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Significant Underestimation of Gaseous Methanesulfonic Acid (MSA) over Southern Ocean
journal contribution
posted on 2019-11-08, 01:29 authored by Jinpei Yan, Jinyoung Jung, Miming Zhang, Suqing Xu, Qi Lin, Shuhui Zhao, Liqi ChenMethanesulfonic
acid (MSA), derived from the oxidation of dimethylsulfide
(DMS), has a significant impact on biogenic sulfur cycle and climate.
Gaseous MSA (MSAg) has been often ignored in previous studies
due to its quick conversion to particulate MSA (MSAp) and
low concentrations. MSAg, MSAp, and nss-SO42– were observed simultaneously for the
first time with high-time-resolution (1 h) in the Southern Ocean (SO).
The mean MSAg level reached up to 3.3 ± 1.6 pptv,
ranging from ∼24.5 pptv in the SO, contributing to 31% ±
3% to the total MSA (MSAT). A reduction of the MSA to nss-SO42– ratios by about 30% was obtained when
MSAg was not accounted for in the calculation, indicating
that MSAg was very important in the assessment of the biogenic
sulfur contributions in the atmosphere. Mass ratios of MSA to nss-SO42– increased first and then decreased with
the temperature from −10 to 5 °C, with a maximum value
at the temperature of −3 °C. Positive correlations between
MSAg to MSAT ratios and temperature were presented,
when the temperature was higher than 5 °C. This study highlights
the importance of MSAg for understanding the atmospheric
DMS oxidation mechanism and extends the knowledge of MSA formation
in the marine atmosphere.