, Volume 17, Issue 2, pp 95-122

Nitrogen and sulfur species in Antarctic aerosols at Mawson, Palmer Station, and Marsh (King George Island)

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Abstract

High volume bulk aerosol samples were collected continuously at three Antarctic sites: Mawson (67.60° S, 62.50° E) from 20 February 1987 to 6 January 1992; Palmer Station (64.77° S, 64.06° W) from 3 April 1990 to 15 June 1991; and Marsh (62.18° S, 58.30° W) from 28 March 1990, to 1 May 1991. All samples were analyzed for Na+, SO 4 2− , NO 3 , methanesulfonate (MSA), NH 4 + ,210Pb, and7Be. At Mawson for which we have a multiple year data set, the annual mean concentration of each species sometimes vary significantly from one year to the next: Na+, 68–151 ng m−3; NO 3 , 25–30 ng m−3; nss SO 4 2− , 81–97 ng m−3; MSA, 19–28 ng m−3; NH 4 + , 16–21 ng m−3;210Pb, 0.75–0.86 fCi m−3. Results from multiple variable regression of non-sea-salt (nss) SO 4 2− with MSA and NO 3 as the independent variables indicates that, at Mawson, the nss SO 4 2− /MSA ratio resulting from the oxidation of dimethylsulfide (DMS) is 2.80±0.13, about 13% lower than our earlier estimate (3.22) that was based on 2.5 years of data. A similar analysis indicates that the ratio at Palmer is about 40% lower, 1.71±0.10, and more comparable to previous results over the southern oceans. These results when combined with previously published data suggest that the differences in the ratio may reflect a more rapid loss of MSA relative to nss SO 4 2− during transport over Antarctica from the oceanic source region. The mean210Pb concentrations at Palmer and Marsh and the mean NO 3 concentration at Palmer are about a factor of two lower than those at Mawson. The210Pb distributions are consistent with a210Pb minimum in the marine boundary layer in the region of 40°–60° S. These features and the similar seasonalities of NO 3 and210Pb at Mawson support the conclusion that the primary source regions for NO 3 are continental. In contrast, the mean concentrations of MSA, nss SO 4 2− , and NH 4 + at Palmer are all higher than those at Mawson: MSA by a factor of 2; nss SO 4 2− by 10%; and NH 4 + by more than 50%. However, the factor differences exhibit substantial seasonal variability; the largest differences generally occur during the austral summer when the concentrations of most of the species are highest. NH 4 + /(nss SO 4 2− +MSA) equivalent ratios indicate that NH3 neutralizes about 60% of the sulfur acids during December at both Mawson and Palmer, but only about 30% at Mawson during February and March.