|
||
|
|
|
|
|
|
|
January
9, 2007 Forest
fires release more mercury into the atmosphere than previously
recognized, a
multidisciplinary research project at the The
study, which has implications for forest management and global mercury
pollution, was published online January 9 in the journal Global
Biogeochemical Cycles. Doctoral
student Abir Biswas, the paper's lead author, came up with the idea for
the
project when he was a student at U-M's Camp Davis Rocky Mountain Field
Station
near "There
I was, watching forest fires around our field camp, and it seemed like
the
ideal place to study the problem," he said. The
study
Biswas read investigated mercury emissions from the combustion of
foliage at
locations around the Over
the
next two summers, under the direction of U-M professor Joel Blum,
Biswas
collected core samples of forest soil from burned and unburned areas,
using
sections of PVC pipe sharpened at one end to obtain the cylindrical
samples. He
and Blum also collaborated with U-M professor Gerald Keeler and former
research
scientist Bjorn Klaue to take air samples at Camp
Davis—measuring mercury and
trace metals over two summers—which provided the scientists
with a picture of
the atmospheric background on which the fires were superimposed. Forests
act as mercury traps because mercury in the atmosphere—which
comes from both
natural and human-generated sources such as coal-fired power plants and
municipal waste incinerators—collects on foliage. When the
foliage dies, it
falls to the forest floor and decomposes, and the mercury enters the
soil.
Because it binds strongly to organic molecules, mercury is most
prevalent in
the top several inches of soil, where organic matter is concentrated.
By comparing
the mercury content of burned soil with that of unburned soil, the
researchers
could estimate how much mercury was released when forests burned. They
found that both the type of trees in the forest and the severity of the
fire
affected the amount of mercury released. The type of tree makes a
difference
because evergreens take up more mercury from the atmosphere on their
needles
than do broad-leafed trees, leading to more mercury accumulation in the
soil
prior to the fire. Based
on
their analysis and estimates of the area of forest and shrub land
burned
annually in the Understanding
the role fires play in mercury emissions is particularly important in
light of
predictions that forest fires will increase as global warming makes
some parts
of the world hotter and drier, said Blum, who is the John D. MacArthur
Professor of Geological Sciences and director of The
findings also have implications for forest fire management, Biswas
said.
"When you let fires run free in an area where they have been suppressed
for a long time, as happened in the In
a
related project, the researchers are trying to identify the sources of
the
atmospheric mercury that ended up in the forests they studied.
Preliminary
results suggest that much of it came from mining operations in the
western Studies
of the sources and fate of mercury pollution are critical, Blum said,
because
it's a problem that won't go away. "Once mercury starts getting emitted
and deposited into a forest, it then gets re-emitted and re-deposited
and
re-emitted again. So the legacy of mercury pollution will be with us
for a very
long time." Funding
was provided by grants from the National Institute of Environmental
Health
Sciences to Blum and from the department of Geological Sciences to
Biswas.
Recommend this Article to a Friend Back to: News |
|
Subscribe to the Earth Observatory About the Earth Observatory Contact Us Privacy Policy and Important Notices Responsible NASA Official: Lorraine A. Remer Webmaster: Goran Halusa We're a part of the Science Mission Directorate |