Telluride Radionuclide Baseline Study

The Colorado Department of Public Health and Environment recently permitted a new uranium mill in the Paradox Valley of western Colorado.  San Miguel County and several municipalities are concerned that aeolian transport and deposition of dust from the mill operations and increased mining activity may degrade water and air quality in eastern San Miguel County.  Even if water and air quality are not degraded, a public perception of degradation could result in a decrease in visitor use and resulting depression of the tourist economy.  Credible scientific data would provide a benchmark for future evaluation of changes from the current conditions.

The local governments of Town of Ophir, Town of Telluride, and San Miguel County in partnership with the U.S. Environmental Protection Agency (U.S. EPA), the University of Colorado-Boulder (UCB), and Mountain Studies Institute (MSI) have agreed that a baseline radionuclide study in eastern San Miguel County would be useful to evaluate any potential changes over time.  The partnership has engaged a number of scientists and other professionals in designing the study, including Dr. Mark Williams from the University of Colorado-Boulder; Dr. Michael Wireman, a hydrogeologist for U.S. EPA Region 8; and Mr. Robert Duraski, an Air Quality Specialist for the U.S. EPA.

The purpose of this study is twofold. First, the study is intended to provide baseline information on the current concentrations of trace metals and radionuclides associated with uranium ore in water bodies and Aeolian particulates in San Miguel County prior to the commencement of any new uranium mining and milling operations. This will provide a benchmark prior to the commencement of activities. Second, the study will develop a structure and protocol for monitoring over time for trace metals and radionuclides associated with uranium ore in water bodies and Aeolian particulates in San Miguel County into the future. 

Mercury Deposition & It's Effects on the San Juans

Why Mercury?

In 2007, MSI began studying mercury in rain and snow, lakes, and forest soils. Mercury is an emerging environmental health concern in the Four Corners. It is neurotoxin to humans and wildlife and becomes more concentrated as it is passed up the food web from plants to herbivores to predators. Mercury is a naturally occurring element in rocks and soil, but it also is emitted into the air by burning mercury-containing coal and waste products. Precipitation falling in Mesa Verde National Park has some of the highest mercury concentrations measured across the United States. Many reservoirs in SW Colorado and NW New Mexico are listed for fish consumption advisories due to bioaccumulation of mercury in game fish.

Back Trajectory Modeling of Mercury Deposition Events at Molas Pass, San Juan County CO.

Since 2009 the national Mercury Deposition Network has been monitoring mercury deposition at Molas Pass. This site is adjacent to the Wemenuchi Wilderness and is within a Class I clean air area. In 2011 MSI in collaboration with the San Juan Public Lands Center conducted a back trajectory modeling exercise to examine the storm tracks that deposited mercury at Molas Pass. The results of this modeling effort determined that storms that produced the greates mercury in precipitation came out of the southwest, where there are a number of coal fired powerplants. 

Mercury in Forest Soils

In 2008 MSI’s Nydick, along with Fort Lewis College student Anya Angst, began looking at mercury in forest soils from burned and unburned areas in Missionary Ridge. “We really want to understand how fire affects mercury bound to forest soils and the transport of this mercury into water bodies” remarked Nydick. MSI is collaborating with researchers from the University of Colorado and the US Geological Survey to study this question.
Preliminary results indicate that low intensity prescribed burning had no effect on the amount of mercury or organic matter in soil, but high intensity wildfire dramatically decreased both organic matter and mercury concentrations. In both cases, mercury and organic matter were highly correlated, indicating the importance of organic material to bind the mercury in these soils.

Sources of Atmospheric Mercury Concentrations and Wet Deposition at Mesa Verde National Park, Southwestern Colorado, 2002-2008

The purpose of this study was to better understand the sources of atmospheric mercury deposited by precipitation events at Mesa Verde National Park. The method of investigation was to conduct various data analyses to determine trends in mercury concentrations in precipitation over time, compare trends in mercury concentrations to other major-ion concentrations, track movement of air parcels involved with precipitation events at Mesa Verde and estimate below vs. above background mercury concentrations. Precipitation, mercury concentrations in precipitation and major-ion concentrations in precipitation data from the National Atmospheric Deposition Program (NADP), National Oceanic and Atmospheric Administration (NOAA) and the Environmental Protection Agency (EPA) was used. This study concluded that the coal-fired power plants south of Mesa Verde National Park are likely an important source of mercury to the Park. The study also showed a decreasing trend in concentrations of sulfate, nitrate, chloride and hydrogen following implementation of emission reductions at two coal-fired power plants. This suggests that similar measures implementing mercury emissions reductions may have a beneficial effect.

Pilot Study of the Ecological Effects of Mercury Deposition in Mesa Verde National Park, Colorado

When atmospheric mercury is deposited by precipitation, it may be converted to methyl mercury, a form that can be taken up by organisms and consequently becomes biomagnified in the food chain. Mercury is most easily converted to methyl mercury in wet environments with low oxygen, so mercury bioaccumulation studies are often focused on aquatic ecosystems. The purpose of this pilot study was to determine if mercury bioaccumulation occurs in wildlife at Mesa Verde National Park and if a full study would be justified. Groups of species examined were wetland songbirds, invertebrates, stream fish and crayfish. The organisms examined did not show toxic levels of mercury, however sub-lethal effects of mercury on wildlife are not well studied and should not be discounted. The scope of this study was limited, and further investigation is recommended.

Mercury in Lakes and Precipitation of Southwestern Colorado

This study provides greater insight into the patterns and processes that affect mercury in the environment of southwestern Colorado. One objective was to determine the amount and concentration of mercury in precipitation falling at high altitude in SW Colorado. “We’ve found rather elevated concentrations of mercury in rain collected at Molas Pass” reported Dr. Koren Nydick, MSI’s chief scientist. As a result, the San Juan National Forest will be installing a long-term precipitation collector on Molas Pass to track mercury deposition for years to come.

MSI also measured mercury in zooplankton from 28 lakes and reservoirs. Zooplankton are small invertebrates that are consumed by fish. “Mercury concentrations in zooplankton varied a lot among lakes from low to quite high”, says Nydick. Six lakes had methyl mercury levels in zooplankton that were higher than the levels measured from two reservoirs with fish consumption advisories. Zooplankton from three lakes had methyl mercury concentrations above the level of concern for fish-eating mammals. Nydick noted, “The variability among lakes was not that surprising because bioaccumulation of mercury depends on a lot of factors in addition to the amount of airborne mercury deposition. However, it was surprising how high mercury concentrations were in a few of the lakes”. MSI plans to use water quality and watershed measurements to identify what makes lakes and reservoirs in our region more or less susceptible to bioaccumulation of mercury.

Lake sediments record a history of mercury accumulation as material is deposited on the lake bottom over time. MSI collected sediment cores from four mountain lakes and Vallecito Reservoir. The cores from the lakes show that mercury input increased since pre-industrial times, peaked between 1960 and 1990, and then decreased or remained constant in the past two decades. “The peak (in mercury input) is pretty consistent with when many coal-fired power plants came online in the western US”, says Nydick. “Recent declines are probably due to regulations that were enacted in the 1990’s on mercury emissions from waste incinerators”. Coal-fired power plants are the largest source of human-caused mercury emissions in the USA, according to the Environmental Protection Agency.

Project Partners

• Mountain Studies Institute

• University of Colorado at Boulder

• Mesa Verde National Park

• BioDiversity Research Institute

• Win Wright - Southwest HydroLogic

Thanks to the Project Supporters!

Major Funders

• US Environmental Protection Agency

• US Forest Service - San Juan National Forest

• National Park Service

Other Funders

• San Miguel County

• US Forest Service - Grand Mesa, Uncompahgre, and Gunnison NFs

• Telluride Institute

Water Sampling In The Weminuche Wilderness

Alpine Lakes are Sensitive to Change

In 2010, MSI began a five year contract with the USGS to take water samples from six alpine lakes in the Weminuche Wilderness. These lakes are part of a twenty-five year study which has analyzed water chemistry in Rocky Mountain lakes to determine changes in the atmospheric deposition of mercury, sulfates and other common pollutants. MSI is in the second year of this five year project with the results from 2010 contributing to the understanding of alpine lake/atmospheric interactions.

The results of this monitoring project will enable long-term trend analyses of water quality. In Mast et al summarizing the first 25 years of monitoring, trends in precipitation chemistry and hydrologic and climatic data were examined as drivers of long-term changes in the chemical composition of high-elevation lakes in three wilderness areas in Colorado during 1985–2008. Sulfate concentrations in precipitation decreased at a rate of -0.15 to -0.55 leq/l/year at 10 high-elevation National Atmospheric Deposition Program stations in the state during 1987–2008 reflecting regional reductions in SO2 emissions. In lakes where sulfate is primarily derived from atmospheric inputs, sulfate concentrations also decreased although the rates generally were less, ranging from -0.12 to -0.27 leq/l/year. The similarity in timing and sulfur isotopic data support the hypothesis that decreases in atmospheric deposition are driving the response of high-elevation lakes in some areas of the state. By contrast, in lakes where sulfate is derived primarily from watershed weathering sources, sulfate concentrations showed sharp increases during 1985–2008. Analysis of long-term climate records indicates that annual air temperatures have increased between 0.45 and 0.93°C per decade throughout most mountainous areas of Colorado, suggesting climate as a factor. Isotopic data reveal that sulfate in these lakes is largely derived from pyrite, which may indicate climate warming is preferentially affecting the rate of pyrite weathering. 

In Mast and Ingersol (2011), many significant trends were evident in lake-water concentrations in the study lakes. About 70 percent of lakes had significant trends in specific conductance, pH, calcium, and sulfate concentrations, whereas less than 20 percent had trends in chloride and nitrate concentrations. Despite widespread declines in sulfate deposition, decreases in lake-water sulfate concentrations were mostly limited to lakes in the Zirkel/Flat Tops Mountains. Because sulfate in these lakes is derived primarily from atmospheric sources, lake chemistry in these two areas appears to be responding to regional and local declines in sulfur dioxide emissions. Many lakes showed upward trends in sulfate concentrations as well as acid neutralizing capacity and calcium concentrations. Upward trends in dissolved constituents appeared to be partly explained by a decline in precipitation between 1995 and 2002, which may have increased base-flow contributions to some lakes. Air temperatures, which increased throughout the region, also may have been a factor in lake-water chemical trends. Warming in alpine areas might increase rates of mineral weathering or cause enhanced melting of ice features such as permafrost, rock glaciers, and glaciers. The effect of melting ice on the chemistry of the study lakes is difficult to assess due to the unknown extent of permafrost as well as a lack of detailed hydrologic data. The notable increases in sulfate concentrations may indicate that warming is enhancing the rate of pyrite weathering, perhaps related to availability of oxygen. Another potential effect of warming might be to increase the frequency of freeze-thaw cycles in alpine areas. This mechanism might provide a possible explanation for the increases in acid neutralizing capacity in addition to sulfate that was observed at many of the lakes.

For some great background information:

Response of lake chemistry to changes in atmospheric deposition and climate in three high-elevation wilderness areas of Colorado written by M. Alisa Mast, et al in Biogeochemistry.

Trends in Lake Chemistry in Response to Atmospheric Deposition and Climate in Selected Class I Wilderness Areas in Colorado, Idaho, Utah, and Wyoming, 1993–2009 by the U.S. Geologic Society and Prepared in cooperation with the U.S. Department of Agriculture Forest Service, Air Resource Management. Written by M. Alisa Mast and George P. Ingersoll.