Potentially toxic elements (PTEs) availability in top soils of urban park, agricultural farm and the San Vitale Pinewood (Ravenna, Italy)

The distribution of potentially toxic elements (PTE) and their mobility in soils were studied in the district of Ravenna (Italy), due to the presence of numerous and long established industrial sites, along with intensively cultivated agricultural land and high vehicular traffic. Extractions of soil samples, collected from the surface and subsurface horizons of an urban park, a suburban pinewood and arable fields, were performed with water and 10mmol LMWOAs solution, consisting of acetic acid, formic acid, citric acid and malic acid at a ratio of 2:2:1:1. Pseudo-total soil content of heavy metals was estimated by aqua regia digestion. Extractable heavy metals (Cr, Cu, Ni, Zn, Cd and Pb) and pseudo-total metal contents were used to estimate the solid/solution distribution coefficients (Kd) of PTE in order to assess the environmental risk with respect to plant uptake and/or leaching throughout the soil profile to groundwater. The soils were analysed for pH, particle size distribution, cation exchange capacity, carbonate content, Fe, Al and Mn oxides and organic C content. Due to the natural enrichment in soil organic matter under the pinewood the determination of active humic substances, namely humic and fulvic acids, in the upper horizons were also performed. The results were interpreted using linear and multiple linear correlation and regression analysis. Soil properties important to heavy metal retention and solubility in these soils are discussed.