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BIOGEOCHEMICAL INVESTIGATIONS OF SOILS AND PLANTS OF THE DON RIVER ESTUARINE REGION AND THE TAGANROG BAY COAST OF THE SOUTH RUSSIA

Tatiana Minkina

Abstract

The purpose of this work was to study specific features of the accumulation and distribution of the total content and mobile forms of heavy metals (HM) in soils and plants of the estuarine ecosystems of the Don river and the Taganrog bay coast (Russian Federation). The soil cover is represented by following soils types: Fluvisols, Haplic Chernozem, Arenosol, Solonchak. The following higher plants were sampled: Phragmites australis Cav., Typha angustifolia L., Carex riparia Curtis, Cichorium intybus L., Bolboschoenus maritimus L. Palla, and Rumex confertus Willd. The total concentrations of Cr, Ni, Mn, Cd, Cu, Zn and Pb in the soils were determined by X-ray fluorescent scanning spectrometer. The concentration of HMs mobile forms was extracted using 1 N NH4Ac, pH 4.8. HMs in plants were prepared for analysis by dry combustion at 450 пїЅC. The biogeochemical indicators of soils and plants were calculated, such as clarks of concentration (CC), clarks of dispersion (CD) and coefficient of biological absorption (CBA). CC is the ratio of element content in the soil (Ci) to its clark in the Earth's soils (K): CC=Ci/K. CD пїЅ inverse value of the clarke concentration: CD=K/Ci. CBA is calculated as based upon the ratio between the content of element in plant and its total content in soil. The results revealed that geochemical differentiation in the investigated soils is based on the ranking of the values of the clarke concentration and the dispersion clarke: CC: Pb > Zn > As > Cu > Cr; CD: Ni < Cd ? Mn. The mobile forms of the studied metals show an exceedance of the maximum permition concentration for Cu, Pb, Zn, and Cd predominantly at the monitoring stations on the southern coast of Taganrog bay and the estuarine riparian zone, where the aquatic systems serve as a sort of biological filter contributing to the purification of water from pollutants. According to the contents of mobile forms in the studied soils, the metals form the series: Mn > Zn > Pb > Cu > Cr > ?d. By the CBA values, Cd, Pb and Zn are elements of strong biological absorption, and Cu, Cr, Mn, Ni are the average biological capture.

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