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Environmental Health - Toxic Substances

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Hardrock Mining in Rocky Mountain Terrain -- Upper Arkansas River, Colorado

Tailings pile with a pond of red acidic water.
Tailings piles, such as this one in California Gulch, Colorado, are a source of metal-rich, acidic water in the upper Arkansas River Watershed, Colo. USGS scientists studied the occurrence of toxic metals in water, colloids, and bed sediments in the Arkansas River downstream from it's confluence with California Gulch.

An embankment along the side of California Gulch, Colo.
Drainage from abandoned mine wastes, such as this embankment along the side of California Gulch, Colorado, can cause potential harm to fish not only adjacent to the wastes but for many miles downstream as well.

A view of California Gulch, Colo.
USGS scientists conducted a diel (daily cycles) study of Arkansas River, Colorado, and its tributary California Gulch, Colorado (in photo), to identify potential photoreduction of iron. The transport of iron in metal-enriched streams is controlled by photoreduction, precipitation, and dissolution.

Acid mine drainage from California Gulch (right) mixes with the Arkansas River, Colo. (left).
Acid mine drainage from California Gulch (right) mixes with the waters of the Arkansas River, Colo. (left). The Gulch was a source of hydrous iron oxides that precipitated as colloids and moved in suspension down the Arkansas River. Historic surges from mine works have released much larger plumes into the Arkansas River that have been visible for miles downstream.

Electron photomicrograph of aggregated hydrous ferric oxide.
Electron photomicrograph of aggregated hydrous ferric oxide, which is commonly found in streams affected by acidic, metal-rich waters. Colloidal iron particles range in size from one nanometer (see detail photo on right) and aggregate to particles greater than 1 micron. This large range of particle sizes poses a problem in defining "dissolved" metal concentrations because the smaller colloidal particles can pass through a 0.45 micrometer filter, which is the filter size usually used to define dissolved concentrations. In order to facilitate geochemical modeling, USGS scientists have studied filtration methods that allow better definitions of that is truly dissolved.

Tangential flow filtration equipment on the tail gate of a truck.
Tangential flow filtration equipment used to study iron and aluminum colloids in streams affected by mine drainage. Understanding the formation and transport of colloids can help understand the movement and storage of contaminants, which is information environmental professionals can use to design more cost effective cleanup programs.

Three sample bottles in front of a news paper box.
Ultrafiltration allows the study of metals transported by colloids in streams affected by mine drainage. The photo shows a raw sample from California Gulch, near Leadville, Colo. (left), the clear ultrafiltrate (center), and the concentrate of colloids for analysis (right). Without ultrafiltration scientists would not be able to collect enough sample to analyze.

USGS scientist on a stream in the woods.
USGS scientists inject tracers, such as lithium chloride in this case, into mountain streams to learn more about stream hydrology and chemistry than can be gained from traditional discharge and water-quality measurements. The methods they are developing to characterize contaminated streams can be used by water-resource managers to make better cleanup decisions.

The large white bottle and other tracer test equipment.
The large white bottle contained a solution of sodium bromide, a conservative tracer, that was injected into the stream to characterize the hydrology of St. Kevin Gulch, Colo.Ņa stream impacted by acid mine drainage. The analysis of tracer injection experiments can yield a wealth of hydraulic information, for example information on time of travel, instantaneous discharge, temporal variation in discharge, and rates of ground-water inflow.

The tracer equipment along the banks of St. Kevin Gulch, Colo.
The site where a tracer, sodium bromide in this case, was injected into St. Kevin Gulch, Colorado, to study the processes that control the transport of metals in mining impacted streams. The small platform on the left side of the stream holds the equipment used to inject the tracer solution into the stream. Tracer tests are one way scientists use to study the effects of back storage on the transport of contaminants in mountain streams.

USGS scientist collecting a water sample from St. Kevin Gulch, Colo.
USGS scientist collecting a water sample from St. Kevin Gulch, Colorado, during a tracer injection experiment. Water-quality monitoring data collected during the experiment is use to characterize both flow in the stream channel and associated flow in bed sediments below the stream channel.

USGS scientist collecting a water-quality sample during a tracer injection experiment.
USGS scientist collecting a water-quality sample during a tracer injection experiment along a segment of St. Kevin Gulch, Colo. The black cylinder to the left of the scientist is an auto sampler used to collect water samples at frequent time intervals.

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Page Last Modified: Wednesday, 05-Aug-2015 11:11:45 EDT