Mountain and foothill black soils of the Caucasus are rare and even unique soils. They have special properties that distinguish them from plain black soils, have water, temperature and air regimes favorable for crop production and are actively used in agriculture. At the same time, mountain soils and ecosystems are particularly vulnerable. Significant differences in the ecological and genetic characteristics of mountain and foothill black soils from plain analogues necessitate an independent assessment of their resistance to chemical pollution and the development of regional maximum permissible concentrations (rPDK) of pollutants in these soils. Heavy metals are the priority pollutants polluting mountain and foothill soils of the Caucasus (TM) and oil.
HM are the most dangerous environmental pollutants due to their high toxicity and ability to accumulate in the environment. Sources of HM pollution of mountain and piedmont soils of the Caucasus are their deposits, motor vehicle emissions, thermal power plants, waste water, landfills, etc.
Oil and oil products are highly toxic, highly polluted, and highly migratory. Sources of soil pollution by oil and oil products are the development and operation of oil fields, ruptures of oil pipelines, unauthorized tapping into oil pipelines, gas stations, boiler houses, etc.
The aim of the study is to compare the stability of flat and mountain black soils of the Central Caucasus and the Caucasus to contamination with Cr, Cu, Ni, Pb and oil; the establishment of indicative values of the maximum permissible content of HM and oil for the development of regional maximum permissible concentration.
Research methods. Tthe objects of study were the types and subtypes of soils: black soils ordinary (Stavropol territory, Kochubeevskiy area, s. Kochubeevskoe), leached black soils (Karachay-Cherkess Republic, the Habezsky district, the village of Ali-Berdukovskiy), ashed black soils (Karachay-Cherkess Republic, the Habezsky district, the village of Kosh-Khabl). Soil contamination was simulated in laboratory conditions. This study investigated the effects of heavy metals (HM): lead (Pb), chromium (Cr), nickel (Ni), copper (Cu) and oil. HM was applied to the soil in the amount of 1, 10, 100 MPC (100, 1000 and 10,000 mg/kg, respectively), oil – in the amount of 1, 5, 10% of the soil mass. HM was introduced into the soil in oxide form: CrO3, CuO, NiO, PbO. Oil pollution was produced in moist soil. Further, contaminated soil samples were placed in vegetation vessels at a temperature of 20-22°C, with the maintenance of soil moisture by weight at 25%.
Biological parameters in soils, such as determination of the activity of oxidoreductases (catalase and dehydrogenase), calculation of the total number of bacteria, cellulolytic activity of the abundance of bacteria of the genus Azotobacter, phytotoxic properties of soils and other indicators, were investigated according to conventional methods. In order to combine a large number of studied soil parameters, an integral indicator of the biological state of the soil was developed and implemented.
Research result. Pollution of black soils of the Central Caucasus and the Caucasus with Cr, Cu, Ni, Pb and oil, as a rule, leads to a decrease in the values of all biological indicators: the number of bacteria, the activity of soil enzymes, the deterioration of plant growth and development. The degree of decline in biological indicators of soil condition depends on the genetic properties of the soil, the nature and concentration of the pollutant. Both foothill and mountain black soils of the Caucasus have shown relatively high resistance to pollution by heavy metals and oil. According to the degree of resistance to pollution with Cr, Cu, Ni, Pb and oil black soils of the Central Caucasus and the Caucasus are as follows: ordinary black soils ≥ leached black soils ≥ ashed.
Heavy metals form the following series of ecotoxicity for the black soils of the Central Caucasus and the Caucasus: Cr > Cu ≥ Ni ≥ Pb. On the basis of the degree of violation of the ecological functions of the soil, the approximate values of the maximum permissible content of Cr, Cu, Ni, Pb and oil in the black soils of the Central Caucasus and the Caucasus, which are appropriate to use for the development of regional environmental standards.
Conclusions. Based on the degree of violation of the ecological functions of the soil, approximate values of the maximum allowable content of lead, chromium, nickel, copper and oil in the black soils of the Central Ciscaucasia and the Caucasus are obtained, which are advisable to use for the development of regional environmental standards (rPDK).
|Issue||2020, № 1 (Т. 12)|
|Key words||pollution, black soils, stability, rationing, regional MPC.|