Seasonal variation and sources of derivatized phenols in atmospheric fine particulate matter in North China Plain

Qualitative and quantitative analyses of derivatized phenols in Beijing and in Xinglong were performed from 2016 to 2017 using gas chromatography-mass spectrometry. The results showed substantially more severe pollution in Beijing. Of the 14 compounds detected, the total average concentration was 100 ng/m³ in Beijing, compared with 11.6 ng/m³ in Xinglong. More specifically, concentration of nitro-aromatic compounds (NACs) (81.9 ng/m³ in Beijing and 8.49 ng/m³ in Xinglong) was the highest, followed by aromatic acids (14.6 ng/m³ in Beijing and 2.42 ng/m³ in Xinglong) and aromatic aldehydes (3.62 ng/m³ in Beijing and 0.681 ng/m³ in Xinglong). In terms of seasonal variation, the highest concentrations were found for 4-nitrocatechol in winter in Beijing (79.1 ± 63.9 ng/m³) and 4-nitrophenol in winter in Xinglong (9.72 ± 8.94 ng/m³). The analysis also revealed diurnal variations across different seasons. Most compounds presented higher concentrations at night in winter because of the decreased boundary layer height and increased heating intensity. While some presented higher levels during the day, which attributed to the photo-oxidation process for summer and more biomass burning activities for autumn. Higher concentrations appeared in winter and autumn than in spring and summer, which resulted from more coal combustions and adverse meteorological conditions. The significant correlations among NACs indicated similar sources of pollution. Higher correlations presented within each subgroup than those between the subgroups. Good correlations between levoglucosan and nitrophenols, nitrocatechols, nitrosalicylic acids, with correlation coefficients (r) of 0.66, 0.69 and 0.69, respectively, indicating an important role of biomass burning among primary sources.