Photochemical Degradation of Organic Pollutants in Liquid Water and Ice

Arctic snow and ice play an important role as reactive media in the environment. A variety of species are photochemically generated from snow/ice, including carbonyl compounds, alkyl halides, molecular halogens, and nitrogen oxides. However, the fate of anthropogenic organic pollutants in snow and ice is largely unknown. Volatile pollutants evaporate from lower, warmer latitudes and condense out in the higher, colder latitudes by a process known as global distillation, leading to enhanced concentrations of a variety of pollutants in polar regions. Here we present recent results of photochemical degradation studies of several important organic pollutants including aldrin, dieldrin, hexachlorobenzene, and 3,3',4,5'-tetrachlorobiphenyl. Direct and indirect (with H2O2) pathways were studied in both liquid water and ice forms. Aldrin and 3,3',4,5'-tetrachlorobiphenyl have shown the most reactivity, both degrading significantly via the direct and indirect pathway in liquid water and ice. Dieldrin has shown reactivity under both direct and indirect liquid conditions, while HCB is only reactive under indirect liquid conditions. These results indicate that ice can serve as an important reactive surface for anthropogenic organic pollutants. Snow/ice photochemistry should be included in models of pollutant fate, but further studies are necessary to determine which pollutants are most affected by ice photochemistry under typical environmental conditions.