Abstract
This study aimed at investigating the effect of consortia of three types of indigenous bacteria (Corynebacterium sp., Sphingobacterium gobiense and Kocuria flava) and earthworm (at 5 and 10 earthworms/kg soil) and their combination on the percentage removal of chlorpyrifos from chlorpyrifos contaminated soil in Sudan. Silt soil (Gerf soil) samples were mixed with known concentration of chlorpyrifos (450 mgkg-1) and incubated for various exposure periods (3, 7, 15 and 45 days) with the bacterial consortia alone, low and high densities of earth worm and their combinations under laboratory conditions. Remaining chlorpyrifos residues were measured by gas chromatograph equipped with flame ionization detector. Degradation rates and half-lives were found to follow biphasic model with an initial fast rate of disappearance followed by a second phase of slow disappearance. All treatments caused significant (PE‚0.05) effect on the degradation rates of chlorpyrifos compared to the control. The bacterial consortia alone induced the highest effect (73.83%) on the percentage removal of chlorpyrifos, followed by the bacterial consortia plus high density of earth worm (71.22%). Earth worm alone induced the least effect on the rate degradation of chlorpyrifos (64.27 and 66.49% for the high and low concentrations respectively). Based on this finding indigenous bacterial consortia represent a promising bioremediation agent for treatment of chlorpyrifos contaminated soil and therefore may deserve further investigation under different experimental conditions as well as validation of results under real contaminated soil conditions. Key words: Sudan, earthworm, indigenous bacteria, chlorpyrifos.
Highlights
Pesticides used in Sudan started in the late 1940s; the irrigated cotton and sugarcane schemes are the major sectors that use pesticides in Sudan
The annual consumption of pesticides in Sudan had changed over time from an average amount of 5000 Metric Ton (MT) before the 1990s to an average of 2000 to 3245 MT after that for many reasons; changes in agriculture policy, reduction in total area of production of cotton, the
Laboratory experiments were conducted at the Faculty of Agriculture, University of Khartoum, to study the degradation of soil contaminated with chlorpyrifos insecticide by two densities of earthworms (Lurbicus teristris L.) and consortia of three types of bacteria
Summary
Pesticides used in Sudan started in the late 1940s; the irrigated cotton and sugarcane schemes are the major sectors that use pesticides in Sudan. FAO with other stakeholders are currently engaged in formulating a project for the disposal of the obsolete stocks in the country (PIF, Project Identification Phase, unpublished). If such project was launched it will most likely focus on disposing of the obsolete stocks and the empty containers leaving the contaminated storage soil behind. Remediation of these sites seems to be the only feasible and attractive method available. Bioremediation using earthworms and consortia of bacteria should be evaluated
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