Effects of Citric Acid on the Phytoextraction Potential of Psium sativium L Grown on Heavy Metals Contaminated Soil

This study assessed the effect on citric acid on the phytoextraction of Psium sativium on heavy metals. The experiment was an outdoor experiment which was done using soil samples obtained from auto-mechanic workshop. The soil sample was analysed for the presence of heavy metals and the presence of the following heavy metals were detected in this order of concentration: Zn>Cu>Fe>Pb>Cd>Cr>Hg. The four plastic cups labeled A, B, C and D were treated with the following concentrations of citric acids: 0, 0.5, 1.0 and 1.5g/kg of citric acid. The plants were allowed to grow for twenty (20) days before they were harvested. The harvested plants were air- dried. The biomass and the length of the root and shoot of the dried plant sample were obtained by weighing with a chemical balance and measuring tape respectively. The heavy metal bioaccumulation of the root and shoot of Psium sativium obtained from plastic cup without citric acid was estimated and the following heavy metals were detected in the root and shoot: mercury, chromium, cadmium, zinc, copper, iron, and lead. There was an increase in the biomass and length of the dried root and shoot of Psium sativium that were planted on soil sample treated with 0.5 g/kg and 1.0 g/kg citric acid but an increase in the concentration of citric acid to 1.5 g/kg decreased the biomass and length of root and shoot when compared with Psium sativium that was planted on soil sample that was not treated with citric acid. The application of citric acid increased uptake of chromium, cadmium, zinc, copper, iron, and lead by the root and shoot of Psium sativium in this order of increasing citric acid concentration: 1.5 g/kg> 1.0 g/kg> 0.5 g/kg while 1.5 g/kg concentration of citric acid reduced the heavy metal uptake by the root and the shoot. The bioconcentration factor for all the heavy metals that were analyzed increased with an increase in citric acid concentration except for mercury that had a reduced bioconcentration factor at citric acid concentration of 1.5g/kg. The traslocation factor of Psium sativium for copper, zinc and iron increased with an increase in citric acid concentration. Psium sativium had the least translocation factor for cadmium and highest translocation factor for chromium at varying concentration of citric acids when compared with other heavy metals. The result of this study shows that Psium sativium is an effective phytoremediation agent of some heavy metals. The study also shows that the application of citric acid could be a useful agent in increasing the phytoextraction of heavy metals from contaminated soil by Psium sativium plants.