Urban trees and air pollution: Effect of drought and salt stress on the production of VOC and absorption of ozone by different city trees

The project aimed to investigate the relationship between urban trees and tropospheric ozone concentration. The project examined the effects of various stresses, such as drought, salt, and ozone, on the emission of special compounds released by trees called BVOCs. These compounds can react with other chemicals in the air and contribute to the formation of ozone.

Experiments were conducted on different tree species experiencing different types of stress. It was observed that drought stress generally led to a decrease in BVOC emissions, although mild drought conditions sometimes resulted in temporary increases in a compound called Isoprene. Prolonged periods of drought, however, ultimately caused decreased emissions. When trees experienced both drought and ozone stress, the closure of their stomata to conserve water but did not affect ozone emissions. Surprisingly, salt stress did not have a clear effect on BVOC emissions. There were variations in the concentrations of compounds in the leaves, such as flavonoids, carotenoids, chlorophylls, and vitamin E, among different tree species. However, stress did not consistently alter the concentrations of these compounds.

To gain further insights into the impact of trees and stressors on ozone levels, computer models were utilized. Formaldehyde levels were used as an indicator of the reactions between BVOCs and ozone. The models revealed that drought stress generally decreased the ozone levels.

Overall, the UOZONE project significantly enhanced our understanding of how trees and different stressors influence air quality in urban environments. The research findings and published articles have important implications for urban planning, decision-making, and environmental management. By comprehending the relationship between tree species, stressors, and tropospheric ozone levels, we can work towards mitigating air pollution in cities and creating healthier living spaces for all.