Rocky Mountain Snowpack Chemistry at Selected Sites, 1993-2010

Project

Chief: George Ingersoll Cooperator: National Park Service; U.S.D.A. Forest Service; Colorado Department of Public Health and Environment; Teton County, Wyoming BACKGROUND: Snowpacks collect atmospheric deposition throughout the snowfall season and offer a unique opportunity to obtain a composite sample of the chemistry of most (roughly November through April) of the annual precipitation at high elevations (> 1800 meters).

This project was created to sample the full snowpack at selected sites to determine sources of acid deposition to sensitive mountain watersheds. Since 1993, the project has become the most expansive and comprehensive snowpack-chemical monitoring network of its kind. Beginning with sampling fewer than 20 sites in Colorado in 1993, the network has expanded to greater than 50 locations along the Continental Divide that have been sampled each year since 1993.

In the process, techniques have been developed that use robust tracers to separate and quantify local and regional sources of atmospheric deposition of airborne pollutants. Through this program, long-term trends (>19 years, generally) are being developed in snowpack chemistry that enable estimation of normal or background levels, and identification of elevated chemical concentrations at a variety of locations where atmospheric deposition of acidic compounds is a concern.

The project primarily monitors federally-managed lands in the Rocky Mountain region including several protected wilderness areas in National Forests and Parks. Applications of this regional snow-chemistry work include identifying regional trends in chemical concentration and deposition as well as monitoring subregional or local effects including power-plant emissions in Colorado or snowmobile usage in Yellowstone and other areas.

OBJECTIVES: To develop methods to accurately represent seasonal snowpack chemistry of a variety of compounds in single, annual samples where repeated sampling is possible in subsequent years. To maintain year-to-year sampling of a core group of 50 sampling locations to develop long-term trends in atmospheric deposition throughout the region. To establish background concentrations of major ions, trace metals, and isotopes of nitrogen and sulfur in atmospheric deposition; identify areas of elevated concentrations relative to background levels.

To identify probable sources of elevated atmospheric deposition to snowpacks, and identify trends in chemistry as emissions change from year-to-year. Distinguish local from regional sources. To support ongoing investigations of process-level studies of effects on sensitive ecosystems of elevated concentrations of acids and other chemicals in atmospheric deposition.

To provide data for future management decisions regarding permitting new emissions sources or planning reduction of existing emissions. [Summary provided by the USGS.]