Prominent Features In Chemical Stratigraphies From Eastern Wilkes Land, Coastal East Antartica

In this work a high resolution data set of ionic composition from a firn core collected at GV7 site (East Antarctica) is presented. An efficient decontamination procedure in cold room and chemical analysis by Ion Chromatography were performed. The most relevant sources delivering aerosol to the Antarctic continent were studied and these results can be pointed out: - as concerning primary marine source (sea salt), a good correlation was found between the main chemical markers related to this input (Na+, Cl-, Mg2+). The highest peaks of sea salt components were found to occur in winter time; - crustal source can be studied through Calcium content and especially its non sea salt fraction (nssCa2+). No clear seasonal pattern was observed in Calcium record at this site; - the markers of secondary marine source (biogenic activity), i.e. Sulfur oxidized compounds (MSA and nssSO42-), show a clear seasonal pattern with concentration maxima in summer, when a large phytoplanktonic bloom occurs in the surrounding ocean causing larger emissions of dimethylsulfide; - NO3- was found not to be affected here by post-depositional effects, that are able to modify its concentration in low accumulation sites. Moreover, thanks to the relatively high accumulation rate at GV7, it was possible to achieve an accurate dating of the core, by counting successive annual snow layers, marked by those parameters presenting a clear seasonal trend along the stratigraphy, or by the presence of specific dated events such as documented volcanic eruptions. nssSO42- was chosen for dating purpose, by using its maxima occurring in full summer period and, starting from the surface, 26 summer peaks were identified along the whole GV7 core. These preliminary results appear to be promising for the obtainment of a record at high temporal resolution on the climatic variability in the last millennium by the chemical and isotopic analysis of the 250 m deep ice core drilled in this site.