Beijing's Willows and Poplars Fuel Ground-Level Ozone During Heat Waves

Urban greenery, traditionally viewed as a defense against smog, can become a source of chemical pollution during extreme heat. Research conducted in Beijing indicates that popular tree species—specifically the weeping willow and the Chinese poplar—act as powerful generators of atmospheric chemical activity when temperatures rise. The study focuses on biogenic volatile organic compounds (BVOCs). While trees are known to absorb carbon dioxide and dust, they also release these organic compounds. In the environment of a megacity, where the air is saturated with nitrogen oxides from vehicle emissions, these natural substances catalyze the formation of ground-level ozone. Researchers from the University of Innsbruck found that in Beijing, trees contribute only 10% of the total volume of volatile compounds. However, due to the high reactivity of isoprene, their contribution to chemical reactions reaches 50%.