Chemical Composition in PM2.5 at an Urban Site in Gwangju and a Pier Site in Youngam in Late Fall and Influence of Shipping Activities at the Pier Site on Light Absorption Properties of Aerosol Particles

In order to investigate the difference in the chemical properties of PM2.5 at two sites (at an urban site in Gwangju and a pier site in Youngam-gun) where the concentrations of gaseous pollutants (CO, NOx, and SO2) emitted during fossil fuel combustion and their diurnal cycles have a large difference, 8-hr integrated PM2.5 samples were simultaneously collected at the two sites for one month in the late fall of 2021, and their chemical composition was analyzed. In addition, real-time observation of aerosol light absorption was conducted using a 7-wavelength aethalometer to evaluate the effect of organic aerosols emitted from the operation of large ships at the pier site on the light absorption of atmospheric aerosol particles. The concentrations of NO, NO2, CO, and SO2 measured at the urban site were much higher than those at the pier site, however, the concentrations of PM2.5 and its carbonaceous and secondary ionic species were high at the pier. Also, the concentration of secondarily-formed O3 was slightly higher at the pier. Despite the concentration of NO2 was fairly low at the pier, high O3 concentration was likely due to the effect of VOCs emitted during the production of ship components in the nearby Daebul industrial complex, suggesting that VOCs/NOx ratio may have played an important role in production of O3 at the pier. Considering the good correlations between the NO2 and NO3- at the two sites, some of the measured NO3- could be formed through the oxidation process of locally emitted nitrogen oxides. However, the concentration of NO3- was higher at the pier site under conditions of low NO2 concentration, strong wind speed, and low relative humidity, than at the urban site. This might be due to impact of aerosol particles transported from polluted regions of China. Diurnal cycles of both the light absorption coefficients by aerosol and brown carbon (BrC) particles at wavelength of 370 nm and the equivalent BC (eBC) concentration at the pier site were very similar to those of NO and NO2, indicating that they were affected by similar emission sources at the pier. In case studies to investigate the effect of particulate matter emitted by shipping activities on the light absorption properties of aerosol particles, it was found that the temporal variations of the aerosol and BrC absorption coefficients, and eBC concentration were greatly affected by the operating time of the cargo ships and the vehicles in the pier. In summary, it was confirmed that the operation of large cargo ships in the pier emits light-absorbing BrC particles to the atmosphere, affecting the increase in light absorption of atmospheric aerosol particles.