Plant accumulation and plant/soil concentration ratios of 210Pb and 210Po at various sites within a uranium mining and milling operation

• Published in: Environmental and experimental botany 1987, Vol.27 (2), p.203-213
• Main Authors: Ibrahim, S.A., Whicker, F.W.
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Ecotoxicology, biological effects of pollution; Fundamental and applied biological sciences. Psychology; isotopes; lead; mined soils; polonium; soil; Terrestrial environment, soil, air; uranium; vegetation
• ISSN: 0098-8472; 1873-7307
• DOI: 10.1016/0098-8472(87)90071-2

The primary objectives of this study were to determine 210Pb and 210Po concentrations in soil and native plants and to estimate plant/soil concentration ratios from various sites around a uranium mining and milling operation that is typical of most in the Western U.S. Soil and vegetation samples were collected at exposed, weathered tailings; near the edge of a tailings pond; downwind from a tailings impoundment; from a reclamation area and at several background locations. The mean concentrations of 210Pb and 210Po in background soil and vegetation were within the reported range for the U.S. Concentrations in soil and vegetation varied significantly among sites and were generally elevated above the background in the disturbed areas near tailings. Both radionuclides occurred at near-radioactive equilibrium in natural soil and tailings and are accumulated by native plants to a similar degree. No demonstrable differences among plant groups were found. A wide range of concentration ratios ( CR) was observed for both radionuclides, and CR values appeared to be related to differences between collection sites. Comparatively high values were estimated for plants growing at the tailings pond edge relative to all other locations. We speculate that acidity and the diminished soil-binding capacity caused by the saturated pond edge are responsible for the enhanced plant uptake at this location. 210Po CR values for plants growing on exposed tailings were higher than previously reported from soil contaminated with polonium oxide. The sulfuric acid leaching process of uranium ore may create a more soluble form of polonium in tailings material. Comparatively low CR values were observed for plants downwind from the tailings source. Evidence is presented for both radionuclides that plant accumulation is a non-linear function of substrate concentration. Thus, the usefulness of a single CR value may be severely limited due to the lack of linear relationship between plant and soil activities.