Phytoextraction trials of cadmium and lead contaminated soil using three weed species

Abstract

Study on the phytoextraction of cadmium (Cd) and lead (Pb) artificially contaminated soil using 3 weed species (Ageratum conyzoides, Syndrella nodiflora and Cleome rutidosperma) was carried out at the Centre for Ecological Studies, University of Port Harcourt. A Randomized Complete Block Design consisting of 2 sets of contamination treatments designated as Cd(T) and Pb(T) with 3 phytoextraction applications for each set. Cd(T) and Pb(T) were contaminated with 100 mg of Cd and Pb in 4 kg soil respectively. There was also a control with pollution but no phytoextraction application for each set. After 13 weeks of phytoextraction trials, results showed percentage reductions in soil Cd in Ageratum conyzoides (35.8%), Syndrella nodiflora (45.1%) and Cleome rutidosperma (55.3%); and Pb was Ageratum conyzoides (68.7%), Syndrella nodiflora (27.3%) and Cleome rutidosperma (24.8%). The plant concentration factor (PCF) for Cd was Ageratum conyzoides (0.39), Syndrella nodiflora (0.73) and Cleome rutidosperma (1.15) and; Pb was Ageratum conyzoides (1.96), Syndrella nodiflora (0.32) and Cleome rutidosperma (0.31). The mobilization ratio for Cd was Ageratum conyzoides (0.91), Syndrella nodiflora (0.88) and Cleome rutidosperma (0.90) and; Pb was Ageratum conyzoides (1.06), Syndrella nodiflora (0.77) and Cleome rutidosperma (0.57). Therefore, Cleome rutidosperma and Ageratum conyzoides are good phytoextraction plants for Cd and Pb respectively. Also Ageratum conyzoides can be regarded as accumulator for Pb with mobilization ratio > 1 while Cleome rutidosperma and Syndrella nodiflora are Cd and Pb excluder plants.

Keywords: weed species, contamination, heavy metals, phytoextraction, Ageratum conyzoides, soil