Miao Ziheng, Carroll Kenneth C, Brusseau Mark L
Department of Soil, Water and Environmental Science, University of Arizona, 429 Shantz Building #38, P.O. Box 210038, Tucson, AZ, USA ; Department of Hydrology and Water Resources, University of Arizona, Harshbarger Building #11, Tucson, AZ, USA.
New Mexico State University, Las Cruces, NM, USA.
J Hydrol (Amst). 2013 Nov 11;504:207-215. doi: 10.1016/j.jhydrol.2013.09.030.
The Monument Valley site, a former uranium mining site located in the state of Arizona in the Southwest USA, has high concentrations of sulfate in groundwater. Stable isotope analysis of S and O for sulfate, in combination with geochemical and hydrogeological data, was used to characterize the sources and fate of sulfate. The results indicate the existence of two discrete sources of sulfate (in excess of baseline levels): sulfuric acid released during ore processing and sulfate generated via sulfide-mineral oxidation. The contributions of the sources are related to spatial distributions of sulfate in the plume through analysis of groundwater travel times. Quantification of the sources using two isotope-analysis methods yielded similar results. The results indicate that sulfuric acid served as the primary source (mean = 427 mg/L, 74%), with sulfide-mineral oxidation providing a smaller contribution (mean = 147 mg/L, 26%). It appears that the major contribution to the sulfide-mineral oxidation component originates from oxidation of sulfide minerals in exposed bedrock residing in the primary recharge zone of the local aquifer, which provides an elevated sulfate background for groundwater. Conversely, the oxidation of sulfide minerals associated with the mine tailings appears to provide a relatively minor contribution (∼8% of the overall total). Interestingly, it appears that sulfuric acid served as a sustained source of sulfate for approximately 40 years. This may be related to the accumulation of sulfate salts (formed after neutralization and disposal of the sulfuric acid) in the source zone due to the arid climate of the site. Contrary to the typical assumption applied at many mining sites that sulfide-mineral oxidation is the primary source of sulfate, these sulfate salts are hypothesized to be the primary source for this site.
纪念碑谷遗址是位于美国西南部亚利桑那州的一个 former 铀矿开采遗址，其地下水中硫酸盐浓度很高。对硫酸盐的硫和氧进行稳定同位素分析，并结合地球化学和水文地质数据，用于表征硫酸盐的来源和归宿。结果表明存在两种离散的硫酸盐来源（超过基线水平）：矿石加工过程中释放的硫酸和硫化物矿物氧化产生的硫酸盐。通过分析地下水流动时间，这些来源的贡献与羽流中硫酸盐的空间分布有关。使用两种同位素分析方法对来源进行量化得到了相似的结果。结果表明，硫酸是主要来源（平均 = 427 mg/L，74%），硫化物矿物氧化的贡献较小（平均 = 147 mg/L，26%）。看来，对硫化物矿物氧化成分的主要贡献源自当地含水层主要补给区暴露基岩中硫化物矿物的氧化，这为地下水提供了较高的硫酸盐背景。相反，与尾矿相关的硫化物矿物氧化似乎贡献相对较小（约占总量的 8%）。有趣的是，硫酸似乎持续作为硫酸盐来源约 40 年。这可能与该遗址干旱气候导致源区硫酸盐盐类（硫酸中和及处置后形成）的积累有关。与许多采矿遗址通常假设的硫化物矿物氧化是硫酸盐的主要来源相反，这些硫酸盐盐类被推测是该遗址的主要来源。
