Activities and summary statistics of radon-222 in stream- and ground-water samples, Owl Creek basin, north-central Wyoming, September 1991 through March 1992

Abstract

Radon-222 activity was measured for 27 water samples from streams and ground water in and near the Owl Creek Basin, a 510-square mile area in north-central Wyoming. Water samples were collected from September 1991 through March 1992. Summary statistics of the radon-222 activities were compiled. The radon-222 activities were measured as part of a comprehensive study of surface-and groundwater quality in the Owl Creek Basin undertaken cooperatively by the U.S. Geological Survey and the Shoshone Tribe and Northern Arapahoe Tribe. Stream-water samples were collected at 16 sites along the main stem of Owl Creek and its tributaries. For the 16 stream-water samples, the arithmetic mean radon-222 activity was 20 pCi/L (picocuries per liter), geometric mean activity was 7 pCi/L, harmonic mean activity was 2 pCi/L, and median activity was 8 pCi/L. The standard deviation of the arithmetic mean was 29 pCi/L. The stream-water samples ranged from 0.4 to 97 pCi/ L. The histogram of stream samples are left-skewed compared to a normal distribution. Groundwater samples were collected at 11 sites from an alluvial aquifer, bedrock aquifers, and a geothermal system. For the 11 groundwater samples, the arithmetic mean radon-222 activity was 486 pCi/L, geometric mean activity was 280 pCi/L, harmonic mean activity was 130 pCi/L, and median activity was 373 pCi/L. The standard deviation of the arithmetic mean was 500 pCi/L. The radon-222 activities in the groundwater samples ranged from 25 to 1,704 pCi/ L. The histogram of groundwater samples are left-skewed compared to a normal distribution.