Study on the Impact of Wildfires on Atmospheric Gas Composition.

The study of wildfires and biomass burning is of great importance for understanding global ecological and climatic processes. Wildfires represent one of the key sources of greenhouse gas and aerosol emissions that significantly influence the chemical composition of the atmosphere. The aim of this research was to quantitatively characterise the impact of wildfires on atmospheric composition based on long-term FTIR measurements of biomass burning tracer gases (HCN, CO, and C₂H₆) over the 2009-2022 period. The main objectives included developing an algorithm for detecting wildfire plumes, assessing their contribution to increased concentrations of the studied gases, and determining emission ratios that characterise combustion processes. The work involved analysis of multi-year measurement time series obtained at St Petersburg University's atmospheric monitoring station using a Bruker IFS 125HR spectrometer system. The developed algorithm for identifying wildfire influence episodes was based on temporal criteria (April-October) and gas concentration exceedances of more than two standard deviations. The results revealed four key episodes (2012, 2013, 2017 and 2018) when wildfire plumes caused significant increases in the concentrations of the studied gases. It was established that background concentrations were two orders of magnitude lower than during wildfire emissions, confirming the importance of accounting for wildfires' contribution to atmospheric composition changes. The analysis determined emission ratios of HCN/CO = 0.0047 and C₂H₆/CO = 0.0071. These results demonstrate the effectiveness of the proposed approach for studying wildfire impacts on the atmosphere and can be used for further research in atmospheric chemistry and climatology.