Chemical transformation of bromine chloride at the air/water interface

The uptake of gaseous bromine chloride (BrCl) on aqueous surfaces was measu red, as a function of temperature and liquid composition, using the droplet train technique coupled to a mass spectrometer. The uptake rate on pure wa ter was too slow to be directly measured (i.e., gamma < 10(-3)). In order t o increase the uptake kinetics above the detection limit of the experimenta l set-up, NaBr, NaI and NaOH were used as scavengers. The uptake kinetics o n sodium bromide solutions were complicated by the interference of Cl-2 and Br-2 which are in equilibrium with gaseous BrCl. Therefore, we report resu lts on the other two scavengers. On sodium hydroxide solutions, the uptake is driven by the bulk reactivity of BrCI toward OH-yielding an average valu e of the mass accommodation coefficients alpha of 0.33 +/- 0.18 in the temp erature range from 270-285 K. On sodium iodide solutions, the uptake kineti cs were again driven by the bulk reactivity of the in-coming bromine chlori de but, in addition a surface reaction channel was found. (C) 2001 Elsevier Science Ltd. All rights reserved.