Seasonal variation of aerosol composition at Cheju Island, Korea

A preliminary assessment of the seasonal variation in chemical composition of aerosols measured at Cheju Island, Korea, is presented. Weekly and monthly averaged aerosol composition derived from 15 months of daily filter measurements are presented. The annual-average non-sea-salt sulfate and nitrate mass concentrations of aerosols measured at Cheju are found to be 6.9 μg m−3 and 1.2 μg m−3, respectively; calcium and potassium are present in nearly equal quantities at 0.5 μgm-3, and ammonium averaged 1.4 μg m−3. Each species is found to follow a seasonal cycle with sulfate, nitrate, ammonium, potassium and calcium all showing up to 50% higher values in the spring. In contrast, chlorine is 30% lower in the spring. Aerosol enrichment factors relative to the composition of seawater and crustal material from the Gobi dust-source region in China are also presented. The aerosol measured at Cheju is found to be enriched in sulfate, nitrate and ammonium, but deficient in chlorine (relative to seawater). These results along with modeling studies suggest that the dust surfaces play an important role in nitrate and sulfate formation.