Background and Objectives: In the field of environmental risk assessment, the earthworms are considered as the major component of the soil, and are important bio- indicators to measure the environmental health and quality of the soil. Hence, the present study aimed to prove the biological effectiveness of Eisenia fetida earthworms in Bioremediation the soils contaminated with chromium and cadmium.
Methods and Materials: The study batch experiments were conducted on the soil samples contaminated with chromium and cadmium. The initial concentration of chromium and cadmium in soil was 0.04 and 0.08 mg/g. 30 worms were added to each 500 g soil samples. Chromium and cadmium concentration in soil and in the body of worms was measured at two time periods of 21 and 42 days. ICP spectrometry we used to measure the concentration of chromium and cadmium. The data were analyzed using SPSS version 11.5 software.
Results: There was a significant correlation between the reduction of chromium and cadmium metals in the soils and the accumulation of chromium and cadmium metals in the worm’s body. A significant decline of chromium levels of the soil was observed in the days 21 and 42 during the study compared to the initial amount of 0.1 mg/g. On the other hand, chromium concentration of the soil decreased from 0.14 to 0.1 mg/g after 42 days.
Conclusion: said the research indicated that increased mortality of worms in the soil at a concentration of 0.08 mg/g of chromium, using the worms for bioremediation is not recommended. Although, this method is effective to remove cadmium from the soils having cadmium with concentrations of 0.04 and 0.08 mg/g but it needs further investigation.
