Abstract

Laboratory and pot experiments were carried out to investigate the effect of different rates of ethylenediaminetetraacetic acid (EDTA) on heavy metal contaminated soils and the potential of Lettuce (Lactuca sativa) plant for phytoremediation of contaminated soils. Soil samples were taken from Teaching and Research Farms of the Federal University of Agriculture, Makurdi, Benue State, during the 2015 and 2016 cropping seasons and passed through a 2 mm sieve for laboratory and pot experiments. Two (2) kg each of the air dried soil samples wrer transferred to plastic pots. Each soil sample was treated 50 mgkg -1 Zn (ZnSO4) as a pollutant. EDTA at the rates of 0, 3, 6 and 12 mmolkg -1 was added to the soil and replicated five times. The pots were arranged in a completely randomized design (CRD), bringing the total number of pots to twenty (20). Forty (40) seeds of lettuce (Lactuca sativa) were sown in each pot and thinned to 5 plants. The result shows that incremental concentrations of EDTA in both seasons led to an increase in the plant tissue concentration of all the heavy metals studied. Generally increasing concentrations of EDTA increased the bioavailability of the Zn metal in plant tissue. The metal concentration in the plant tissue increased with increasing concentration of EDTA. The highest bioaccumulation factor (BCF) values obtained with Zn is an indication that lettuce (Lactuca sativa) was able to take up more of the element from the soil solution. This shows that lettuce has good potential in the phytoremediation Zn. The accumulated Zn levels in the plants were above the WHO permissible limits, EDTA addition of up to 12 ppm could be used in the solubilization of heavy metal (Zn) in any phytoremediation programme of contaminated soil.