Impact of mechanical street cleaning and rainfall events on the quantity and heavy metals load of street sediments.

The paper presents and analyses the results of a street sediments monitoring campaign carried out during dry weather in order to quantify the impact of mechanical street cleaning and rainfall events on the quantity and heavy metals load of street sediments. The study has been carried out in an experimental catchment in a medium traffic street of a residential/commercial area in the city of Reggio Calabria (Italy). Thanks to acquired data, it was possible to assess the amount and the degree of pollution of street sediments, the efficiency of mechanical street cleaning in terms of sediments and pollutants removal, the wash-off of street sediments during rainfall events and the related potential impact on receiving water bodies. The results obtained confirm that street sweeping is generally scarcely effective as a practice for urban storm run-off quality control and that run-off is, on the contrary, quite effective in street sediments removal especially for smaller particles. Moreover, chemical analyses indicate that, although the concentration of heavy metals is higher in sediments particles having a diameter lower than 0.075 mm, the greatest part of the pollutants load is associated to larger particles.