Geochemical balance for the evaluation of the agro-environmental quality of a complex territorial system: the case study of the Ravenna area – report one year later

The S. Vitale Pinewood represents an historical landmark in coastal Romagna. It developed on an old dune system in the north of Ravenna area, and is bordered by the Pialassa Baiona lagoon. After the first year of integrated studies on the different environmental matrices present in this area, some preliminary results are reported. Waters from the saturated zone are rarely composed of freshwater; they are generally brackish waters of variable composition, ranging from NaCl, Na-CaCl, NaCl-HCO3,Ca-MgHCO3 and NaHCO3, suggesting the different effects of intrusion and freshening. In particular, soil waters from the southernmost area of the Pinewood are generally the more saline. Chemical analyses of more than 30 major and trace ions, including the REE not usually determined in both surface and underground water samples, have shown no evidence of significant pollution by human activities. Sr, B, H and O isotopes have revealed to be useful markers for tracing the seawater intrusion in terms of both conservative parameters and cation-exchange processes. In addition, Sr isotopes have allowed to determine the possible sources of Sr and Ca as a proxy, thus providing information on a basic nutrient for the Pinewood vegetation, and giving indications on the possible contribution of fertilizers to the Sr isotopic budget. The apparent underground water flow encompasses about 75 years on the basis of the measured 226Ra/222Rn ratios. Chemical and mineralogical analyses of the soil horizons of 9 profiles located in the Pinewood have provided a bulk characterization integrated by the evaluation of the bioavailable fractions of both nutrient and toxic elements, including the REE and PGE. In particular, there is a significant enrichment of Pb and, to a lower extent, Zn and Cu in the topmost horizons. Sr isotopes have brought evidence of the significant contribution of seasalts to soils by atmospheric deposition, and have supported the origin of the dune sands from the basins of both the Po river and Romagna’s Apenninic rivers. As a whole, the integrated water-soil study allows for setting some constraints to the balance between seawater intrusion and freshening processes in coastal aquifers and on heavy metal accumulation and mobility within soil profiles. These preliminary results authorize to advance some hypotheses on the causes affecting health of the pinetrees, that constitute the most valuable and historical landmark of the S.Vitale Pinewood