Air pollution experiment. Plants being examined by a researcher in an experiment into the effects of elevated levels of nitrogen pollutants on plant g

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Air pollution experiment. Plants being examined by a researcher in an experiment into the effects of elevated levels of nitrogen pollutants on plant growth. Human activities have caused increased atmospheric nitrogen pollution, mainly nitrogen oxides and ammonia. This nitrogen is eventually taken up by plants, increasing plant growth. This is shown by using tracer isotopes of nitrogen (15 N) to follow the nitrogen through the air and plants. However, if saturation levels are reached, the plants may be adversely affected by further pollution. This research site is part of UMBS (the University of Michigan Biological Station), Pellston, Michigan, USA.

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Photo credit: © DAVID HAY JONES/SCIENCE PHOTO LIBRARY / Alamy / Afripics
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