Carbonyl compounds from typical combustion sources: Emission characteristics, influencing factors, and their contribution to ozone formation

Abstract

Fuel combustion is an important primary source of carbonyl compounds (CCs), yet the emission factors and influencing factors of CCs in different sources remain unclear. The emission characteristics, influencing factors, and ozone formation potentials of CCs from four combustion sources, including biomass burning (BB), residential coal combustion, on-road sources, and agricultural machinery, were investigated by field measurements. Results indicate that the emission factors of CCs from four combustion sources exhibit significant differences. Specifically, the emission factors of CCs from BB (1968.2 ± 661.2 mg kg-1) are significantly higher than those from other sources, being an order of magnitude greater than those from the on-road sources (117.8 ± 78.3-576.3 ± 47.4 mg kg-1). Fuel type is a key factor affecting the CC components. BB primarily emits formaldehyde and acetaldehyde, whereas residential coal combustion exhibits a higher proportion of aromatic aldehydes and acetone. The addition of ethanol in on-road sources and biodiesel in agricultural machinery effectively promotes the formation of acetaldehyde and unsaturated aldehydes, respectively. The formation of CCs in solid and liquid fuel sources is more sensitive to combustion temperature and emission standard, respectively. Higher combustion temperatures and stricter emission standards can reduce CC emissions by 94.6 % in solid fuels and by 61.3 % in liquid fuels, respectively. High temperatures promote the cyclization of small molecules, supplying ample precursors for the formation of acetone and aromatic aldehydes. More attention should be paid to the ozone formation potentials of CCs from BB and agricultural machinery to alleviate the oxidizing capacity of regional atmospheres.