Source apportionment of heavy metals in soils around a coal gangue heap with the APCS-MLR and PMF receptor models in Chongqing, southwest China

This study studied the characteristics and source apportionment of heavy metal pollution in the agricultural soil surrounding a gangue coal heap in Chongqing, China by using absolute principal component scores-multiple linear regression (APCS-MLR) model and positive matrix factorization (PMF) model. The applicability of the models was compared in the assessment of source apportionment. The results showed that the average contents of Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn in the surface soil were 0.46, 0.14, 9.66, 31.2, 127, 95.6, 76.0, and 158 mg/kg, respectively. Combined with the spatial distribution and correlation analyses, the results of source apportionment were consistent for both the APCS-MLR and PMF models. Cd, Hg, As, and Pb were mainly affected by the gangue heap accumulation, with respective contributions of 74.6%, 79.4%, 69.1%, and 67.2% based on the APCS-MLR model and respective contributions of 69.7%, 60.7%, 57.4%, and 41.9% based on the PMF model. Ni and Zn were mainly affected by industrial and agricultural activities, while Cr and Cu were mainly affected by natural factors. The results of the source apportionment were approximately consistent between the APCS-MLR and PMF models. The combined application of the two receptor models can make the results of source apportionment more comprehensive, accurate, and reliable.