Typical amounts of the atmosphere's most important oxidant, the hydroxyl radical (OH), can increase 1,000-fold when atmospheric electrical discharges such as lightning occur (Brune et al., 2021). This lightning-generated OH contributes to the total atmospheric oxidation of many atmospheric pollutants, including the greenhouse gas methane, improving air quality, and slowing climate change. However, these OH reactions can also lead to the formation of ozone and small aerosol particles, negatively affecting air quality and climate. Therefore, understanding all the potential sources of OH is important for predicting future air quality and climate.Only recently have electrical discharges in thunderstorm anvils been shown to be a potentially significant source of global OH, accounting for as much as 2%-16% of global atmospheric OH oxidation (Brune et al., 2021). Laboratory measurements confirmed that OH and the closely related hydroperoxyl radical (HO 2 ) are generated in extreme amounts by both spark discharges and pulsed weak invisible discharges called subvisible discharges (Jenkins et al., 2021). Corona discharges, or simply corona, were not investigated in these previous studies, but they also generate chemical species including the hydrogen oxides (HO x = OH + HO 2 ), ozone (O 3 ), and the nitrogen oxides (NO x ) (
Atmospheric electrical discharges are now known to generate unexpectedly large amounts of the atmosphere’s primary oxidant, hydroxyl (OH), in thunderstorm anvils, where electrical discharges are caused by atmospheric charge separation. The question is “Do other electrical discharges also generate large amounts of oxidants?” In this paper, we demonstrate that corona formed on grounded metal objects under thunderstorms produce extreme amounts of OH, hydroperoxyl (HO 2 ), and ozone (O 3 ). Hundreds of parts per trillion to parts per billion of OH and HO 2 were measured during seven thunderstorms that passed over the rooftop site during an air quality study in Houston, TX in summer 2006. A combination of analysis of these field results and laboratory experiments shows that these extreme oxidant amounts were generated by corona on the inlet of the OH-measuring instrument and that corona are easier to generate on lightning rods than on the inlet. In the laboratory, increasing the electric field increased OH, HO 2 , and O 3 , with 14 times more O 3 generated than OH and HO 2 , which were equal. Calculations show that corona on lightning rods can annually generate OH that is 10–100 times ambient amounts within centimeters of the lightning rod and on high-voltage electrical power lines can generate OH that is 500 times ambient a meter away from the corona. Contrary to current thinking, previously unrecognized corona-generated OH, not corona-generated UV radiation, mostly likely initiates premature degradation of high-voltage polymer insulators.
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