Single-Particle Characterization of Summertime Antarctic Aerosols Collected at King George Island Using Quantitative Energy-Dispersive Electron Probe X-ray Microanalysis and Attenuated Total Reflection Fourier Transform-Infrared Imaging Techniques

摘要

ABSTRACT: Single-particle characterization of Antarctic aerosols was performed to investigate the impact of marine biogenic sulfur species on the chemical compositions of sea-salt aerosols in the polar atmosphere. Quantitative energy-dispersive electron probe X-ray microanalysis was used to characterize 2900 individual particles in 10 sets of aerosol samples collected between March 12 and 16, 2009 at King Sejong Station, a Korean scientific research station located at King George Island in the Antarctic Two size modes of particles, i.e., PM2.5_ 10 and PM1.0-2.5, were analyzed, and four types of particles were identified, with sulfur-contain ing sea-salt particles being the most abundant, followed by genuine sea salt particles without sulfur species, iron-containing particles, and other species including CaCO3/CaMg(CO3)2, organic carbon, and alumino silicates. When a sulfur-containing sea-salt particle showed an atomic concentration ratio of sulfur to sodium of >0.083 (seawater ratio), it is regarded as containing nonsea-salt sulfate (nss-SO42 ) and/ or methanesulfonate (CH3SO3~), which was supported by attenuated total reflection Fourier transform-infrared imaging measurements. These internal mixture particles of sea-salt/CH3SO3~/SO42~ were very frequently encountered. As nitrate containing particles were not encountered, and the air-masses for all of the samples originated from the Pacific Ocean (based on S-day backward trajectories), the oxidation of dimethylsulfide (DMS) emitted from phytoplanktons in the ocean is most likely to be responsible for the formation of the mixed sea-salt/CH3SO3-/SO42~ particles.