(ORDO NEWS) — During a thunderstorm, the leaves of trees and other plants create mini-electric discharges that can significantly change the quality of the surrounding air. But researchers aren’t sure if it’s helpful or harmful.
When lightning flashes above, the plants on the ground can respond in kind.
Scientists have long known that plants and trees can emit small, visible electrical discharges from the tips of their leaves when the plants are trapped in the electrical fields created by a thunderstorm high above the ground.
These discharges, known as coronas, are sometimes visible as faint blue sparks that glow around charged objects.
Now, according to new research, these sparks from plants can change the quality of the surrounding air in ways that no one had ever guessed before. But whether the impact of these mini-shocks in the atmosphere is positive or negative remains unclear.
In a study published Aug. 9 in the Journal of Geophysical Research: Atmospheres, researchers recreated electric fields from thunderstorms in the lab and analyzed the coronas emitted by eight plant species under various conditions.
The results showed that all coronas create large amounts of radicals – chemicals containing unpaired electrons that react with other compounds – that can significantly alter ambient air quality.
“While little is known about how widespread these discharges are, we hypothesize that crowns formed on trees during thunderstorms can have a significant effect on the surrounding air,” study lead author Jena Jenkins, research scientist, said in a statement. atmosphere from Pennsylvania State University.
The two radicals given off by plant crowns, hydroxyl (OH) and hydroperoxyl (HO2), are both negatively charged and are known to oxidize or steal electrons from a number of different chemical compounds, thus converting them into other molecules.
The researchers were particularly interested in the concentration of hydroxyl radicals, as they have a greater impact on air quality.
“The hydroxyl radical contributes to the overall atmospheric oxidation of many atmospheric pollutants,” study co-author William Bruhn (opens in a new tab), a meteorologist at Pennsylvania State University, said in a statement.
For example, if the hydroxyl radical reacts with greenhouse gases such as methane, it could remove harmful molecules from the atmosphere and help fight climate change, Brun said.
But if the same radical reacts with oxygen, it can form ozone, which, despite its important role in the upper atmosphere, is toxic to humans. Radicals can also create aerosol particles that degrade air quality, he added.
This isn’t the first time researchers have shown a link between thunderstorms and hydroxyl radicals.
In 2021, a research team led by Brune found that lightning is the main source of hydroxyl radicals in the atmosphere. In their paper, published in the journal Science, the team suggested that thunderstorms could be directly responsible for one-sixth of the hydroxyl radicals in the atmosphere.
In September, another group led by Brune published in the journal Earth, Atmospheric and Planetary Sciences the results of a re-study that showed that crowns created by metal objects such as telephone poles and power poles produce slightly higher levels of hydroxyl radicals than plant crowns.
However, the levels of radicals produced by the plant and artificial corona are significantly lower than those generated directly from lightning.
“Even though the charge generated by the [plant] corona was weaker than the sparks and lightning we looked at earlier, we still saw a huge amount of hydroxyl radicals,” Jenkins said.
Given the sheer number of trees growing in lightning-prone areas, plant crowns may represent a little-studied source of radicals that have unpredictable effects on air quality, she added.
“There are about two trillion trees in the world where thunderstorms are most likely, and there are 1,800 thunderstorms at any given time,” Jenkins said.
As a result, researchers want to continue studying these coronals in more detail to fully understand the impact they have on air quality in local areas and on a larger global scale.
“The hydroxyl radical is the most important air cleaner,” Jenkins said. “So a more accurate account of where it forms can give us a better understanding of what’s going on in the atmosphere.”
Other studies show that thunderstorms may become more frequent and more powerful due to the effects of anthropogenic climate change, so understanding the impact of thunderstorms on air quality is critical, she added.
During the experiments, the team made another discovery that could help accelerate this area of research: Sheet discharges emitted sharp bursts of ultraviolet radiation. This could allow the team to indirectly study corona occurrence sites in the field and measure their impact on air quality nearby.
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