Characteristics and Sources of Nitrated Phenols in Atmospheric Fine Particles of Northern Suburban Nanjing

Abstract

Nitrated phenols are a group of nitrogen-containing organics ubiquitously present in ambient air, which are also important components of atmospheric light-absorbing organic matter (brown carbon) that have significant impacts on climate change, air quality, and human health. In this study, we collected a total of 265 daily filter samples of fine particles (PM2.5) in northern suburban Nanjing from March 2019 to January 2020. We used ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) to detect and quantify eight nitrated phenolic species. The results showed that the average annual concentration of total nitrated phenols in the sampling site was 18.77 ng·m-3, and the average concentrations in spring, summer, autumn, and winter were 16.82, 8.59, 17.28, and 44.79 ng·m-3, respectively. Such concentrations were obviously higher than those determined in other countries but were similar to those in domestic cities, such as Jinan. 4-Nitrophenol was the most abundant nitrated phenol, followed by 4-nitrocatechol and 2-methoxy-5-nitrophenol. Correlation analysis showed that 3-nitrosalicylic acid was from a specific source different from that of other species. Finally, we used a positive matrix factorization model to quantify the source contributions of nitrated phenols. The major sources were vehicle emissions (32%), mixed coal and biomass burning emissions (44%), and industrial emissions (24%). The mixed coal and biomass burning emissions were dominant in autumn and winter. The mass fraction of 3-nitrosalicylic acid in the factor of industrial emissions was>90%, consistent with the results of the correlation analysis. Overall, this study provides valuable insights into the understanding of concentrations, characteristics, and sources of atmospheric nitrated phenols in ambient air.