The amount of mercury in precipitation, soil and wildlife in Southwest Colorado, while not alarmingly high, should be of concern, research recently released by Silverton-based Mountain Studies Institute shows.
In 2007 we began to study mercury because very little was known about its presence in Southwest Colorado other than that reservoirs had fish-consumption advisories, and that precipitation sometimes deposited heavy concentrations of mercury at Mesa Verde National Park, former institute director Koren Nydick said last week by telephone.
As result of mercury accumulation in fish, the state of Colorado has posted advisories at McPhee, Totten, Narraguinnep and Vallecito reservoirs and Najavo Lake cautioning about consumption of fish from those waters.
Kelly Palmer, a Bureau of Land Management hydrologist, said as a result of the Mountain Studies Institute pilot study at Molas Pass, the San Juan National Forest in 2009 initiated a long-term mercury-monitoring program there.
It appears the levels of mercury are notable, Palmer said last week.
MSI has commissioned an analysis of storm directions there, she said.
There also are monitoring stations at Navajo Lake and Farmington, Bloomfield and the Valles Caldera in New Mexico.
Nydick, the former director, said the Mountain Studies Institute did age-dating of sediment cores at four high-elevation lakes in the San Juan Mountains where mercury concentrations were found to be up to six times above pre-industrial times.
We also saw that the rate of mercury accumulation held steady or decreased in sediment cores after 1990, Nydick said. This could be attributed to Clean Air Act amendments, which reduced mercury emissions from sources such as waste incineration.
Analysis of mercury and weather data collected from 2002 to 2008 at Mesa Verde points to coal-fired power plants in New Mexico as potential sources of mercury. Analysis of pollution components as well as potential sources and storm pathways support the theory, Nydick said.
But they dont pinpoint specific sources and dont definitely rule out the possibility that storms were carrying pollution from elsewhere when they passed over the New Mexico plants.
Continued monitoring is essential to determine if recent power plant technology upgrades and any changes in emissions will alter the amount of mercury emitted in the Four Corners, Nydick said.
Since last September, Nydick has been the science coordinator at Sequoia and Kings Canyon national parks in California.
Mercury and highly-toxic methyl mercury the latter produced by microorganisms pose health threats when consumed by humans and wildlife, Nydick said.
Mercury is a highly toxic element found throughout the world, principally in cinnabar ore, and it is used in medicine, industry and commerce.
Atmospheric mercury is found naturally in emissions from volcanoes and evaporation from soil and oceans. It also is produced by human activities such as coal-fired combustion, mining of metals and municipal- and medical-waste incineration.
The Mountain Studies Institutes recent reports summarize findings from its studies conducted from 2007 to 2009 and analyze data collected by federal monitoring networks since 2002. The reports look at mercury that reaches Southwest Colorado in rain and snow at Molas Pass near Silverton and Mesa Verde National Park near Cortez.
The studies also looked at mercury in lake sediment and in the blood of songbirds.
In 2007 and 2008 (April-October each year), the institute measured mercury in precipitation at Molas Pass, where 3 to 29 nannograms of mercury per liter were recorded. Levels above 12 nannograms are of concern.
The concentration of mercury in precipitation at Molas Pass was lower than at Mesa Verde, but the larger amount of rain and snow in the mountain produced similar total amounts in the periods studied.
Airborne mercury settles in bodies of water where micro-organisms convert it to methyl mercury, in which form it enters the food chain. Fish eat algae and zooplankton and pass it along to aquatic birds, mammals such as raccoons and people who eat fish.
The MSI studies of mercury zooplankton found that the level of mercury is of concern in some lakes and reservoirs in Southwest Colorado and not others. Those surrounded by forest or wetlands tend to have more mercury than those in more barren sites.
A University of Colorado researcher received funding in July to study mercury in the soil around Vallecito Reservoir and the effect that fire such as the high-intensity 2002 Missionary Ridge Fire has on mercury.
Fire can change the chemical properties of mercury so that it leaches into bodies of water more easily, Nydick said.
In June 2009, researchers from MSI and other agencies spent a day in Mancos Canyon trapping and releasing songbirds after testing their blood for mercury. They also collected crayfish, spiders, sow bugs, cicadas and centipedes and planned to return to electro-shock fish for testing.
Wetland-dependent songbirds were chosen for study, in addition to fish and crayfish, because research shows they can accumulate methyl mercury, Nydick said at the time. It appears they accumulate methyl mercury from prey such as spiders that are a link between the aquatic and terrestrial food webs. That is why we collect invertebrates, soil and dead foliage to analyze for mercury, too.
Tests showed that the accumulation of mercury in the blood of songbirds was low compared to sites elsewhere with known sources of contamination, Nydick said.
Kate Williams, a biologist at the BioDiversity Research Institute in Gorham, Maine, participated in the Mancos Canyon project and said songbirds in the eastern United States where there is point-source mercury contamination tend to have higher levels of mercury in their blood.
Virginia and New York are good examples, Williams said by telephone this week. The College of William and Mary has done a lot of work in the field.
Williams said that in general wildlife in the East has high levels of mercury. The mercury levels are a combination of local sources and mercury that blows in from the Midwest, she said.