 Researchers David Gay, coordinator of the National Atmospheric
Deposition Program, Illinois State Water Survey, and Jeffrey
Levengood, wildlife toxicologist with the Illinois Natural History
Survey, and their colleagues selected fish common to two rural
streams in Illinois. In 2006 and 2007, fish were collected from
Panther Creek in Jasper County, considered a "high mercury" site due
to mercury levels reported previously, and from Saline Branch Ditch
in Champaign County, considered a "low mercury" site.
Findings showed that as predicted, fish from Panther Creek had
higher concentrations of mercury than did those from Saline Branch
Ditch. Although there were no point sources of mercury upstream in
either location, there are more and larger power plants in the
vicinity of Panther Creek than around Saline Branch.
Although the history of land use, the makeup of soils in the area
and a wider stream corridor at Panther Creek could all contribute to
the observed findings, "our results are consistent with the higher
wet deposition of mercury in the area and the state's sport fish
consumption advisories for Jasper and neighboring counties, which
indicate higher mercury loads in large species of fish in this
region," Levengood said.
To examine mercury concentrations over time, the researchers also
tested preserved blackstripe topminnows collected in 1900 and 1961
from Panther Creek. They found a dramatic decrease (64 percent) in
mercury levels from the turn of the century to the early 1960s,
which is consistent with the changing use of coal during that time
period.
The most prevalent anthropogenic sources of mercury historically
were domestic heating and industry, although coal was also used to
power locomotives and steam shovels, and was even used in
medications and beauty products and to make hats. This changed with
the discovery of petroleum and advent of coal-fired power plants. In
Illinois, most of the coal production and use was, and still is,
located in the southern and western portions of the state.
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Mercury concentrations in the fish from Panther Creek increased
slightly between 1961 and 2006. The researchers surmised that this
could be due to landscape changes that have taken place in that time
frame, such as the advent of intensive row crop agriculture and
continued conversion of more natural habitats to farmland. Such
changes would allow mercury deposited atmospherically for many years
to leach into streams at a faster rate.
As a pollutant, mercury can stay in the atmosphere for years, Gay
said. Distributed by rain and wind, mercury found in Illinois
streams may originate from both local and distant sources.
"If mercury is in a water body, there is no guarantee that it is
only from a local source," Gay said. "The difficulty is in
distinguishing among sources."
Mercury monitoring is important in setting regulatory benchmarks
and for measuring the success of environmental controls. The
researchers hope to conduct a more intensive study of mercury in
small fish from various locations in Illinois.
The results of the study, "Mercury in small Illinois fishes:
Historical perspectives and current issues," were recently published
in the international journal Environmental Monitoring and Assessment
(Volume 185(8):6485-6494). David Soucek and Chris Taylor of the
Illinois Natural History Survey were co-authors.
[Text from file received
from
Prairie Research
Institute, University of Illinois] |
