High Resolution Chemical Stratigraphies of Atmospheric Depositions from a 4 m Depth Snow Pit at Dome C (East Antarctica)

In this work, we present chemical stratigraphies of two sampling lines collected within a 4 m depth snow pit dug in Dome C during the Antarctic summer Campaign 2017/2018, 12 years after the last reported snow pit. The first sampling line was analyzed for nine anionic and cationic species using Ion Chromatography (IC); the second sampling line was analyzed for seven major elements in an innovative way with Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) after sample pre-concentration, allowing the study of deposition processes of new markers especially related to crustal source. This coupled analysis, besides confirming previous studies, allowed us to investigate the depositions of the last decades at Dome C, enriching the number of the detected chemical markers, and yielding these two techniques complementary for the study of different markers in this kind of matrix. As a result of the dating, the snow layers analyzed covered the last 50 years of snow depositions. The assessment of the accumulation rate, estimated about 9 cm yr(-1), was accomplished only for the period 1992-2016, as the eruption of 1992 constituted the only tie-point found in nssSO(4)(2-) depth profile. Na, the reliable sea salt marker, together with Mg and Sr, mainly arose from marine sources, whereas Ca, Al and Fe originated from crustal inputs. Post-depositional processes occurred on Cl- as well as on NO3- and methanesulfonic acid (MSA); compared to the latter, Cl- had a more gradual decrease, reporting a threshold at 2.5 m for the post-depositional process completion. For NO3- and MSA, instead, the threshold was shallower, at about 1 m depth, with a loss of 87% for NO3- and of 50% for MSA.

Automated summary

This study utilized different analytical techniques to analyze the chemical compositions in a 4 m deep snow pit at Dome C in Antarctica, revealing the deposition processes of the past 50 years and confirming the presence of chemical markers from various sources. Sea salt markers Na, Mg, and Sr were found to originate mainly from marine sources, while Ca, Al, and Fe originated from crustal inputs. Post-depositional processes were observed for Cl-, NO3-, and MSA, with Cl- showing a more gradual decrease compared to the other two components.