Boreal Forest Fires Release Increased Mercury Into Atmosphere
Pastor Dale Morgan
Boreal Forest Fires Release Increased Mercury Into Atmosphere*
by Staff Writers
Washington DC (SPX) Aug 22, 2006
Climate change appears to be contributing to the waking of a toxic
sleeping giant in the most northern wetlands of North America. Mercury,
released into the atmosphere most prodigiously with the launching of the
industrial age, falls back onto Earth and accumulates, particularly in
North American wetlands.
Researchers at Michigan State University, the U.S. Geological Survey,
the National Center for Atmospheric Research, and the Canadian Forest
Service find that wildfires, which are becoming more frequent and
intense, are unleashing this sequestered mercury at levels up to 15
times greater than previously calculated. Their report was published 19
August in Geophysical Research Letters.
"This study makes the point that while peat lands are typically viewed
as very wet and stagnant places, they do burn in continental regions,
especially late in the season when water tables are depressed," said
Merritt Turetsky, lead author of the study.
"When peat lands burn, they can release a huge amount of mercury that
overwhelms regional atmospheric emissions. our study is new in that it
looks to the soil record to tell us what happens when peat soil burns,
soil that has been like a sponge for mercury for a long time."
Normal atmospheric conditions naturally carry the mercury emitted from
burning fossil fuel and other industry northward, where it eventually
settles on land or water surfaces. The cold, wet soils of the boreal
forest region in Alaska and northern Canada have been efficient in
retaining, or sequestering, mercury.
"When we walk across the surface of a peat land, we are standing on many
thousands of years of peat accumulation," Turetsky said. "This type of
wetland is actually doing us a service. Peat lands have been storing
mercury from the atmosphere since well before and during the Industrial
Revolution, locking it in peat where it's not causing any biological
harm, away from the food web."
In addition to industrial activity, climate change also appears to be
disrupting the mercury cycle. Increasingly, northern wetlands are drying
out. Forest fires are burning more frequently, more intensely, and later
in the season, which Turetsky believes will make peat lands more
vulnerable to fire.
In May, Turetsky co-authored with Eric Kasischke of the University of
Maryland another Geophysical Research Letters paper that documented
recent changes in North American fires and proposed that more frequent
summer droughts and severe fire weather have increased burn areas.
"We are suggesting that environmental mercury is just like a
thermometer. Levels will rise in the atmosphere with climate change, but
due to increasing fire activity in the north and not solely due to
warming, said Jennifer Harden, soil scientist at the U. S. Geological
Survey and a co-author of the study.
In the newly published paper, Turetsky and her co-authors measured the
amount of mercury stored in soils and vegetation of forests and peat
lands, then used historical burn areas and emission models to estimate
how much of that mercury is released to the atmosphere at a regional
scale during fires.
The group studied more than five years of prescribed burns and natural
fires to measure the influence of burning on terrestrial mercury
storage. They also sampled smoke plumes to measure atmospheric mercury
levels as fires blaze.
Their findings indicate that drier conditions in northern regions will
cause soil to relinquish its hold on hundreds of years of mercury
accumulation, sending that mercury back into the air at levels
considerably higher than previously realized.
We're talking about mercury that has been relatively harmless, trapped
in peat for hundreds of years, rapidly being spewed back into the air,"
Turetsky said. "Some of it will fall back onto soils. Some will fall
into lakes and streams where it could become toxic in food chains. our
findings show us that climate change is complex and will contribute to
the pollution of food chains that are very far away from us, in remote
regions of the north."
The research was funded by the U.S. Geological Survey, the National
Center of Atmospheric Research (supported by the National Science
Foundation), and the Electric Power Research Institute. Turetsky's work
also is supported by Michigan State University's Michigan Agricultural
Research Station.