Heavy Metal Remediation Potential of a Tropical Wetland Earthworm, <i>Libyodrilus violaceus</i> (Beddard)

Abstract

Wetlands play important strategic ecological and life-supporting roles. As a result, they are continuously exposed to pollutants inflow including heavy metals. The aim of this research was to evaluate the heavy metal remediation potential of a tropical wetland earthworm, <em>Libyodrilus</em> <em>violaceus</em>. <em>L</em>. <em>violaceus</em> were exposed to soils contaminated with different concentrations of heavy metals using natural optimal soil density of 18 worms per kg soil, for 12 weeks. Relative to their initial concentrations, there were significant reductions of Zn, Pb and Cd at the end of the experiment. From the soil contaminated with a combination of Zn, Pb and Cd, the highest significant (p < 0.05) Cd reduction of 8.08 mg/kg soil occurred in the 12^th week, the highest significant (p < 0.05) Zn reduction of 37.47 mg/kg soil occurred in the 8^th week, while Pb recorded the highest but not significant (p > 0.05) reduction of 19.07 mg/kg in the 12^th week. The effect of addition of cow dung on the ability of <em>L</em>. <em>violaceus</em> to reduce heavy metals was generally low. <em>L</em>. <em>violaceus</em> is recommended as a good candidate for the remediation of low to moderate heavy metal contamination in wetland ecosystem..