Plant leaves spark with electricity during thunderstorms — and could be altering our air quality in unpredictable ways

Plant leaves spark with electricity during thunderstorms — and could be altering our air quality in unpredictable ways

By Harry Baker – Live Science – October 2022

During thunderstorms🌩️, leaves from trees and other plants create mini electric discharges that can significantly alter the surrounding air quality. Researchers are unsure if this is beneficial or harmful.

Electrical discharges given off by the leaves of plants during a thunderstorm can significantly alter the surrounding air quality. When lightning ⚡flashes above, plants on the ground may respond in kind.

Scientists have long been aware that plants and trees can emit small, visible electric discharges from the tips of their leaves when the plants are trapped beneath the electrical fields generated by thunderstorms high overhead. These discharges, known as coronas, are sometimes visible as faint, blue sparks that glow around charged objects.

Now, new research suggests those plant-based sparks may be altering the surrounding air quality in ways never recognized before. But whether the impacts of these minishocks in the atmosphere are positive or negative remains unclear.

In the study, published Aug. 9 in the Journal of Geophysical Research: Atmospheres, researchers recreated the electrical fields from thunderstorms in a laboratory and analyzed the coronas given off by eight plant species under a range of conditions. The results showed that all of the coronas created a high abundance of radicals — chemicals containing unpaired electrons that are highly reactive with other compounds — which can significantly alter the surrounding air quality.

“While little is known about how widespread these discharges are, we estimate that coronas generated on trees under thunderstorms could have substantial impacts on the surrounding air,” lead study author Jena Jenkins, an atmospheric scientist at Penn State University, said in a statement.

The two radicals given off by the plant coronas are hydroxyl (OH) and hydroperoxyl (HO2), both of which are negatively charged and are known to oxidize, or steal electrons from, a number of different chemical compounds, thereby transforming them into other molecules. The researchers were particularly interested in the concentrations of hydroxyl radicals because they have a greater impact on air quality.

“The hydroxyl radical contributes to the total atmospheric oxidation of many atmospheric pollutants,” study co-author William Brune a meteorologist at Penn State University, said in the statement.

For example, if a hydroxyl radical reacts with greenhouse gases, such as methane, then it can remove the damaging molecules from the atmosphere and help combat climate change, Brune said. But if the same radical reacts with oxygen, it can create ozone, which, despite playing an important role in the upper atmosphere, is toxic to humans. The radicals can also create aerosol particles that harm air quality, he added.

Coronas can be seen discharging at the tips of leaves during the experiments. Photo: Penn State

This is not the first time that researchers have shown the link between thunderstorms and hydroxyl radicals.

In 2021, a research team led by Brune found that lightning was a major progenitor of hydroxyl radicals in the atmosphere. In their paper, published in the journal Science the team theorized that thunderstorms could be directly responsible for up to one-sixth of the hydroxyl radicals in the atmosphere.

In September, another team led by Brune released a follow-up study, published in the journal Earth, Atmospheric and Planetary Sciences, that showed coronas produced by metallic objects such as telephone poles and transmission towers produce a slightly higher level of hydroxyl radicals than plant coronas. However, the levels of radicals produced by plant and artificial coronas are both significantly less than those produced directly from lightning.

“Even though the charge generated by the [plant] corona was weaker than the sparks and lightning we looked at before, we still saw extreme amounts of this hydroxy radical being made,” Jenkins said.

Researchers want to continue studying these coronas in greater detail to fully understand the effect they have on localized air quality and on a wider global scale.

“The hydroxyl radical is the atmosphere’s most important cleanser,” Jenkins said. “So having a better accounting of where this stuff is being made can give us a more complete understanding of what’s happening.

Other studies suggest that thunderstorms may become more frequent and powerful due to the effects of human-caused climate change, so understanding the effects of thunderstorms on air quality is vital, she added.

During the experiments, the team made another discovery that could help accelerate this field of research: The leafy discharges gave off sharp spikes of ultraviolet radiation. This could allow the team to indirectly study where coronas are occurring in the field and measure their effects on nearby air quality