Post-fire ecological consequences within the drained site of the Great Vasyugan Mire: retrospective water-thermal regime and pyrogenic disturbance estimation

The aim of this research is to carry out an assessment of pyrogenic load after the fire event in 2016 within the drained site of Great Vasyugan mire (Bakchar bog, North-East part of The Great Vasyugan mire). Specifically, the objectives of this study were to: 1) perform a retrospective analysis of the water-thermal regime of the area under study according to monitoring data on the nearby site for estimation of development emergence of a fire-dangerous situation conditions; 2) determine the quantitative characteristics of vegetation and microtopography fire transformation based on field data; 3) estimate zone of contamination by combustion products and 4) estimate the hydrocarbons composition of mire and river water, peat and typical plants of the pyrogenic disturbed bog. The water-thermal retrospective analysis confirmed that in August 2016, the most favourable conditions for the emergence of a fire-dangerous situation were developed. The area of fire spread was 5.54 km2, including within the mire of 4.44 km2. The area of Zn and Pb pollution covers an area of 8 km, which is consistent with the prevailing wind direction and atmospheric deposition data for 2016. The zone of extreme pollution of heavy metal peat deposits is limited mainly by the zone of intensive burning of the surface, however, and beyond it, there was also a significant (2 times) Zn, Cd and Pb concentration (except Cu) increase, mainly due to the migration of elements with water flow. Carbon losses for the burned area of 1 square metre to a depth of 30 cm were about 3,800 gC/m2. Against the background of a decrease in the content of n-alkanes, their share in the composition of peat lipids of the burnt area increases slightly, and among them the content of homologues C23–C25 increases, C29–C33 decreases and the CPI value decreases.