Light absorbing carbonaceous aerosols, namely Black Carbon (BC) and Brown Carbon (BrC), have significant impacts on radiative balance and atmospheric visibility. In this study, continuous measurement of carbonaceous aerosol in terms of concentration and light absorbing properties were performed using an Aethalometer, a Total Carbon Analyzer and a semicontinuous organic and elemental carbon analyzer at a suburban coastal site of Hong Kong from August 2021 to August 2022. The measurements were used to investigate light absorbing characteristics of BC and BrC at seven wavelengths. Simple Aethalometer model showed most light absorption was caused by BC, with heavier influence of BrC in wintertime. Six episodes had been identified with the aid of meteorological data from the site, backward t...[ Read more ]

Light absorbing carbonaceous aerosols, namely Black Carbon (BC) and Brown Carbon (BrC), have significant impacts on radiative balance and atmospheric visibility. In this study, continuous measurement of carbonaceous aerosol in terms of concentration and light absorbing properties were performed using an Aethalometer, a Total Carbon Analyzer and a semicontinuous organic and elemental carbon analyzer at a suburban coastal site of Hong Kong from August 2021 to August 2022. The measurements were used to investigate light absorbing characteristics of BC and BrC at seven wavelengths. Simple Aethalometer model showed most light absorption was caused by BC, with heavier influence of BrC in wintertime. Six episodes had been identified with the aid of meteorological data from the site, backward trajectory analysis and clustering, most of them associated with continental airmass from central China. Mass Absorption Efficiencies of BC and BrC at 370 nm were 11.83 (± 0.73) m² g^-1 and 2.47 (± 0.11) m² g^-1, respectively, and the Absorption Angstrom Exponent (AAE) of BrC is 2.16. Based on the spectral profiles, a spectral balance model is developed to apportion carbonaceous aerosol into three categories, namely BC, BrC and non-light absorbing White Carbon (WtC). The average concentration of BC, BrC and WtC in the site are 0.71(± 0.61) μg m^-3, 0.99 (± 1.32) μg m^-3 and 0.79 (± 1.08) μg m^-3 respectively with a significantly higher concentration in winter (BC: 0.79 μg m^-3, BrC: 1.54 μg m^-3, WtC: 1.04 μg m^-3) than in summer (BC: 0.47 μg m^-3, BrC: 0.29 μg m^-3, WtC: 0.29 μg m^-3) in all three categories of carbon. Diurnal variation of BC depicted peaks in rush hours with elevated vehicular emission. Evaluation of Potential Source Contribution Function revealed possible sources of carbonaceous aerosols were from Eastern China during episodic events.