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影响在全世界人群中都很明显。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、地表水和地下水中的传播已被反复记录。为确定影响地下含水层中砷分布的控制、调节和途径，已作出了大量努力。关于控制地热流体中砷的迁移和运输的调查较少。由于地热流体是地表水砷污染的主要途径之一，因此了解地热环境中砷的形态和迁移控制是十分必要的。拟议的项目是了解阿尔沃德盆地地热流体中砷形态和流动性的生物控制的第一步。该项目的目的是研究影响地表地表地热流体中砷形态的地球化学和生物过程。我们建议表明，亚砷酸盐的快速氧化主要是由于微生物过程，并且在其观察到的范围内，流体的pH值、温度和氧化状态对发生亚砷酸盐氧化的弹簧中的亚砷酸盐氧化有轻微影响。此外，我们将使用分子工具来确定在pH、温度和溶解氧地球化学参数相等的情况下，泉水流出通道亚砷酸盐氧化带内的微生物种群是否在春季与春季之间一致。最后，我们将富集和分离在发生快速亚砷酸氧化的泉水中主持的嗜热亚砷酸氧化微生物。这些基础研究将为今后地表水中砷的形态控制、地表水中砷的生物地球化学循环以及微生物利用砷作为能量来源的代谢机制的研究奠定基础。知识价值。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受温度和流体氧化电位的控制，但定义砷在地热流体中的溶解度的原理一直难以捉摸。因此，了解微生物在调节砷溶解度中的作用对于建立精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与砷化合物之间发生的相互作用类型。更广泛的影响。PI项目的主要目标之一是让环境科学和地质学专业的学生接触微生物学。与地质科学学院教员合作，将实地调查纳入已建立的跨学科实地课程是实现这一目标的直接手段。此外，PI、联合PI和PI内部部门的教师之间的持续合作将为开发一个强大的跨学科生物地球科学项目提供必要的基础设施。

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.