Reactivity of urban environments towards legislative actions. The case of Roma (Italy)

The investigation of sediment chronostratigraphy was performed in order to reconstruct heavy metals (Pb, Cd, Cu, and Zn) and major elements (Fe, Al and Mn) fluxes in a heavy traffic site located in Roma (Italy). This city represents an ideal situation from a geochemical point of view (outcropping rocks are enriched rocks in terms of heavy metals content) where anthropic emissions are exclusively associated to traffic and heating systems. The impact of biological activity and soil erosion on sedimentation process were investigated in one urban lake, where the sedimentation model was defined using radiometric determinations (137Cs and unsupported 210Pb). Fluxes calculations and isotopic composition of lead were performed in order to enhance the metal distribution through the collected core. Statistical analysis allowed discriminating elements in two main groups: traffic related metals and urban aero-disperse elements. Indexes, which can estimate the elemental affinity to the urban dust, were calculated for metal source definition. Lake sediments recorded the fall of Pb air content that occurred after leaded gasoline phasing out and after about 10 years the total amount of Pb decreased of about 90%