Are ice phase electrochemical processes in deep convective clouds inducing OH-radical and H₂O₂ formation in the troposphere?

Oxidants in the atmosphere, especially in the troposphere, play an important role for aerosol chemistry, air quality, and for our climate system. The most important oxidant for the self-cleaning and oxidation capacity of the atmosphere is the hydroxyl radical. Identifying atmospheric sources of OH radicals as well as their underlying mechanisms is therefore necessary for our understanding and predicting of atmospheric oxidation processes. With the observation of intense new particle formation processes, in the outflow region of tropospheric clouds where ice formation and deep convection are predominant, the question occurred whether the necessary oxidants for these processes may result from in-cloud chemistry. It is already observed that there is spontaneous H₂O₂ formation in micro-sized water droplets. Even though the mechanism is still under discussion, one of the most important hypotheses is that a strong electric field at the air-water interface induces electrochemical formation of OH-radicals that recombine to form H₂O₂. Since strong potential differences have been shown to occur at the liquid-solid interface of freezing aqueous salt solutions (Workman-Reynolds effect), we investigate the extent to which the formation of hydrogen peroxide and OH radicals can be observed in freezing aqueous solutions and droplets. First results of liquid phase H₂O₂ and OH-radical measurements will be presented.