Transport, Transformation, and Retention of Arsenic in a Headwater Stream: Hydrologic, Biological, and Geochemical Controls

众所周知，砷是一种有毒和致癌的元素，很容易在天然沃茨中迁移，其形态、物种形成和浓度受地球化学反应的影响。 在本提案中，我们讨论了受过去采矿活动影响的河流含水层系统中砷的迁移、转化和保留。 鉴于我们目前对与矿山密切接触的河流含水层系统结构的了解，我们提出了一些关于水文、地球化学和生物过程控制砷的形态和浓度的作用的问题。 这项研究将集中在解决两个中心问题：（1）是什么因素控制砷通量的空间和时间变化？(2)潜流过程如何影响砷在水流中的滞留？为了解决这些问题，我们将利用现场，实验室和建模技术相结合，以评估流内的砷流动性的控制，特别强调表征的作用，作为砷的来源或汇的潜流区。 拟议的研究内容包括采用水文和地球化学监测，以表征地下水和地表水的端元，以及描述在hyporheic区的地球化学条件。 此外，瞬态存储模型将被用来评估的水文特征的潜流区，并通过纳入反应性吸收条款，以解决的作用，潜流区在延缓或促进砷运输到stream.Results的建议的研究将有影响，我们的一般理解氧化还原敏感的微量元素，如砷的地球化学循环。 最近将含砷饮用水标准从50微克/升提高到10微克/升，这将促使联邦和州政府机构密切审查自然和人为砷污染的来源。 提高对控制砷流动性的过程的了解将大大有助于这些机构制定保护和处理饮用水供应的计划。

0207784SchreiberIt is well-known that arsenic, a toxic and carcinogenic element, is readily transported in natural waters and that its forms, speciation, and concentrations are affected by biogeochemical reactions. In this proposal, we address the transport, transformation and retention of arsenic in a stream-aquifer system impacted by past mining activities. Given our current understanding of the structure of stream-aquifer system in close contact with the mine, we developed a number of questions regarding the role of hydrologic, geochemical and biological processes controlling the speciation and concentration of arsenic. The proposed research will center on addressing two central questions: (1) what factors control spatial and temporal variations in arsenic fluxes to the stream? (2) How do hyporheic processes influence retention of arsenic in the stream?To address these questions, we will utilize a combination of field, laboratory, and modeling techniques to evaluate the controls on arsenic mobility within the stream, with specific emphasis on characterizing the role of the hyporheic zone in acting as a source or a sink for arsenic. The proposed research elements include employing hydrologic and geochemical monitoring to characterize groundwater and surface water end-members as well as to describe biogeochemical conditions within the hyporheic zone. In addition, transient storage models will be used to evaluate the hydrologic characteristics of the hyporheic zone and, through incorporation of reactive uptake terms, to address the role of the hyporheic zone in retarding or promoting arsenic transport to the stream.Results of this proposed research will have implications for our general understanding of the biogeochemical cycling of redox-sensitive trace elements such as arsenic. The recent tightening of the arsenic drinking water standard from 50 to 10 ug/L will drive federal and state agencies to closely examine sources of both natural and human-introduced arsenic contamination. Improving the knowledge of the processes that control arsenic mobility will greatly aid these agencies in developing plans for protecting and treating drinking water supplies.