Simulation of the chemical evolution of biomass burning organic aerosol

Abstract

Abstract. The chemical transport model PMCAMx was extended to investigate the effects\nof partitioning and photochemical aging of biomass burning emissions on\norganic aerosol (OA) concentrations. A source-resolved version of the model,\nPMCAMx-SR, was developed in which biomass burning emissions and their\noxidation products are represented separately from the other OA components.\nThe volatility distribution and chemical aging of biomass burning OA (BBOA)\nwere simulated based on recent laboratory measurements. PMCAMx-SR was applied\nto Europe during an early summer period (1–29\xa0May 2008) and a winter period\n(25\xa0February–22\xa0March 2009). During the early summer, the contribution of biomass burning (both primary\nand secondary species) to total OA levels over continental Europe was\nestimated to be approximately 16\u2009%. During winter the contribution was\nnearly 47\u2009%, due to both extensive residential wood combustion but also\nwildfires in Portugal and Spain. The intermediate volatility compounds\n(IVOCs) with effective saturation concentration values of 10 5 and\n10 6 µ g\u2009m −3 are predicted to contribute around one third of\nthe BBOA during the summer and 15\u2009% during the winter by forming secondary\nOA (SOA). The uncertain emissions of these compounds and their SOA formation\npotential require additional attention. Evaluation of PMCAMx-SR predictions\nagainst aerosol mass spectrometer measurements in several sites around\nEurope suggests reasonably good performance for OA (fractional bias less\nthan 35\u2009% and fractional error less than 50\u2009%). The performance was\nweaker during the winter suggesting uncertainties in residential heating\nemissions and the simulation of the resulting BBOA in this season.