REY and Sr-Nd isotopes of soils from Ravenna (northern Italy) and their significance for environmental studies

The delta Sr-87 and epsilon(Nd) of 9 samples from a soil of the San Vitale Pinewood (P) and a nearby farm (F) soil from Ravenna in northern Italy have been determined after sequential chemical analysis. The REY (REE + Y) concentrations in the HCl extracts from the two soils have also been determined. The NH4-acetate extracts display the highest Sr and Ca concentrations (38-292 mg/kg, and 231-49.12 g/kg respectively), while the water extracts provide the lowest ones (0.5-6.1 mg/kg and 0.08-033 g/kg, respectively). The REV concentrations range narrowly in the P soil (24.3-31.4 mg/kg), while they distinguish along with Sr and Ca between the upper and lower horizons in the F soil (51.5-63.3 and 19.8-27.1 mg/kg respectively). In particular, as the lower horizons display concentrations similar to those of the P soil, this suggests a common origin of those sediments. The PAAS-normalized patterns in the HCl extracts of both the soils show either a middle REE enrichment, suggestive of phosphate dissolution and/or REY complexation with organic matter, and a small positive Gd anomaly, referred to as the contribution from marine carbonates and phosphates. The range of delta Sr-87 (12.4-13) of the insoluble residue of the P soil indicates that Sr is is derived from crust silicates, that also provided the Sr of the insoluble residue of the F soil (delta Sr-87 = 9.3-17.1), but the larger range and the vertical decrease of values through the latter profile support the distinction in the upper and lower horizons. Asthese latter horizons display close delta 87Sr to the values of the P soil, the common origin of these sediments is confirmed. The overlapping ranges of epsilon(Nd) of the insoluble residue from both the soils (from -8.4 to -6.85 and from -7.8 to -7, respectively) suggest that Nd is also derived from crust silicates. The range of delta Sr-87 of the NH4-acetate extracts of the P soil (from -0.8 to -0.41) is close to the torresponding range of the lower horizons (from -0.31 to -0.27) of the F soil suggest Sr origin from Late Cenozoic carbonates. In contrast, the higher delta Sr-87 (from 0.09 to 0.25) of the upper horizons of the F soil, suggest some input of radiogenic Sr from crust silicates. The ranges of delta Sr-87 of the HCl extracts of the two soils largely overlap (the P soil from -0.9 to 0.3, the F soil from -0.72 to -0.34), suggesting a broadly common source, likely dolomite and phosphates of the Late Cenozoic. The narrow and overlapping ranges of epsilon(Nd) of the HCl extracts from the two soils (the P soil from -8.9 to -7.1, the F soil from -8.1 to -7.8) indicate that labile Nd is also provided by the same source, likely marine phosphates. Lastly, as the Sr-Nd isotopic ranges of geogenic and anthropogenic sources overlap in the study area, it is not possible to evaluate the potential impact of pollution on the two soils. (C) 2014 Elsevier B.V. All rights reserved.