Optical characteristics of water at the mouth of the Ob River

Abstract

As a result of the field studies (August 25 – September 1, 2020), new data were obtained on the optical characteristics of water at the Ob River mouth near the Salemal village (Yamal region, Yamal-Nenets Autonomous Okrug) during the lowest water level and the maximum development of hydrobiocenoses. We calculated the light attenuation coefficient ε(λ) in the spectral range from 400 to 800 nm, which varied from 1.5 to 21.5 m^–1 during the study period, and the light absorption by yellow substance κ_ys(λ) from 0.1 to 12.2 m^–1. Concentrations of yellow substance C_ys and chlorophyll а Chl were determined. For instance, chlorophyll а concentrations in water samples taken at different stations of the Ob River ranged from 12.5 to 22.7 mg∙m^–3. The maximum content of chlorophyll а in our case was recorded at a depth of 14 m (station 5.3), which was 22.7 mg∙m^–3. The yellow substance concentration determined optically by the calculated yellow substance light absorption coefficient at wavelength λ=450 nm ranged within 18.8 and 26.9 g∙m^–3 with an average value of 22.1 g∙m^–3. The average value of κ_ys(λ) at λ=450 nm over the study period was 4.7 m^–1