Sources of heavy metals in soils in densely populated areas based on the UNMIX model

Abstract

To estimate heavy metal sources in soils under the influence of a high-density population, the concentrations of heavy metals, namely, Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Hg, Pb, and Fe, were determined in 23 soil samples from different sites at Suzhou University campus. Factor analysis (FA) and source analysis were completed based on the UNMIX model; the results showed that the contents of Ni, Cu, As, Cd, and Hg in the samples are 40.06, 60.75, 25.03, 0.10, and 0.12 mg/kg, respectively, which are higher than their soil background values in China. Three factors were obtained, agricultural activities, natural pedogenesis, and domestic waste; these accounted for a total of 76.49% of the explained covariance. The results for the three sources calculated using the UNMIX model are consistent with the FA results. The contribution of these sources to heavy metals in soils of the study area was also calculated; the contribution rates were 5.01, 29.25, and 65.74%, respectively. In conclusion, heavy metals in soils in the study area are mainly inherited from the weathering of parent rock (source 3, 65.74%) and are affected by agricultural activities such as chemical fertilizer use (source 2, 29.25%), whereas the effects of domestic waste such as batteries (source 1, 5.01%) is weak.