Influencing Factors and Oxidative Effects of NCl ₃ in Coastal Atmosphere

Abstract Chlorine atom (Cl) plays a crucial role in regulating atmospheric composition and air quality. Trichloramine (NCl 3 ), a potential precursor of Cl, has not been thoroughly investigated in terms of sources and atmospheric implications. In this study, nocturnal peaks of NCl 3 were frequently observed in a coastal city in Southeast China. Through integrated analysis of field measurements and machine learning modeling, nitryl chloride (ClNO 2 ), molecular chlorine (Cl 2 ), ultraviolet (UV) radiation, and ammonia (NH 3 ) were identified as the predominant factors affecting the distribution of NCl 3 . Meanwhile, the generation of NCl 3 may be primarily attributed to reactions involving ClNO 2 , Cl 2 , and NH 3 , while intense UV radiation induced its rapid loss via photolysis. Model simulations revealed that NCl 3 ‐driven chemistry substantially boosts Cl production, amplifying RO x · and O 3 formation up to 10%. Our study not only fills the gap in observational research on NCl 3 in coastal regions to some extent but also deepens the understanding of its atmospheric formation and loss mechanisms.