Changes in Enzyme Activity in Post-Pyrogenic Soils (Physical Model Experiment)

Presented data on changes in the enzymatic activity of soils under pyrogenic effects in model experiments simulating natural fires. A series of experiments aimed at studying pyrogenic inhibition of enzyme activity and dynamics of their recovery in post-pyrogenic soils were performed under laboratory and natural conditions. The objects of the study were sandy soil (Seropeski, Arenosol) and migratory-segregation black soil (Haplic Chernozem (Loamic, Pachic) Rostov region. Model experiments were carried out by treating soil samples with gas burner flame (amount of heat 87–435 × 103 J) and pyrogenic action of wood fuel combustion (10–279 × 106 J). In the first case, the exposure duration was 1 to 5 min, and in the second case from 1 to 120 min. The response of enzymes (catalase, invertase, urease, peroxidase and phosphatase) to low-temperature plasma exposure (1–120 min) was found to differ depending on the enzyme group and degree of exposure. It was found that the depth of penetration of thermal effects in simulated fires was limited to the top soil layer (0–10 cm), and the radius of spread relative to the combustion source did not exceed 20 cm. Temperature values varied according to time, source of exposure and amount of fuel (400–600°C). Sandy soils and chernozem were heated and cooled down at different rates. The activity of catalase, invertase and urease were found to be inversely related to the intensity of pyrogenic exposure. The dynamics of enzyme activity recovery in post-pyrogenic soils was traced. Invertase activity recovered faster than catalase and urease activity, but full recovery after a year does not occur. The results obtained indicate a significantly prolonged effect of inhibition of enzymatic activity during simulation of natural fires.