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

EAR-0545336/EAR-0544960Philip C.Bennett&Amp；Annette S.ENGELEL Tatio是已知最大的间歇泉地区之一，有100多处绘制的热液地貌，是智利第二大区的文化瑰宝和区域旅游资源。间歇泉水支持着原本贫瘠的高海拔地区孤立的微生物席群落，并排放的水构成了里奥萨拉多河的源头，后者是下游农村村庄的基本水源。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As和Sb的生物地球化学、微生物循环和最终迁移率仍然是该生态系统和水资源的关键未知参数。这个项目将解决四个广泛的研究问题：As和Sb移动性的生物地球化学控制是什么？间歇泉流体组成的时空变化如何影响溶质微生物群落？As和Sb是否被用作化石菌的化学能量来源，或者是金属呼吸细菌的电子受体？Sb和As对间歇闪锌矿中的石器时代群落有什么影响？埃尔塔蒂奥是一个独特的极端环境，有别于更深入研究的间歇泉地区；然而，与经典的热液系统相比，埃尔塔蒂奥几乎是未知的。这个天然实验室提供了在很高浓度下原位研究As和Sb生物地球化学的机会，并直接观察基本的地球化学关系。我们将使用跨学科的野外和实验室、地球化学和微生物学方法来表征间歇泉水和间歇式丝光沸石(二氧化硅)中As和Sb氧化还原形态的生物地球化学控制。这将包括利用基于分子和培养的技术，审查浮游生物和石器内群落的生境、水文地球化学和微生物群落组成之间的关系。野外降水实验将辅之以实验室连续提取方法和水热二氧化硅沉淀实验，以考察As和Sb的分配行为。将对水和二氧化硅固体中的Sb同位素比率进行表征，以测试潜在的微生物分馏。对排放量和化学成分的时间研究将被用来估计有毒金属流向下游社区的质量流量。El Tatio可以提供对控制和定义地球地质系统中极端环境的微生物生态的参数的洞察。在这种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提供对早期地球栖息地和生命起源的洞察。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和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.