Approaches to the development of environmental regional standards for the content of lead in the soils of the Black Sea coast of the Caucasus on the basis of an integral indicator of the biological state of the soil

Introduction. The Black Sea coast of the Caucasus is an actively developing region with a progressively growing tourism and recreation infrastructure. However, there are rare and unique soils, such as southern chernozems (chestnut), brown soils of dry subtropics, yellow soils.

Lead (Pb) is a priority group of toxicant metals. However, the use of uniform, common standards of Pb content in all types of soils is impractical, since local regional ecological and geochemical features of soils are not taken into account when calculating them.

Materials and methods. Soil contamination of 100, 1000, 10,000 mg Pb per 1 kg of soil was modelling, corresponding to 1, 10 and 100 MPC of this element in Germany and several other countries. After 30 days, changes in biological parameters (the number of bacteria, the activity of soil enzymes and length of roots of radish) were evaluated. To combine the values of the studied biological indicators with different units of measurement into one common indicator, an integral indicator of the biological state (IIBS) of the soil was used.

Results. In most cases, there was an inhibition of the biological properties of the studied soils. According to the resistance to Pb pollution, the soils of the Black Sea coast of the Caucasus form the series including southern chernozems (Haplic Chernozems Pachic) (85) > сinnamonics typical (Haplicisols Eutric) (79) ≥ soddy-carbonate typical (Rendzic Leptosols Eutric) (77) ≥ cinnamonics leached (Haplic Cambisols Eutric) (76) ≥ сinnamonics carbonate (Haplic Cambisols Eutric) (74) = sod-calcareouses leached (Rendzic Leptosols Eutric) (74) = yellow soils (Albic Luvisols Abruptic ) (74) > brown forest weakly-unsaturated (Haplic Cambisols Eutric) (67) ≥ brown forest acid (Haplic Cambisols Eutric) (65) > brown forest acid podzolized (Haplic Cambisols Dystric) (59).

On the base of the analysis of the degree of failure of environmental functions of soils, regional values of maximum permissible concentrations (rMPC) of Pb in soils of the Black Sea coast of the Caucasus are established. Regional values of maximum permissible concentrations of Pb for southern chernozem is 120 mg/kg, for cinnamonics typical, cinnamonics leached, cinnamonics carbonate, sod-calcareouses leached, sod-calcareouses typical soils and yellow soil — 100 mg/kg, for brown forest acid, brown forest weakly-unsaturated — 70 mg/kg, 65 mg/kg for brown forest acid podzolized.

Limitations. The proposed maximum permissible concentrations of Pb in soils are applicable primarily to the territory of the Black Sea coast of the Caucasus.

Conclusion. The proposed maximum permissible concentrations of Pb in the soils of the Black Sea coast of the Caucasus can be used by environmental, agricultural and scientific institutions.

Contribution:

Kuzina A.A. — collection of literature data, text writing, editing;

Kolesnikov S.I. — research concept and design, text writing, editing;

Minnikova T.V. — collection of material and data processing, editing;

Nevedomaya E.N., Ter-Misakyants T.A. — collection of material and data processing, statistical data processing;

Kazeev K.Sh. — collection of material and data processing, editing.

All authors are responsible for the integrity of all parts of the manuscript and approval of the manuscript final version.

Conflict of interests. The authors declare that there is no conflict of interest.

Acknowledgment. The research was carried out within the framework of the state assignment in the field of scientific activity (No. 0852-2020-0029), under the state program of support for young Russian scientists — candidates of sciences and leading scientific schools of the Russian Federation (grants of the President of the Russian Federation MK-2688.2022.1.5 and NSH-449.2022.5).

Received: September 17, 2021 / Accepted: November 25, 2021 / Published: April 08, 2022