Formation of nitrogen-containing gas phase products from the heterogeneous (photo)reaction of NO2 with gallic acid

• DOI: 10.1038/s42004-023-01003-3
• Publication Date: 2023-09-16T11:01:44Z
• Authors: Pan Li; Rachel Gemayel; Xue Li; Jiangping Liu; Mingjin Tang; Xinming Wang; Yan Yang; Hind A. Al-Abadleh; Sasho Gligorovski
• Keywords: Chemistry; [SDE]Environmental Sciences; 540; QD1-999; 01 natural sciences; Article; 0105 earth and related environmental sciences

AbstractHeterogeneous reaction of gas phase NO2 with atmospheric humic-like substances (HULIS) is potentially an important source of volatile organic compounds (VOCs) including nitrogen (N)-containing compounds, a class of brown carbon of emerging importance. However, the role of ubiquitous water-soluble aerosol components in this multiphase chemistry, namely nitrate and iron ions, remains largely unexplored. Here, we used secondary electrospray ionization ultrahigh-resolution mass spectrometry for real-time measurements of VOCs formed during the heterogeneous reaction of gas phase NO2 with a solution containing gallic acid (GA) as a proxy of HULIS at pH 5 relevant for moderately acidic aerosol particles. Results showed that the number of detected N-containing organic compounds largely increased from 4 during the NO2 reaction with GA in the absence of nitrate and iron ions to 55 in the presence of nitrate and iron ions. The N-containing compounds have reduced nitrogen functional groups, namely amines, imines and imides. These results suggest that the number of N-containing compounds is significantly higher in deliquescent aerosol particles due to the influence of relatively higher ionic strength from nitrate ions and complexation/redox reactivity of iron cations compared to that in the dilute aqueous phase representative of cloud, fog, and rain water.