Advances in Earthworms as Biological Remediators of Polluted Soils

Agricultural soils receive many environmental contaminants through organic fertilization (e.g., composts, animal manure, and biosolids), irrigation with wastewater, and chemical control of pests. Thus, it is not surprising to detect a wide range of pollutants in soil, such as metals, nanoparticles, microplastics, pesticides, polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers, phthalates, pharmaceuticals, personal care products, or perfluorinated substances. Furthermore, predictive models indicate that soil pollution will be exacerbated by global climate change. Therefore, transitioning to an organic agricultural system and environmentally friendly, bio-based soil remediation systems can be suitable measures to improve soil health and resilience. Accordingly, inoculating agricultural soils with earthworms or stimulating the native population of these organisms could be seen as an opportunity to increase the natural attenuation of soil against contaminant input and as a bioremediation strategy. To propose the use of earthworms in the remediation of polluted agricultural soils (vermiremediation), this chapter provides an overview of the main physicochemical and biological impacts of earthworms in agricultural soils. It then moves on to the drilosphere concept and the relationship between soil microorganisms and earthworm gut symbionts for removing pollutants. Vermiremediation depends on earthworm sensitivity to pollutants and bioaccumulation capacity, which are discussed in the context of earthworm ecotypes. A final section includes new integrative approaches in which earthworms interact with other biotic factors (exogenous microorganisms and mesofauna) and abiotic factors (biochar or hydrochar) to improve vermiremediation.