Collaborative Research: Field and Experimental Iron Isotope Investigation of Sedimentary Pyrite Dissolution in Appalachian Coal Mine Drainage

来自废弃地下矿井的酸性矿井排水（AMD）是并且长期以来一直是美国矿区最严重的水质和流域退化问题。由于地下煤和金属开采作业，黄铁矿（FeS 2）暴露于水，导致其溶解并释放铁和硫酸到溶液中，以及来自酸诱导的其它矿物质溶解的金属和其它成分。 此外，全球河流硫酸盐通量的很大一部分来自黄铁矿溶解，由于采矿活动，贡献正在增加。 虽然黄铁矿溶解在硫循环和AMD形成中非常重要，但我们对该过程的理解和建模能力非常有限。 本项目将利用铁同位素测量技术的最新进展，在实验室和现场以一种新的方式研究黄铁矿溶解。 一个重要的目标将是测试和证明使用铁同位素的力量，以量化和源跟踪的溶解黄铁矿在废弃的煤矿流出。 据推测，56 Fe/54 Fe同位素比值将是不同的沉积黄铁矿在不同的条件下形成的，黄铁矿溶解的过程本身可能会导致可测量的同位素分馏。 为了验证这一点，56 Fe/54 Fe同位素比值在沉积黄铁矿从阿巴拉契亚盆地的不同沉积环境将被确定。 这些样品中的一些溶解速率，以及由此产生的水相同位素分馏，将在实验室中使用一个间歇式反应器进行研究，该反应器专门用于在严格控制的氧化还原和水相条件下定量黄铁矿溶解。 实验室和现场数据将使我们能够评估我们的能力，使用56 Fe/54 Fe作为示踪剂的主要来源的铁在AMD流出。 所获得的结果将提供进一步研究更复杂的系统，特别是系统与细菌存在，可以调解黄铁矿溶解过程的基础。

0228903DzombakAcid mine drainage (AMD) from abandoned underground mines is and has long been the most serious water quality and watershed degradation problem in the mining regions of the U.S. As a result of underground coal and metal mining operations, pyrite (FeS2) becomes exposed to water, resulting in its dissolution and release of iron and sulfuric acid to solution, as well as metals and other constituents from acid-induced dissolution of additional minerals. Moreover, a significant fraction of the global fluvial sulfate flux arises from pyrite dissolution, and the contribution is increasing due to mining activities. While pyrite dissolution is of great importance in sulfur cycling and in AMD formation, our understanding of this process and our ability to model it are very limited. This project will exploit recent advances in iron isotope measurement techniques to study pyrite dissolution in a novel manner in the laboratory and in the field. An important objective will be to test and demonstrate the power of using iron isotopes to quantify and source-track the dissolution of pyrite in abandoned coal mine outflows. It is hypothesized that the 56Fe/54Fe isotopic ratio will be distinct for sedimentary pyrites formed under different conditions, and that the process of pyrite dissolution itself could lead to measurable isotopic fractionation. To test this, the 56Fe/54Fe isotopic ratio in sedimentary pyrite from different depositional environments of the Appalachian basin will be determined. The rates of dissolution of some of these samples, and resulting aqueous phase isotopic fractionation, will be investigated in the laboratory using a batch reactor developed specifically for quantifying pyrite dissolution under tightly controlled redox and aqueous phase conditions. The laboratory and field data will allow us to evaluate our ability to use 56Fe/54Fe as a tracer for the primary source of Fe in AMD outflows. Results obtained will provide the basis for moving forward with additional studies of more complex systems, especially systems with bacteria present that can mediate the pyrite dissolution process.