GEOLOGIC CONTROLS ON 137CS CYCLING BY TERRESTRIAL VEGETATION IN THE EASTERN U.S

¹³⁷Cs is a radioactive trace metal (T_1/2 = 30 y) which was dispersed globally by nuclear weapons testing in the 1950s-1960s. Prevailing winds caused some areas far from the test sites to receive significant fallout, which is still easily measured in soils, sediments and even some vegetation in the Eastern United States. Recent work near Chernobyl and Fukushima indicates that trace levels of ¹³⁷Cs can harm insects and ecological function. It’s been established that in areas with low soil potassium, ¹³⁷Cs is cycled in vegetation; however, soil potassium alone doesn't consistently predict the ¹³⁷Cs content of plants. We hypothesize that local geology more broadly influences the cycling of ¹³⁷Cs by vegetation, which ultimately controls potassium concentrations, clay mineralogy, and slope. We collected foliage and soil samples from sites in Tennessee and Virginia to examine geologic controls affecting ¹³⁷Cs uptake in vegetation. Our sites span Conglomerate, Quartzite, Dolostone, Graywacke, and detrital sediment. Across this gradient of soil parent material, foliage concentrations of ¹³⁷Cs ranged from undetected (0.1 Bq/kg) to 5.7 Bq/kg. Foliage at each site had widely varying ¹³⁷Cs, indicating that there is a species control on uptake. By comparing the ratio of ¹³⁷Cs in plants to soil, I found Quartzite bedrock showed almost no ¹³⁷Cs uptake, and Graywacke had the highest with a median of 21%. The next steps are to examine plant available potassium and illite content in the soil samples from each site. This research will help us understand how geology affects ¹³⁷Cs and trace metal cycling and thus predict which plant or animal species could be at increased risk to radiation exposure.