Eastern Mineral Resources Team
Overview of Lake Superior study
Accomplishments and Description of Field Work
Key Findings
Products
Contact for further information
Geologists Connie Dicken, Laurel Woodruff, and Shana Pimley
(l. to r.) preparing to sample soil, Voyageurs National Park.
Overview:
Mercury as an environmental contaminant is a concern in the Lake Superior region
including some National Parks where there are high levels of mercury in game
fish in many Park lakes. This contamination can create health problems both
for humans and wildlife that consume fish. A critical question for land and
resource managers and regulators is whether this contamination is from local
sources, including anthropogenic sources, vs. regional or global mercury emissions.
Our research in Isle Royale
National Park, Michigan, and Voyageurs
National Park, Minnesota, and in nearby Superior
and Chequamegon
National Forests, is helping to define the factors that control mercury accumulations
in forests, and the relationship between mercury content in forest soils and
mercury contamination of aquatic ecosystems.
In particular we have identified forest fires as a principal
factor in the mercury cycle because of the ability of fire to volatilize mercury
sequestered in forest floor organic material.
Field Work:
Working in conjunction with the National Park Service and the US Forest Service,
we have been collecting soil samples in several studies areas in the Lake
Superior region. Typically we collect three soil samples from a single site:
O-, A-, and C-horizon soils. On Isle Royale we also collected paired lichen
samples from soil sample sites. Samples are air dried and submitted for geochemical
analysis to the USGS.
To study the effects of fire on soil geochemistry, we have sampled across
the 1936 burn areas in Voyageurs and Isle Royale National Parks. The fires
of 1936 were particularly severe in the Upper Midwest, killing large stands
of timber and in many areas burning soils down to bare bedrock.
At Snowbank Lake in the Superior Forest, we sampled before a prescribed burn
in 2000 and resampled the same sites 4 times in the following 3 years.
For 3 years we have been monitoring post-fire response in soils in a prescribed burn area in Superior National Forest near Snowbank Lake, Minnesota. Preliminary results are presented in a number of abstracts listed below (products section).
Key Findings:
Our studies in Voyageurs and Isle Royale National Parks have shown:
Cannon, W.F., and Woodruff, L.G., 2003, The geochemical landscape of northwestern
Wisconsin and adjacent parts of northern Michigan and Minnesota (geochemical
data files): U.S.
Geological Survey Open-File report 03- 259, onine only, version 1.0.
Cannon, W.F. and Woodruff, L.G., 2000, Some factors that control the distribution
of mercury in surficial materials in Isle Royale National Park- earth, wind,
and fire (abs): Institute
on Lake Superior Geology, 46th Annual Meeting, Proceedings Volume 46, p.
8-9
Cannon, W.F., Dean, W.E., and Bullock, J.H., 2001, Eleven thousand years of
mercury deposition in Elk Lake, Minnesota: effects of climate and vegetation
change on the mercury cycle (abs): 2001, Geological Society of America, 2001
Annual Meeting, Abstracts with Program, v. 33, p. 186.
Cannon, W.F., Dean, W.E., and Bullock, J.H., 2001, Eolian deposition of mercury
in Elk Lake, Minnesota - the impact of Holocene climate fluctuations on the
mercury cycle (abs): International
Association of Great Lakes Research, 45th Conference, p. 19.
Woodruff, L.G. and Cannon, W.F., 2002, Impact of fire on the forest floor and
mineral soils, Snowbank Lake, Minnesota (abs): Institute
on Lake Superior Geology, 48th Annual Meeting, Proceedings Volume 48, p.
54-55.
Woodruff, L.G., Cannon, W.F., Dicken, C.L., Bennett, J.P., and Nicholson, S.W.,
2003, Bedrock, Soil, and Lichen Geochemistry from Isle Royale National Park,
Michigan: U.S.
Geological Survey Open-File Report 03-276, Version 1.0 .
Woodruff, L.G., Cannon, W.F., Dicken, C.L., and Pimley, S., 2002, Bedrock and
Soil Geochemistry from Voyageurs National Park, Minnesota:
U.S. Geological Survey Open-File Report 02-196, Online Only, Version 1.0.
Woodruff, L.G., and Cannon, W.F., 2001, The effect of fire on mercury and carbon
in forest soils: results from northern Michigan and Minnesota (abs): Geological
Society of America, 2001 Annual Meeting, Abstracts with Program, v. 33, p. 186.
Woodruff, L.W., Harden, J.W., Cannon, W.F., and Gough, L.P., 2001, Mercury loss
from the forest floor during wildfire (abs): EOS Transactions of American Geophysical
Union, 82(47), Fall Meeting Supplement, Abstract B32B-0017.
Woodruff, L.W., Cannon, W.F., and Dicken, C.L., Impact of fire on the geochemistry
of forest soils: poster available on line at http://firescience.cr.usgs.gov/html/woodruff_abs02.html
.
USGS Geologists William Cannon and Connie Dicken sampling
soils in Isle Royale National Park. Samples are carefully collected according
to soil horizon to determine soil mass per unit area.
William F. Cannon, Geologist
U.S. Geological Survey
Eastern Mineral Resources
954 National Center
Reston, VA 20192
(703)648-6345
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