A missing source of aerosols in Antarctica – beyond long-range transport, phytoplankton, and photochemistry
Understanding the sources and evolution of aerosols is crucial for constraining the impacts that aerosols have on a global scale. An unanswered question in atmospheric science is the source and evolution of the Antarctic aerosol population. Previous work over the continent has primarily utilized low...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-01-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/1/2017/acp-17-1-2017.pdf |
| Summary: | Understanding the sources and evolution of aerosols is crucial for
constraining the impacts that aerosols have on a global scale. An unanswered
question in atmospheric science is the source and evolution of the Antarctic
aerosol population. Previous work over the continent has primarily utilized
low temporal resolution aerosol filters to answer questions about the
chemical composition of Antarctic aerosols. Bulk aerosol sampling has been
useful in identifying seasonal cycles in the aerosol populations, especially
in populations that have been attributed to Southern Ocean phytoplankton
emissions. However, real-time, high-resolution chemical composition data are
necessary to identify the mechanisms and exact timing of changes in the
Antarctic aerosol. The recent 2ODIAC (2-Season Ozone Depletion and
Interaction with Aerosols Campaign) field campaign saw the first ever
deployment of a real-time, high-resolution aerosol mass spectrometer (SP-AMS
– soot particle aerosol mass spectrometer – or AMS) to the continent. Data obtained from the AMS, and a suite of other
aerosol, gas-phase, and meteorological instruments, are presented here. In
particular, this paper focuses on the aerosol population over coastal
Antarctica and the evolution of that population in austral spring. Results
indicate that there exists a sulfate mode in Antarctica that is externally
mixed with a mass mode vacuum aerodynamic diameter of 250 nm. Springtime
increases in sulfate aerosol are observed and attributed to biogenic sources,
in agreement with previous research identifying phytoplankton activity as the
source of the aerosol. Furthermore, the total Antarctic aerosol population is
shown to undergo three distinct phases during the winter to summer
transition. The first phase is dominated by highly aged sulfate particles
comprising the majority of the aerosol mass at low wind speed. The second
phase, previously unidentified, is the generation of a sub-250 nm aerosol
population of unknown composition. The second phase appears as a transitional
phase during the extended polar sunrise. The third phase is marked by an
increased importance of biogenically derived sulfate to the total aerosol
population (photolysis of dimethyl sulfate and methanesulfonic acid (DMS and
MSA)). The increased importance of MSA is identified both through the direct,
real-time measurement of aerosol MSA and through the use of positive matrix
factorization on the sulfur-containing ions in the high-resolution mass-spectral data. Given the importance of sub-250 nm particles, the
aforementioned second phase suggests that early austral spring is the season
where new particle formation mechanisms are likely to have the largest
contribution to the aerosol population in Antarctica. |
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| ISSN: | 1680-7316 1680-7324 |