GEOCHEMICAL FEATURES OF POST-PYROGENIC CHANGES OF POLISSYA SOILS (LOW FIRE)

Geochemical post-pyrogenic soil changes are one of the most important factors in determining the state of the forest ecosystem. For the first time the content of microelements (Hg, As, Ba, Mg, Mn, Mo, Cd, Co, Cr, Cu, Pb, Zn, V, Ni) in post-pyrogenic sod-podzolic soils under the pine forest of Zhytomyr Polissya (Ukraine) was determined by the ICP-MS method. The study is based on a comparison of the content of trace elements in the sod-podzolic soils of the background area and burnt areas (grassland fire in 2019). The analysis of microelements in the soil profile of the burned and background areas to a depth of 10 cm (after 1 cm) and set the limit - 3-5 cm (humus-eluvial horizon), after which you can record the accumulation or scattering of elements after a fire on the surface. By calculating the percentage change (relative to background soils), intensive accumulation (more than 20%) of elements in post-pyrogenic soils - Cu, Ni, Co, V and moderate accumulation (up to 10%) - Pb, Mo, Mg, Ba, Cr and intensive scattering - Hg, As, Cd, Zn, Mn. The increase in the pH of post-pyrogenic soils (from 4.2 to 7.5) was determined, spatial map-schemes were constructed, due to which the direction of the fire was revealed - from the south-east to the north-west. The change of the content of ionic forms of metals (Cu, Pb, Zn, Mn) in the soil solution at different pH values (from 4 to 8 with a step of 0.2) is modeled (PHREEQC program) and the current trend is revealed: Pb - linear dependence, Cu, Zn, Mn is polynomial. The pH limits are calculated, where there are free forms of metals that enter the plants: Pb 3.9-8.2; Zn 5.5-7.5; Cu 5-8.2; Mn 5-11.5. The post-fire transformation of soils was revealed, which is expressed in the increase of pH (before the fire - 4.2-4.8; after the fire - 6.5-7.2; a year after the fire - 4.5-5.5). The obtained results confirmed the need for geochemical monitoring of post-pyrogenic soils for ecosystem restoration and plant biodiversity.