Biomass-burning derived particles from a wide variety of fuels: Part 1: Properties of primary particles

Abstract. Relationships between various optical, physical, and chemical properties of biomass combustion derived particles are characterized for particles produced from a wide range of fuels and burn conditions. The modified combustion efficiency (MCE), commonly used to parameterize biomass particle emissions and properties, is shown to generally have weak predictive capabilities, especially for more efficient combustion conditions. There is, however, a strong relationship between many intensive optical properties (e.g. single scatter albedo, Angstrom absorption exponent, mass absorption efficiency) and the organic aerosol-to-black carbon ([OA] / [BC]) mass ratio over a wider range than previously considered (0.3 to 105). The properties of brown carbon (BrC, i.e. light absorbing organic carbon) also vary with [OA] / [BC]. The contribution of coating-induced enhancements (i.e. lensing effects) to absorption by black carbon are shown to be negligible for all conditions. The BC-OA mixing state varies strongly with [OA] / [BC]; the fraction of OA that is internally mixed with BC decreases with [OA] / [BC] while the relative amount of OA coated on BC increases. In contrast, there is little relationship between many OA bulk chemical properties and [OA] / [BC], with the O : C and H : C atomic ratios and the relative abundance of a key marker ion (m/z = 60, linked to levoglucosan) all showing no dependence on [OA] / [BC]. In contrast, both the organic nitrate fraction of OA and the OA volatility do depend on the [OA] / [BC]. Neither the total particle or BC-specific size distributions exhibit any clear dependence on the burn conditions or [OA] / [BC], although there is perhaps a dependence on fuel type. Overall, our results expand on existing knowledge to contribute new understanding of the properties of particles emitted from biomass combustion.