Air Pollution

[Mona Miller]

http://www.virginia.edu/uvatoday/newsRe ... hp?id=4814
Flowers' Fragrance Diminished by Air Pollution, University of
Virginia Study Indicates

April 10, 2008 - Air pollution from power plants and automobiles is
destroying the fragrance of flowers and thereby inhibiting the
ability of pollinating insects to follow scent trails to their
source, a new University of Virginia study indicates. This could
partially explain why wild populations of some pollinators,
particularly bees - which need nectar for food - are declining in
several areas of the world, including California and the Netherlands.

The study appears online in the journal Atmospheric Environment.

"The scent molecules produced by flowers in a less polluted
environment, such as in the 1800s, could travel for roughly 1,000 to
1,200 meters; but in today's polluted environment downwind of major
cites, they may travel only 200 to 300 meters," said Jose D. Fuentes,
a professor of environmental sciences at the University of Virginia
and a co-author of the study. "This makes it increasingly difficult
for pollinators to locate the flowers."

The result, potentially, is a vicious cycle where pollinators
struggle to find enough food to sustain their populations, and
populations of flowering plants, in turn, do not get pollinated
sufficiently to proliferate and diversify.

Other studies, as well as the actual experience of farmers, have
shown that populations of bees, particularly bumblebees, and
butterflies have declined greatly in recent years. Fuentes and his
team of U.Va. researchers, including Quinn McFrederick and James
Kathilankal, believe that air pollution, especially during the peak
period of summer, may be a factor.

To investigate this, they created a mathematical model of how the
scents of flowers travel with the wind. The scent molecules produced
by flowers are very volatile and they quickly bond with pollutants
such as ozone, hydroxyl and nitrate radicals, which destroy the
aromas they produce. This means that instead of traveling intact for
long distances with the wind, the scents are chemically altered and
the flowers, in a sense, no longer smell like flowers. This forces
pollinators to search farther and longer and possibly to rely more on
sight and less on smell.

The scientists calculated scent levels and distances that scents can
travel under different conditions, from relatively unpolluted pre-
industrial revolution levels, to the conditions now existing in rural
areas downwind from large cities.

"It quickly became apparent that air pollution destroys the aroma of
flowers, by as much as 90 percent from periods before automobiles and
heavy industry," Fuentes said. "And the more air pollution there is
in a region, the greater the destruction of the flower scents."

The National Science Foundation funded the investigation.