Leaching Behavior and Potential Environmental Effects of Trace Elements in Coal Gangue of an Open-Cast Coal Mine Area, Inner Mongolia, China

Liu Yang,Bo Song,Jianfei Song,Ruduo Wang,Xue Bai,Jianli Jia,Tianhao Zhou,Haixia Pu

doi:10.3390/min6020050

Abstract

In order to better understand the role of coal gangue in potential environmental and ecological risks, the leaching behavior of trace elements from coal gangue has been investigated in an open-cast coal mine, Inner Mongolia, China. Four comparative column leaching experiments were conducted to investigate the impacts of leaching time, pH values and sample amount on the leaching behavior of trace elements. Enrichment factors (EF), maximum leached amount (Lam), maximum leachability (Lrm), effects range low (ERL) and effects range median (ERM) were employed to evaluate potential environmental and ecological hazards resulting from the leaching behavior of environment-sensitive trace elements from coal gangue. Leaching time and sample amount display important effects on trace element concentrations, leached amounts and leachability. The pH values exhibit a weak influence on the leaching behavior of the selected trace elements (e.g., As, V, Cr, Co, Ni, Cu, Zn, Se, Cd, Sn, Pb and Hg). The coal gangue are enriched in As, Co, Se and Pb and, in particular, show higher environmental pollution levels of As and Se (EF > 2). Lam values suggest that all of the elements investigated do not show potential risk to soils and vegetation, but have a high hazard risk for ground water. Elements including Ni, As, Cr and Zn are inclined to show high or moderate biological toxicity.

Highlights

In recent years, coal has accounted for 74% of China’s total primary energy consumption and will continue to be the major energy source in the decades [1]
The results indicated that all of the selected trace elements from coal gangue in the study area had no potential risk to soils and vegetation, based on comparing the leached amount (Lam) values with the corresponding concentrations of the elements defined by the environmental quality standard for soils and limits of contaminants in foods (Tables 9 and 10)
Based on the results of leaching behavior, the potential environmental and ecological hazards were evaluated through different methods

Summary

Introduction

Coal has accounted for 74% of China’s total primary energy consumption and will continue to be the major energy source in the decades [1]. Environmental hazards were caused as a result of the release and dispersal of harmful trace elements contained in coal, coal gangue and coal combustion residues [2,3,4,5]. The rapid development of coal mining in China over the last twenty years has led to a huge coal gangue accumulation in coalfields. 1.5 thousands square kilometers of land in China [6]. This could result in substantial environmental hazard and ecological risk, such as soil and water pollution and ecological deterioration, if reasonable precautions are not taken [7,8].

Methods

Results

Discussion

Conclusion