Collaborative Research: Chemical Hydrogeologic Investigations of Tungsten: Field, Laboratory, and Modeling Studies of an Emerging Environmental Contaminant

NV法伦等地的儿童白血病簇已初步与邻近含钨矿床和选矿作业联系起来。由于法伦居民的身体系统中W的负荷很高，因此有人认为W可能是儿童白血病高发的原因。此后的研究表明，W可能有毒，并可能致癌。了解环境中的铅也很重要，因为它越来越多地被用作弹药和捕鱼砝码中的铅替代品。在这里，W的使用最初被认为是一种无毒的惰性金属，环境流动性低，因此它是一种限制向环境中添加有毒Pb的方式。然而，W在氧化后很容易在环境中被动员，实际上对其在环境中的生物地球化学，特别是其在真实地下水流动系统中的迁移和运输知之甚少。本项目将研究W在环境中的反应和迁移的生物地球化学。具体而言，该项目将评估地下水、含水层矿物质、有机物和原位微生物群落之间的生物地球化学反应如何改变地下水溶液组成和氧化还原条件，从而使W浓度沿着地下水流动路径演变。为了开展这项研究，该项目将：1)测量表征良好的含水层中沿流动路径的W浓度，以及氧化还原敏感参数[例如，Fe物种，S(-II)]和其他地球化学成分，以确定溶液组成和氧化还原条件的变化如何影响含水层中的W；2)检查含水层沉积物中固相W的形态（例如，XANES， EXAFS，顺序萃取）；3)测量硫钨酸盐配合物在硫化物水溶液中的稳定性常数，建立溶液络合模型，用于预测好氧和厌氧地下水中W的形态；4)建立一个概念性的生物地球化学模型，该模型结合了硫钨酸盐配合物的稳定性常数以及目前可用的钨酸盐氧阴离子的热力学数据，以探测W沿地下水流动路径的生物地球化学行为。本项目以作为重要饮用水源的原始含水层为研究对象，研究含水层中W的自然地球化学循环。由此产生的“基线”数据和概念模型将为其他研究人员研究人为来源的W对环境的影响提供重要资源。

Childhood leukemia clusters in e.g. Fallon, NV have been tentatively linked to the proximity to tungsten (W)-bearing ore deposits and ore-processing operations. Because residents of Fallon were shown to have high body-burdens of W in their systems, it has been suggested that W may be responsible for the high incidence of childhood leukemia. Studies have since shown that W can be toxic and may be carcinogenic. The need to understand W in the environment is also important due to its increasing use as a replacement for lead in ammunition and in fishing weights. Here, the use of W was originally thought to be a non-toxic, inert metal of low environmental mobility, it was thus a manner in which to limit the addition of toxic Pb to the environment. However, W is readily mobilized in the environment following oxidation and very little is actually known about its biogeochemistry in the environment, and in particular, its mobility and transport in real groundwater flow systems. This project will investigate the biogeochemistry of W reaction and transport in the environment. Specifically, the project will evaluate how W concentrations evolve along groundwater flow paths as biogeochemical reactions between groundwaters, aquifer minerals, organic matter, and in situ microbial communities, modify the groundwater solution composition and redox conditions. To conduct the study, the project will: 1) measure W concentrations along flow paths in well characterized aquifers along with redox sensitive parameters [e.g., Fe species, S(-II)], and other geochemical constituents to determine how changing solution composition and redox conditions affect W in aquifers; 2) examine solid-phase W speciation in aquifer sediments (e.g., XANES, EXAFS, sequential extractions); 3) measure stability constants for thiotungstate complexes in sulfidic aqueous solutions to develop a solution complexation model that will allow prediction of W speciation in aerobic and anaerobic groundwaters; and 4) assemble a conceptual, biogeochemical model that incorporates the stability constants for thiotungstate complexes along with the currently available thermodynamic data for the tungstate oxyanion to probe the biogeochemical behavior of W along groundwater flow paths. The project focus on pristine aquifers that are important drinking water sources to investigate the natural geochemical cycling of W in aquifers. The resulting 'baseline' data and conceptual model will provide an important resource for other investigators studying the effects of anthropogenic sourced W in the environment.