Geochemical Reactions in the Unsaturated Zone of the Pyritic Mine Wastes

黄铁矿矿山废料非饱和带的地球化学反应

• 批准号: 0003364
• 负责人: James Rimstidt
• 金额: $ 19.52万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-02-01 至 2005-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0003364&HistoricalAwards=false
• 关键词: Geochemical; Reactions; Unsaturated; Zone; Pyritic

ABSTRACTGeochemical Reactions in the Unsaturated Zone of Pyritic Mine WastesBy J. Donald Rimstidt There are over 60 billion tons of mine wastes from non-fuel mineral production in the US today and more are being produced at a rate of about 2 billion tons annually. Although most of these wastes are relatively benign, consisting of common rocks and soils, a significant fraction contains iron sulfide minerals, especially pyrite, that can oxidize to produce an acidic sulfate solution, often containing high concentrations of toxic metals. Discharge of this acid mine drainage (AMD) into nearby streams and lakes is responsible for the ecological impairment of thousands of miles of streams. Furthermore, AMD reduces water quality often making it unfit for human consumption or for use as industrial process water. Thus, AMD is a multi-billion dollar societal problem that can benefit significantly from an organized scientific and engineering research program. We propose to study chemical reactions that occur at the air/mineral and air/brine/mineral interfaces in the unsaturated parts of pyritic waste piles. Specifically, we will measure the rates of oxidation of pyrite in moist air as a function of the partial pressure of oxygen, relative humidity, and temperature. This oxidation produces sulfuric acid and ferrous sulfate and is the primary mode of acid production. Furthermore, we will investigate the evolution of the ferrous sulfate as it evolves via oxidation, dehydration, and neutralization through a series of ferrous/ferric hydroxysulfate minerals. These minerals are a secondary source of acid production and are hosts of many of the trace metals that cause environmental degradation. They are of particular concern because they are quite soluble so they dissolve rapidly during rain events to release large amounts of acidity and trace metals to nearby receiving waters. Our goal is to provide details about the thermodynamic stability and rates of transformation of these sulfate minerals so we can predict the evolution of this reservoir of latent acidity and trace metals. We believe that this information will provide valuable guidance to the engineers and geochemists that are designing new waste disposal facilities or who are preparing remediation plans for abandoned mine wastes.

在美国，目前有超过600亿吨来自非燃料矿物生产的矿山废物，而且每年还在以大约20亿吨的速度产生更多的废物。虽然这些废物大多数是相对无害的，由普通的岩石和土壤组成，但很大一部分含有硫化铁矿，特别是黄铁矿，可以氧化产生酸性硫酸盐溶液，通常含有高浓度的有毒金属。这种酸性矿山废水（AMD）排放到附近的河流和湖泊是造成数千英里河流生态损害的原因。此外，AMD降低了水质，通常使其不适合人类消费或用作工业工艺用水。因此，AMD是一个价值数十亿美元的社会问题，可以从有组织的科学和工程研究计划中受益匪浅。我们建议研究的化学反应发生在空气/矿物和空气/盐水/矿物界面的不饱和部分的黄铁矿废物堆。具体来说，我们将测量黄铁矿在潮湿空气中的氧化率作为氧分压，相对湿度和温度的函数。这种氧化产生硫酸和硫酸亚铁，是酸生产的主要方式。此外，我们将研究硫酸亚铁的演变，因为它通过氧化，脱水和中和通过一系列的亚铁/羟基硫酸铁矿物演变。这些矿物质是酸生产的第二来源，并且是导致环境退化的许多微量金属的宿主。它们特别令人关注，因为它们非常易溶，因此在下雨时会迅速溶解，向附近的受纳沃茨释放大量的酸性物质和微量金属。我们的目标是提供有关这些硫酸盐矿物的热力学稳定性和转化率的详细信息，以便我们可以预测潜在酸度和微量金属的演变。我们相信，这些信息将为正在设计新的废物处理设施或正在为废弃矿山废物制定补救计划的工程师和地球化学家提供有价值的指导。