C. Piel

Postdepositional losses of methane sulfonate, nitrate, and chloride at the European Project for Ice Coring in Antarctica deep‐drilling site in Dronning Maud Land, Antarctica

nitrate and typically 51 ± 20% of MSAwere lost, while for chloride, no significant depletion could be observed in firn older than one year. Assuming a first order exponential decay rate, the characteristic e-folding time for MSAis 6.4 ± 3 years and 19 ± 6 years for nitrate. It turns out that for nitrate and MSAthe typical mean concentrations representative for the last 100 years were reached after 5.4 and 6.5 years, respectively, indicating that beneath a depth of around 1.2-1.4 m postdepositional losses can be neglected. In the area of investigation, only MSAconcentrations and postdepositional losses showed a distinct dependence on snow accumulation rate. Consequently, MSA � concentrations archived at this site should be significantly dependent on the variability of annual snow accumulation, and we recommend a corresponding correction. With a simple approach, we estimated the partial pressure of the free acids MSA, HNO3, and HCl on the basis of Henrys law assuming that ionic impurities of the bulk ice matrix are localized in a quasi-brine layer (QBL). In contrast to measurements, this approach predicts a nearly complete loss of MSA � ,N O3 , and Cl � . INDEX TERMS: 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0330 Atmospheric Composition and Structure: Geochemical cycles; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 1827 Hydrology: Glaciology (1863); 1863 Hydrology: Snow and ice (1827); KEYWORDS: postdepositional loss, snow chemistry, methane sulfonate

Seasonal variability of crustal and marine trace elements in the aerosol at Neumayer station, Antarctica

Atmospheric trace element concentrations were measured from March 1999 to December 2003 at the Air Chemistry Observatory of the German Antarctic station Neumayer, by inductively coupled plasma–quadrupol mass spectrometry (ICP–QMS) and ion chromatography (IC). This continuous five-year long record derived from weekly aerosol sampling revealed a distinct seasonal summer maximum for elements linked with mineral dust entry (Al, La, Ce, Nd) and a winter maximum for the mostly sea salt derived elements Li, Na, K, Mg, Ca and Sr. The relative seasonal amplitude was around 1.7 and 1.4 for mineral dust (La) and sea salt aerosol (Na), respectively. On average, a significant deviation regarding mean ocean water composition was apparent for Li, Mg and Sr, which could hardly be explained by mirabilite precipitation on freshly formed sea ice. In addition, we observed all over the year, a not clarified high variability of element ratios Li/Na, K/Na, Mg/Na, Ca/Na and Sr/Na. We found an intriguing co-variation of Se concentrations with biogenic sulphur aerosols (methane sulphonate and non-sea salt sulphate), indicating a dominant marine biogenic source for this element, linked with the marine biogenic sulphur source.

Atmospheric methane sulfonate and non‐sea‐salt sulfate records at the European Project for Ice Coring in Antarctica (EPICA) deep‐drilling site in Dronning Maud Land, Antarctica

Abstract. During three summer campaigns in January/February 2000, 2001 and 2002 the ionic compo-sition of the aerosol at the EPICA deep-drilling site at Kohnen Station was measured in daily resolution. In 2000 and 2002 we observed mean (±std) non-sea salt sulfate (nss-SO42-) con-centrations of 353±100 ng m-3 and 320±250 ng m-3, as well as methane sulfonate (MS) con-centrations of 59±36 ng m-3 and 74±80 ng m-3, respectively. For the summer campaign in 2001, significantly lower nss-SO42- and MS levels of 164±150 ng m-3 and 19±12 ng m-3, respectively, were typical. The mean MS/nss-SO42- ratio ranged from about 0.1 to 0.2. MS and nss-SO42- concentrations and their variability were roughly comparable to coastal stations at summer. Supported by air mass back trajectory analyses this finding documented an effi-cient long-range transport to Kohnen via the free troposphere. MS/nss-SO42- ratios exhibited a strong dependence on the MS concentration with systematically higher ratios at higher MS concentrations, a peculiarity which is also evident in a firn core drilled at this site.