Global plant emissions are estimated at 500 to 600 million tons of isoprene annually, constituting about half of all gaseous organic compounds released by vegetation.
The Amazon rainforest was found to be responsible for over a quarter of these emissions.
Rainforest emissions beyond the canopy Previously, scientists believed that isoprene in the Amazon basin broke down rapidly and did not reach higher layers of the atmosphere. This breakdown was attributed to hydroxyl radicals – highly reactive molecules formed near the ground during daylight hours – that destroy isoprene within hours.
“However, we have now established that this is only partly true,” said Joachim Curtius, an atmospheric scientist at the Goethe University Frankfurt and lead author of a recent study.
“There are still considerable amounts of isoprene in the rainforest at night, and a substantial proportion of these molecules can be transported to higher atmospheric layers.”
Thunderstorms and rainforest emissions Tropical thunderstorms play a pivotal role in elevating isoprene molecules. These storms act like vacuum cleaners, pulling isoprene to altitudes between 8 and 15 kilometers.
When the sun rises, hydroxyl radicals react with the isoprene molecules, but the frigid temperatures at these heights transform the compounds differently than near the ground.
The molecules combine with nitrogen oxides – produced by lightning during storms – to form clusters of aerosol particles just a few nanometers in size. Over time, these particles grow and serve as condensation nuclei for water vapor, significantly influencing cloud formation in tropical regions.
“We were able to shed light on these processes with the help of research flights that started two hours before sunrise and then continued through the day,” explained
Study senior author Jos Lelieveld is the director at the Max Planck Institute for Chemistry in Mainz and also head of the CAFE-Brazil research project.