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.

A field experiment in Mineral Creek, Colorado, used 18 drive point wells along a 33-meter study reach to sample for groundwater inflow to the stream of metal-rich water (copper, zinc, and other metals) from abandoned mine sites. Identification of such inflows, when no surface manifestation occurs, is one of the applications of stream-tracer injections.

USGS scientists display some of their precautions used to prepare a sodium hydroxide solution. The solution was used for a pH modification experiment in Mineral Creek, Colorado. The pH modification experiment was designed to study the changes in geochemical conditions that affect the transport of metals in streams during remediation of acidic mine drainage.

Solutions of lithium bromide (right tank) and sodium hydroxide (left tank) used for of a pH-modification experiment in Mineral Creek, Colorado. The experiment was designed to simulate remediation of acid mine drainage systems that artificially raise the pH of streams.