Journal of Food, Agriculture and Environment

The bioremediation potential of earthworms (Oligochaeta: Lumbricidae) in a soil polluted with heavy metals

Author(s):

Mădălina Iordache*, Iacob Borza

Recieved Date: 2011-12-20, Accepted Date: 2012-04-28

Abstract:

The aim of the study was to distinguish the earthworms’ capacity to remediate the quality of soils polluted with heavy metals (Zn, Cu, Mn, Pb) as a result of using the swine residual water in agriculture (50 m³ ha^-1). The study has been conducted in a Chernozem (FAO System), in a culture of Zea mays L. The collected data consisted of soil analyses and tissue analyses to establish the heavy metal uptake by earthworm species. Determination of the heavy metal contents of soil has been realized in two depth intervals: 0-10 cm and 10-20 cm, through the method of flame atomic absorption spectrometry. Earthworm extraction was done using formaldehyde according to the methodology in force at six months since the residual water has been applied on soil. Both for earthworm number and earthworm weight there were significant differences (p<0.05) between the values recorded in controls and  treatments, i.e. the earthworm number considerably increased in the variants fertilised with swine residual water and also the earthworm weight, which confirm the earthworm preference for the organic matter provided by the residual water. Also there were significant differences (p<0.05) between the three analyzed earthworm species regarding the accumulation process of the investigated microelements and, among them, Lumbricus rubellus showed in its tissues the lowest concentration of microelements and Allolobophora rosea the highest concentrations. There were also much lower concentrations of the studied microelements in the earthworm tissues as compared with the adjacent soil in all analyzed species, and among them there was recorded the lowest content of heavy metals in Lumbricus castaneus. This aspect and also the fact that this species has been the best represented as numeric abundance in the experimental soil confirm the good capacity of this species to tolerate the presence of the heavy metals in soil and to metabolize them with the soil ingestion within the feeding process. The results of this study support the idea claiming the earthworms bioremediator potential of the soils polluted with heavy metals, as a possibility to restore their quality by maintaining in appropriate levels the earthworm populations in the agricultural lands. These findings also come to sustain the specialization of this role on earthworm species. 

Keywords:

Bioremediation, heavy metals, zinc, copper, manganese, lead, earthworms, residual water, Lumbricus rubellus, Lumbricus castaneus, Allolobophora rosea

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Journal: Journal of Food, Agriculture and Environment
Year: 2012
Volume: 10
Issue: 2
Category: Environment
Pages: 1183-1186

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