Soil geochemical survey of abandoned mining sites in the Eastern-Central Peloritani Mountains, Sicily, Italy

This investigation focused on topsoils (n = 122) and vertical profiles (n = 6) distributed over an area of 250 km² in the eastern-central Peloritani Mountains, northeastern Sicily. Georeferenced concentration of 53 elements (including potentially harmful ones), determined by ICP-MS after an aqua regia leach, were used to produce geochemical maps by means of a GIS-aided spatial interpolation process. Results show that there are two distinct areas: the larger, located between the Fiumendinisi, Budali and Ali villages, and the other between C. Postlioni and Femmina Morta, which contain anomalous As (up to 727 mg/kg), Sb (up to 60 mg/kg), Ag (up to 1 mg/kg) and Au (up to 0.1 mg/kg) concentrations. Most of the investigated areas have high contamination levels for As, Zn, Sb, and Pb that exceed the threshold values (As = 20 mg/kg, Zn = 150 mg/kg, Sb = 10 mg/kg and Pb = 100 mg/kg) established for soils by the Italian Environmental Law (Decreto Legislativo 2006, number 152).

The isotopic ratios of ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb have been measured in selected soils on both leaches [using 1M HNO₃–1.75M HCl (50:50)] and residues thereof. Soil leach reflects possible anthropogenic contamination, whereas soil residues indicate geogenic contributions. Results suggest that most of contamination in the soils is related to the presence of sulphide and sulphosalt rock-forming minerals in the surveyed area. The soil fraction contains a Pb value >1600 mg/kg and has ratios of 1.1695 for ²⁰⁶Pb/²⁰⁷Pb and 2.4606 for ²⁰⁸Pb/²⁰⁷Pb. Only one soil leach isotopic composition could reflect possible anthropogenic contamination. The correlation among As, Zn, Pb contents v. Pb isotopic signatures of ²⁰⁶Pb/²⁰⁷Pb indicates that surface and deep soils collected from profiles are dominated by geogenic compositions.