Reaction of Chlorine Nitrate with Hydrogen Chloride and Water at Antarctic Stratospheric Temperatures | CU Experts

; Laboratory studies of heterogeneous reactions important for ozone depletion over Antarctica are reported. The reaction of chlorine nitrate (ClONO; 2; ) with H; 2; O and hydrogen chloride (HCl) on surfaces that simulate polar stratospheric clouds [ice and nitric acid (HNO; 3; )—ice and sulfuric acid] are studied at temperatures relevant to the Antarctic stratosphere. The reaction of ClONO; 2; on ice and certain mixtures of HNO; 3; and ice proceeded readily. The sticking coefficient of ClONO; 2; on ice of 0.009 ± 0.002 was observed. A reaction produced gas-phase hypochlorous acid (HOCl) and condensed-phase HNO; 3; ; HOCl underwent a secondary reaction on ice producing dichlorine monoxide (Cl; 2; O). In addition to the reaction with H; 2; O, ClONO; 2; reacted with HCl on ice to form gas-phase chlorine (Cl; 2; ) and condensed-phase HNO; 3.; Essentially all of the HCl in the bulk of the ice can react with ClONO; 2; on the ice surface. The gaseous products of the above reactions, HOCl, Cl; 2; O, and Cl; 2; , could readily photolyze in the Antarctic spring to produce active chlorine for ozone depletion. Furthermore, the formation of condensed-phase HNO; 3; could serve as a sink for odd nitrogen species that would otherwise scavenge the active chlorine.;

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