Chlorine chemistry and its impacts in the polluted urban and marine-coastal atmosphere

Atmospheric chlorine radical plays essential roles in tropospheric photochemical processes, such as affecting the oxidation capacity and aerosol formation. Tropospheric chlorine chemistry was initially known to be important in the marine and polar atmosphere; nevertheless, more and more recent studies have indicated that chlorine chemistry was also active in polluted areas including the urban and marine-coastal environment. Here, we will present the vital chlorine radical precursors, such as nitryl chloride (ClNO₂), molecular chlorine (Cl₂) and hypochlorous acid (HOCl) that were observed recently in a typical polluted urban (Shijiazhuang) and a marine-coastal (Zhuhai) atmosphere of China. We measured significant concentrations of ClNO₂, Cl₂, and HOCl at the polluted urban and marine-coastal sites, showing there is active chlorine chemistry at both environments. We will discuss the formation mechanism of these species, as well as the possible of influence from anthropogenic chlorine sources. We will finally discuss their contribution the radical formation and impacts on the atmospheric oxidation capacity at both environments.