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.

0229079约翰逊该项目将开发铬（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。 铬污染很普遍，因为电镀、皮革鞣制和木材处理工业使用大量高浓度的Cr（VI）（六价铬）溶液。 Cr（VI）作为高度可溶的含氧阴离子很容易与地下水一起移动，但在许多地下水系统中，它会发生化学还原，形成溶解度较低且毒性较小的Cr（III）。 该小组的初步工作表明，这种还原反应涉及稳定同位素53 Cr和52 Cr的分馏。 还原反应的产物相对于反应物富含较轻的同位素52 Cr，并且随着还原的进行，剩余的未还原的Cr（VI）相对于其起始组成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53 Cr/52 Cr比率提供了Cr（VI）减少量的定量指标。 该项目解决了在以前的工作中提出的几个基本问题，这些问题必须在这种新方法可以定量使用并在实际应用中有信心之前得到回答。 主要目的是：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（如果有的话），3）评估污染源中53 Cr/52 Cr的变化。这项工作将涉及在实验室进行的几项实验，分析来自Cr（VI）污染羽流的地下水样品，以及分析工业和天然Cr。 这项实验室研究将得到其他来源资助的实地研究的补充。 它将作为研究生的三个独立项目进行，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内容可能适用于地球化学和海洋学的其他领域。