Trace metals accumulation on the Po river prodelta, North Adriatic Sea

The Po River delta (northern Italy) is a complex system composed of terrestrial, transitional and coastal-marine ecosystems strongly influenced by different natural and anthropogenic stressors. In this study, we aimed to provide the anthropic impact during the last 200 years through geochemical concentration of heavy metals. In order to reach this objective, trace Metals (TMs: Pb, Zn, Cu, Cr, Cd and Ni), major elements (Al, Fe and Mn) and natural/artificial radionuclides (210Pb/137Cs) were analysed on the sediment core (EL14-C01) collected in 2014 in the Po River prodelta. We assumed the TMs mean concentrations during the pre-industrial time (before 1850) as the natural background in this area. Sediments deposited after 1850 exhibited a TMs gradual rise compared to the concentrations recorded in the pre-industrial era, in particular Pb, Zn and Cu (PZC). PZC vertical profiles show that the contamination has increased dramatically after the Second World War, during the so called ‘‘Italian Economic Miracle’’ period, exceeding up to 2.5, 2 and 1.5 (Pb>Zn>Cu) times the concentrations of the pre-industrial era. Post-war years saw the birth of the mechanical, chemical, ceramics Italian industries, and the switch from coal to oil and the plastic derivatives it entailed (Romano et al. 2013). The PZC concentrations reached the maximum between 1970s and 1980s, in agreement with anthropogenic atmospheric emissions changes. The distributions of ZPC indicate a sharp contamination decrease from the second half of the 1980s. Probably this reduction was related to the introduction of the Italian Law 319/76 and to the implementation of anti-pollution policies on automotive Pb (unleaded fuels). Recently, the levels of anthropogenic ZPC pollution are similar to the pre-WWII values. During the XXth century, the geochemical analysis show some TMs/Al peaks corresponding to the seven major Po floods with discharges above 8000 m3/s occurred in 1917, 1926, 1928, 1951, 1976, 1994, and 2000.