Pedochemical fractionation of potentially toxic elements within the context of soil–plant interactions at abandoned heap-field of Caporciano (Italy)

Abstract

Technosols from the heap of the abandoned Italian Cu deposit Caporciano contain important amounts of potentially toxic elements (Cr_tot., Co, Ni, Cu, Zn, As, Cd and Pb). Copper contents exceed the Italian law limits for industrial/commercial sites. The studied metals in Pinus sylvestris and Quercus petraea (Matt.) Liebl. show strategy of excluders (bioconcentration factor < 1.0) except Ni and Pb (calculated for branches and leaves in Pinus sylvestris) while the translocation factor indicates preferential metal accumulation to leaves/needles (translocation factor > 1.0) in both plant speciments.At the heap the contents of the chlorophyll in leaves in the photosynthetic tissues of Quercus petraea (Matt.) Liebl. (8.56 CCI—chlorophyll content index) are significantly lower as those measured at reference area (17.71 CCI). The goal of the study is to use a modified methodology for the fractional analysis of soils for the determination of the potential bioavailability of potentially toxic elements in six steps. The innovative steps of sequential analysis are adapted with respect to the release of PTEs from the clay mineral surfaces. (fraction I: 1 M ammonium acetate at pH 7; fraction II: ammonium acetate at pH 5; fraction III: H₂O₂ in ammonium acetate buffer solution; fraction IV: acidic 0.2 M ammonium oxalate (pH 3.2); fraction V: 0.2 M ammonium oxalate and 0.1 M ascorbic acid mixture; fraction VI: 0.5 M ammonium acetate; pH 6). The best bioavailable metals are Cd, Cu, Zn and Pb. The obtained results enable international comparison with similar Cu-deposits.