ENHANCED PHYTOREMEDIATION OF SOIL CONTAMINATED WITH LEAD AND CADMIUM USING GOMPHRENA CELOSIODES AND PLANT GROWTH PROMOTING BACTERIA (BACILLUS SAFENSIS)

Abstract

ABSTRACT This study was carried out to assess the phytoextraction potential of Gomphrena celosiodes (gomphrena weed) for lead and cadmium enhanced with plant growth promoting bacteria. The pot experiment was done in triplicates and a total of 26 pots were used. Gomphrena celosiodes were transplanted into 5 kg of loamy soil, each plastic 3

pot having control, 5, 10, 15 and 20 ppm of lead (Pb) and cadmium (Cd), respectively. The experiment was carried out for a period of 8 weeks under natural conditions. The plant growth promoting bacteria (Bacillus safensis) were confirmed using standard molecular techniques. Physical and chemical properties of the soil were also determined using standard methods. The study revealed that pH, nitrogen, phosphorus, organic carbon, sodium and magnesium contents of the soil increased while organic matter and calcium contents reduced in polluted soil remediated with Gomphrena celosiodes when compared to the unpolluted soil. There was decrease in the bacterial counts in the soil contaminated with Pb and Cd from week zero to week 8 ranging from 8.6x106 to 4.8 x106 cfu/g compared to the unpolluted soil with counts ranging from 3.0 x106 to 7.0 x106 cfu/g. The plant mopped up a substantial concentration of Pb 0.059 and Cd 0.041 mg/kg in its shoots after 8 weeks compared to the concentrations in the roots 0.014 mg/kg. The heavy metal contents in the soil remediated with Gomphrena celosiodes showed the reduction of Cd and Pb in the soil from week zero to 8 ranging from Cd 0.085 to 0.047 mg/kg and Pb 0.66 mg/kg to 0.067. The phytoextraction ability of the plant was assessed in terms of its bioconcentration factor (BCF) and translocation factor (TF). It was observed that after 8 weeks of remediation, Pb and Cd showed more bioavailable pool in its shoots than its roots with highest BCF of soil contaminated with Pb 0.279 mg/kg and Cd 0.112 mg/kg and TF of soil contaminated with Pb 1.320 mg/kg and Cd 1.411 mg/kg respectively. These results showed that Gomphrena celosiodes has phytoextraction ability and could be used in restoring soil polluted with Pd and Cd.