Year-round chemical aerosol records at Kohnen, Antarctica obtained by automatic samplings

Aimed at year-round recording of the chemical aerosol composition in central Antarctica, an unattended operating aerosol sampler was successfully deployed at the EPICA deep drilling site in Dronning Maud Land (Kohnen Station). Analyses of teflon/nylon filter packs consecutively collected over bi-weekly intervals during the February 2003 to December 2005 period allowed to evaluate seasonal concentration variations of methane sulphonate (MS), Cl-, NO3-, non-sea salt (nss-)SO42- and Na+, while NH4+ and mineral dust related ion results remained below detection limits. For MS and nss-SO42 distinct late summer maxima around 44 and 200 ng/m3, respectively, were found, while (total) NO3- showed a broad November maximum of about 52 ng m-3. In contrast, the highest concentrations of Na+ with peak values of up to 160 ng/m3 were observed during the winter half year. The seasonality of these species broadly coincided with long-term observations at the coastal Neumayer Station, including surprisingly comparable NO3- levels. However, the biogenic sulphur and sea salt concentrations were lower at Kohnen by typically a factor of 2-3 and 10, respectively. The arrival of sea ice derived sea salt particles at Kohnen could not clearly detected, since even during mid-winter the nss-SO42- to Na+ ratio was generally too high to unambiguously identify a sulphur depleted sea salt SO4**2- fraction.