Low-molecular-weight carbonyl volatile organic compounds on the North China Plain

To understand the photochemical pollution characteristics of low-molecular-weight carbonyl compounds on the North China Plain (NCP), 2,4-dinitrophenylhydrazine (DNPH) was used to sample low-molecular-weight carbonyl compounds in the atmosphere in Beijing, Tianjin, Shijiazhuang, Xianghe and Xinglong from June 2019 to January 2020, and the samples were then analyzed by a high-performance liquid chromatography (HPLC) to obtain the concentration, daytime variations, seasonal variations, OH radical loss rate, ozone formation potential and sources of five low-molecular-weight carbonyl compounds in the NCP region. The total concentrations at the five sites were 7.70 ± 1.94 ppbv (Beijing), 10.20 ± 1.83 ppbv (Tianjin), 15.31 ± 2.35 ppbv (Shijiazhuang), 10.53 ± 1.82 ppbv (Xianghe) and 5.42 ± 1.15 ppbv (Xinglong), respectively. The contribution of primary source from anthropogenic emission was higher in Tianjin, Shijiazhuang and Xianghe than that in Beijing. The primary and secondary generation contributions were similar in Xinglong. The concentration in Beijing was highest in autumn and lowest in winter. For Tianjin, Shijiazhuang, Xianghe and Xinglong, the highest concentrations occurred in summer. At the five sites, formaldehyde and acetaldehyde contributed the most to L·OH and OFP, while acetone contributed the least. Both L·OH and OFP in Shijiazhuang were the highest, and those in Xinglong were the lowest. The North China Plain was mainly influenced by short-range airflow from the sea and coastal areas during the summer, with the airflow mainly coming from the south in autumn, while the long-range air mass transport was more influential during the winter. In addition, most pollutants were found to be generated locally. By utilizing a source-tracer-ratio method in the source analysis, with the change of season, the anthropogenic source contribution of each site was found to gradually increase while that of other sources gradually decreased.