HETEROGENEOUS REACTION OF HOBR WITH HBR AND HCL ON ICE SURFACES AT 228-K

Motivated by the recent observations of springtime ozone loss in the A rctic boundary layer, we have studied the heterogeneous reactions HOBr + HBr --> Br2 + H2O and HOBr + HCI --> BrCl + H2O using a low tempera ture flow tube coupled to a mass spectrometer. By monitoring the decay of HOBr in an excess of either HBr or HCI, both reactions have been s hown to occur readily on ice surfaces at 228 K with reaction probabili ties of 0. 12 (+/-0.03) and 0.25 (+0.10/-0.05), respectively. The gas- phase reaction products, Br2 and BrCl, have been observed. Also, it ha s been shown that HOBr interacts strongly with supercooled 60 wt % sul furic acid solutions, being taken up with a sticking coefficient of gr eater than 0.06. The atmospheric implications of the heterogeneous rea ctivity of HOBr and HBr are discussed.