Journal article
Mercury isotope signatures of digests and sequential extracts from industrially contaminated soils and sediments
The Science of the total environment, Vol.636, pp.1344-1354
15/09/2018
PMID: 29913595
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Abstract
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 Na4P2O7 (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 Na4P2O7 extracts. Sulfides and colloidal oxide minerals were possible additional sources of Hg in some samples. The inconsistent comparative performance of NaOH and Na4P2O7 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 (δ202Hg: −0.80‰ ± 0.14‰ to 0.25‰ ± 0.13‰, Δ199Hg: −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 δ202Hg = −0.47‰ ± 0.11‰ and Δ199Hg = −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.
Details
- Title
- Mercury isotope signatures of digests and sequential extracts from industrially contaminated soils and sediments
- Creators
- Andrew R. C. Grigg - ETH ZurichRuben Kretzschmar - ETH ZurichRobin S. Gilli - ETH ZurichJan G. Wiederhold - University of Vienna
- Publication Details
- The Science of the total environment, Vol.636, pp.1344-1354
- Publisher
- Elsevier
- Grant note
- Canton of Valais (Dienststelle fur Umwelt)
We thank Stephan Kraemer (University of Vienna) for his support of this project. The review of literature for the baseline Hg signature was undertaken in conjunction with Flora Brocza. Sample material was collected by M. Anor, A. Sauty, P. Bouvin and H. Vermeulen from the University of Applied Science and Arts Western Switzerland, and further material was kindly made available by David Trude! (Arcadis Switzerland). Research at this site is supported by the Canton of Valais (Dienststelle fur Umwelt). Measurements of Hg isotope ratios were performed in the Environmental Geochemistry Lab, University of Vienna, Austria. Measurements of DOC were undertaken in the Geoecology laboratories of the University of Vienna, with the help of Dipl.-Ing. Andreas Maier. Soil carbon measurements were conducted by Kurt Barmettler in the Soil Chemistry Group, IBP, ETH Zurich. We thank Runsheng Yin and one anonymous reviewer for their helpful comments.
- Identifiers
- 991013371560002368
- Copyright
- © 2018 Elsevier B.V. All rights reserved.
- Academic Unit
- Faculty of Science and Engineering
- Language
- English
- Resource Type
- Journal article