Air pollution research. David Karnovsky, director of the FACE (Free-Air CO2/O3 Enrichment) project, examining trees. FACE studies the effects of ozone (O3) and carbon dioxide (CO2) pollution on plants. A system of pipes (white, background) supply O3 and/or CO2. The pipes are 2.5 metres tall, and Karnovsky is examining plants at canopy level using a walkway. Ozone is a gas formed by chemical reactions between oxygen and pollutants in the lower atmosphere. Carbon dioxide is formed by burning fossil fuels. Levels of both pollutants are predicted to rise. Carbon dioxide increases plant growth; ozone reduces it. The FACE site, started 1989, is in Wisconsin, USA.
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