Large seasonal and interannual variations of biogenic sulfur compounds in the Arctic atmosphere (Svalbard; 78.9° N, 11.9° E)
Authors: Jang Sehyun , Park Ki-Tae , Lee Kitack , Yoon Young Jun , Kim Kitae , Chung Hyun Young , Jang Eunho , Becagli Silvia , Lee Bang Yong , Traversi Rita , Eleftheriadis Konstantinos , Krejci Radovan , Hermansen Ove 
Published: June 2021

Abstract. Seasonal to interannual variations in the concentrations
of sulfur aerosols (< 2.5 µm in diameter; non sea-salt sulfate:
NSS-SO42-; anthropogenic sulfate: Anth-SO42-; biogenic
sulfate: Bio-SO42-; methanesulfonic acid: MSA) in the Arctic
atmosphere were investigated using measurements of the chemical composition
of aerosols collected at Ny-Ålesund, Svalbard (78.9∘ N,
11.9∘ E) from 2015 to 2019. In all measurement years the
concentration of NSS-SO42- was highest during the pre-bloom period
and rapidly decreased towards summer. During the pre-bloom period we found a
strong correlation between NSS-SO42- (sum of Anth-SO42-
and Bio-SO42-) and Anth-SO42-. This was because more
than 50 % of the NSS-SO42- measured during this period was
Anth-SO42-, which originated in northern Europe and was
subsequently transported to the Arctic in Arctic haze. Unexpected increases
in the concentration of Bio-SO42- aerosols (an oxidation product
of dimethylsulfide: DMS) were occasionally found during the pre-bloom
period. These probably originated in regions to the south (the North
Atlantic Ocean and the Norwegian Sea) rather than in ocean areas in the
proximity of Ny-Ålesund. Another oxidation product of DMS is MSA, and
the ratio of MSA to Bio-SO42- is extensively used to estimate
the total amount of DMS-derived aerosol particles in remote marine
environments. The concentration of MSA during the pre-bloom period remained
low, primarily because of the greater loss of MSA relative to
Bio-SO42- and the suppression of condensation of gaseous MSA onto
particles already present in air masses being transported northwards from
distant ocean source regions (existing particles). In addition, the low
light intensity during the pre-bloom period resulted in a low concentration
of photochemically activated oxidant species including OH radicals and BrO;
these conditions favored the oxidation pathway of DMS to Bio-SO42-
rather than to MSA, which acted to lower the MSA concentration at
Ny-Ålesund. The concentration of MSA peaked in May or June and was
positively correlated with phytoplankton biomass in the Greenland and
Barents seas around Svalbard. As a result, the mean ratio of MSA to the
DMS-derived aerosols was low (0.09 ± 0.07) in the pre-bloom period
but high (0.32 ± 0.15) in the bloom and post-bloom periods. There was
large interannual variability in the ratio of MSA to Bio-SO42-
(i.e., 0.24 ± 0.11 in 2017, 0.40 ± 0.14 in
2018, and 0.36 ± 0.14 in 2019) during the bloom and post-bloom
periods. This was probably associated with changes in the chemical
properties of existing particles, biological activities surrounding the
observation site, and air mass transport patterns. Our results indicate that
MSA is not a conservative tracer for predicting DMS-derived particles, and
the contribution of MSA to the growth of newly formed particles may be much
larger during the bloom and post-bloom periods than during the pre-bloom
period.