Characteristics of water-soluble inorganic species in PM10 and PM2.5 at two coastal sites during spring in Korea

Özet

PM10 and PM2.5 were collected during spring at East (“Gangneung”) and West (“Taean”) coastal sites of the Korean peninsula to investigate chemical characteristics and likely formation routes of their watersoluble inorganic species. The Gangneung site is inland, about 4.5e5.0 km from the East Sea; the Taean site is about 200 m from the coastline and about 400 km from eastern China. The total water-soluble ionic species contributions to PM10 and PM2.5 were respectively 28.8 and 37.4% at the Gangneung site and 46.8 and 53.1% at the Taean site. Concentrations of SO4 2, NH4 þ, and NO3 in both PM10 and PM2.5 were found to be two times higher at the Taean site than at the Gangneung site. The potential source contribution function (PSCF) maps indicate that the enhancement of PM10 and its secondary aerosol species concentrations at two sites were primarily the result of atmospheric processing during longrange transport from the polluted regions of eastern China. Also upwind sources (“the capital region of Korea”) and local emissions influenced the concentration levels of secondary inorganic species at Gangneung. SO4 2 events, defined by PM10 SO4 2 concentrations exceeding the average by one standard deviation, were identified at the two sites e six at Gangneung and four at Taean e to investigate possible mechanisms for the formation of SO4 2 and NO3 . High SO4 2 and high NO3 at the Gangneung site were strongly associated with either high RH (89e94%) and low wind speed or high O3 (62e103 ppb), suggesting that either gas-phase oxidation or aqueous phase oxidation played a critical role in the enhanced SO4 2 production. On the other hand, at the Taean site the association was with both high RH (76e92%) and high O3 (53e79 ppb), indicating that these conditions trigger aqueous-phase and gas-phase reactions to produce secondary SO4 2 and NO3 particles. Also long-range transport of air masses could be one possible factor for enhanced SO4 2 and NO3 concentrations during the events at the two coastal sites, as evidenced by PSCF maps.