Measurements of Water Soluble Acidic Gases in Seoul Metropolitan Area during the Pre-campaign Period of KORUS-AQ

Simultaneous hourly measurements of atmospheric acidic gases such as HCl, HNO2, HNO3 and SO2/3 were made during the Pre-Campaign (May 18 to June 19, 2015) in the city of Seoul, Korea. Measurement method was based upon diffusion scrubber (DS) coupled ion chromatography (IC) with conductivity detection. Sample air was withdrawn at a flow rate of 0.5 liter per minute to DS where the analyte gases were quantitatively absorbed in deionized water which flew in opposite direction at 50 microliter per minute. Deionized water channel was separated by thin polypropylene membrane. At the experimental condition SO2 and SO3 signals appeared separately, but final data were presented as their sums because SO2 was suspected be partly oxidized to SO3 during the measurement steps.The observed mean concentrations of HCl, HNO2, HNO3 were 0.06, 15.2, 0.4 ug/m3, respectively. The measured concentrations were gradually increased throughout the Campaign except for sulfur oxides. Among four gases HNO2 was of particular interest: its concentrations were highly elevated in comparison to the previously reported data, its daytime and nighttime variation was hardly distinguishable and if exist, it was in opposite direction. The ratio of HNO2 / HNO3 concentration was also particularly low. The present findings are compared with similar measurements worldwide, and its implications will be discussed.