Effect of low molecular weight organic acids on the uptake of 226Ra by corn (Zea mays L.) in a region of high natural radioactivity in Ramsar-Iran

To study the benefit of including citric and oxalic acid treatments for phytoremediation of Ra-226 contaminated soils a greenhouse experiment with corn was conducted. A soil was sampled from a region of high natural Ra-226 radioactivity in Ramsar, Iran. After cultivation of corn seed and using organic acid treatments at 1,10 and 100 mM concentrations, plants (shoots and roots) were harvested, digested and prepared to measure Ra-226 activity. Simultaneously, sequential selective extraction were performed to estimate the partitioning of Ra-226 among geochemical extraction. Results showed that the maximum uptake of Ra-226 in plants was observed in citric acid (6.3%) and then oxalic acid (6%) at 100 mM concentration. These treatments increased radium uptake by a factor of 1.5 than the control. Enhancement of radium uptake by plants was related to soil pH reduction of organic acids in comparison to control. Also, the maximum uptake of this radionuclide in all treatments was obtained in roots compared to shoots. Ra-226 fractionations results revealed that 91.8% of radium was in the residual phase of the soil and the available fractions were less than 2%. As the main percent of Ra-226 was in the residual phase of the soil in this region, it seems that organic acids had not significant effect on the uptake of Ra-226 for phytoremediation by corn in this condition. (C) 2016 Elsevier Ltd. All rights reserved.