Rapid Summertime Transformation of Biomass Burning and Other Emissions to Highly Aged Toxic Background Organic Aerosol

CHRISTINA N. VASILAKOPOULOU, Angeliki Matrali, Ksakousti Skylakou, Evangelia Siouti, Maria Georgopoulou, Kalliopi Florou, David Patoulias, Andreas Aktypis, Christos Kaltsonoudis, Athanasios Nenes, Spyros Ν. Pandis, University of Patras, Greece

     Abstract Number: 165
     Working Group: Aerosol Exposure

Abstract
Wildfires are a significant source of biomass burning organic aerosol (bbOA) during summer, with major environmental impacts on air quality and global climate. Measurements were conducted in a remote continental eastern Mediterranean forest site during summer 2022, to study the bbOA produced from European wildfires. An Aerosol Mass Spectrometer (AMS) was used for the measurements of the particle phase. Other on-line instrumentation included a PTR-MS, SP2, aethalometer, SMPS, OPS, and gas-monitors. Samples were collected for the measurement of additional ions, metals, oxidative potential (OP) and ¹⁴C. The average OA was 7.4 μg m^-3, a high level for a remote area.

The PM_2.5 fire emissions for that month in Europe were estimated to be 25,000 tn d^-1. However, the AMS Positive Matrix Factorization (PMF) results did not indicate any fresh bbOA. Three highly oxygenated secondary factors were identified: biogenic OOA (bOOA) (23% of the total OA), a less-oxidized OA (LO-OOA) (37%) and a more-oxidized OA (MO-OOA) (40%). Using potassium measurements and typical biomass emission composition data for Europe, we estimated that bbOA should be of the order of 5 μg m^-3. Analysis of the evolution of selected major fires in the Balkans suggests that the corresponding bbOA is converted in 1-2 days mostly to MO-OOA. High OP values were observed for the whole period (average DDT_v equal to 0.34 nmol min^-1 m^-3) and the days influenced more by fires (higher potassium levels) had the highest DDT_v. Chemical transport modeling with PMCAMx suggested that fires from Portugal affected this remote site in Greece thousands of kilometers away. The aged biomass burning OA contributes significantly to the background OA over Europe during the summer and due to its toxicity is estimated to have significant health effects on citizens of most European countries living far from the actual fires.