Radiocesium contamination behavior and its effect on potassium absorption in tropical or subtropical plants

The accumulation and long-term decline of radiocesium contamination in tropical plant species was studied through measurements of gamma-ray spectra from pomegranate (Punica granatum) and chili pepper (Capsicum fructescens) trees. The plants were originally grown at a (137)Cs contaminated site (where a radiological accident occurred in the city of Goiania, Brazil, in 1987), and transplanted to uncontaminated soil, so that the main source of contamination of the new leaves and fruits would be the fraction of the available radiocesium in the body of the plants. Measurements of (137)Cs and (40)K concentrations along the roots, main trunk, twigs, leaves and fruits before and after the transplant process of both plant species indicated a direct competition between Cs and K ions, suggesting that these elements could have a common accumulation mechanism. Cesium transfer factors from soil to pomegranate, green and red chili pepper fruits were evaluated as 0.4 +/- 0.1, 0.06 +/- 0.01 and 0.05 +/- 0.01, respectively. Biological half-life values due to (137)Cs translocation from the tree reservoir (BHL(T)) were calculated as 0.30 years for pomegranate, 0.12 years and 0.07 years for red and green peppers, respectively.