Geochemical characterization of surface sediments from the northern Adriatic wetlands around the Po River delta. Part II: aqua regia results

•Geochemical characterization of surface sediments in the Po River deltaic system•Geochemical information about a further 20 elements are provided.•Extractability degree evaluated for 28 elements•Confirmed contamination by harmful heavy metals of a lagoon near Ravenna•Necessity to use geochemical information for the management of the investigated area

Sediment characterization is crucial when assessing environmental quality of aquatic systems. In a previous study, we assessed the geochemical composition of surface sediments of several wetlands within the historical Po deltaic system by using X-ray fluorescence, and we evaluated the anthropogenic influence on the metal levels comparing data with background and calculating enrichment indexes. In the area, geochemical information is poor and quality standard levels for sediments are still lacking in regulation frameworks. As a further investigation of the previous study, we investigated the pseudo-total concentrations, after aqua regia digestion, of Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Hg, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Pd, Pt, Rb, S, Sb, Sc, Se, Sn, Sr, Th, Ti, Tl, U, V, Y, Zn, and Zr in sediments from 4 coastal wetlands belonging to the historical Po deltaic system (NE Italy) (Valli di Rosolina, Valle Bertuzzi, Valli di Comacchio, and Pialassa della Baiona). The aims were (1) to study relationships among elements by applying multivariate statistics, (2) to evaluate the extractability degree with respect to the total contents, and (3) to better understand the environmental relevance of the trace elements in the study area by comparing pseudo-total contents with background concentrations, screening values provided by Italian legislation and reference values reported in environmental guidelines and recent scientific literature. According to the results of this study: 1) shellfishing is legal, and also illegally practiced, in the site the most affected by heavy metal pollution; 2) part of the Pb enrichments in most sites could be originated by lead shot in the sediment; and 3) habitat and species conservation in these investigated Special Protected areas should consider geochemical aspects.