Quantification of Hexavalent Cr Reduction in Groundwater Using Cr Stable Isotopes

使用 Cr 稳定同位素定量地下水中六价 Cr 的还原

• 批准号: 0229079
• 负责人: Thomas Johnson
• 金额: $ 20.73万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-01 至 2006-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0229079&HistoricalAwards=false
• 关键词: Quantification; Hexavalent; Cr; Reduction; Groundwater

0229079JohnsonThis project will develop chromium (Cr) stable isotope ratios as a new tool for understanding how this toxic element moves in contaminated groundwater. Cr contamination is widespread, because the electroplating, leather tanning, and wood treatment industries use large volumes of highly concentrated Cr(VI) (hexavalent Cr) solutions. Cr(VI) moves readily with groundwater as a highly soluble oxyanion, but in many groundwater systems, it undergoes chemical reduction to Cr(III), which is less soluble and less toxic. Preliminary work by this group has demonstrated that this reduction reaction involves a fractionation of the stable isotopes 53Cr and 52Cr. The products of the reduction reaction are enriched in 52Cr, the lighter isotope, relative to the reactants, and as reduction proceeds, the remaining unreduced Cr(VI) becomes progressively more enriched in the heavier isotope relative to its starting composition. The working hypothesis of this project is that the 53Cr/52Cr ratio of the Cr(VI) in groundwater provides a quantitative indication of the amount of Cr(VI) reduction that has occurred. This project addresses several basic questions raised in previous work that must be answered before this new approach can be used quantitatively and with confidence in practical applications. The primary objectives are 1) to assess variability in the size of the isotopic fractionation during Cr(VI) reduction, 2) determine the isotope fractionations, if any, that are induced by Cr(VI) sorption and Cr(III) oxidation, and 3) assess 53Cr/52Cr variability among contaminant sources. The work will involve several experiments in the laboratory, analysis of groundwater samples from Cr(VI) contamination plumes, and analysis of industrial and natural Cr. This laboratory-based study will be complemented by a field study to be funded from other sources. It will be carried out as three separate projects for graduate students, who will be trained in environmental geochemistry, hydrogeology, and isotope geochemistry. The focus is on groundwater contamination, but most of what is learned here may be applied to other areas of geochemistry and oceanography.

0229079Johnson 该项目将开发铬 (Cr) 稳定同位素比率，作为了解这种有毒元素如何在受污染的地下水中移动的新工具。 Cr 污染非常普遍，因为电镀、皮革鞣制和木材处理行业使用大量高浓度的 Cr(VI)（六价铬）溶液。 Cr(VI) 作为一种高度溶解的氧阴离子很容易与地下水移动，但在许多地下水系统中，它会发生化学还原，生成溶解度较低且毒性较小的 Cr(III)。 该小组的初步工作表明，该还原反应涉及稳定同位素 53Cr 和 52Cr 的分馏。 还原反应的产物富含 52Cr（相对于反应物而言较轻的同位素），并且随着还原的进行，剩余的未还原的 Cr(VI) 相对于其起始成分逐渐变得更富含较重的同位素。 该项目的工作假设是地下水中 Cr(VI) 的 53Cr/52Cr 比率提供了已发生的 Cr(VI) 还原量的定量指示。 该项目解决了之前工作中提出的几个基本问​​题，在这种新方法能够定量地并在实际应用中充满信心地使用之前必须回答这些问题。 主要目标是 1) 评估 Cr(VI) 还原过程中同位素分馏大小的变化，2) 确定由 Cr(VI) 吸附和 Cr(III) 氧化引起的同位素分馏（如果有），以及3) 评估污染物源之间 53Cr/52Cr 的变异性。这项工作将涉及实验室中的多项实验、对六价铬污染羽流中的地下水样本进行分析，以及对工业和天然铬进行分析。 这项基于实验室的研究将得到其他来源资助的实地研究的补充。 它将作为三个独立的研究生项目进行，研究生将接受环境地球化学、水文地质学和同位素地球化学方面的培训。 重点是地下水污染，但这里学到的大部分知识可能适用于地球化学和海洋学的其他领域。