Anthropogenic and natural hydrocarbons in water and sediments of the Kara Sea.

Abstract

The results on the content and composition of aliphatic (AHСs) and polycyclic aromatic hydrocarbons (PAHs) at the geochemical barrier between the Kara Sea and the Ob and Yenisei Rivers are discussed in comparison with those in the mouth areas of the Lena, Khatanga, Indigirka and Kolyma. It has been established that hydrocarbon concentrations sharply decrease in the river-sea mixing zones, and their composition, and the ratio of their dissolved and suspended forms change. Besides, the research season plays a great role, as the highest content of hydrocarbons and particulate matter was found in the Ob Gulf during the flood, when the concentrations of AHCs in surface waters reached 325μg/L, PAHs -15ng/L, particulate matter-15.5mg/L. In the Kara Sea itself, AHC concentrations increased on average from 20 to 59μg/L, that is most likely associated with the melting of seasonal ice and floods. Anthropogenic influence was found in river waters, where the proportion of naphthalenes, which marks oil products, and pyrene, which marks pyrogenic PAHs, is increased. In the Ob Gulf is linked to an increase in navigation along the Northern Sea Route and the functioning of the port of Sabetta. In the mouth area of the Yenisei, the concentrations of both AHC and PAH in surface waters and sediments varied in a smaller range than in the mouth area of the Ob, which is due to the nature of the rocks that make up the catchment areas of these rivers, as well as the regulation of the Yenisei runoff. The hydrological features of the estuarine areas can lead to increased AHC concentrations (the mouth of the Khatanga, up to 189μg/L, 2.6μg/mg SPM). The minimum AHC content in SPM and sediments in the river transects was established in the East Siberian rivers (Indigirka, Kolyma), associated with the decreasing productivity in waters from the Western Arctic seas to the Eastern.