Geochemical processes of mercury transformation in the river-sea system

Abstract

In this paper, the average concentrations of mercury in river water and suspension in seawater were presented. The authors gave the spatial distribution of mercury in the dissolved and suspended forms and in the bottom sediments. The studies were carried out at 30 stations twice a year (in the period of high water and low water) in the period 2014 – 2016. Samples of the bottom sediments were collected in the surface layer. The spatial distribution of mercury was performed by Kriging interpolation in ArcGIS 10.2.2. It was shown that the river flow is dominated by dissolved forms of mercury at the top and suspended forms in the mouths of watercourses, while the sea is dominated by dissolved forms. The geochemical transformation processes of the river sedimentary substance (dissolved and suspended forms of mercury) in the mixing zone of the river and sea waters (in the area of the so-called marginal ocean filter) have been studied in detail. It has been shown that, the marginal filter is characterized by flocculation of inorganic and organic dissolved substances with concomitant capture of dissolved forms of metals, which can lead to an increase in the proportion of mercury carried on the suspended substance. The content of suspended forms of metal was reduced due to the self-purification of the water system from the river material and the transition to marine conditions.