Compositional and metabolic quotient analysis of heavy metal contaminated soil after electroremediation

Heavy metal soil contamination provides a danger both to human and environmental ecosystem health and is still on the rise in many developing countries. Electroremediation provides an innovative method to remedy contamination of soils by heavy metals. Fundamental to the acceptance of any soil remedial technique is proof that positive benefits outweigh the negative impacts, in terms of soil health. The environmental effect of electroremediation of heavy metals contaminated soil by some biological indicators was evaluated. A soil contaminated with Zn, Pb, Ni, and Cd was used in a laboratory experiment. Treatment was imposed with a constant voltage gradient of 0.83 V/cm for 20 days. Results indicated that the physicochemical changes caused by the electroremidiation process on the soil microbial population (actinomycetes and gram-positive and negative bacteria), soil respiration and microbial biomass were significant (p < 0.01). At the commencement of the study, soil microbial activity was reduced, due to physicochemical changes in pH, amount of moisture and the changes in the levels of heavy metals in the soil. The greatest reduction on the microbial activity was close to the cathode where high levels of heavy metal concentrations and high pH were demonstrated. The metabolic quotient index [qCO₂] was used to achieve a more refined evaluation, compared to analysis of soil respiration and microbial biomass alone. Accordingly, high amounts of qCO₂ near the cathode show the unfavorable living conditions of such microorganisms in these sections.