several ongoing field investigations of the environmental geochemistry of Cr and Se in magnetite- and clay-bearing sediments being conducted by associate investigators from the USGS and LBL. The objectives of this proposed research are (1) to define quantitatively reaction stoichiometries and the geometry and composition of Cr(III) and Cr(VI) complexes sorbed on magnetite and of Se(IV) and Se(VI) complexes sorbed on magnetite, kaolinite, and smectite; (2) to characterize the magnetite surface before and after sorption using various spectroscopic and scattering techniques; (3) to utilize the results of our spectroscopic measurements in developing a predictive macroscopic model of sorption behavior and fluid-solid partitioning of chromium and selenium ions; and (4) to study the speciation of chromium and selenium in natural sediments and soils from two field sites. The proposed research builds on NSF-funded studies of sorption processes of inorganic solutes at mineral-water interfaces of the past six years and is a natural extension to systems involving redox-sensitive inorganic solutes.