Effect of Pellet Boiler Exhaust on Secondary Organic Aerosol Formation from α-Pinene

Interactions between anthropogenic and biogenic emissions, and implications for aerosol production, have raised particular scientific interest. Despite active research in this area, real anthropogenic emission sources have not been exploited for anthropogenic-biogenic interaction studies until now. This work examines these interactions using α-pinene and pellet boiler emissions as a model test system. The impact of pellet boiler emissions on secondary organic aerosol (SOA) formation from α-pinene photo-oxidation was studied under atmospherically relevant conditions in an environmental chamber. The aim of this study was to identify which of the major pellet exhaust components (including high nitrogen oxide (NO_x), primary particles, or a combination of the two) affected SOA formation from α-pinene. Results demonstrated that high NO_x concentrations emitted by the pellet boiler reduced SOA yields from α-pinene, whereas the chemical properties of the primary particles emitted by the pellet boiler had no effect on observed SOA yields. The maximum SOA yield of α-pinene in the presence of pellet boiler exhaust (under high-NO_x conditions) was 18.7% and in the absence of pellet boiler exhaust (under low-NO_x conditions) was 34.1%. The reduced SOA yield under high-NO_x conditions was caused by changes in gas-phase chemistry that led to the formation of organonitrate compounds.