Prodigious amounts of hydrogen oxides generated by corona discharges on tree leaves

Prodigious amounts of the hydroxyl radical (OH) are generated by weak electrical discharges, such as corona discharges induced on trees during thunderstorms. As was observed in studies of sparks and subvisible discharges, corona discharges on leaves produce OH and hydroperoxyl (HO2) amounts that are several orders of magnitude larger than usual. Our laboratory studies demonstrate that production rates of OH and HO2 depend on the applied electric field that generates the corona discharge, leaf dryness, and the presence of liquid water on the leaf, but were independent of eight different leaf types and the corona discharge polarity for a given corona ultraviolet (UV) flux. Production rates of OH, HO2, and O3 strongly correlate with UV flux. Field measurements of OH, HO2, and O3 produced by corona discharges on trees are required to determine the importance of this production for global to local atmospheric oxidation and for tree and forest ecology.