【一般講演】 環境

[1K0414-19-05] Impact of snow accumulation and snowmelt on groundwater quality in the mine waste dump

○Sereyroith Tum¹, Shinji Matsumoto¹, Miu Nishikata¹, Tetsuo Yasutaka¹ (1. Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology (AIST))

司会：沖部 奈緒子（九州大学）

キーワード：Winter, snow melting season, pH, electrical conductivity (EC), groundwater level (GL)

In order to reduce the expense of treating acid mine drainage (AMD) in the legacy mines, minimizing the AMD generation is necessary. Therefore, we conducted a field investigation at one of the mine wastes dumps (MWD) in Hokkaido prefecture, Japan. Previous report mentioned that summer rainfall was one of the sources of sulfide minerals dissolution in MWD, but the study of snowfall and snowmelt effect to MWD remain uncertain. Thus, the objective of this research is to investigate the impact of snow accumulation and snowmelt on groundwater quality in MWD.
Three monitoring wells were installed in MWD to measure the pH, electrical conductivity (EC), and groundwater level (GL) from July 2021 to September 2022. Winter was assigned from December 2021 to March 2022 when snow accumulated on the surface soil of MWD. Snow melting season was assigned from March to May 2022. The fluctuation of GL in relation to pH, and EC were evaluated to interpret the impact on groundwater quality during winter and snow melting season. As a result, there was no significant change in pH, EC, and GL during winter. Snow accumulation on the surface soil during winter acted as the natural ice barrier preventing the infiltration of groundwater from further recharge into MWD. During snow melting season, the pH and EC fluctuated in respond to GL. The recharge sources from snowmelt and rainfall enhanced sulfide mineral dissolution in MWD. The stable pH, EC, and GL during winter indicated that preventing the water recharge to MWD can minimize the AMD generation.