Distribution of chloride and bromide across the snow-sea ice-seawater interface in natural and mesocosm environments and its implication for halogen activation in polar regions
Halogen chemistry in the polar boundary layer has received much scientific attention in recent years due to the observations of high concentrations of reactive halogens in springtime. The source of reactive halogens and the site for halogen activation remain a subject of debate. In this thesis, chloride, bromide and sodium ions across the snow-sea ice-seawater interface were measured to study the cryospheric halide distribution and halogen activation in the Arctic. The results show halides/Na+ molar ratios (Br−/Na+ and Cl−/Na+ ratios) in snow are commonly higher than that in seawater, suggesting snow scavenges halides from sources other than sea salt. The decrease in the halides/Na+ ratios in the surface snow layer indicates a loss of halides from the snow, supporting snow as an important substrate for halogen activation. Furthermore, a mechanism for snow-assisted halogen activation is proposed based on the variation of the Br−/Cl− ratio in the snow.