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Other studies hinted at high levels
Herald Staff Writer
Several studies in the Four Corners support the concern about mercury, particularly methyl mercury, a neurotoxin for humans and animals:
•In 2007 and 2008 (April-October each year) a monitor installed by the Mountain Studies Institute, a nonprofit based in Southwest Colorado, recorded 3 to 29 nannograms per liter of mercury in rain and snow. Levels above 12 nannograms are of concern.
•The institute has found mercury in zooplankton in mountain lakes and reservoirs and in lake sediment. Sediment samples show mercury content peaked from 1960 to 1990 - a period that corresponded to the construction of coal-fired power plants in the Four Corners.
•Mesa Verde National Park has measured mercury in precipitation for eight years. While the amount per storm can be high, total accumulation can't be compared to points in the eastern United States because there are many more rainy and snowy days there.
"The key is knowing how much dry precipitation we have," said George San Miguel, natural resource conservation chief at Mesa Verde. "And we'll soon be measuring it."
At the end of the month, Mesa Verde will install a monitor similar to the one the Environmental Protection Agency is placing alongside a BLM monitor near Silverton. It will be in place for one year, San Miguel said.
Airborne mercury settles into bodies of water where bacteria convert it to methyl mercury - in which form it enters the food chain, said Kelly Palmer, a Bureau of Land Management hydrologist.
Methyl mercury passes from algae and zooplankton to forage fish and then to game fish, which become a meal for aquatic birds and humans.
Six reservoirs in Southwest Colorado have posted advisories cautioning people to limit consumption of fish from those waters.
Researchers theorize, too, that songbirds are accumulating mercury from eating spiders that feed on aquatic life.
A coalition of environmental interests last month took samples of songbird blood in three places in Southwest Colorado to test the theory. Results are pending.
"We're starting to look beyond 'how much' to the effects of mercury," said Koren Nydick, executive director of the Mountain Studies Institute, a participant in the songbird project.
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