DBpia

In this study, measurement of aerosol light absorption with 1-minute time resolution was made using a dual-spot multi-wavelength aethalometer equipped with a PM_2.5 impactor between October 23 and November 01, 2018 at a port of Gangneung. In addition, real-time measurements of PM₁₀ and PM_2.5 concentrations were carried out with a GRIMM light scattering monitor. Over the study period, PM₁₀, PM_2.5, black carbon (BC₃₇₀) and aerosol light absorption coefficient (b_abs,370) at 370 nm wavelength peaked mostly in the morning (06:00~09:00) and evening hours (18:00~21:00), which are fairly coincident with activity hours of fishing boats at harbor. Furthermore, absorption Ångström exponent (AAE) values in the wavelength range of 370~520 nm (AAE_370-520) and contribution of brown carbon (BrC) absorption at 370 nm (b_BrC,370) to aerosol b_abs,370 were enhanced during the excursion. As the difference between BC₃₇₀ and BC₈₈₀ (BC at 880 nm) concentrations increases, the AAE_370-520 values increased. During the excursion, maximum AAE_370-520 and b_BrC,370/b_abs,370 were in the range of 1.76~2.50 and 7.8~59.9%, respectively. These suggest the impact of light-absorbing organic aerosols to total aerosol light absorption at the site. Light absorption by BrC particles exhibited strong spectral dependence with increasing tendency in shorter visible wavelengths. Finally, enhanced BC₃₇₀, b_abs,370, b_BrC,370, AAE_370-520, and BrC absorption contribution at 370 nm indicate the existence of light-absorbing organic aerosols in ship engine emissions at the seashore site in the absence of traffic, industrial sources, and biomass burning emissions.