Dr. Hanson et al., REACTION OF BRONO2 WITH H2O ON SUBMICRON SULFURIC-ACID AEROSOL AND THE IMPLICATIONS FOR THE LOWER STRATOSPHERE, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 101(D4), 1996, pp. 9063-9069
Uptake of BrONO2 onto submicron sulfuric acid aerosol was studied in a
cylindrical flow reactor coupled to a chemical ionization mass spectr
ometer. On aerosol particles of similar to 0.1 mu m radius, the reacti
on of BrONO2 with H2O to produce HOBr and HNO3 is very efficient, with
the reaction probability gamma approximate to 0.8 for H2SO4-content l
ess than or equal to 70 wt%. The equilibrium constant for the gas phas
e process, BrONO2 + H2O reversible arrow HOBr + HNO3, was measured and
the heats of formation of the bromine compounds were deduced. The con
version of HOBr back into BrONO2 via reaction with HNO3 can be neglect
ed in the stratosphere. The heterogeneous hydrolysis of BrONO2, follow
ed by photolysis of the HOBr product, is a major source of HOx in the
lower stratosphere. The role of bromine as an activator of chlorine is
also discussed.