The chemistry of Br species associated with sea salt ice and aerosols has been implicated
in the episodes of ozone depletion reported at Arctic sunrise. However, Br. is only a
minor component in sea salt, which has a Br./Cl. molar ratio of ~0.0015. Sea salt is a
complex mixture of many different species, with NaCl as the primary component. In
recent years experimental and theoretical studies have reported enhancement of the large,
more polarizable halide ion at the liquid/vapor interface of corresponding aqueous alkali
halide solutions. The proposed enhancement is likely to influence the availability of sea
salt Br. for heterogeneous reactions such as those involved in the ozone depletion
episodes. We report here ambient pressure x-ray photoelectron spectroscopy studies as
well as molecular dynamics simulations showing direct evidence of Br. enhancement at
the interface of an aqueous NaCl solution doped with bromide. The experiments were
carried out on samples with Br./Cl. ratios in the range 0.1% to 10%. This is the first
direct measurement of interfacial enhancement of Br. in a multi-component solution with
particular relevance to sea salt chemistry.