Fluorescent dissolved organic matter (FDOM) intensity (Parafac components and FDOM indices) in the surface water during 4 expeditions from spring to fall in 2019, Mackenzie Delta Region (CA)

Fluorescent dissolved organic matter intensity was measured with an Aqualog®. Measurements were corrected for inner-filter effects and for the Raman and Rayleigh scattering (Murphy et al., 2013; doi:10.1039/C3AY41160E). The different fluorescent components of DOM were isolated from combined signal by PARAFAC modeling using the “drEEM Toolbox” and following the recommendation of Murphy et al. (2013; doi:10.1039/C3AY41160E). The DOM components derived from PARAFAC modeling were compared with PARAFAC components from other studies through the OpenFluor database (Murphy et al., 2014; doi:10.1039/C3AY41935E). The coble-peaks indicate major fluorescent components (Coble 1996; doi:10.1016/0304-4203(95)00062-3) in marine FDOM EEMs (Excitation-Emission-Matrix). Peaks T represents protein-like compounds (tyrosine and tryptophane), peaks A and C are indicators of humic-like components whereas peak M was associated to marine humic-like fluorescence. The fluorescence index (FI) is calculated as the ratio of fluorescence at emission 450 nm and 500 nm, at fixed excitation of 370 nm. The HIX index is the ratio of the areas of two spectral wavelength regions in the emission spectra for an excitation at 254 nm and it is obtained as: HIX = H∕L, where H is the area between 435 and 480 nm in the emission spectra and L is the area in the emission spectra between 300 and 345 nm (Zsolnay et al., 1999; doi:10.1016/S0045-6535(98)00166-0). The BIX index is obtained by calculating the ratio of the emission at 380 and 430 nm, excited at 310 nm: BIX = IEm380∕IEm430 (Huguet et al., 2009; doi:10.1016/j.orggeochem.2009.03.002).