Heavy metals in soils from a representative rapidly developing megacity (SW China): Levels, source identification and apportionment

Soil heavy metal pollution now is a major environmental concern in China particularly in some rapidly developing areas with intensified agricultural practices. High-spatial-resolution sampling (1664 surface (0-20 cm) and 416 deep (150-200 cm) soil samples) was undertaken in four typical agricultural Counties of Municipality Chongqing (SW China) and consequently eight priority heavy metals (HMs; As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) and other elements were measured. Classic and advanced multivariate statistics and multi-linear regression with factor analysis (FA-MLR) receptor modeling were applied for characterization and sources apportionment of HMs in soils. There was notably spatial variability in eight priority HMs with the mean concentrations decreasing as follows: Zn > Cr > Ni > Pb > Cu > As > Cd > Hg. Soil contamination was enhanced by As, Cd, Cr, while obvious enrichment of Cd and Hg in surface soils in comparison with deep soils should be noted. We revealed dominant anthropogenic contributions (64%-90%) of metal - bearing industrial emission, fuel consumption and agriculture to certain HMs, while the abundant elements of Si, Al and Fe were natural in origin. Our study will be helpful for improving soil environment and strengthening the capacity of multivariate statistic techniques and models in soil pollution research.