Optical properties of fresh biomass burning aerosol produced from realistic combustion of boreal peat

Brown carbon (BrC), a class of light-absorbing organic carbon arising in part from combustion processes, including biomass burning, can affect climate significantly by altering Earth's radiative balance. Although many field measurements and laboratory experiments have provided evidence for the existence of BrC, the species responsible for its light-absorbing properties in the UV and visible range still have not been fully investigated; thus, the total radiative impact of biomass burning aerosols remains unclear.

In this study, we use size exclusion chromatography (SEC) with diode array UV-vis absorbance detection to investigate the size-dependent optical properties of fresh biomass burning aerosol generated by combustion of boreal peat sampled in northern Alberta, Canada. In particular, we focus for the first time on the relationship between aerosol optical properties and peat moisture content and sampling depth. Biomass burning aerosol was sampled using a particle-into-liquid sampler (PILS) and quartz fiber filters, which allowed for the investigation of the influence of sampling technique on observed optical properties. The results of this study provide insight into whether small, individual chromophores or large, conjugated species are primarily responsible for BrC absorbance and climate impact.