Characterization of the organic functional group composition and sources of summertime aerosols in an eastern city of China

An intensive field campaign was carried out in Hefei, a city in the Yangtze River Delta in eastern China, in the summer of 2020 to examine the composition and sources of organic aerosols (OA). Time-resolved filter samples were collected and quantified to obtain the concentrations for organic functional groups (OFGs), including alkane, hydroxyl, carboxylic acid, non-acid carbonyl, amine, and aromatic groups using Fourier transform infrared (FTIR). Inorganic aerosol components and gas-phase pollutants were also measured to facilitate the data analysis. The OA concentration ranged from 2.8 to 41.8 μg m−3, with a mean value (±standard deviation) of 12.5 (±5.8) μg m−3, which accounted for 53.6% of the PM2.5 mass. The most abundant OFG in OA was the hydroxyl group (35.2%), followed by alkane (24.0%) and carboxylic (22.4%) groups. The positive matrix factorization (PMF) was applied to the IR spectra of OA that identified three major sources, i.e., aged fossil fuel combustion, biomass burning, and vegetative detritus/dust. Their campaign-average contributions to OA were 38.3%, 28.3%, and 33.4%, respectively. The OFG composition of the aged fossil fuel combustion component was similar to the OFG composition of oxidized alkane products, indicating that alkanes may be important precursors of OA at the sampling site. Cluster and air mass trajectory analyses showed that the OFG concentration was highest when the air masses originated from the eastern Yangtze River Delta, suggesting the influence of the transported industrial emissions on the particulate pollution at the sampling site.