The influence of a large city on some soil properties and metals content

Urban soils differ from the rural ones by the fact that they are more strongly influenced by anthropogenic activities. This influence is often reflected by a high degree of contamination. To investigate the influence a large city can have on its soils and on the surrounding ones, samples within the city of Torino, Italy were compared with a set of surrounding soils developed from the same alluvial parent material. City–country trends were investigated by spatially managing the samples. Results show that the city plays a key role in concentrating some pollutants, such as Pb, Zn, and Cu within its borders. Lead is the element most enriched in the city, presenting a pollution index of 7.5 calculated comparing the two sets of samples. Ni and Cr appear to have a strong natural contribution. The spatial distributions for Pb, Cu and Zn present an abrupt division between urban and rural samples. Unexpectedly, the transport of pollutants from the city to the surrounding areas seems to be limited as no city–country trends with distance are identified. The pH and the sand fraction result also influenced by the city, showing high values. The investigation of possible city–country distance trends has shown to be effective in evaluating the impact a city can have on its soils and on the transport and deposition of contaminants on the surrounding ones.