Identification of trace element sources and associated risk assessment in vegetable soils of the urban-rural transitional area of Hangzhou, China.

In the urban-rural transitional area of Hangzhou, China, 74 topsoil samples were collected from vegetable fields to measure the contents of arsenic (As), copper (Cu), cobalt (Co), cadmium (Cd), chromium (Cr), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn). The combination of multivariate statistical and geostatistical methods successfully separated the contaminating elements (As, Cd, Cu, Hg, Pb and Zn) from uncontaminated elements (Co, Cr, Ni and Mn). A significant correlation was found between these uncontaminated elements and total Al2O3, Fe2O3, and SiO2 of the soils, indicating that the source of these elements was mainly controlled by soil-forming factors. On the other hand, these contaminating elements showed relatively weaker correlation and higher spatial variability, indicating that their enrichment and spatial heterogeneity were mostly affected by anthropic inputs. Through the pollution evaluation, it was found that only 30.8% of the study area did not suffer from moderate or severe pollution.