Abstract

Residential wood combustion is one of the major sources of fine particles. The chemical composition of the particles plays a key role in both adverse health and environmental effects. It is important to understand how chemical composition of particulate emissions varies during different combustio... Show moreResidential wood combustion is one of the major sources of fine particles. The chemical composition of the particles plays a key role in both adverse health and environmental effects. It is important to understand how chemical composition of particulate emissions varies during different combustion processes and conditions. In this work, combustion of wood chips was studied in a moving step-grate burner in different combustion conditions (efficient, intermediate, and smoldering) in the laboratory. The particulate emissions were measured with an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS). It was found that two phases were occurring frequently in the intermediate and smoldering combustion. Phase 1 took place when gaseous carbon monoxide (CO) was rapidly increasing after the new fuel addition. Phase 2 was a stable, burn-out period with low CO emissions until the new fuel addition and automatic removal of fuel leftovers from the grate. The analysis on the organic aerosol by positive matrix factorization (PMF) extracted out five factors: hydrocarbon-like organic aerosol (HOA), low-volatile-oxidized organic aerosol (LV-OOA), biomass burning organic aerosol (BBOA), and two additional factors of “polycyclic aromatic hydrocarbon (PAH) factor” and “aromatic factor”. PAH and LV-OOA were found to be forming mainly during phase 1. HOA showed similar behavior as a PAH factor and LV-OOA in a time series. BBOA was consistent with levoglucosan formation during the combustion and became higher during phase 2. The aromatic factor was mainly composed of fragment ions of n-butyl benzenesulfonamide compound, which was observed in both phases. To our knowledge, this is the first work to report the particulate organics of combustion aerosols and PAH distinguished by PMF. The results prove that the particulate organic emissions can be reduced efficiently when keeping combustion efficiency high. This may help in targeting the efforts on emission reduction better in the future. Show less