Department of Geology, Kansas State University, Manhattan, KS, 66506, USA.
Department of Geology, Kansas State University, Manhattan, KS, 66506, USA; Department of Geological Sciences, University of Texas at San Antonio, San Antonio, TX, 78249, USA.
Chemosphere. 2020 Dec;260:127577. doi: 10.1016/j.chemosphere.2020.127577. Epub 2020 Jul 11.
Tungsten (W) occurrence and speciation was investigated in sediments collected from Fallon, Nevada where previous studies have linked elevated W levels in human body fluids to an unusual cluster of childhood leukemia cases. The speciation of sedimentary W was determined by μ-XRF mapping and μ-XANES. The W content of the analyzed surface sediments ranged between 81 and 25,908 mg/kg, which is significantly higher than the W content in deeper sediments which ranged from 37 to 373 mg/kg at 30 cm depth. The μ-XANES findings reveal that approximately 20-50% of the total W in the shallow sediment occurs in the metallic form (W); the rest occurs in the oxide form (WO). Because W does not occur naturally, its elevated concentrations in surface sediments point toward a possible local anthropogenic origin. The oxidation of metallic W with meteoric waters likely leads to the formation of WO. The chief water-soluble W species was identified as WO by chromatographic separation and speciation modeling. These results led us to postulate that W particles from a currently unknown but local source(s) is (are) deposited onto the soils and/or surface sediments. The W in interaction with meteoric water is oxidized to WO, and as these sediment-water interactions progress, WO is formed in the water at pH ∼7. Under pH < 7, and sufficient W concentrations, tungstate tends to polymerize, and polymerized species are less likely to adsorb onto sediments. Polymerized species have lower affinity than monomers, which leads to enhanced mobility of W.
钨（W）的存在形式和形态在弗拉伦（Fallon）采集的沉积物中进行了研究，此前的研究将人体液中高水平的 W 与不寻常的儿童白血病病例群联系起来。沉积物中 W 的形态通过微 X 射线荧光映射和微 X 射线吸收近边结构（XANES）来确定。分析的表层沉积物的 W 含量介于 81 和 25908mg/kg 之间，明显高于 30cm 深的深层沉积物的 W 含量，范围为 37 至 373mg/kg。微 XANES 研究结果表明，浅层沉积物中总 W 的约 20-50% 以金属形式（W）存在，其余部分以氧化物形式（WO）存在。由于 W 不是自然存在的，其在表层沉积物中的高浓度表明可能存在局部人为来源。与大气水的金属 W 氧化可能导致 WO 的形成。通过色谱分离和形态模拟，确定了主要的水溶性 W 物种为 WO。这些结果使我们假设，目前未知但来自本地的 W 颗粒沉积在土壤和/或表层沉积物上。与大气水相互作用的 W 被氧化为 WO，随着这些沉积物-水相互作用的进行，WO 在 pH 约为 7 的水中形成。在 pH < 7 且 W 浓度足够的情况下，钨酸盐倾向于聚合，聚合的物种不太可能吸附到沉积物上。聚合的物种比单体的亲和力低，这导致 W 的迁移性增强。
