Urban soil contamination by potentially risk elements

A high displacement of inhabitants into large towns, presence of industry, and constantly growing traffic have a high impact on the environment and considerable exposure of human health to environmental risks. Therefore, putting emphasis on the best environmental quality is necessary. In this work, the pollution level of urban parks was studied, the influence of the type of pollution source was analysed, and the effect of shading by trees was studied. The analyses were carried out on soil samples taken from thirteen parks in two towns of the Czech Republic, in Prague, a town considered to be mainly residential, and Ostrava, a predominantly industrial town (steel working plant). The sampling points were selected to cover the whole towns equally. In each park, two sampling points were chosen, the first one under trees, the second one in the open area. The sampling was done in the summer of 2006 in the depths of 0-10 and 10-20 cm. In addition to basic soil analyses performed by routine methods, potentially risk elements (Zn, Cd, Pb, Cu, and As) in cold 2M HNO3 extract were determined. Differences between the sampling points shaded and not shaded by trees were evidenced, with higher concentrations of risk elements under trees. The element contents differed between both towns as well. Significantly higher values of lead (mean 86 mg/kg) and copper (mean 28 mg/kg) were found in Prague, as a traffic consequence, compared to Ostrava, where lead reached the mean of 41 mg/kg and copper of 18 mg/kg. Maximum permissible limits were exceeded in Ostrava parks especially with Cd, in Prague with Pb.