USGS - science for a changing world

Environmental Health - Toxic Substances

Crosscutting Topics

Methods

Field and laboratory environmental measurement methods

The U.S. Geological Survey (USGS) Toxic Substances Hydrology Program develops field methods to measure a wide range of environmental properties, and develops approaches and protocols used to assess or characterize contamination.

The Program also develops laboratory analytical methods to measure a wide variety of chemicals in environmental media.

A view of the Big Hole River in southwestern Montana.
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 -- from the Diurnal Metal Variations Photo Gallery

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