Biological and Geochemical Influences on Arsenic Speciation in a Geothermal Environment

儿童长期暴露于高水平砷的毒理学效应在全球人群中很明显。砷现在被广泛认为是一种全球性的环境污染物，砷在土壤、沉积物、地表水和地下沃茨中的扩散已被反复记录。人们已经作出了大量努力，以确定影响地下含水层中砷分布的控制、调节和途径。对地热流体中砷的流动性和迁移的控制进行的调查较少。由于地热流体是地表水砷污染的主要手段之一，因此必须了解地热环境中砷的形态和流动性的控制。拟议的项目是了解生物控制的砷形态和流动性在阿尔沃德盆地内的地热流体的阿尔沃德盆地，OR的第一步。拟议的项目的目标是调查地球化学和生物过程影响砷形态的表面表达的地热流体。我们建议表明，亚砷酸盐的快速氧化，主要是由于微生物的过程，并在其观察范围内的pH值，温度和氧化状态的流体中的亚砷酸盐氧化发生在弹簧中的亚砷酸盐氧化有轻微的影响。此外，我们将使用分子工具，以确定是否在泉水流出通道的砷氧化带内的微生物种群是一致的，从春天到春天的pH值，温度和溶解氧的地球化学参数是相等的。最后，我们将丰富和分离嗜热亚砷酸盐氧化微生物主持的快速亚砷酸盐氧化发生的泉水。预计这些基础研究将为今后研究地表地热沃茨中砷形态的控制、地热沃茨中砷的地球化学循环以及利用砷作为能源的微生物的代谢机制奠定基础。拟议研究的完成将对地球科学和生命科学学科产生直接影响。人们认识到，砷在地热环境中的流动性部分是由温度和流体的氧化电位控制，但定义砷在地热流体中的溶解度的原则一直难以捉摸。因此，了解微生物在调节砷溶解度中的作用对于建立准确的地球化学模型至关重要。此外，微生物积极参与砷氧化还原反应的认识是相对较新的，因此需要进一步研究微生物和砷化合物之间发生的相互作用类型。PI计划的主要目标之一是让环境科学和地质学课程的学生接触微生物学。将实地调查纳入与地质科学教师合作的跨学科领域课程是实现这一目标的直接手段。此外，PI，共同PI和PI的家庭部门内的教师之间的持续合作将提供一个强大的跨学科生物科学计划的发展所需的基础设施。

EAR-0617648CHILDERSThe toxicological effects of prolonged exposure to elevated levels of arsenic are apparent in populations worldwide. Arsenic is now widely recognized as a global environmental contaminant and dissemination of arsenic in soils, sediments, surface and ground waters has been repeatedly documented. Intensive efforts have been put forth to determine the controls, regulation and pathways affecting the distribution of arsenic in subsurface aquifers. Fewer investigations have been initiated regarding controls on arsenic mobility and transport in geothermal fluids. Because geothermal fluids are one of the primary means of surface water arsenic contamination, it is imperative to understand controls on arsenic speciation and mobility in geothermal environments. The proposed project is a first step towards understanding the biological controls on arsenic speciation and mobility in geothermal fluids of springs within the Alvord Basin, OR.The goal of the proposed project is to investigate the geochemical and biological processes effecting arsenic speciation of surface-expressed geothermal fluids. We propose to show that rapid oxidation of arsenite to arsenate is primarily due to microbial processes, and that over their observed range the pH, temperature and oxygenation status of the fluids has a minor impact on arsenite oxidation within springs in which arsenite oxidation is occurring. Furthermore, we will use molecular tools to determine if microbial populations within arsenite oxidizing zones of spring outflow channels are consistent from spring to spring when geochemical parameters of pH, temperature and dissolved oxygen are equivalent. Finally, we will enrich for and isolate thermophilic arsenite oxidizing microorganisms presiding in springs in which rapid arsenite oxidation is occurring. It is anticipated that these basic studies will set the groundwork for future research investigating the controls on arsenic speciation in surface geothermal waters, the biogeochemical cycling of arsenic in geothermal waters, and the metabolic mechanisms employed by microorganisms utilizing arsenic as an energy source.Intellectual Merit. The completion of the proposed studies will have an immediate impact on the earth science and life science disciplines. It is recognized that arsenic mobility in geothermal environments is partly controlled by temperature and the oxidation potential of fluids, yet the principles defining arsenic solubility in geothermal fluids have been elusive. Thus it is critical to understand the role of microorganisms in regulating arsenic solubility for accurate geochemical models to be developed. Furthermore, the recognition that microorganisms actively participate in arsenic oxidation-reduction reactions is relatively recent, thus there is a demand for further studies investigating the types of interactions occurring between microorganisms and arsenic compounds.Broader Impacts. One of the primary goals of the PI's program is to expose students in the Environmental Sciences and Geology programs to microbiology. The incorporation of field investigations into an established interdisciplinary field class in collaboration with faculty in the Geological Sciences is a direct means of achieving that goal. Furthermore, continued collaborations among the PI, co-PI and faculty within the PI's home department will provide the infrastructure necessary for the development of a strong interdisciplinary biogeosciences program.