Research on long-term migration behaviors of heavy metals after close-distance coal seam backfill mining

Junmeng Li; Yanli Huang; Yingshun Li; Shenyang Ouyang; Shiqi Wang; Zizhao Ding

doi:10.1016/j.jhazmat.2024.134140

Research on long-term migration behaviors of heavy metals after close-distance coal seam backfill mining

J Hazard Mater. 2024 May 15:470:134140. doi: 10.1016/j.jhazmat.2024.134140. Epub 2024 Mar 27.

Authors

Junmeng Li¹, Yanli Huang², Yingshun Li³, Shenyang Ouyang³, Shiqi Wang³, Zizhao Ding³

Affiliations

¹ School of Mines, China University of Mining & Technology, Xuzhou 221116, China; Key Laboratory of Coal Resources and Green Mining in Xinjiang, Ministry of Education, Xinjiang Institute of Engineering, Urumqi 830000, China; Key Laboratory of Deep Coal Resource Mining of Ministry of Education, China University of Mining & Technology, Xuzhou 221116, China.
² School of Mines, China University of Mining & Technology, Xuzhou 221116, China; Key Laboratory of Coal Resources and Green Mining in Xinjiang, Ministry of Education, Xinjiang Institute of Engineering, Urumqi 830000, China; Key Laboratory of Deep Coal Resource Mining of Ministry of Education, China University of Mining & Technology, Xuzhou 221116, China. Electronic address: 5306@cumt.edu.cn.
³ School of Mines, China University of Mining & Technology, Xuzhou 221116, China.

PMID: 38574658
DOI: 10.1016/j.jhazmat.2024.134140

Abstract

The backfill mining of coal-based solid waste in goaf poses a potential risk of heavy metal pollution to the groundwater environment, and the migration behavior of heavy metals differs significantly under the disturbance of backfill mining in close-distance multi-layer coal seams and single-layer coal seams. In this study, a migration model of heavy metals after solid backfilling in the goaf of shallow-buried close-distance thick coal seams was established, and the impact of the overburden damage and the layered distribution of the filling body on the long-term migration behavior of heavy metals were analyzed. The results show that the migration of heavy metals after close-distance coal seam backfill mining exhibits a higher risk of heavy metal pollution. The peak permeability of overburden after close-distance coal seam backfill mining is about 600 × 10^-19 m² higher than that after single-layer coal seam backfill mining. The migration distance of heavy metals in the floor after backfill mining of close-distance coal seams is 7.41 m farther than that of single-layer coal seam backfill mining, and its migration time of heavy metals to the surface is 27 a earlier than that of single-layer coal seam. This research provides theoretical and empirical support for the ecological risk assessment and heavy metal pollution control in close-distance coal seam backfill mining. ENVIRONMENTAL IMPLICATION: The main filling material of close-distance coal seams backfill mining is coal gangue. Heavy metal elements such as Mn and Cr will be released in the underground environment for a long time, and the migration behavior of heavy metal elements will have an impact on the groundwater environment for more than 1000 years. This research provides theoretical and empirical support for the ecological risk assessment of close-distance coal seam backfill mining and the mitigation of heavy metal pollution.

Keywords: Close-distance coal seams; Environmental effects; Heavy metals migration; Solid backfill mining.