Flow and geochemical modeling of drainage from Tomitaka mine,Miyazaki,Japan

• Published in: Journal of environmental sciences (China) Vol. 36; no. 10; pp. 130 - 143
• Main Authors: Yamaguchi, Kohei, Tomiyama, Shingo, Metugi, Hideya, Ii, Hiroyuki, Ueda, Akira
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.10.2015
• Subjects: Environmental Monitoring; Groundwater - analysis; Hydrogen isotope; Japan; Kinetics; Mine drainage; Mining; Models, Chemical; Oxygen isotope; Rain; Rock–water interaction; Water movement; Water Movements; Water Pollutants, Chemical - analysis; 建模; 日本; 有色金属矿床; 氧化还原电位; 水化学变化; 水地球化学; 矿井排水; 酸性矿山; Japan; INW, Japan; Oxygen isotope; Hydrogen isotope; Water movement; Mine drainage; Rock–water interaction
• ISSN: 1001-0742; 1878-7320
• DOI: 10.1016/j.jes.2015.05.012

The chemistry and flow of water in the abandoned Tomitaka mine of Miyazaki, western Japan were investigated. This mine is located in a non-ferrous metal deposit and acid mine drainage issues from it. The study was undertaken to estimate the quantities of mine drainage that needs to be treated in order to avoid acidification of local rivers, taking into account seasonal variations in rainfall. Numerical models aimed to reproduce observed water levels and fluxes and chemical variations of groundwater and mine drainage. Rock–water interactions that may explain the observed variations in water chemistry are proposed. The results show that：（1） rain water infiltrates into the deeper bedrock through a highly permeable zone formed largely by stopes that are partially filled with spoil from excavations（ore minerals and host rocks）;（2） the water becomes acidic（p H from 3 to 4） as dissolved oxygen oxidizes pyrite;（3） along the flow path through the rocks, the redox potential of the water becomes reducing, such that pyrite becomes stable and p H of the mine drainage becomes neutral; and（4） upon leaving the mine, the drainage becomes acidic again due to oxidation of pyrite in the rocks. The present numerical model with considering of the geochemical characteristics can simulate the main variations in groundwater flow and water levels in and around the Tomitaka mine, and apply to the future treatment of the mine drainage.