Contributors: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China; Colorado State University Fort Collins (CSU); IRCELYON-Catalytic and Atmospheric Reactivity for the Environment (CARE); Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON); Université Claude Bernard Lyon 1 (UCBL); Université de Lyon-Université de Lyon-Institut de Chimie - CNRS Chimie (INC-CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL); Université de Lyon-Université de Lyon-Institut de Chimie - CNRS Chimie (INC-CNRS)-Centre National de la Recherche Scientifique (CNRS); Institut de Combustion, Aérothermique, Réactivité et Environnement (ICARE); Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut des Sciences de l'Ingénierie et des Systèmes - CNRS Ingénierie (INSIS - CNRS); Leibniz Institute for Tropospheric Research (TROPOS); Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science & Engineering, Fudan University, Shanghai; ANR-16-CE01-0013,SEA-M,Impact des échanges air-mer sur la qualité de l'air dans les mégalopoles du littoral(2016)
نبذة مختصرة : International audience ; Abstract Chlorine atoms (Cl) are highly reactive and can strongly influence the abundances of climate and air quality-relevant trace gases. Despite extensive research on molecular chlorine (Cl2 ), a Cl precursor, in the polar atmosphere, its sources in other regions are still poorly understood. Here we report the daytime Cl 2 concentrations of up to 1 ppbv observed in a coastal area of Hong Kong, revealing a large daytime source of Cl2 (2.7 pptv s−1 at noon). Field and laboratory experiments indicate that photodissociation of particulate nitrate by sunlight under acidic conditions (pH < 3.0) can activate chloride and account for the observed daytime Cl2 production. The high Cl2 concentrations significantly increased atmospheric oxidation. Given the ubiquitous existence of chloride, nitrate, and acidic aerosols, we propose that nitrate photolysis is a significant daytime chlorine source globally. This so far unaccounted for source of chlorine can have substantial impacts on atmospheric chemistry.
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