Organic geochemistry of polar ice and snow

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Greenland and Antarctica ice cores have been analyzed for fatty acids, dicarboxylic acids, UCM hydrocarbons, polycyclic aromatic hydrocarbons (PAH) using a capillary gas chromatography and GC/mass spectrometer. The Greenland ice core showed that the concentrations of fatty acids of marine origin (C_<12>-C_<18>) were almost constant in 1500s to 1800s, increased in 1930-1950 years, decreased in 1970s, then again increased in 1980s. Their variations in 1900s were found to be consistent with the variations of the Arctic air temperature. This study demonstrated that the ice core recorded the past information on the sea to air emission of marine-derived fatty acids that should depend on the progress/retreat of sea ice as well as variations of low pressure systems in the arctic regions. We also found an increase in the concentration ratios of azelaic acid (C_9 diacid) to unsaturated fatty acids in the twentieth century with a large peak in 1940s. Because the former acid is the specific photo-oxidation product of the latter, this suggests that the atmospheric oxidizing capability has increased in that period.The Antarctic ice core showed that the presence of anthropogenic organic components such as PAH and UCM, whose concentrations increased after 1900s. This indicates that organic pollutants transported over the Antarctica have been stored in the Antarctic ice. The azelaic acid/unsaturated fatty acid ratios showed a large increase after 1970 AD.Such an increase suggests that the stratospheric photo-oxidizing capability was enhanced over the Antarctica, probably as a result of the destruction of stratospheric ozone layer.The organic geochemical study of polar ice cores demonstrated a noble approach for the reconstruction of past atmospheric conditions in the polar regions.