Optical properties of dissolved organic matter of the surface layer of Laptev sea water

Features of fluorescence of humic compounds transported by the Lena River runoff in September 2015 are considered. The change in optical properties of dissolved organic matter, namely, fluorescence spectra and absorption coefficients at a wavelength of 350 nm, on the transect from the Lena River delta to the continental slope is demonstrated. For humic compounds of terrigenous origin, the position of the fluorescence maximum has been determined at excitation wavelengths of 270, 310, and 355 nm. It has been shown that fresh riverine waters of Lena River propagate throughout the entire shelf and humic compounds are the main component of the colored fraction of dissolved organic matter. In samples collected near the continental slope, the presence of labile autochthonous organic matter has been revealed. The content of dissolved organic matter in riverine water in 2015 is comparable with results of previous investigations and amounts to 548 $\mu$M/L.