Content and distribution features of heavy metals in the tissue of Cyprinus carpio L. in the Ural River basin

This paper discusses regional features of environmental pollution by heavy metals. The authors have studied the content of heavy metals in the water of the Ural River within the Republic of Bashkortostan (RB), Chelyabinsk and Orenburg Regions, as well as its right tributary, the Khudolaz River, located in the zone of influence of industrial enterprises of the city of Sibay and characterized by a high content of pollutants. It is noted that in the considered segment with a length of about 60 km downstream of the Ural River, a gradual decrease in the concentration of toxic elements is observed as a result of self-purification processes. Studies of the elemental composition of muscle tissue and scales of the common carp (Cyprinus carpio L.), living in the Khudolaz River on the territory of the city of Sibay, showed high concentrations of heavy metals in them. Muscle tissue and scales accumulate heavy metals to varying degrees, which is due to the functional feature of these organs, their accumulative activity and the chemical properties of the metal itself. The greatest amount of Cu, Fe, Co accumulate in muscle tissue, while Zn, Mn – in scales. No similar pattern has been revealed for the accumulation of Ni and Pb. In muscle tissue, the elements are distributed as follows: Fe > Zn > Ni > Mn = Co > Cu > Pb, in scales – Zn > Fe > Mn > Co > Ni > Cu > Pb. Fe, Zn predominate in both series of element distribution, while the lowest concentrations are characteristic of Pb. A correlation analysis has revealed a presence of a direct statistically significant relationship between the content of heavy metals in water and the tissues of common carp: strong – in muscles (r = 0,95–0,98) and medium – in scales (r = 0,34–0,55).