Risk assessment of potentially toxic elements in intermittent rivers, “fiumara”, flowing in the Gulf of Milazzo (Sicily, Italy)

Increasing human activities in coastal areas need careful assessments of both environmental and human health risk. Particular attention needs rivers, as they are responsible for the drainage and transport of contaminant loads. Such aspects have been poorly investigated in intermittent rivers and ephemeral streams (IRES) despite they represent most of water pathways in the world. In five IRES of the highly anthropized Gulf of Milazzo (North-Eastern Sicily, Mediterranean Sea), silty-clay sediments from dry riverbed have been investigated to evaluate environmental risk by heavy metal contamination. The ICP-MS analysis, apart from a minor enrichment in Mn, showed average concentrations of Zn, Cu, Pb, Ni, Co, and Cd lower than warm-temperate coastal areas and European rivers, background continental crust, background shale, and to the quality guidelines for sediments (SQGs). The investigated IRES were found unpolluted, and their air-exposed riverine sediments cannot be considered responsible for human health risk. However, the slight increase in some contaminant concentrations locally reported needs to be carefully considered, since clearly associated to a condition of disorderly anthropization. Lastly, the needing to better understand the IRES role in dynamics of HMs contamination in Mediterranean, subtropical, and semiarid regions worldwide, is suggested.