Seasonal Attenuation and Release of Arsenic by Pyrite Weathering Products, Southern Mother Lode Gold District, California

9902859鸟本项目主要研究加州母矿脉矿区露天金矿砷黄铁矿风化释放到环境中的砷的地球化学循环。砷通过共沉淀和吸附在黄铁矿风化产物（硫酸铁和氢氧化物）上被浓缩。这些次生相由于季节变化的环境条件和物理运输进入露天矿的碱性湖泊环境而不稳定。它们只是砷的临时水槽，有可能通过解吸或溶解将砷释放到水生环境中。我们通过一系列的现场和实验室观察/实验和理论模型来进行这项研究，包括：(1)现场和实验室分析砷在坑矿原生矿物中的分布；露头风化产物中砷的分布与形态矿坑、湖泊、泉水和地下水中砷的浓度和形态；(2)室内实验，评价黄铁矿氧化的主要产物黄铁矾对砷的吸收和形态；③坑湖演化地球化学模拟。研究结果将季节性野外观测和风化矿物学分析观测与坑湖水质联系起来，有助于进一步认识次生矿物对砷衰减和释放的控制作用。评价砷的生物利用度需要了解其氧化状态和结合环境。我们的研究将涉及固相（通过x射线吸收光谱）和水相砷形态，使我们能够预测次生矿物中砷的释放，这将适用于其他含黄铁矿的环境，如煤田，矿山和工厂尾矿，以及低品位矿化露头。

9902859 Bird This project focuses on the geochemical cycle of arsenic released to the environment by weathering of arsenian pyrite at an open pit gold mine in the Mother Lode Mining District of California. Arsenic is concentrated by coprecipitation and sorption on pyrite weathering products (iron sulfates and oxyhydroxides). These secondary phases are destabilized by seasonally changing environmental conditions and by physical transport into the alkaline lake environment of the open pit mine. They are only temporary sinks for arsenic, with the potential to release arsenic to aquatic environments via desorption or dissolution. We approach this study through a series of field and laboratory observations/experiments and theoretical models, including: (1) field and laboratory analysis of arsenic distribution in primary minerals of the pit mine; the distribution and speciation of arsenic in outcrop weathering products; and arsenic concentration and speciation in the mine pit lake, springs, and groundwater; (2) laboratory experiments to evaluate arsenic uptake and speciation in jarosite, a major product of pyrite oxidation; and (3) geochemical modeling of pit lake evolution. Results will improve our understanding of the controls on arsenic attenuation and release by secondary minerals, linking seasonal field and analytical observations of weathering mineralogy with pit lake water quality. Evaluation of arsenic bioavailability requires knowledge of its oxidation state and bonding environment. Our study will address both solid-phase (by X-ray absorption spectroscopy) and aqueous arsenic speciation, enabling us to make predictions about arsenic release from secondary minerals which will be applicable to other pyrite-bearing environments such as coalfields, mine and mill tailings, and low-grade mineralized outcrops.