Heavy Metals in the Water, Plants, and Bottom Sediments of the Volga River Mouth Area

Deltaic landscapes occupy a special place in environmental geochemical studies of water bodies. Their ecotone position at the land sea boundary determines the biological richness of the deltaic ecosystems and creates a unique variety of landscape geochemical conditions. The Volga River delta is one of the largest in the world. It serves as a geochemical "focus" that reflects the character of fluxes of substances of natural and anthropogenic origin in the entire system of the Volga basin. This paper presents the results of long-term environmental geochemical research of aquatic landscapes in the mouth area of the Volga River. The study has shown the high spatial and temporal variability of the chemical element migration in the area due to the influence of hydrodynamic conditions, variations in water and sediment discharge, and local features of the aquatic systems that determine their geochemical identity. The environmental geochemical conditions of the Volga delta are still relatively safe, especially compared with many other estuaries of the major rivers. Contamination of aquatic systems is manifested mainly in excess of heavy metals (Cu, Pb, and Cd) in suspended matter over the global background values, most notably in the flood period. The content of heavy metals in the water and sediments during the most recent decades remains low; pollution of the bottom sediments is largely insignificant and local.