USGS - science for a changing world

Environmental Health - Toxic Substances


Other Fundamental Research and Methods Development

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


The Toxics Program supports the development of knowledge and methods for the collection, analysis, and interpretation of data related to fundamental questions about contamination in the hydrologic cycle. What is the significance of these activities in relation to the field investigations?

Microbial Geochemistry



Contaminant Geophysics


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