Biogeochemical evaluation of historical sediment contamination in the Gulf of Palermo (NW Sicily): Analysis of pseudo-trace elements and stable isotope signals

Sedimentary biogeochemical data from the Gulf of Palermo, which borders one of the major urban and industrial areas of the central Mediterranean, provide a decennial–centennial-scale record of the effects of human activity on this coastal environment. In this study we report trace elements (TE), Corg/Ntot ratios, δ13Corg, and δ15Ntot from dated (210Pb) sediments collected in two coastal stations variably influenced by urban/fluvial loadings and illegal dumping and we compare them with published data for offshore sediments, in order to investigate at a large spatial scale the influence of on-land activities on sedimentary marine system. TE were generally low except for Hg and Pb, which exhibited moderate enrichments. Low TE enrichment factors with respect to Corg indicate that trace elements were mainly trapped by sedimentary organic matter. Corg/Ntot, δ13Corg, and δ15Ntot depth profiles showed that sediments received organic matter derived from marine sources mixed with organic matter from the erosion of terrestrial material as well as unregulated sewage discharges. Superimposed on these patterns, repeated shifts in δ13Corg towards values higher than those typical of offshore Palermo sediments were concomitant with higher Corg/Ntot. These shifts observed in the core portions covering the last 40 years reflect enhanced eutrophication as result of elevated nutrient input into marine waters. The results of this study have traced the origin and extent of the organic enrichment and emphasized the importance of utilizing a complete range of chemical and isotopic analyses from sedimentary records to reconstruct the environmental history of coastal ecosystems impacted by urbanization processes.