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

Radon-222 activity was measured for 27 water samples from streams, an alluvial aquifer, bedrock aquifers, and a geothermal system, in and near the 510-square mile area of Owl Creek Basin, north- central Wyoming. Summary statistics of the radon- 222 activities are compiled. For 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 is 29 pCi/L. The activities in the stream-water samples ranged from 0.4 to 97 pCi/L. The histogram of stream-water samples is left-skewed when compared to a normal distribution. For 11 ground-water 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 is 500 pCi/L. The activity in the ground-water samples ranged from 25 to 1,704 pCi/L. The histogram of ground-water samples is left-skewed when compared to a normal distribution. (USGS)