Understanding the Transformation Pathway of Nitrogen-Containing Emerging Contaminants to Reactive Nitrogen Species by Ozonolysis

Nitrogen-containing emerging contaminants (N-EC) are attracting growing attention, and they show a unique transformation pathway that may contribute to atmospheric reactive nitrogen species, such as HONO and NO x . The thermal and photochemical ozonolysis of N-EC was investigated in terms of kinetics, products, mechanism, and environmental implications. O 3 uptake was observed on various N-EC under dark conditions, with the average O 3 uptake coefficient ( γ av ) in the range of (0.32–1.21) × 10 –5 . Light generally promoted O 3 uptake on N-EC, and the extent of enhancement was correlated to hydroxyl radicals ( • OH) and singlet oxygen ( 1 O 2 ) derived from the photoexcited N-EC. However, light was found to suppress HONO production from the ozonolysis of nitenpyram (NPM), a representative N-EC. HONO can be generated from either the O 3 attack or the electrophilic addition of • OH on the C═C–NO 2 structure by the photochemical ozonolysis of NPM, but HONO production by the • OH attack was less efficient than that from the O 3 attack. Our results indicate that the O 3 uptake process on N-EC containing C═C–NO 2 would contribute to the atmospheric HONO source in the range of 74–740 ppt h –1 .