Critical loads and exceedences of Cd and Pb in a Northern Italy area

The ecosystems sensitivity to toxic heavy metals atmospheric depositions can be evaluated calculating the Critical Load, an essential indicator for better understanding the evolution of environmental deterioration phenomena. In this work, the Steady State Mass Balance methodology with a semi-dynamic approach has been used to evaluate the Critical Loads for Cadmium and Lead for terrestrial ecosystems in four EMEP grids 10x10 Km representative of Bologna province. In order to evaluate the areas where the Cd and Pb depositions exceed the Critical Loads, the results of a long term characterisation of wet and dry atmospheric depositions, carried out in Bologna suburbs, has been used. Results highlight that CL values strongly depend on the soil characteristics. According to the degree of sensitivity associated to the CL estimated values, no excess of Cd and Pb has been found for the agricultural soils, while, almost everywhere, deciduous forest soils show exceedances. Grasslands show negligible exceedances for Cd but significant for Pb; Pb exceedances also occur in coniferous forest soils.