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

基本信息

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

项目摘要

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这个项目着重于通过在加利福尼亚州母矿山矿区的一个开放坑金矿上风化的Arsenian Pyrite释放到环境中的地球化学周期。砷通过在黄铁矿风化产物（硫酸铁和氧化物）上的共沉淀和吸附来浓缩。这些次要阶段因季节性变化的环境条件以及进入开放坑矿山碱性湖环境而造成了不稳定。它们只是砷的临时下沉，具有通过解吸或溶解来释放砷至水生环境的潜力。我们通过一系列的现场和实验室观察/实验和理论模型来对待这项研究，包括：（1）矿山原始矿物质中砷分布的现场和实验室分析；砷风化产品中砷的分布和物种；以及矿山湖，泉水和地下水中的砷浓度和物种；（2）评估黄铁矿氧化的主要产物Jarosite中砷摄取和物种形成的实验室实验；（3）坑湖进化的地球化学建模。结果将提高我们对砷衰减和二级矿物释放的控制的理解，将风化矿物学与维特湖水质量联系起来的季节性领域和分析观察结果。砷生物利用度的评估需要了解其氧化状态和粘结环境。我们的研究将解决固相（通过X射线吸收光谱法）和砷水性物种形成，从而使我们能够对二次矿物的砷释放进行预测，这些矿物适用于其他黄铁矿环境，例如煤田，矿山和矿山，矿山尾矿和低级矿化矿物质露头。