Removal of benzo (a) pyrene from soil using an endogeic earthworm Pontoscolex corethrurus (Müller, 1857)
B. Hernández-Castellanos, A. Ortíz-Ceballos, S. Martínez-Hernández, J.C. Noa-Carrazana, M. Luna-Guido, L. Dendooven, S.M. Contreras-Ramos
Instituto de Biotecnología y Ecología Aplicada (INBIOTECA), Universidad Veracruzana, Av. de las Culturas Veracruzanas No. 101 Col. Emiliano Zapata, C.P. 91090 Xalapa, Veracruz, Mexico.
The endogeic earthworm Pontoscolex corethrurus (Müller, 1857) was the most abundant species (75%) in soil contaminated with hydrocarbons, mostly benzo(a)pyrene (BaP), in the state of Tabasco (Mexico). The earthworm P. corethrurus was tested for its capacity to remove 100 mg BaP kg−1 from an Anthrosol soil (sterilized or not) and amended with legume Mucuna pruriens (L.) DC. var. utilis (Wall. ex Wight) Baker ex Burck (3%) or the grass Brachiaria humidicola (L.) DC (3%) (recently renamed as Urochloa humidicola(Rendle) Morrone & Zuloaga) in an aerobic incubation experiment. P. corethrurus removed 26.6 mg BaP kg−1from the sterilized soil and application of B. humidicola as feed increased this to 35.7 mg BaP kg−1 and M. pruriens to 34.2 mg BaP kg−1 after 112 days. The autochthonous microorganisms removed 9.1 mg BaP kg−1from the unsterilized soil and application of B. humidicola increased this to 18.0 mg BaP kg−1 and M. pruriens to 11.2 mg BaP kg−1. Adding P. corethrurus to the unsterilized soil accelerated the removal of BaP and 36.1 mg kg−1 was dissipated from soil. It was found that the autochthonous microorganisms removed BaP from soil, but addition of P. corethrurus increased the dissipation 4-fold. The endogeic earthworm P. corethrurus can thus be used to remediate hydrocarbon-contaminated soils in tropical regions.