Development of Chromium Stable Isotopes for Chromium Transport Studies and Other Geoscience Applications

0001153约翰逊该项目是一项为期一年的探索性研究，需要检查的可行性铬同位素测量作为指标的铬（六）减少和铬污染源。 铬是一种常见的地下水污染物，因为它用于电镀和其他工业过程。 铬的复杂氧化还原化学决定了它的流动性和生物利用度，在大多数铬污染的网站，铬（VI）还原是一个重要的自然衰减机制。 Cr也是海洋学和沉积学研究的兴趣，因为Cr（VI）和Cr（III）都存在于海洋和河口水中，Cr浓度和形态数据保存有关氧化还原条件的信息。氮和硫的稳定同位素比值已被证明在跟踪硝酸盐和硫酸盐还原到较低的氧化态，以及确定地下水中硝酸盐和硫酸盐的来源方面很有用。 该项目是朝着开发类似的铬同位素能力迈出的第一步。 对于氮和硫，较轻的同位素优先被还原，因此自然界中的同位素比变化提供了还原反应正在发生的证据，并指示了还原的程度。 这是可能的，在铬酸盐还原，52铬将优先减少相对于53铬，并观察到的变化，在地下水中的铬53铬/52铬的比例将表明铬（六价）的减少。 因此，铬同位素是一种有前途的新的地球化学收费，但同位素分馏必须在控制实验中观察到之前，可以进行广泛的研究，拟议的研究将测量这种动力学同位素效应的大小，并评估铬同位素的应用潜力。 三个实验计划，其中Cr（VI）的减少将发生在简单的解决方案，矿物表面，并在泥沙泥浆。 此外，从一个现场的地下水中的铬同位素比值的变化将被检查，以观察这种动力学同位素效应在自然界中，并建立实际的测量precision.This研究有潜在的影响，在获得的铬同位素系统的理解，然后可以用于进一步的研究应用于地下水，地表水，海洋学和沉积学研究。 铬同位素最终可能是一个实用的工具，用于了解铬源和运输污染的网站。 该项目旨在成为博士学位的一部分。论文的研究生，将结合类似的工作硒同位素是在进行中。

0001153JohnsonThis project is a one-year exploratory study needed to examine the feasibility of Cr isotope measurements as indicators of Cr(VI) reduction and Cr contamination sources. Cr is a common groundwater contaminant because of its use in electroplating and other industrial processes. The complex redox chemistry of Cr determines its mobility and bioavailability, and in most Cr-contaminanted sites, Cr(VI) reduction is an important natural attenuation mechanism. Cr is also of interest in oceanographic and sedimentological studies, as both Cr(VI) and Cr(III) are present in ocean and estuarine water, and Cr concentration and speciation data hold information about redox conditions.Stable isotope ratios of nitrogen and sulfur have proven useful in tracking reduction of nitrate and sulfate to lower oxidation states, and in identifying sources of nitrate and sulfate in groundwater. This project is an initial step toward developing a similar capability for Cr isotopes. For nitrogen and sulfur, lighter isotopes are reduced preferentially, and thus isotope ratio shifts in nature provide evidence that reduction reactions are occurring, and indicate the degree of reduction. It is likely that in chromate reduction, 52Cr will be reduced preferentially relative to 53Cr, and observed shifts in 53Cr/52Cr ratio of the Cr in groundwater would indicate Cr(VI) reduction. Cr isotopes are thus promising as a new geochemical toll, but the isotopic fractionations must be observed in controlled experiments before extensive research can be undertaken.The proposed study will measure the size of this kinetic isotope effect and assess the potential for Cr isotope applications. Three experiments are planned, in which Cr(VI) reduction will occur in simple solutions, on mineral surfaces, and in sediment slurries. Also, Cr isotope ratio variations in groundwater from one field site will be examined in order to observe this kinetic isotope effect in nature and establish the practical measurement precision.This research has potential impacts in gaining an understanding of Cr isotope systematic that may then be used in further studies applied to groundwater, surface water, oceanographic, and sedimentological studies. Cr isotopes may ultimately be a practical tool for the use in understanding Cr sources and transport at contaminanted sites. This project is designed to be part of a Ph.D. dissertation for a graduate student, to be combined with similar work on Se isotopes that is in progress.