INFLUENCE OF SILVER POLLUTION ON THE ACTIVITY OF SOIL CATALASE IN SOUTH OF RUSSIA
Authors: Tsepina N. I. , Sudina L. V. , Minnikova T. V., , Kolesnikov S. I. 
Published: August 2020

Due to the widespread use of products based on silver nanoparticles, the risk of contamination of the soil cover and surface water increases, since an element in this form can leach out of the material. The amount of silver emissions into the environment is increasing every year. There is growing evidence of silver toxicity for living organisms of not only aquatic, but also terrestrial ecosystems. Silver, accumulating in soil in large quantities, like other heavy metals, can have a toxic effect on the physical, chemical and biological properties of the soil.High doses of the element can have a significant effect on the biological properties and ecological condition of soils. The study of enzyme activity can be used to identify major changes in the soil under the influence of silver. In this regard, it is relevant to study the effect of silver on catalase activity, since this enzyme is an indicator of the potential biological activity of the soil and reflects the intensity of mineralization processes in it.

The aim of the work was to study the effect of silver pollution on the activity of soil catalase most characteristic of the southern regions of Russia.

The object of the study identified soils characteristic of southern Russia: ordinary chernozems, seropesks and brown forest soils. For model studies, soil samples were taken from the upper arable layer (0‑10 cm), since silver accumulates in the surface soil layers.

Silver pollution was modeled in a laboratory. Used silver nitrate at a concentration of 1 mg / kg, 10 mg / kg and 100 mg / kg, the experiment was 3 times biological repetition. The choice of biological indicators is due to the fact that oxidoreductases are most sensitive to chemical pollution among enzymes. This enzyme is an indicator of the biological activity of the soil and reflects the intensity of the mineralization processes in it. Laboratory and analytical studies were carried out using generally accepted methods in biology, soil science and ecology. Catalase activity was determined by the volumetric method according to A.Sh. Galstyan.

As a result of the study of the effect of silver on three types of soils, the most characteristic of the southern regions of Russia, a decrease in catalase activity was noted. The degree of reduction of this indicator depended on the dose of the element introduced into the soil. The degree of resistance to silver contamination has the following sequence: common chernozem> sulfur sands ≥ brown forest soil. This is probably due to the light particle size distribution of sulfur sand and the acidic reaction of the environment of brown forest soils (pH = 5.8), as well as a low content of organic matter (1.8 % and 2.3 %, respectively), which contributes to high mobility, and therefore and high ecotoxicity of silver in these soils.

A decrease in the activity of catalase of ordinary chernozem was observed for 90 days. At 1 UDC on the 30th and 90th day of the experiment, the same decrease in the studied parameter was observed. A similar pattern was observed at 10 UDC at the same experimental time. At 100 UDC (100 mg / kg) on the 90th day after contamination, a tendency toward restoration of catalase activity was observed, however, control values before silver contamination were not achieved. Chernozems have a high number of microorganisms and their high activity, and pollution tolerance mechanisms provide detoxification of soils from exposure to silver.