The influence of citric acid on mobility of radium and metals accompanying uranium phytoextraction

Abstract

  We have investigated the plant uptake of radium, iron and other elements linked with phytoextraction of uranium induced by citric acid. Experiments were carried out on soil from the surroundings of a uranium mine. Enhancement of U bioavailability was successful. Now we focused our attention on the uptake of the most important elements accompanying uranium in phytoextraction. Radium was analyzed in leaves of willows and sunflowers. Mainly in willows, Ra was accumulated 3–4 times more than in the control group. Analyses of sunflower leaves showed an increasing tendency of Ra activity; however, not as significant as in the willow. During the experiment, we recorded irregular increases of metal contents in leaves week by week. Whereas U did not increase significantly, iron reached a value 9.3 times higher than in the control group. This is the evidence of more effective iron mobilization than of uranium when citric acid was added into the soil. Manganese also competes with uranium in plant uptake. Its content in leaves increases after citric acid treatment and is always higher than uranium uptake. The uptake of ubiquitous metal elements is one of the limiting factors for phytoextraction.