Microbial and Heavy Metal Determination of Contaminated Soil Using Melissa officinalis L

Abstract

In Nigeria and other part of the world, heavy metal pollutions are becoming increasingly common. Heavy metals are natural elements of the environment. This research was designed to remediate a heavy metal polluted environment of Angwa Kawo (AK) in Rafi Local Government Area, Niger State, Nigeria with M. officinalis L. Microbial loads of the soil was monitored and the bacterial counts ranges from 1.0±1.0 to 4.0±0.57 x105 cfu/g while the fungal counts has 0.33±0.33 to 2.0±0.57 x102 cfu/g. Physicochemical properties (Organic carbon, pH, Total nitrogen, Phosphorous, Organic matter, moisture, trace elements, Electrical conductivity, Exchangeable acidity and cationic exchange) of the soil were done using standard methods. The plant (M. officinalis L) mopped up heavy metals (Cd, As, Pb) and their concentration varied from 0.007 to 0.33 mg/kg, As (0.09 to 4.39 mg/ kg) and Pb (0.07 to 10.35 mg/kg) respectively. The concentration of Cd in the residual soil varied from 0.026 to 0.58 mg/kg, As from 0.32 to 5.48 mg/kg, Pb from 5.88 to 12.37 mg/kg. Soil remediation was further confirmed using scanning electron microscopy (SEM) analyses, which revealed structural and morphological changes of the soil. Melissa offinalis L proved to have the potential to remediate heavy metal polluted soil as revealed in this study.