Origins and chemical characteristics of fine aerosols during the northeastern Asia regional experiment (Atmospheric Brown Cloud-East Asia Regional Experiment 2005)

Abstract

As a part of ABC-EAREX 2005 (Atmospheric Brown Cloud-East Asia Regional Experiment 2005), trace gases and compositions of PM 2.5 were measured at Gosan supersite in Jeju Island during 13-30 March 2005. Aerosol constituents were determined continuously on site at 1-a intervals. The mean concentrations of gases were 56 ppbv for O 3, 297 ppbv for CO, 3.2 ppbv for SO 2, and 2.2 ppbv for NO x, For PM 2.5, the average mass concentration was 27.3 μg/m 3, and mean concentrations of nsS-SO 4 2-, organic carbon (OC), and elemental carbon (EC) were 3.34 μg/m 3, 4.22 μg/m 3, and 1.00 μg/m 3, respectively. The simultaneous measurements of gaseous and aerosol species revealed that the composition Of PM 2.5 was mainly determined by anthropogenic plumes from nearby lands. Most of pollution plumes were associated with the passage of cold frontal systems, when all major species were greatly enhanced. Of these, two episodes were followed by dust incidents. In general, EC and nss-SO 4 2- were well correlated with CO while OC was in good agreement with O 3. Particularly, the variations of OC/EC ratios exhibited a maximum in the afternoon corresponding to the peak of O 3 /CO ratios, suggesting OC/EC as a marker representing the degree of chemical processing of fine aerosol. The ratios of OC/CO for all measurements fell between emission ratios of China and South Korea. For pollution episodes, the correlations of CO with nss-SO 4 2- and EC were significant and their relative enhancement was suggested as an indicator to distinguish different types of pollution plumes. Copyright 2007 by the American Geophysical Union.