Bioremediation of the Soils Contaminated with Cadmium and Chromium, by the Earthworm Eisenia fetida

Abstract

One of the most important environmental problems in the world is the soils contamination by heavy metals in the industrial areas, and especially the contamination of the agricultural lands. The use of earthworms to bioremediate the soils results in reducing the pollutants concentration through a bioaccumulation mechanism on the contaminants in the earthworm's body. Hence, the present study aimed to prove the biological effectiveness of Eisenia fetida earthworms in bioremediation the soils contaminated with chromium and cadmium. Concentration of chromium and cadmium pollution in soil was determined to be 0.04 mg/g and 0.08 mg/g respectively. 30 worms were added to 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. To measure the concentration of chromium and cadmium we used ICP spectrometry. Software in usage was SPSS version 17. 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 initial amount of 0.1 mg/g. on the other hand chromium concentration of the soil decreased from 0.14 mg/g to 0.1 mg/g after 42 days. Comparison of mortality in two different time periods showed that by passing the time and by increase in soil chromium and cadmium concentrations the death toll of worms rises. The increased mortality of worms in the soil at a concentration of 0.08 mg/g of chromium, say that using the worms for bioremediation is not recommended at such concentration of chromium but using the worms for the removal of cadmium at concentrations of 0.04 mg/g and 0.08 mg/g in the soil is recommended. Keywords: Chromium; Cadmium; Eisenia fetida; bioremediation ResumoUm dos problemas ambientais mais importantes do mundo é a contaminação dos solos por metais pesados nas áreas industriais e, principalmente, a contaminação das terras agrícolas. O uso de anelídeos para biorremediar os solos resultam na redução da concentração de poluentes por meio de um mecanismo de bioacumulação dos contaminantes no corpo dos anelídeos. Assim, o presente estudo teve como objetivo comprovar a eficácia biológica dos anelídeos Eisenia fetida em biorremediação dos solos contaminados com cromo e cádmio.A concentração de cromo e cádmio em solo poluídos foi determinadao como sendo 0,04 mg/g , e de 0,08 mg/g respectivamente. Trinta anelídeos foram adicionados a 500 g de amostras de solo. A concentração de cromo e cádmio no solo e no corpo dos anelídeos foi medida em dois períodos, de 21 e 42 dias . Para medir a concentração de cromo e cádmio usamos espectrometria de ICP . O software em uso foi o SPSS versão 17. Houve uma correlação significativa entre a redução dos metais cromo e cádmio nos solos e da acumulação de metais de cromo e cádmio no corpo dos anelídeos. Também houve uma diminuição significativa na concentração de crom...

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“…Cunninghamella elegans was reported as promising organism against heavy metals released by textile wastewater 49 . Recently cadmium and chromium metals are checked for their bioremediation with the help of Earthworm Eisenia fetida who showed the tolerance up to 0.06 and 0.14 mg/l respectively 50 . Among the wide range of microorganisms used for bioremediation, there are many fungal strains that are used for the purpose.…”

The Roles of Earthworms in Agroecosystem

“…The use of earthworms on soil bioremediation is a biological method, so that the pollutant concentrations in the soil are reduced through bioaccumulation mechanisms in the body of the earthworms [30]. The most important applications of these organisms consist of the treatment in the waste management process acting as a biosorbent in soil detoxification and bioremediation out of heavy metals, persistent hydrocarbons and some organic pesticides.It also causes the population growth of the beneficial microorganisms in the soil and strengthen their enzyme activities as well as improve the soil quality and agricultural development [31].…”