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

加利福尼亚州南主矿金区黄铁矿风化产品造成砷的季节性衰减和释放

• 批准号: 9902859
• 负责人: Dennis Bird
• 金额: $ 14.25万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-01 至 2002-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9902859&HistoricalAwards=false
• 关键词: Seasonal; Attenuation; Release; Arsenic; Pyrite

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.

9902859 Bird本项目重点研究加州Mother矿脉矿区露天金矿中砷黄铁矿风化释放到环境中的砷的地球化学循环。 砷是通过共沉淀和吸附在黄铁矿风化产物（硫酸铁和氢氧化铁）上而富集的。这些次生相由于季节性变化的环境条件和物理迁移到露天矿的碱性湖环境中而不稳定。它们只是砷的临时汇，有可能通过解吸或溶解将砷释放到水生环境中。 本研究通过一系列野外和室内观测/实验以及理论模型进行研究，包括：（1）野外和室内分析矿坑原生矿物中砷的分布，露头风化产物中砷的分布和形态，矿坑湖泊、泉水和地下水中砷的浓度和形态;（2）黄钾铁矾（黄铁矿氧化的主要产物）对砷的吸收和形态的实验研究;（3）坑湖演化的地球化学模拟。 研究结果将提高我们对次生矿物对砷衰减和释放的控制的理解，将季节性现场和风化矿物学的分析观察与坑湖水质联系起来。评价砷的生物利用度需要了解其氧化态和结合环境。我们的研究将解决固相（通过X射线吸收光谱）和水砷形态，使我们能够预测砷从次生矿物中释放，这将适用于其他含黄铁矿的环境，如煤田，矿山和选矿厂尾矿，以及低品位矿化露头。