Investigating the effect of concentration of heavy metals in the soil on the bioaccumulation factor and Survival of Eisenia foetida

In recent years, earthworms have been used to clean soil contaminated with heavy metals. The aim of this study was to investigate the Bioaccumulation factor of earthworms in soils contaminated with heavy metals. The sewage sludge added to soil at levels of 0, 10, 20, 30, 40 and 50 tons per hectare. Earthworm (Eisenia foetida) was added to the polluted soil in order to study the effect of organic amendments. The total concentration and fractionation of heavy metals, the weight and mortality of earthworm were evaluated after 42 days. Sampling of earthworms was performed at eight weeks. The maximum accumulation of heavy metals by earthworms was found in 20 tons per hectare treatment. Bioaccumulation factor was more than 1 for the zinc and cadmium which shows the ability of earthworm (Eisenia foetida) for accumulation of these metals in the contaminated soil with heavy metals. The loss of weight was found for all treatment during the experimental period. Despite earthworm weight loss in all treatments, the highest number of deaths was observed in the control group which were free of sewage sludge. In general, the results showed that the use of earthworms could play an important role in clearing heavy metals in the soil.