Source apportionment of soil heavy metals based on multivariate statistical analysis and the PMF model: A case study of the Nanyang Basin, China

Analyzing the spatial variation characteristics of heavy metals in soil and identifying their sources is crucial for preventing, controlling, and managing regional environmental pollution. In this study, 5778 surface soil samples were collected from the Nanyang Basin. The content characteristics of five heavy metals (As, Cr, Cd, Hg, and Pb) were determined and analyzed. The spatial distribution characteristics of these heavy metals in the soil were investigated using inverse distance interpolation and spatial autocorrelation analysis. Additionally, the sources of heavy metals in the soil were qualitatively and quantitatively explored through PCA and PMF models. The results revealed that the mean values of all elements, except As and Hg, exceeded the country soil background values. Spatially, the distribution of soil heavy metal elements showed evident heterogeneity and autocorrelation, with obvious differences between the western and eastern regions, where heavy metal concentrations were generally higher in the west and lower in the east. Four sources of heavy metals were identified in the study area: mining sources, natural sources, transportation sources, and a combined source of atmospheric deposition and agricultural activities. The element As was primarily derived from natural sources (80.90%). The element Cr was influenced by multiple factors, mainly from mining sources (66.20%) and natural sources (31.80%). Transportation sources (46.30%) and mining sources (44.80%) were the primary influences on the element Cd. The element Pb was influenced by transportation sources (64.70%) and natural sources (18.11%). The element Hg was mainly influenced by both atmospheric deposition from coal combustion and agricultural activities (90.50%).