A study on the effect of in situ purification on coal mine drainage by loess

Abstract

Two in situ tests, in an unsaturated loess zone and an unconfined aquifer (northern Shaanxi Loess Plateau, Shaanxi, China), were conducted to investigate the potential of loess to purify coal mine drainage water. The first test involved the analysis of loess samples that were collected at the start of the test and at 20 days after the termination of the test. Results indicated general declines in the loess of two heavy metals: Cd declined from ∼3 to <1.5 mg/kg and Pb from ∼4 to <1.0 mg/kg. This demonstrated the capacity for removal of Cd and Pb through the irrigation of unsaturated loess. A second test indicated that, although the concentrations of a number of water quality variables remained high in the groundwater of the unconfined aquifer, after irrigation of loess there was a steady decline in the concentrations of Cd and petroleum, as well as a decline in electrical conductivity (EC). From the drainage source to a lower elevation site (of 5 m), the concentration of Cd and petroleum declined from 1.835 to 0.808 μg/L and 1.20 to 0.82 mg/L, respectively, while EC declined from 3.41 to 1.89 ms. We concluded that the unconfined loess aquifer had the potential to purify the infiltrating coal mine drainage water and to protect groundwater quality.

Keywords:

• Coal mine drainage water
• In situ test
• Unconfined aquifer
• Loess
• Purification

Acknowledgements

This study is funded by Program 111 of Innovation and Knowledge Introduction Plan as Colleges and Universities Subject of Ministry of Education and State Administration of Foreign Experts Affairs (No. B08039), and the projects “Groundwater Survey in the Northern Shaanxi Energy Base” (No.1212010535207) and “Evaluation and investigation of groundwater pollution in the main cities of Northwest China (No.1212011220982)” from China Geological Survey.