Comprehensive Evaluation of Soil Quality: a Case Study from a Semi-Arid Area Experiencing Coal Mine Related Subsidence in China

Soil quality strongly influences the growth of vegetation and other environmental factors. While generating economic value, mining activities also damage soil and vegetation. Ecological restoration of areas subjected to mining activities has become a major cost borne by government agencies and mining enterprises. Restoration depends on comprehensive assessment of soil and environmental quality. This study addressed impacts of subsidence occurring around the Bulianta Coal Mine of the Shenfu coalfield in China. Using non-subsiding areas as a control, the research compared soil quality parameters defined by the Integrated Fertility Index (IFI) and Potential Ecological Risk Index (RI) frequently used in environmental monitoring and remediation. The results showed that subsided areas exhibited greater soil bulk density (SBD) and pH values relative to soils from areas not experiencing subsidence. Soils from subsided areas contained lower available nitrogen (AN), available potassium (AK), organic matter (SOM) relative to soils from non-subsidence areas. Different soil layers also exhibited considerable variation in available phosphorus (AP), AK, and SOM that attained significance at the P<0.05 level. Soils from subsided areas showed lower concentrations of Cd, Cu, Pb, and Zn than that measured from non-subsidence areas. The heavy metal content of non-subsided soils varied considerably with the depth of soil layer analyzed. Lead was the most abundant species of heavy metal detected in the soil of the mining area, and Cd showed the greatest potential risk of soil pollution in the mining area. The soil fertility index in the study area depended on subsidence, which showed some degree of spatial continuity. The subsided area showed poor soil quality and the entire area categorized as a slight potential ecological risk. This research supports management and ecological restoration of the mining area and may serve as a reference for similarly impacted areas around the world.