Water quality and potential sources in alluvial bore, downstream of the tailings storage facility, Oyu Tolgoi copper mine, Mongolia

Authors: Puntsag, T; Tulganyam, S; Sededpurev, O; Bazardorj, S-E; Bayanzul, B; Myagmar, B; Sarangerel, T; Danzan, A; Natsagdorj, M; Nyambuu, P

Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2515_96

Cite As:
Puntsag, T, Tulganyam, S, Sededpurev, O, Bazardorj, S-E, Bayanzul, B, Myagmar, B, Sarangerel, T, Danzan, A, Natsagdorj, M & Nyambuu, P 2025, 'Water quality and potential sources in alluvial bore, downstream of the tailings storage facility, Oyu Tolgoi copper mine, Mongolia ', in S Knutsson, AB Fourie & M Tibbett (eds), Mine Closure 2025: Proceedings of the 18th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-14, https://doi.org/10.36487/ACG_repo/2515_96

Download citation as:   ris   bibtex   endnote   text   Zotero


Abstract:
Understanding water pathways and salinity transformations associated with tailings storage facilities (TSFs) is critical for long-term groundwater protection and effective mine closure planning, particularly in arid regions such as Mongolia’s South Gobi region. This study examines increasing total dissolved solids (TDS) observed in shallow alluvial monitoring bore OTMB16-79, located downstream of the Oyu Tolgoi (OT) TSF. Isotopebased (δ¹⁸O, δ²H, δ³⁴S, ⁸⁷Sr/⁸⁶Sr) and elemental analyses (major, trace, and rare earth elements) were applied to distinguish TSF seepage from natural geochemical processes, including evaporative concentration, bedrock weathering, and displaced groundwater. Parameters such as δ³⁴S, ⁸⁷Sr/⁸⁶Sr, Na, and Cl were identified as key geochemical signatures for source differentiation. Results indicate that direct TSF seepage contributes less than 10% to the salinity at OTMB16-79, while approximately 31% originates from water collected and returned by the French drain system. These findings demonstrate the value of multivariate geochemical and isotopic tools in identifying source contributions and support the refinement of OT’s conceptual hydrogeological model. The outcomes will contribute to establishing a risk-informed monitoring system and help prevent seepage migration, thereby supporting more effective and optimal TSF management.

Keywords: total dissolved solids, tailings storage facility seepage, strontium, d-excess value, sulphur isotope

References:
Avanzinelli, R, Boari, E, Conticelli, S, Francalanci, L, Guarnieri, L, Perini, G, … Ulivi, M 2005, ‘High precision Sr, Nd, and Pb isotopic analyses using the new generation Thermal Ionization Mass Spectrometer Thermo Finnigan Triton-Ti®’, Periodico di Mineralogia, vol. 75, pp. 147–166.
Brand, WA, Coplen, TB, Vogl, J, Rosner, M & Prohaska, T 2014, ‘Assessment of international reference materials for isotope-ratio analysis’, Pure and Applied Chemistry, vol. 86, pp. 467–472.
Clark, I & Fritz, P 1997, Environmental Isotopes in Hydrogeology, CRC Press, Boca Raton.
Craig, H 1961, ‘Isotopic variations in meteoric waters’, Science, vol. 133, no. 3465, pp. 1702–1703.
Hummel, RM, Elizabeth, A, Claassen, RD & Wolfinger, RD 2021, JMP® for Mixed Models, SAS Institute Inc., Cary.
Krouse, HR & Coplen, TB 1997, ‘Reporting of relative sulphur isotope-ratio data’, Pure and Applied Chemistry, vol. 69, pp. 293–295.
London Mining Network 2024, Rio Tinto: Get Serious About Addressing Community Harm, viewed 13 April 2025,
Matthew, M & Cecilia, LS 2020, Final Report: Hydrogeochemical Assessment of Water Emergence at the Tailings Storage Facility (TSF), Oyu Tolgoi (OT), prepared for Oyu Tolgoi LLC, Ulaanbaatar.
McCulloch, MT, Holcomb, M, Rankenburg, K & Trotter, JA 2014, ‘Rapid, high‐precision measurements of boron isotopic compositions in marine carbonates’, Rapid Communications in Mass Spectrometry, vol. 28, pp. 2704–2712,
rcm.7065
Milliken, GA 2000, ‘Mixed models analysis using JMP® software 4.0’, Proceedings of the Twenty-Fifth Annual SAS Users Group International Conference, SAS Institute Inc., Cary, pp. 276–282.
Nisi, B, Raco, B & Dotsika, E 2014, ‘Groundwater contamination studies by environmental isotopes: a review’, Threats to the Quality of Groundwater Resources: Prevention and Control, Springer, Berlin, pp. 115–150.
Oyu Tolgoi LLC 2024, Independent Environmental and Social Consultant Audit Report: September 2024, Oyu Tolgoi LLC, viewed 13 April 2025,
Philip, HE, Chiarizia, R & Dietz, ML 1992, ‘A novel strontium-selective extraction chromatographic resin’, Solvent Extraction and Ion Exchange, vol. 10, pp. 313–336,
Puntsag, T, Mitchell, MJ, Campbell, JL, Klein, ES, Likens, GE & Welker, JM 2016, ‘Arctic vortex changes alter the sources and isotopic values of precipitation in northeastern US’, Scientific Reports, vol. 6, no. 22647.
Remy, M, Clode, K, Motchan, T & Kerr, H 2024, ‘Water treatment development plan for Rio Tinto closure assets’, in AB Fourie, M Tibbett & G Boggs (eds), Mine Closure 2024: Proceedings of the 17th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1311–1320,
Russell, WA, Papanastassiou, DA & Tombrello, TA 1978, ‘Ca isotope fractionation on the Earth and other solar system materials’, Geochimica et Cosmochimica Acta, vol. 42, pp. 1075–1090,
Steiger, RH & Jäger, E 1977, ‘Subcommission on geochronology: Convention on the use of decay constants in geo- and cosmochronology’, Earth and Planetary Science Letters, vol. 36, pp. 359–362,
Tuvdendorj A, Sanjdorj S & Ulziibayar G 2008, Report on Groundwater Exploration in the Gunii Khooloi Deposit (in Mongolian), Open File Report, Ministry of Nature and Environment, Ulaanbaatar, pp. 22–30.




© Copyright 2025, Australian Centre for Geomechanics (ACG), The University of Western Australia. All rights reserved.
View copyright/legal information
Please direct any queries or error reports to repository-acg@uwa.edu.au