Optical characterization of black carbon-derived DOM: Implication for the fluorescence detection of fuel combustion products in marine waters

Among pollutants released from shipping, black carbon (BC), also known as soot carbon, is of great interest due to its impacts on climate, air quality, human health and ecosystems. BC emitted from ships may enter marine waters and partially transfer to the seawater dissolved phase. In this study, we investigated the optical properties (absorbance and fluorescence) of dissolved organic matter (DOM) derived from BC particles (DOMBC) emitted by ships, which were compared to those of DOMBC of other origins (diesel-powered industrial machine, biomass burning, urban dust), and to terrestrial and marine DOM (DOMTER, DOMMAR). Ship and diesel DOMBC displayed higher ratios of fluorescence maximum intensity to dissolved organic carbon concentration (Fmax/DOC), higher specific UV absorbance at 254 nm (SUVA254), and lower fluorescence emission wavelengths than the other tested materials. The parallel factor analysis (PARAFAC)-derived fluorophores of the ship and diesel DOMBC exhibited significant correlations with the concentration of dissolved black carbon (DBC), determined using the benzenepolycarboxylic acid (BPCA) method. Based on these results, we propose the Combustion indeX (COX), to help detecting and tracking ship/fuel combustion pollutions in marine waters. •Black carbon-derived DOM exhibits high Fmax/DOC ratios and SUVA254.•Fluorescence and absorbance index of black carbon-derived DOM strongly depends on soot origin.•Specific signature of black carbon-derived DOM exists among natural FDOM found in coastal area.•A new fluorescence index can help to detect and track ship/fuel combustion pollutions in marine waters.