The effect of Eisenia fetida earthworm on bioavailability of lead-contaminated soils in the presence of organic matter

The aim was to evaluate the efficacy of Eisenia fetida soil earthworms in the biological treatment of Lead-contaminated soils in the presence of organic matters. 6 soil samples from zero to 15 cm depth were collected at different distances around the mine and a soil sample (control) was collected from the non-contaminated area. This experiment was investigated as a factorial in the form of a complete randomized block design with first factor of organic fertilizers (cow manure, carrot pulp, vermicompost and control) and the second factor of the presence or absence of earthworms. 12 earthworms weighing between 0.3 and 0.6g were selected for each soil sample (300g). For 42 days, the worms were exposed to lead-contaminated soils with a concentration of 133.19 to 13250 mg/kg. At the end of the experiment, the concentration of lead in soil and earthworms body was measured. Results of this study show that the highest concentration of lead in the body of earthworms was found in all treatments at S3 and S2, which were more polluted than other sampling points to this metal. Soil earthworms have different capacities for absorbing and accumulating lead. The amount of bioaccumulation factor for lead metal at point S7 was greater than one, which was similar to previous studies. A significant increase in the amount of exchange lead (50 mg/kg) was observed in the treatment of cow manure without inoculation with earthworms. While the application of organic fertilizer with earthworm reduced the amount of Lead metal in the carbonate sector.