Trees emit a compound that may have underestimated impacts on the composition of the global atmosphere

The study by the of the Spanish National Research Council (CSIC) and the at University of Helsinki is the first to quantify the total emissions of diterpenes emitted by vegetation worldwide and their potential to form aerosols, which represents a modification of atmospheric models to date.

Terpenes are volatile natural compounds emitted by plants and are essential for plant communication, pollination, and defense against herbivores. They are, for example, responsible for the characteristic “forest scent” after rain or on a hot day. Once in the atmosphere, terpenes react with other compounds such as ozone, giving rise to particles (also called aerosols). These aerosols affect air quality and respiratory health, reflect solar radiation, and act as seeds for cloud droplets.

The reason diterpenes had not been considered in atmospheric models was because they were thought to be non-volatile due to their high molecular weight. However, thanks to more modern and powerful analytical techniques, the scientific team has shown that diterpenes are indeed emitted into the air in appreciable quantities and can contribute to aerosol formation. 

The results of laboratory experiments, using the diterpene kaurene, showed that diterpenes can indeed be rapidly transformed into particles upon reactions with ozone, with an efficiency of around 10 percent.

“This 10 percent efficiency means that a tenth of the kaurene mass emitted to the atmosphere will form aerosol. Based on our previous chemical knowledge of how molecular structures impact aerosol formation, we expect that most other diterpenes can form aerosol at even higher efficiencies,” says , professor at University of Helsinki, who lead the laboratory experiments of the study. The oxidation and aerosol-forming potential of different terpenes has been a key focus of his research group at INAR over the last decade.

"This study represents a paradigm shift in our understanding of atmospheric composition, as until now, diterpenes were not considered key elements in aerosol formation," says Ana María Yáñez-Serrano, a researcher at Institute of Environmental Assessment and Water Research (IDAEA-CSIC) and first author of the study.

The research results were published in Communications Earth & Environment ().