ABSTRACT: Economic, Environmental, and Health Implications of Uraniferous Montane and Subalpine Wetlands

Douglass E. Owen

Wetlands are common in montane and subalpine settings in the western United States, and many contain significant concentrations of uranium (U). Sorption by organics, complexing of uranyl, UO_2²⁺, with humic and fulvic acids, and bacterial action can produce geochemical enrichment factors of 10,000 to 1 or greater between peat and uranium-bearing waters. In 67 of 145 wetlands sampled by the U.S. Geological Survey (USGS) in Colorado, moderate (20-99.9 ppm) or higher (100 to >3,000 ppm) concentrations of uranium (dry weight basis) were found. The USGS calculated that two small wetlands in the Carson Range of Nevada contain 15,000 and 24,000 kg of U. The only wetland uranium deposit in the United States that has been mined is the Flodelle Creek deposit in Stevens County, Washington, which the USGS estimated to contain 450,000 kg of U. However, only about 500 kg was produced before the low price of uranium forced the mine to close. Development of wetland uranium deposits is impractical unless uranium prices increase.

Because the processes responsible for concentrating uranium and other metals in organic-rich wetland sediments are reversible, both anthropogenic and natural disturbances may have serious environmental consequences. If a wetland is partly or completely drained, the subsequent oxidation of organic-rich sediments may liberate metals that have been accumulating from very dilute solutions for thousands of years. Acid leaching or other geochemical processes may also release uranium from wetlands and impact water quality. The use of uranium- or other metal-bearing peat for agricultural purposes may cause foodstuffs to accumulate elevated levels of uranium or other metals.

AAPG Search and Discovery Article #91002©1990 AAPG Rocky Mountain Section Meeting, Denver, Colorado, September 16-19, 1990