ISSN 00014370, Oceanology, 2010, Vol. 50, No. 4, pp. 498–512. © Pleiades Publishing, Inc., 2010. Original Russian Text © D.N. Gar’kusha, Yu.A. Fedorov, E.V. Yakushev, 2010, published in Okeanologiya, 2010, Vol. 50, No. 4, pp. 534–547.
MARINE CHEMISTRY
Methane in the Water and Bottom Sediments of the Mouth Area of the Severnaya Dvina River (White Sea) D. N. Gar’kushaa, b, Yu. A. Fedorova, and E. V. Yakusheva a
Southern Federal University, Rostovondon, Russia b Hydrochemical Institute, RostovonDon, Russia Email:
[email protected]
Received February 19, 2008; in final form, June 16, 2009
Abstract—The mouth area of the Severnaya Dvina River is characterized by a high level of methane in the water (from 1.0 to 165.4 μl/l) and in the bottom sediments (from 14 to 65000 μl/kg), being quite comparable to the productive mouth areas of the rivers in the temperate zone. The maximum methane concentrations in the water and sediments were registered in the delta in the segments of channels and branches with low rates of tidal and runoff currents to which domestic and industrial wastewaters are supplied. In the riverine and marine water mixing zone with its upper boundary situated far into the delta and displaced depending on the phase of the tidal cycle, a decrease of the methane amount with the salinity increase was observed. The pre vailing role in the formation of the methane content level in the water of the mouth area pertains to the bottom sediments, which is testified to by the close correlation between the gas concentrations in these two media. The existence of periodicity in the variations of the methane content level in the water of the river downstream caused by the tidal effects was found. DOI: 10.1134/S0001437010040065
INTRODUCTION The environmental conditions at the drainage basin of the Severnaya Dvina River promote the for mation of a high organic matter (OM) content in its waters, both of allochthonous substance concerned with the humus of soil and marsh origin and of autoch thonous matter formed in the proper river [1]. In the delta where Arkhangel’sk—the greatest industrial center of the north of the European part of Russia—is located, the role of anthropogenic factors in the OM supply to the riverine system is pronouncedly increased. All these factors, along with the decreased oxygen content at the bottom during the winter and summer lowwater periods [1], provide conditions for the occurrence of intense processes of the OM anoxic decomposition, pa