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

Abstract This study researched the characteristics and source apportionment of heavy metal pollution in the agricultural soil surrounding a gangue coal heap in Nanchuan, Chongqing using APCS-MLR and PMF receptor models. The applicability of the models were compared in the assessment of source apportionment. The results, in combination with those from soil profile data, showed that the average contents of Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn in the topsoil were 0.46, 0.14, 9.66, 31.2, 127, 95.6, 76.0, and 158mg/kg, respectively. The spatial distribution and correlation analysis indicated that Cd, Hg, As, and Pb had a significant positive correlation (r = 0.45–0.70, P < 0.01), with the highest concentrations near the gangue heap in the northwest of this study area. Cr and Cu had a significant positive correlation (r = 0.47, P < 0.05), with the highest concentrations in the northwest and southeast of this study area. Ni and Zn had a significant positive correlation (r = 0.88, P < 0.01), with the lowest concentrations in the northwest of this study area. The analysis of pollution sources showed that 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% from the APCS-MLR analysis and 69.7%, 60.7%, 57.4%, and 41.9% from the PMF analysis. 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 consistent with those of APCS-MLR and PMF. This study demonstrates that the combined application of the two receptor models can make the results of source apportionment more comprehensive, accurate, and reliable.