Geochemistry of sulfur in the surface layer of bottom sediments in the Northern Dvina estuarine region was studied. It was established that the intensification of redox processes, manifested in the accumulation of reduced sulfur forms, reactive iron, and humic substances, as well as the redistribution of these forms within them, is localized in specific areas and occurs in channel sediments under the influence of primarily technogenic factors, while in the river delta, it is influenced by processes occurring at the river–sea geochemical barrier.
Kokryatskaya et al. (Mon,) studied this question.