Preventing Pyrite Oxidation: A Geomicrobial Strategy for Source Control of Acid Mine Drainage

防止黄铁矿氧化：酸性矿山排水源头控制的地微生物策略

• 批准号: 0540593
• 负责人: JoAnn Silverstein
• 金额: $ 19.6万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0540593&HistoricalAwards=false
• 关键词: Preventing; Pyrite; Oxidation; Geomicrobial; Strategy

PROJECT SUMMARYAcid mine drainage (AMD) is the contamination of water by acidity, iron, sulfate and heavy metals leached from waste rock by chemical and bacterially catalyzed oxidation of pyrite minerals and other sulfidic source rock. There are an estimated 45 billion tons of waste rock in abandoned mine sites in the United States alone, resulting in pollution of thousands of kilometers of streams and aquatic habitat and a significant loss of biodiversity (General Accounting Office, 1996). Current technologies for remediation of AMD sites and secondary contamination areas are costly and cause further environmental disruption (e.g., excavation and removal, addition of lime). Moreover, many of these sites are small and dispersed over mountainous terrain; so that many streams are impacted before a large treatment process such as a reactive barrier or wetland can be installed. At low pH, pyrite-oxidizing bacteria - typically acidophilic, autotrophic, and aerobic strains such as Acidithiobacillus ferrooxidans -- catalyze acid generation. Research is proposed to investigate the hypothesis that pyrite oxidation may be inhibited at the rock-water interface by enhancing the growth of native populations of heterotrophic bacteria, which will consume oxygen and release organic constituents that are able to complex metals, trap precipitates and, eventually, give rise to alkalinity-generating reactions such as anaerobic Fe(III) and sulfate respiration, blocking reactive sites and enabling long-lasting site restoration.Intellectual Merit. This exploratory research project aims to understand the coupling ofmicrobial community structure and fundamental biogeochemistry at the rock-water interface with flow and transport processes through waste rock formations. Experiments at scales of a single rock fragment and waste-rock columns will be conducted to test whether addition of biodegradable organic substrate will result in a shift in the dominant bacterial populations from autotrophic to heterotrophic metabolism that, in turn, will impact oxygen consumption, iron and sulfur cycling and metal leaching. We will also investigate the influence of hydrologic variables (e.g. formation saturation conditions, water detention time) and rock properties (e.g. porosity, pyrite fraction) on the effectiveness of heterotrophic bacterial growth and inhibition of AMD generation. In addition to understanding the interrelations between rock media, drainage flow, the microbial community, and geochemical reactions, our experiments will enable quantification of the carbon required to inhibit bacterial pyrite oxidation and evaluate the long-term sustainability of the biogeochemical changes caused by carbon addition. A mechanistic reactive transport model will be developed to quantify fundamental microbial-geochemical-hydrologic processes at the single rock scale and provide a framework for upscaling to the rock column and field scales. This model will be used to design carbon addition and remediation strategies for pilot field-scale applications.Broader Impacts. It has been estimated that there are over 100,000 abandoned mine sites in theWestern US producing acid mine drainage. The engineering application of the results of this research will be a novel cost-effective process for long-term remediation of acid-generating waste rock by localized addition of a benign soluble organic substrate. There will be associated benefits to the habitat and to local communities in AMD-impacted watersheds enabling recreation, tourism, and reliable water resources. Because the process design envisioned is based on fundamental biogeochemical and flow processes, such a remediation strategy could be modified for application at a variety of acid-generating field sites. AMD is a topic of significant public concern in Colorado and other mountain states with historic mining activity. There are two local stakeholder groups in watersheds with significant AMD discharges that already have ties to researchers at the University of Colorado and have expressed interest in sustainable site restoration methods that minimize disruption of their communities and can be implemented at low cost. However, at this time, too little is understood about both the fundamental mechanisms of the proposed restoration method to attempt field-scale applications. The results from this exploratory research would allow a field trial of carbon addition and enable collaboration of university researchers, mining companies, public land agencies, and residents in AMD impacted watersheds. Finally, the faculty investigators are committed to involving a diverse student population in research activities by participating in research programs for underrepresented minority students at the University of Colorado, Boulder such as the Colorado Diversity Initiative in Science, Math and Engineering.

项目概述酸性矿山排水（AMD）是指通过化学和细菌催化氧化黄铁矿矿物和其他硫化物源岩，从废石中浸出的酸性、铁、硫酸盐和重金属对水的污染。据估计，仅在美国，废弃的矿场就有450亿吨废石，污染了数千公里的溪流和水生生境，并严重丧失了生物多样性（总审计局，1996年）。目前用于补救AMD场地和二次污染区域的技术是昂贵的，并且导致进一步的环境破坏（例如，挖掘和移除，添加石灰）。此外，这些地点中有许多都很小，分散在山区，因此在安装反应屏障或湿地等大型处理工艺之前，许多溪流就受到了影响。在低pH值下，黄铁矿氧化细菌-通常是嗜酸、自养和好氧菌株，如氧化亚铁硫杆菌-催化酸的产生。提议开展研究，以调查这样一种假设，即通过促进原生异养细菌种群的生长，可以抑制岩石-水界面处的黄铁矿氧化，异养细菌将消耗氧气并释放能够络合金属、捕获沉淀物的有机成分，并最终引起产生碱性的反应，如厌氧Fe（III）和硫酸盐呼吸，阻止反应性站点并实现持久的站点恢复。智力优势。该探索性研究项目旨在了解岩石-水界面微生物群落结构和基本地球化学与废物岩层流动和运输过程的耦合。将进行单个岩石碎片和废石柱规模的实验，以测试添加可生物降解的有机基质是否会导致主要细菌种群从自养代谢转变为异养代谢，这反过来会影响氧气消耗，铁和硫循环以及金属浸出。我们还将研究水文变量（如地层饱和度条件，水滞留时间）和岩石性质（如孔隙度，黄铁矿分数）的异养细菌生长和AMD生成抑制的有效性的影响。除了了解岩石介质，排水流量，微生物群落和地球化学反应之间的相互关系，我们的实验将使量化所需的碳抑制细菌黄铁矿氧化和评估的长期可持续性的生物地球化学变化所造成的碳添加。将开发一个机械反应传输模型，以量化单个岩石尺度上的基本微生物-地球化学-水文过程，并为岩石柱和现场尺度的升级提供一个框架。这一模型将用于设计碳添加和补救战略，以供试点实地应用。据估计，在美国西部有超过10万个废弃的矿场产生酸性矿井废水。本研究结果的工程应用将是一个新的具有成本效益的长期修复产酸废石通过本地添加一个良性的可溶性有机基质的过程。在受AMD影响的流域，栖息地和当地社区将获得相关的利益，从而实现娱乐，旅游和可靠的水资源。 由于设想的工艺设计是基于基本的生物地球化学和流动过程，这样的补救策略可以修改应用在各种产酸现场。AMD是科罗拉多和其他有历史采矿活动的山区州的一个重大公众关注的话题。有两个地方利益相关者团体在流域与显着AMD排放已经有联系的研究人员在科罗拉多大学，并表示有兴趣在可持续的网站恢复方法，最大限度地减少其社区的中断，并可以在低成本实施。然而，在这个时候，太少的理解这两个基本机制的建议恢复方法，尝试现场规模的应用。这项探索性研究的结果将允许进行碳添加的现场试验，并使大学研究人员、矿业公司、公共土地机构和受AMD影响流域的居民能够合作。最后，教师调查人员致力于通过参与研究计划，为代表性不足的少数民族学生在科罗拉多，博尔德大学，如科学，数学和工程的科罗拉多多样性倡议，在研究活动中涉及不同的学生群体。