Pollution characteristics and quantitative source apportionment of soil heavy metals using PMF and APCS-MLR models in an industrial park in Northwest China

Soils in typical coal industrial areas are often enriched with heavy metals. In the Ningdong industrial park of Northwest China, rapid economic development and pollutant emissions have endangered the surrounding soil environment. Understanding the spatial distribution, hazards, and sources of heavy metals is crucial to mitigate their contamination in soil. The intense industrial activities in the region lead to complex and diverse origins of heavy metals, making single-source apportionment methods inadequate. In this study, we methodically collected 95 soil samples from a coal-electricity production base in the Ningdong industrial park, and determined the concentrations of Cu, Pb, Cd, Cr, As and Hg. It is found that the concentrations of Cu, Pb, Cd, Cr, As and Hg are 1.29 to 18.45 times higher than the background values. Comprehensive pollution indices indicated that 89.47% of the samples were severely polluted, with Cd and Hg posing the highest ecological risks. Positive Matrix Factorisation and Absolute Principal Component Score-Multiple Linear Regression models identified industrial sources, coal processing, traffic-coal combustion, and mining as primary contributors. Both models yielded similar results, with industrial and coal-related activities being dominant. Heavy metal concentrations were significantly higher in the northwestern and southeastern areas compared to the central region, closely associated with industrial and mining activities. These findings highlight the importance of targeted prevention and management strategies for heavy metal contamination in industrial parks.