Operationally defined availability from sequential extractions compared to plant uptake of 137Cs and 90Sr

The operationally defined bioavailable fraction from a commonly used sequential extraction (SE) procedure was compared to biological availability represented by plant uptake of Cs-137 and Sr-90. Experiments were conducted at two locations in the Ukraine and at several field locations on the Savannah River Site, South Carolina. A significant regression existed between plant uptake and the ammonium acetate fraction (r(2) = 0.65), however, ratios of predicted uptake from the SE procedure to observed plant uptake ranged from 0.03 to 5.2. Data suggest that the SE procedure was useful for qualitative interpretations of biological availability but lacked sufficient rigor to be useful for quantitative predictions.