Potential ecological risk assessment for trace metal(loid)s in soil surrounding coal gangue heaps based on source-oriented

Coal is the predominant energy source in China, resulting in coal gangue. We used the absolute principal component score multiple linear regression (APCS-MLR) model and the geo-detector method (GDM) for determining the potential ecological risk, apportioning sources, and identifying driving factors for trace metal(loid)s (TMs) in soil surrounding coal gangue heaps. The average contents for the concerned TMs (Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn) in the soil of interest were 0.48, 0.18, 11.0, 36.0, 129, 99.2, 68.3 and 141 mg/kg, respectively. Potential ecological risk indicated that the soil was primarily within the "Moderate risk" level, and Cd was the primary pollutant. "The number of coal gangue units" and "the distance between the sampling point and the coal gangue heap" were the key driving factors included in the geo-detector method. Combining APCS-MLR model and GDM, the source apportionment was enhanced in terms of accuracy and reliability. Natural, mining, and unrecognized sources contributed 41.1 %, 39.2 %, and 19.7 % of the TM distribution, respectively. Considering the relationship between TMs, their sources, and corresponding potential ecological risks, mining sources (mainly affected by gangue accumulation) presented a primary linkage with Cd, and its contribution to potential ecological risk was the highest, accounting for 58.2 %. Therefore, further research should focus on effectively managing and controlling the potential ecological risks originating from mining sources and Cd.