Distribution of Dissolved Matter in the Yenisei Estuary and Adjacent Kara Sea Areas and Its Inter-Annual Variability

Abstract

The distribution of dissolved matter (major ions, nutrients, and trace elements) in the estuary of the Yenisei River and nearby areas of the Kara Sea was studied based on natural observations data acquired in 2009–2016. These results were compared with literature hydrochemical data on the area. It was demonstrated that the transport of major ions (Na, K, Mg, Ca, and SO₄) and some trace elements (Li, Rb, Cs, Sr, B, F, Cr, Ge, As, Mo, and U) is described by equations (which remain unchanging during long periods of time) of conservative mixing between riverine and marine waters. Although alkalinity is a conservative component, its distribution exhibits a significant spatiotemporal variability, which is caused by the complex hydrological structure of the Yenisei Bay and adjoining part of the Kara Sea. Concentrations of P_min, Si, and V in the desalinized waters of the photic layer decrease seaward during the vegetation period owing to uptake by phytoplankton. The losses of these elements reach 30–57, 30, and 9%, respectively, of their supply with riverine runoff. The contents of dissolved P_min and V in the intermediate and bottom water layers of the Yenisei estuary strongly increase with increasing salinity due to the regeneration of the precipitated organic matter, whereas silica remineralization is much less intense. As much as 20–100% dissolved Ba in the riverine runoff is intensely desorbed from suspended matter, depending on seasonal variations in chemical composition of the runoff, throughout the whole estuary. The transport of dissolved forms of heavy metals (Mn, Fe, and Pb) and hydrolysate elements (Al, Ti, Y, La, Ce, and Pr) in the mixing zone of riverine and marine water masses is likely controlled by the coagulation and flocculation of organic and organomineral colloids, as follows from the decrease (by 20–61%) in the concentrations of these elements during initial salinization and subsequent approach to the characteristics of the seawater.