Stability of chemical species in firn layers from Antarctica.

In the framework of PNRA (Programma Nazionale di Ricerche in Antartide), EPICA (European Programme for Ice Goring in Antarctica) and ITASE (International Trans-Antarctica Scientific Expedition) Projects three stations located along an ideal transect from the coast to plateau and characterised by different snow accumulation rates have been sampled by snow-pits and firn cores: the coastal site of Hercules Neve (160.4 kg m(-2) y(-1)), the semi-plateau site of Tales Dome, (84.5 kg m(-2) y(-1)) and the typical plateau site of Dome G (38.0 kg m(-2) y(-1)). On the samples collected at these stations, Na+, Mg2+, Cl-, NO3-, SO42-, methanesulfonic acid (MSA) contents were measured by ion chromatography (I.C.) and H2O2 by spectrofluorimetric flow injection analysis (F.I.A.). For all the species the temporal variability (and, when possible the seasonal variability), the background values and the relative superimposed paricular events were studied and discussed. Particular attention was paid to the study of the influence of post-depositional effects on the component concentrations, also as function of the glaciological characteristics of the sampling station. Moreover, we examined the relative contributions of various sources to the chemical composition of the snow and the different kind of information (more related to seasonal inputs or to global events) obtainable from the analysis of snow and firn layers as we move inlands from the coast.