Enhanced light absorption due to aerosol particles in ship plumes observed at a seashore site

Özet

This study investigates the existence of light-absorbing organic aerosols in ship emissions measured at a seashore site. In-situ measurements of aerosol light absorption at a port of Gangneung located on the East Sea on the Korean Peninsula were made using a multi-wavelength aethalometer for approximately 10 days. Moreover, 7- to 24-hr integrated filter-based measurements were performed to analyze the concentration of water-soluble or- ganic carbon (WSOC). During the study period, short-term excursions of black carbon (BC) concentrations at 880 nm (BC 880 ) and aerosol light absorption coefficients at 370 nm (b abs,370 ) occurred repeatedly, as did ab- sorption Ångström exponent (AAE) values at 370–520 nm (AAE 370-520 ). The b abs,370 values during the excursions were 4.8 times higher than the background absorption levels. The AAE 370-520 values were close to 1.0 at the onset of the excursion; however, they increased to 1.9–2.3 during the excursion. Furthermore, the contribution of brown carbon (BrC) light absorption at 370 nm (BrC b abs,370 ) to the total light absorption ranged from 2.5–11.0% at the onset of the excursion to 45.2–59.8% during the excursion. The WSOC showed good-to-strong correlation with the b abs,370 , b abs,880 , and BrC b abs,370 , with R 2 of 0.63–0.77. This suggests that primary combustion sources contributed to the aerosol light absorption. Enhanced BC 880 , b abs,370 , AAE 370-520 , and contribution of BrC absorption at the seashore site without traffic and industrial sources could be attributed to the light-absorbing organic aerosols in ship emissions. It was observed that ab- sorption by BrC in ship engine exhaust can be as important as BC absorption in shorter visible wavelengths.