Soluble/insoluble (dilute-HCl-extractable) fractionation of Cd, Pb and Cu in Antarctic snow and its relationship with metal fractionations in the aerosol

Abstract

A chemical fractionation methodology for determination of the (water) soluble and the insoluble (dilute-HCl-extractable) fractions of Cd, Pb and Cu in Antarctic snow was set-up and verified for the additivity of the two fractions detected. Molten samples were filtrated and the water-insoluble fraction was extracted by dilute ultrapure HCl (pH ∼1.5). Metal determinations were carried out in the two fractions by square wave anodic stripping voltammetry. The total metal concentrations in samples collected in the 2000-2001 austral summer in a clean area (Faraglione Camp) in the neighbourhood of the Mario Zucchelli Italian Station were of the order of Cd 10-20 pg g-1, Pb 20-40 pg g-1, Cu 60-120 pg g-1 with an approximate equidistribution between soluble and insoluble fractions. These fractionations compare well (and show a quite consistent temporal trend) with those observed in the aerosol samples collected in the same area/period and confirm the close relationship between metal distributions in snow/ice and in the aerosol. At the station metal concentrations increase due to anthropic contribution and the distribution changes with Cd predominantly present in the soluble fraction (∼80%), while Pb and Cu are more concentrated in the insoluble fraction, 70-80% and ∼70%, respectively.