Changes in Soil Physical and Chemical Properties after a Coal Mine Subsidence Event in a Semi-Arid Climate Region

Abstract

This study describes the effects of coal mine collapse on soil physical and chemical properties in the semi-arid Bulianta mining area of northwest China. Statistical analysis of soil data from 2006, 2012 and 2019 show systematic long term changes of soil physical and chemical properties in response to a 2004 subsidence event. Results show that soil moisture content increased while soil bulk density (SBD) decreased gradually with the passage of time. Samples from different years since the subsidence event showed no significant difference in soil pH (P>0.05). The 0-5 cm soil layers showed the highest organic matter levels but values decreased with soil depth. The average organic matter content of soils in the subsided area increased with time since the subsidence event. Variation coefficients and average rate of change for available nitrogen (AN), available phosphorus (AP) and available potassium (AK) all decreased as contents tended to stabilize over time. Changes in soil physicochemical properties caused by subsidence represent long term economic, social and environmental costs. The results from this study demonstrate the benefits of early stage remediation or preemptive avoidance of risks posed by mine construction. They also provide references for long term monitoring of soil quality and restoration of mining areas.