Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, CHN, ETH Zurich, Zurich, Switzerland; Environmental Geochemistry Group, Department of Environmental Geosciences, University of Vienna, Vienna, Austria.
Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, CHN, ETH Zurich, Zurich, Switzerland.
Sci Total Environ. 2018 Sep 15;636:1344-1354. doi: 10.1016/j.scitotenv.2018.04.261. Epub 2018 May 5.
Environmental mercury (Hg) pollution is a matter of global concern. Mercury speciation controls its environmental behaviour, and stable isotope ratios can potentially trace Hg movement through environmental compartments. Here we investigated Hg in industrially contaminated soils and sediments (Visp, Valais, Switzerland) using concentration and stable isotope analysis (CV-MC-ICP-MS) of total digests, and a four-step sequential extraction procedure. The sequential extraction employed (1) water (labile Hg species), (2) NaOH or NaPO (organically-bound Hg), (3) hydroxylamine-HCl (Hg bound to Mn and Fe (oxyhydr)oxides), and (4) aqua regia (residual Hg pools). The majority of Hg was extracted in step 4 and up to 36% in step 2. Mercury bound to organic matter was the dominant source of Hg in water, NaOH and NaPO extracts. Sulfides and colloidal oxide minerals were possible additional sources of Hg in some samples. The inconsistent comparative performance of NaOH and NaPO extractions showed that these classical extractants may not extract Hg exclusively from the organically-bound pool. Samples taken at the industrial facility displayed the greatest isotopic variation (δHg: -0.80‰ ± 0.14‰ to 0.25‰ ± 0.13‰, ΔHg: -0.10‰ ± 0.03‰ to 0.02‰ ± 0.03‰; all 2SD) whereas downstream of the facility there was much less variation around average values of δHg = -0.47‰ ± 0.11‰ and ΔHg = -0.05‰ ± 0.03‰ (1SD, n = 19). We interpret the difference as the result of homogenisation by mixing of canal sediments containing Hg from the various sources at the industrial facility with preservation of the mixed industrial Hg signature downstream. In contrast to previous findings, Hg isotopes in the sequential extracts were largely similar to one another (2SD < 0.14‰), likely demonstrating that the Hg speciation was similar among the extracts. Our results reveal that Hg resides in relatively stable soil pools which record an averaged isotope signature of the industrial sources, potentially facilitating source tracing studies with Hg isotope signatures at larger spatial scales further downstream.
环境汞（Hg）污染是一个全球性问题。汞的形态控制着它的环境行为，而稳定同位素比值则有可能追踪汞在环境介质中的迁移。在这里，我们使用总消解物的浓度和稳定同位素分析（CV-MC-ICP-MS）以及四步连续提取程序，研究了瑞士瓦莱州维斯普（Visp）受工业污染的土壤和沉积物中的汞。连续提取采用（1）水（可提取的汞物种）、（2）NaOH 或 NaPO（有机结合的汞）、（3）羟胺盐酸（与 Mn 和 Fe（氢氧化物）氧化物结合的汞）和（4）王水（残留的汞库）。大部分汞在第 4 步中被提取，在第 2 步中最多可达 36%。水、NaOH 和 NaPO 提取物中，与有机质结合的汞是汞的主要来源。在一些样品中，硫化物和胶体氧化物矿物可能是汞的额外来源。NaOH 和 NaPO 提取的对比性能不一致，表明这些经典的提取剂可能不能专一地从有机结合池中提取汞。在工业设施中采集的样品显示出最大的同位素变化（δHg：-0.80‰±0.14‰至 0.25‰±0.13‰，ΔHg：-0.10‰±0.03‰至 0.02‰±0.03‰；均为 2SD），而在设施下游，围绕 δHg=-0.47‰±0.11‰和 ΔHg=-0.05‰±0.03‰（1SD，n=19）的平均值的变化要小得多。我们将这种差异解释为由于来自工业设施各种来源的汞在运河沉积物中的混合而导致的均匀化，而下游则保留了混合的工业汞特征。与以前的发现不同，连续提取物中的汞同位素彼此之间非常相似（2SD<0.14‰），这可能表明提取物中的汞形态相似。我们的结果表明，汞存在于相对稳定的土壤库中，这些土壤库记录了工业来源的平均同位素特征，这可能有助于在更大的空间尺度上进一步下游进行汞同位素特征的源追踪研究。
