Analysis of biomass burning derived aerosol under different combustion and oxidation regimes at the EUPHORE chambers

Biomass burning (BB), including wildfires, agricultural burning and domestic heating results in the emission of complex mixture of particle and gas phase species, among which volatile organic compounds and organic aerosols (primary organic aerosol – POA) are prevailing, in the atmosphere. These emissions and their chemical aging products, including both gas-phase pollutants and secondary organic aerosols (SOA), under different atmospheric and combustion conditions, remain poorly understood and have significant but still uncertain impacts on air quality, human health and climate.

The experimental campaign in the EUPHORE outdoor photoreactors focused on studying the gas and particle phase emissions and aging processes from the combustion of different types of wood (orange tree, vineyard and beech), as well as a diesel engine car exhaust, under diurnal and nocturnal operating regimes. It consisted of an ambitious campaign that involved a wide range of analytical instrumentation, highlighting state-of-the-art mass spectrometers (PTR-ToF-MS and API-ToF-CIMS coupled to a Figaero inlet) for both gas and particle phase analysis and a newly released 9λ Aethalometer model AE36s (Aerosol Magee Scientific) for improved characterization of aerosol optical properties. This work focuses on the analysis of the particulate phase emissions and their aged SOA products using the instrument API-ToF-Iodide-CIMS+Figaero inlet.

From the analysis of the chemical composition of the particulate phase in this extensive set of experiments, significant information, similarities and differences are derived, both between different types of wood fuels and between distinct combustion regimes (smoldering vs. flaming) and aging conditions (daytime vs. night-time). In the mass spectra (MS) analysis, a general emission of higher POA m/Q compounds is observed in the smoldering combustion compared to the flaming one. After several hours of aging, evolution and differentiation from the initial fume mass spectra is observed, with a gradual transition to MS with a more significant presence of higher molecular weight compounds. Diverse compound types have been identified, including phenolic, furanic, organonitrate products, non-oxygenated and oxygenated PAHs and other BB tracers, such as levoglucosan.

Combined dark and light aging experiments reveal changing trends in the formation and evolution of numerous compounds due to light conditions shift. Aerosol night-time aging periods lead to the formation and accumulation of organonitrate BB derived products, such as nitroanisole, nitroguaiacol and nitrocatechol, leading to its degradation after the chamber opening and the exposure to natural light. This is an ongoing work currently under investigation with great potential to provide with new valuable information that can enhance our understanding of the complex aging pathways of biomass-burning pollutants and to improve model results.

This work is part of a project supported by the European Commission under the Horizon 2020 – Research and Innovation Framework Programme through the ATMO-ACCESS Integrating Activity (grant agreement N. 101008004) and by the R+D project ATMOBE (PID2022-142366OB-I00), funded by MCIN/AEI/10.13039/501100011033/, the "ERDF A way of making Europe”, the Valencian Regional Government (GVA) and the EVER project CIPROM/20200/37.