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Post depositional losses of MSA-, NO3-, and Cl- at the EPICA deep-drilling site in Dronning Maud Land, Antarctica

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Citation:
Weller, R. (2003): Post depositional losses of MSA-, NO3-, and Cl- at the EPICA deep-drilling site in Dronning Maud Land, Antarctica , EGS-AGU-EUG Joint Assembly Nice, FranceApril 2003. .
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Abstract:

We quantifed the post depositional losses of methanesulfonate (MSA-), nitrate, and chloride at the EPICA drilling site in Dronning Maud Land (DML, 75°S, 0°E). Analyses of four intermediate deep ice cores, 13 snow pits were considered. We found that about 29% of the once deposited nitrate and typically 57% of MSA- were 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 MSA- is 6.4 a and 19 a for nitrate. It turns out that for nitrate and MSA- the typical mean concentrations representative for the last 100 years were reached after 5.4 a and 6.5 a, repectively, indicating that beneath a depth of around 1.2-1.4 m post depositional losses can be neglected. With a simple approach based on basic physico-chemical processes we estimated the supersaturation of the corresponding free acids MSA, HNO3, and HCl based on Henrys law and assuming that ionic impurities of the bulk ice matrix are localised in a quasi brine layer.

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