Hydrogeochemical And Water Cycle Features Of Groundwater At A Western Arid Coal Mine In The Ordos Jurassic Coal Province, China
CUMT, China, People's Republic of
Nowadays, the Ordos Jurassic coal province of China is becoming the central bases of China coal industry. However, it has been gradually revealed that, even in this western semi-arid and ecologically fragile region, the mining hydrogeologic conditions of coal mines are actually not as simple as it had been explored and expected to be for quick sand catastrophes, hazardous coal-aquifer water inrush, gigantic mine water inflow, extra-thick overlying aquifers, etc. For mining safety and water protection purposes, it is urgent and of importance to investigate the hydrogechemical and water cycle features of groundwater for the Ordos basin.
Xiaojihan coal mine located in the east of the Ordos basin is typical of the regional hydrogeologic background and commenced coal mining in 2014. To investigate water quality and cycle features, 20 water samples of related underground aquifers were collected for water quality tests, 14 samples for isotopes of D/18O and T tests, and 6 samples for 14C tests. It showed that, definitely distinguished from the modern water in the Pleistocene sand aquifers and the middle Cretaceous semi-cemented aquifers, the groundwater occurring in the middle Jurassic coal bearing formations could commonly characterized as neutral pH, increasingly high SO42-, Na+ and TDS, and depleted D/18O. It would be reasonable to infer that the large amount of groundwater stored in the middle Jurassic aquifers had been occurring as the paleo-Mesozoic basins gradually evolving into the current topographic plateau and was eventually driven by the recharge at the N-S ridges of the Ordos Plateau to discharge from the middle to the surrounding Yellow river and its tributaries.
Preferably, as taking measures to control mine water hazards and protect rare ground water resources, we are expected to understand the dynamics of ground water at a coal mine on its regional context and to always remind ourselves that, for lacking or ununiformed aquifuges, the water in the modern sand and the Cretaceous aquifers could vertically leak down into or laterally reach the mining voids from a far distance.