Formaldehyde (HCHO) and Hydrogen Peroxide (H2O2) in Air, Snow and Interstitial Air at South Pole During ISCAT 2000

For the first time, continuous HCHO and H₂O₂ mixing ratio gradients were measured in the lowest meter above the snowpack at South Pole Station. The results indicate a net HCHO and H₂O₂ release from the top snow layers at South Pole in summer, consistent with elevated atmospheric mixing ratios. Using the measured gradients, corresponding fluxes were calculated and compared with independent estimates based on simultaneous changes in surface snow composition on the one hand and measured gas phase mixing ratios in the interstitial air in the top snow layers on the other hand. In order to separate physical from photochemical processes the findings were compared with physically based air-snow transfer modeling. Results were validated with shading experiments in which the impact of shading and un-shading of the snowpack on HCHO and H₂O₂ mixing ratios in the interstitial air was investigated. The current measurements and experiments were consistent with previous results from Summit, Greenland, and suggests that temperature-driven (re)cycling of HCHO and H₂O₂ between snow and air has important implications for the interpretation of ice-core records as well as for boundary-layer photochemistry in polar regions and in the vicinity of snowpacks in general.