Natural Emission from Some Tree Leaves Worsen Ozone, Says Study

The increase in planting of sweet gum, oak, and poplar trees in former farmlands in the south is being blamed for an increase in ozone, according to a study in Global Change Biology.

Isoprene, a VOC (volatile organic compound) is being blamed. It comes from unburned fuel from the tail pipes of vehicles, but also from certain tree leaves. When isoprene reacts with nitrogen oxides and sunlight they form ozone. It is estimated that the oaks in the Ozarks emit up to 300 tons of isoprene a day.

The study notes that ?EUR??,,????'??vegetal sources of monoterpenes and isoprene rose by up to 17% from the 1980s to the 1990s.?EUR??,,????'??

The scientists, from Princeton, University of Toronto, Harvard and the University of New Hampshire analyzed data collected by the U.S. Forest Service on 2.7 million trees.

Source: Purves D, et al. Human-induced changes in US biogenic volatile organic compound emissions: evidence from long-term forest inventory data. Global Change Biology, vol. 10 Oct. 2004, pp 1737-1755.