Watershed Contamination from Metal and Uranium Mining

Picture of the freshwater snail—Lymnaea stagnalis—used in the laboratory exposure tests to understand uranium uptake and bioavailability. Photo Credit: Javier Garcia-Alonso, USGS.

USGS scientists have been studying the biogeochemical processes controlling dissolved uranium bioavailability to understand the ecological risk posed by uranium mining to federally managed lands such as the Grand Canyon area. This is a picture of the study area located in the Grand Canyon, Arizona. Photo Credit: Marie-Noële Croteau, USGS.

USGS scientists collecting soil samples inside the perimeter fence at the Canyon Mine, Arizona. The mine's headframe and mine workshop are visible in the background. USGS scientists developed an approach to quantitatively assess offsite migration of mine-related contaminants. Photo Credit: Kit MacDonald, U.S. Forest Service.

A map showing the locations of decision units surrounding the Canyon Mine, Arizona. The scientists used a incremental sampling methodology to collect samples from the predefined decision units. The points (squares and circles) indicate locations where surface soil subsamples were collected during June 2013. Modified from figure 2 from Naftz and Walton-Day, 2016. 2015 base map data from Google Earth^©.

Upper workings of the Pennsylvania Mine in the headwaters of Peru Creek, Colorado. USGS scientists have developed an improved approach for identifying the major sources of contaminants to streams in watersheds, such as this one, impacted by acid mine drainage. Photograph by Robert L. Runkel, USGS.

A former uranium mill tailings site near Rifle, Colorado, is next to the Colorado River. A team of scientists has documented multiple chemical reactions that transform hexavalent uranium to more insoluble forms of tetravalent uranium in the subsurface at the site. Photo credit: John Bargar, SLAC National Accelerator Laboratory.

A USGS scientist collects a water sample for analysis of mineral particles know as colloids. Toxic metals (such as copper in excess) bind to the particles, which are then ingested by aquatic animals. Photo credit: Daniel Cain, USGS.

Diffusive Gradients in Thin Films (DGT) samplers deployed in High Ore Creek, Montana, accumulated dissolved metals during deployment, enabling scientists to do a time-integrated evaluation of varying concentrations of metals in the stream. Photo credit: Laurie Balistrieri, USGS.

The influx of metal-rich groundwater from natural springs (foreground) to Cement Creek, Colorado (background) can complicate the selection of best management practices. USGS scientists have developed methods for evaluating strategies to reduce acid mine drainage in streams. Photo credit: Briant Kimball, USGS.

Big Hole River in southwestern Montana. USGS scientists and their university colleagues have shown that photosynthesis by aquatic plants causes large diel (daily) cycles in pH, dissolved oxygen concentrations, and the isotopes of oxygen and carbon. In addition, the aquatic plants are thought to cause large changes in streamflow as oxygen production during photosynthesis stiffens the plants and thereby retards downstream flow during the day.

Deposit of iron-cemented stream gravel (ferricrete) with embedded wood fragments that can be age dated using radiocarbon to determine the age of the ferricrete deposit. Knowing the age of the ferricretes helps scientists determine if the associated enrichment of metals in streams occurred before or after mining in the watershed started.

The Silver Ledge Mine in the area of upper Mineral Creek, near Silverton, Colorado, is one of many abandoned mine sites in the watershed. USGS scientists have developed methods for identifying the largest sources of acid mine drainage amongst many in a watershed. Photo credit: Philip Verplanck, USGS.

Mineral Creek watershed in southwestern Colorado has natural and mining-related sources of contamination. In the background of this photo is a large naturally occurring seep that discharges acidic, metal-rich water to a tributary of Mineral Creek. Natural sources of contamination like this one make it difficult to determine appropriate water-quality standards for cleanup actions.

Field experiment designed to compare survival of trout fry (newly hatched fish) exposed to constant versus varying metal concentrations, High Ore Creek, Montana Water stored in the streamside tanks was used to refresh plastic containers in the stream. Water in the tanks had high, medium, or low metal concentrations. The fourth tank contained metal-free water used as an experimental control.

Scientists checking fish held in plastic containers that were exposed to a constant metal concentration as part of a field experiment to compare survival of trout fry (newly hatched fish) exposed to constant versus varying metal concentrations, High Ore Creek, Montana.

Fish held in flow-through containers are exposed to metal concentrations with daily high and low cycles (diel cycles). Scientists conducted a field experiment to compare survival of newly hatched trout (fry) exposed to constant versus varying metal concentrations, High Ore Creek, Montana The experiment will help scientists understand the effect of diel variations in the concentration of metals on fish in mining affected areas.