Geo-fluid analysis for the natural purification mechanism of Arsenic and Iron in Yotsugi mill tailings pond

Kawasaki, Yohei*; Yagisawa, Makoto*; Fukuta, Hiroki*; Granata, G.*; Tokoro, Chiharu*; Ohara, Yoshiyuki

The presence of arsenic in mine/rock drainage is an important issue in environmental research. In Ningyo-toge mine, mine/rock drainage is conducted to Yotsugi Mill Tailing Pond in which several toxic ions such as arsenic and iron can be naturally oxidized and removed as precipitates. In this study, the dynamic behavior of arsenic and iron in the Yotsugi Mill Tailings Pond at Ningyo-toge mine was investigated. For the geo-fluid analysis, a geosphere fluid modeling software (GETFLOWS) was utilized. GETFLOWS can model the dynamic behavior of contaminants in terms of advection-dispersion in porous media, chemical reactions and adsorption, for both point source and non-point source pollutants. The profile concentrations of As(III) and Fe(II) determined by simulations were found to be in good agreement with the values measured on the field. Result also highlighted the key role of phosphate in the natural removal of the arsenic from the pond: where high concentrations of phosphates were present in the pond, the natural removal of arsenic would be dramatically diminished.