[A-HW22] Hydrological Cycle and Water Environment

[AHW22-21] Distribution and chemical speciation of molybdenum in river and pond sediments affected by mining activity in Erdenet city, Mongolia

*Solongo Tsetsgee¹, Fukushi Keisuke², Altansukh Ochir³, Takahashi Yoshio⁴, Akitoshi Akehi¹, Baasansuren Gankhurel¹, Davaadorj Davaasuren⁵, Noriko Hasebe² (1.Division of Global Environmental Science and Engineering, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan, 2.Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan, 3.Department of Environment and Forest Engineering, School of Engineering and Applied Sciences, National University of Mongolia, Ulaanbaatar, Mongolia, 4.Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan, 5.Department of Geography, School of Art & Sciences, The National University of Mongolia, Ulaanbaatar 210646, Mongolia)

Keywords:Erdenet mine , molybdenum, sediment, chemical speciation, XAFS , sequential extraction

Abstract: Rivers and ponds near the Erdenet mine, among the world’s largest copper–molybdenum mines, exhibit high concentrations of molybdenum (Mo). This study was conducted to evaluate the distribution and chemical speciation of Mo in sediments from ponds and rivers in Erdenet city to elucidate the mobility and solubility of Mo in the aquatic environments in the area. The waters and sediments were collected in two ponds connected to the tailing pond and three rivers flowing through Erdenet city. The distribution and chemical speciation of Mo in the sediments were examined using five-step sequential extraction and X-ray absorption fine structure (XAFS) analyses. The XAFS spectra of the sediments showed that large amounts of Mo in the river and pond sediments are molybdate or polymeric molybdate, weakly adsorbed onto ferrihydrite. Sequential extraction consistently showed a large amount of Mo distributed in the labile fraction. Results suggest that the pond and river sediments play a role as a secondary contamination source of Mo rather than as a sink of Mo in the area.

Acknowledgments: The authors would like to thank Professor J. Batkhuu, Department of Chemical and Biological Engineering, National University of Mongolia and Environmental Authority of Orkhon aimag in Erdenet city. Financial support was provided by the Higher Engineering Education Development Project, Functional material based on Mongolian Natural Minerals for Environmental Engineering, Cementitious and Float Process (No. J11A15), Biological Active Compounds and Useful Genes from Mongolian Plants, Microorganisms and their Application (No. J12A15), the Japan Society Promotion of Science (No. 17H06458) and the Environmental Research Project (No. 163288) from the Sumitomo Foundation. The study was performed as a cooperative research program of the Institute of Nature and Environmental Technology, Kanazawa University (No. 17039).

Contacts:
MSc. Tsetsgee Solongo
Division of Natural System
Graduate School of Natural Science and Technology
Kanazawa University
E-mail: [e-mail]
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