In this study, mass concentrations and chemical compositions of PM2.5, including water-soluble ions and elements were determined at the 1,100 m-highland of Mt. Hallasan in Jeju Island across four seasons from August 2013 to August 2014. The average mass concentration of PM2.5 was 12.5±8.41 /m3 with 45.8% of the contribution from eight water-soluble ionic species. Three ionic species (SO4 2-, NH4 +, and NO3 -) comprised 96.2% of the total concentration of ions contained in PM2.5 and were the dominant ions, accounting for 43.5% of the PM2.5 mass at Mt. Hallasan. On the basis of the mass concentration level, seasonal variation, enrichment factor, and relationship among elements, we can presume that Mg, K, Ca, Mn, Fe, Co, Sr, Ba, Nd, and Dy originated mainly from crust or soil and that V, Cr, Ni, Cu, Zn, As, Cd, and Pb were significantly enriched in PM2.5 owing to the effects of the anthropogenic emissions. These results and the local distribution of emission sources and topographic characteristics near this sampling site suggest that the compositions of PM2.5 collected at the 1100 m-highland of Mt. Hallasan were largely influenced by inflow from outside of Jeju Island.

The ambient mass concentration and chemical composition of the PM2.5 were determined at the highland site with 1,100 m above sea level on Jeju Island from June 2013 to November 2014. Yearly averaged mass concentration of PM2.5 was 11.97±8.63 /m3. PM2.5 concentrations were highest during the spring, while they tended to be lowest during the summer. Eight water soluble ionic species attributed 45.5% to PM2.5 mass. SO4 2-, NO3 - and NH4 + were major ions, which occupied to 27.9%, 3.7% and 12.3%, respectively. The greatest contributors to total mass concentration of water-soluble ions contained in PM2.5 were sulfate, ammonium and nitrate. These three ions accounted for 96.6% in total ions mass concentration of PM2.5. We could infer that these three secondary ions exist mostly in the form of (NH4)2SO4 and NH4NO3. Ca2+ and Mg2+ had a good relationship and with r=0.9. The molar ratio of Mg2+/Ca2+ in this study was lower than the value observed in sea water and higher than that in soil dust, indicating that these two ions originated from other sources rather than ocean and soil dust in this study.