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TV & Radio 10 Dr Karl 11 Play 12 News in Science 13 Print Print 14 Email Email to a friend Pine trees may help create smog, acid rain Thursday, 13 March 2003 pine tree Could pine trees be making things worse? Latest research suggests they contribute to smog Rather than being a global warming solution, pine trees may be inducing smog and acid rain by releasing vast amounts of nitrogen oxide into the air, researchers have discovered. Under some circumstances, needles from Scots pine trees can release nitrogen oxides directly into the atmosphere, according to a report in today's issue of the journal, 15 Nature. A team led by Professor Pertti Hari of the 16 University of Helsinki in Finland, conducted experiments with new pine shoots from Pinus sylvestris, measuring the amount of nitrogen oxides they emitted when exposed to sunlight. Nitrogen oxides (NOx), along with hydrocarbon gases and sunlight, are the three ingredients needed to make photochemical smog that clogs the skies of many urban centres, as well as acid rain. The researchers were surprised to find NOx produced by the pine needles, and that levels rose when shoots were exposed to ultraviolet radiation from the Sun. While the amount produced was insignificant on a local scale, "our findings suggest that global NOx from boreal coniferous forests may be comparable to those produced by worldwide industrial and traffic sources," said the authors. While the gases produced by pine trees could in theory deliver as much air pollution as worldwide industrial emissions, in reality most trees do not grow in air that has the very low background levels of nitrogen oxides needed for the trees to emit NOx in the first place. The study did show for the first time that forests can produce two of the three critical ingredients for smog, and it had been previously established that trees produce hydrocarbons. Australia does not have a lot of boreal or 'needle tree' - forests, because they tend to exist in high latitude areas. But the findings could be relevant on a local scale in Australian pine plantations, Griffith said. Large scale planting of pine trees to act as 'carbon sinks' has been promoted by some, the theory being that fast-growing trees absorb and retain carbon dioxide from the air. Carbon dioxide is widely cited one of the major contributors to global warming. Danny Kingsley - ABC Science Online Related Stories 18 Tracking global grime, News in Science 31 May 2001 19 Cut-price solution to global warming, News in Science 7 Oct 1999 More News 20 Health & Medical .
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