In this study, hourly measurements of PM2.5 and its major chemical constituents such as organic and elemental carbon (OC and EC), and ionic species were made between January 15 and February 10, 2018 at the air pollution intensive monitering station in Gwangju. In addition, 24-hr integrated PM2.5 samples were collected at the same site and analyzed for OC, EC, water-soluble OC (WSOC), humic-like substance (HULIS), and ionic species. Over the whole study period, the organic aerosols (=1.6×OC) and NO3- concentrations contributed 26.6% and 21.0% to PM2.5, respectively. OC and EC concentrations were mainly attributed to traffic emissions with some contribution from biomass burning emissions. Moreover, strong correlations of OC with WSOC, HULIS, and NO3- suggest that some of the organic aerosols were likely formed through atmospheric oxidation processes of hydrocarbon compounds from traffic emissions. For the period between January 18 and 22 when PM2.5 pollution episode occurred, concentrations of three secondary ionic species (=SO42-+NO3-+NH4+) and organic matter contributed on average 50.8 and 20.1% of PM2.5, respectively, with the highest contribution from NO3-. Synoptic charts, air mass backward trajectories, and local meteorological conditions supported that high PM2.5 pollution was resulted from long-range transport of haze particles lingering over northeastern China, accumulation of local emissions, and local production of secondary aerosols. During the PM2.5 pollution episode, enhanced SO42- was more due to the long-range transport of aerosol particles from China rather than local secondary production from SO2. Increasing rate in NO3- was substantially greater than NO2 and SO42- increasing rates, suggesting that the increased concentration of NO3- during the pollution episode was attributed to enhanced formation of local NO3- through heterogenous reactions of NO2, rather than impact by long-range transportation from China.
In this study, hourly measurements of <TEX>$PM_{2.5}$</TEX> and its major chemical constituents such as organic and elemental carbon (OC and EC), and ionic species were made between January 15 and February 10, 2018 at the air pollution intensive monitering station in Gwangju. In addition, 24-hr integrated <TEX>$PM_{2.5}$</TEX> samples were collected at the same site and analyzed for OC, EC, water-soluble OC (WSOC), humic-like substance (HULIS), and ionic species. Over the whole study period, the organic aerosols (=<TEX>$1.6{\times}OC$</TEX>) and <TEX>$NO_3{^-}$</TEX> concentrations contributed 26.6% and 21.0% to <TEX>$PM_{2.5}$</TEX>, respectively. OC and EC concentrations were mainly attributed to traffic emissions with some contribution from biomass burning emissions. Moreover, strong correlations of OC with WSOC, HULIS, and <TEX>$NO_3{^-}$</TEX> suggest that some of the organic aerosols were likely formed through atmospheric oxidation processes of hydrocarbon compounds from traffic emissions. For the period between January 18 and 22 when <TEX>$PM_{2.5}$</TEX> pollution episode occurred, concentrations of three secondary ionic species (<TEX>$=SO{_4}^{2-}+NO_3{^-}+NH_4{^+}$</TEX>) and organic matter contributed on average 50.8 and 20.1% of <TEX>$PM_{2.5}$</TEX>, respectively, with the highest contribution from <TEX>$NO_3{^-}$</TEX>. Synoptic charts, air mass backward trajectories, and local meteorological conditions supported that high <TEX>$PM_{2.5}$</TEX> pollution was resulted from long-range transport of haze particles lingering over northeastern China, accumulation of local emissions, and local production of secondary aerosols. During the <TEX>$PM_{2.5}$</TEX> pollution episode, enhanced <TEX>$SO{_4}^{2-}$</TEX> was more due to the long-range transport of aerosol particles from China rather than local secondary production from <TEX>$SO_2$</TEX>. Increasing rate in <TEX>$NO_3{^-}$</TEX> was substantially greater than <TEX>$NO_2$</TEX> and <TEX>$SO{_4}^{2-}$</TEX> increasing rates, suggesting that the increased concentration of <TEX>$NO_3{^-}$</TEX> during the pollution episode was attributed to enhanced formation of local <TEX>$NO_3{^-}$</TEX> through heterogenous reactions of <TEX>$NO_2$</TEX>, rather than impact by long-range transportation from China.