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/* Style Definitions */table.MsoNormalTable{mso-style-name:"Table Normal";mso-tstyle-rowband-size:0;mso-tstyle-colband-size:0;mso-style-noshow:yes;mso-style-priority:99;mso-style-parent:"";mso-padding-alt:0cm 5.4pt 0cm 5.4pt;mso-para-margin:0cm;mso-para-margin-bottom:.0001pt;mso-pagination:widow-orphan;font-size:10.0pt;font-family:"Calibri","sans-serif";} Bulletin of the Geological Society of Malaysia, Volume 58, December 2012, pp. 23 – 271Department of Geology, Faculty of Science, Chulalongkorn University, Phayathai Road, Pathumwan, Bangkok, Thailand 10330
2National Center of Excellence for Environmental and Hazardous Waste Management (NCE-EHWM), Chulalongkorn University, Bangkok, Thailand 10330.
3Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, IA, USA.
4Environmental Research Institute, Chulalongkorn University, Phayathai, Pathumwan, Bangkok, Thailand 10330
5Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Phayathai, Pathumwan, Bangkok, Thailand 10330
*Email address: lertc77@yahoo.com
Abstract: Contamination of underlying aquifers in gold mining areas is usually a great concern and prevention plans need to be implemented. To assess the potential risk of heavy metal contamination, the simulation of heavy metal transport was carried out using variable leachate fluxes and chemical nonequilibrium two-site sorption parameters derived from column experiments. This study applied a numerical model, called the HYDRUS-2D, to simulate the transport of Mn2+ under a single metal and multi-metal systems with 2 variable leachate fluxes (0.002 and 0.0026 m/day) through a lateritic aquifer approximately 5 km downgradient of the tailing pond. This model could be used as an environmental monitoring tool for gold mining management. The model assumed that the compacted clay layer of the tailing storage facility (TSF) has cracked and this led to Mn2+ and some other elements to contaminate the shallow groundwater. The simulations showed that the time needed to reach from contamination to the Thailand drinking water standard at a specific location for Mn2+ in a multi-metal system was faster than those in the binary metal system and single metal system, respectively. With increasing leachate flux from 0.002 to 0.0026 m/day (30% increase), the time to reach the drinking water standard at well no. 1 (1 km downgradient, the nearest well to the source) was about 57 and 106 years (17 and 19% decrease, respectively) for Mn2+ under the multi-metal and single metal systems. In addition, the timing of the heavy metal contamination leached from the tailings may be a source of pollution for over hundreds to thousands of years. As indicated by the simulation results, the predicted impacts of contamination of the TSF on the groundwater quality in the lateritic aquifer indicate that sorption parameters and leachate fluxes should be carefully monitored. These visible descriptions should be used as management tools for planning well installations under field conditions.
Keywords: lateritic aquifer, chemical nonequilibrium sorption, HYDRUS-2D, modeling
https://doi.org/10.7186/bgsm58201204
