Collaborative Research: Biogeochemical Controls on Antimony and Arsenic Mobility in a Siliceous Hydrothermal System

el Tatio是已知的最大的间歇泉区之一，有超过100个已绘制的热液特征，它是智利第二地区的文化宝藏和区域旅游资源。间歇泉的水在贫瘠的高海拔地区支持孤立的微生物群落，排放的水形成了里约热内卢Salado的源头，这是下游农村的重要水资源。然而，El Tatio也是影响区域水质和水政策的有毒元素砷（As）和锑（Sb）的天然来源。该系统中的生物地球化学、微生物循环以及砷和锑的最终迁移率仍然是该生态系统和水资源的关键未知参数。该项目将解决四个广泛的研究问题：生物地球化学对砷和锑迁移的控制是什么？间歇泉流体组成的时空变化如何影响流体微生物群落？砷和锑是否用作化学养石生物的化学能来源，或用作金属呼吸细菌的电子受体？锑和砷对硅辉石内石器群落的影响是什么？El Tatio是一个独特的极端环境，与更深入研究的间歇泉地区不同；然而，与经典的热液系统相比，El Tatio几乎是未知的。这个天然实验室提供了在非常高的浓度下原位研究砷和锑生物地球化学的机会，并直接观察基本的地球化学关系。我们将利用跨学科领域和实验室地球化学和微生物学方法表征生物地球化学对间歇泉水和硅辉石中As和Sb氧化还原形态的控制。这将包括使用基于分子和培养的技术检查生境水文地球化学和浮游生物和内生生物群落的微生物群落组成之间的关系。现场沉淀实验将辅以实验室顺序萃取方法和热液二氧化硅沉淀实验，以检查As和Sb的分配行为。Sb同位素比率将在水和二氧化硅固体中进行表征，以测试潜在的微生物分馏。排放量和化学成分的时间研究将用于估计有毒金属流入下游社区的质量通量。El Tatio可以提供对控制和定义地球地质系统极端环境中微生物生态的参数的见解。在这个独特的硅质栖息地中，紫外线胁迫与有毒金属生物地球化学之间的关系也将为了解早期地球栖息地和生命起源提供见解。此外，El Tatio对区域村庄的影响涉及在保护不可替代的自然资源与了解有毒金属对水质的影响之间取得平衡。

EAR-0545336/EAR-0544960Philip C. BENNETT & Annette S. ENGELEl Tatio is one of the largest geyser zones known, with over 100 mapped hydrothermal features, and it is a cultural treasure and regional tourism resource for Chile Region II. Geyser water supports isolated microbial mat communities in the otherwise barren high altitude landscape and discharge water forms the headwaters of the Rio Salado, an essential water resource for downstream rural villages. El Tatio is also however a natural source of the toxic elements arsenic (As) and antimony (Sb) that impact regional water quality and water policy. The biogeochemistry, microbial cycling, and ultimate mobility of the As and Sb in this system remain as critical unknown parameters to this ecosystem and water resource. This project will address four broad research questions: What are the biogeochemical controls on As and Sb mobility? How do the spatial and temporal variations in geyser fluid composition influence lotic microbial communities? Are As and Sb used as sources of chemical energy for chemolithotrophs, or electron acceptors for metal-respiring bacteria? What are the influences of Sb and As on the endolithic communities in the geyserite? El Tatio is a uniquely extreme environment distinct from the more intensely studied geyser regions; yet, compared to the classic hydrothermal systems El Tatio is almost unknown. This natural laboratory offers the opportunity to study As and Sb biogeochemistry in situ at very high concentration and to directly observe fundamental geochemical relationships. We will characterize the biogeochemical controls on As and Sb redox speciation in the geyser waters and geyserite (silica) using interdisciplinary field and laboratory geochemical and microbiological methods. This will include an examination of the relationships between habitat hydro-geochemistry and microbial community composition of both the planktonic and endolithic communities using molecular- and culture-based techniques. Field precipitation experiments will be supplemented by laboratory sequential extraction methods and hydrothermal silica precipitation experiments to examine the partitioning behavior of As and Sb. Sb isotope ratios will be characterized in the water and silica solids to test for potential microbial fractionation. Temporal studies of discharge volume and chemical composition will be used to estimate the mass flux of toxic metals to the down stream communities.El Tatio can provide insight into the parameters that govern and define the microbial ecology of extreme environments in Earth's geologic systems. The relationship between UV stress and toxic metal biogeochemistry in this unique siliceous habitat will also provide insight into early-earth habitats and the origins of life. Further, the influence of El Tatio on the regional villages involves balancing preservation of an irreplaceable natural resource with understanding of the impacts of toxic metals on water quality.