Potentially toxic elements concentrations in schoolyard soils in the city of Coronel, Chile

Urban areas are constantly growing. By 2050, the urban world population, it is predicted to reach 6 billion. Being component of cities environment, urban soils have elevated levels of potentially toxic elements from anthropogenic action. The aims of this study are (1) to establish background levels of potentially toxic element in soils in the city of Coronel and (2) to assess the pollution and identify its origin. Samples (129 in total) were collected in Coronel, from 43 sites in schoolyards. Three samples were taken at each site: 0-10 cm, 10-20 cm and 150 cm depth. Principal component analysis (PCA), cluster analysis (CA) and depth ratios were applied to distinguish the origin of the contamination. The geoaccumulation index, contamination factor and the integrated pollution index were used to estimate the pollution. The median concentration of the chemical elements in 0-10 cm depth was Ba 38 mg kg^-1; Co 15 mg kg^-1; Cr 18 mg kg^-1; Cu 22 mg kg^-1; Mn 536 mg kg^-1; Ni 35.5 mg kg^-1; Pb 6 mg kg^-1; V 94 mg kg^-1; Zn 65 mg kg^-1. Principal component analysis and CA suggested that Co, Ni and Mn were mainly derived from geogenic origin, while Ba, Cr, Cu, Pb, V and Zn from anthropic origin. Contamination factor indicated that some soil samples were classified as considerable contaminated to very highly contaminated by Ba, Pb, Zn and V.