Ageing of biomass burning organic aerosol in the FORTH atmospheric simulation chamber: chemical characterization by H-NMR

With the aim of identifying biomass burning (BB) SOA formation pathways, we performed ageing experiments of BB primary emissions at the FORTH Atmospheric-Simulation-Chamber in Patras, Greece. Different biofuels were employed using the most common types in Greece: olive-tree logs and pellets (residuals of pine-wood). SOA formation was investigated under different conditions in term of oxidants (OH or NO3 radicals), photochemical conditions (illumination vs. dark), and relative humidity (up to 80%) in order to simulate both diurnal and nocturnal chemical ageing and assess the effects of humidity on SOA condensation and chemical transformation. The evolution of organic aerosol was monitored using a HR-ToF-AMS, while filter samples were collected for offline chemical characterization of the water-soluble organic fraction (WSOC) by means of proton-Nuclear Magnetic Resonance (H-NMR) spectroscopy. H-NMR spectra of fresh and aged samples showed considerable variability between experiments. High relative humidity demonstrated to strongly influence the chemical features of aged BBOA.