Potential of earthworms to accelerate removal of organic contaminants from soil: A review

• Review on the use of earthworms in the remediation of contaminants from soil.
• Remediation efficiency depends on contaminant concentration.
• Efficiency also depends on earthworm abundance, species and colonization capacity.
• Contaminant removal stimulated by earthworm-mediated effects on microbial activity.
• The use of earthworms in the remediation of soil also has its limitations.

Earthworms can accelerate the removal of contaminants from soil. Earthworms change the physical and chemical properties of soil by mixing it with organic material and through their burrowing they improve aeration and render contaminants available for microorganisms. The presence of earthworms in contaminated soil indicate that they can survive a wide range of different organic contaminants, such as pesticides, herbicides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and crude oil, at least when concentrations of the contaminant are not too high. The improvement of the soil due to their activity and the microorganisms in their digestive track can contribute to the accelerated removal of contaminants from soil, but sometimes their casts adsorb the pollutant so that its dissipation is delayed. There are limits, however, on how earthworms can be used to remediate soil, which will be discussed in this review.