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137Cs Lake Sediment Depth Profiles and Inventories Within Four Lakes of Idaho’s Sawtooth Wilderness

Bishop, Benjamin Thomas; Brey, Richard1

doi: 10.1097/HP.0000000000000908
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A total of 68 sediment cores from four freshwater alpine lakes in Idaho’s Sawtooth Wilderness were collected during the summer of 2017. The objectives of the study were to determine depth distributions of 137Cs in the cores using gamma spectrometry and to estimate the sedimentation rates of the lakes from the identified geochronological peaks linked to nuclear fallout. The 137Cs radioactivity above reference-area values was detected in all studied lakes. The maximum 137Cs concentrations measured in each lake’s sediment ranged from 74.0 ± 6.09 to 255 ± 7.48 Bq kg−1. Factors such as elevation, latitude, and pH showed no correlation to total 137Cs deposition. However, the data developed during this investigation suggested that characteristics such as geological location or lake flushing patterns are important factors in the total 137Cs deposition observed. Three of the lakes had 137Cs sediment depth distributions that resembled the deposition pattern of weapons testing as a function of time. Mean sedimentation rate estimates ranged from 0.08 ± 0.3 to 0.1 ± 0.05 cm y−1 and decreased with increasing altitude.

1Idaho State University, Health Physics Program, Campus Box 8106, Pocatello, ID 83209-8106.

The authors declare no conflicts of interest.

For correspondence contact: Richard Brey, Idaho State University, Health Physics Program, Campus Box 8106, Pocatello, ID 83209-8106, or email at breyrich@isu.edu.

(Manuscript accepted 24 April 2018)

© 2018 by the Health Physics Society