HEAVY METALS IN SOILS OF PINE FORESTS AFTER PYROGEN INFLUENCE

Abstract

Experimental studies allowed revealing the consequences of the post-pyrogenic transformation of the physical and chemical parameters of soils after the pyrogenic factor, both the recent influence of fires and after a long period of time. There is a definite dependence of the postpyrogenic transformation on the age of the fire impact on the soil. Relatively recent consequences of a fire of medium intensity on the soil are marked by a clear reaction of the complex of their properties. Physical-chemical properties of soils during the fire period deteriorate due to the fact that the amount of nutrients in the soil is significantly reduced: humus burns, the content of nitrate nitrogen decreases. Consequently, fires, on the one hand, improve the conditions for the penetration of seeds into the soil, but worsen the conditions for the growth, growth and development of coniferous tree species. The acid-alkaline reaction according to the pH indicator in soils exposed to fires shifts to neutral, which should be explained by the saturation of the absorbing complex of soils with alkaline earth elements. Forest fires significantly transform the morphological appearance of the upper part of the soil profile. As a result, the surface horizons of soils change, in particular, a new pyrogenic horizon is formed, which differs from natural analogues in a certain way in terms of physical and chemical properties and the content of ash elements. Under the influence of fires, there are changes in such parameters as pH, the content of exchangeable cations, gross and mobile forms of nitrogen, etc. It should also be taken into account that the behaviour and content of heavy metals in the forest litter is determined, in addition to the influence of fire, by the geochemical state of the region – the rate of water migration and biological absorption, the topography of the area. The concentration of heavy metals in the surface horizons of the soils of pine forests increases several times and exceeds background concentrations due to the mineralization of the forest floor and grassy vegetation from combustion and the subsequent migration of chemical elements, which represents an ecological hazard.