October 2013 Vol. 1 No. 8

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Full Length Research Paper

Heavy metals concentration in tannery effluents, associated surface water and soil at Ejersa Area of East Shoa, Ethiopia

Aklilu Asfaw

Department of Natural Resource Management, School of Agriculture, Adama Science and Technology University, Adama, Ethiopia, P. O. Box 1888

E-mail: aklilplanet49@gmail.com or akhir@ethionet.et

Accepted October 07, 2013

Abstract

Discharges from tanneries are the major causes of environmental contamination in Ethiopia. A field experiment was carried out during 2012/2013 to assess the contamination of surface water (effluent) and soil by heavy metals. Surface water and soil samples collected from tannery industry located near Ejersa area of East shoa, Ethiopia from six different sample areas in triplicates from the tannery outlet up to Koka lake by dividing in S₀ (control, out of effluent point), S₁ (near the out let, upstream), S₂ (0.75 km), S₃ (1.50 km), S₄ (2.25 km) and S₅ (3.0km at Koka lake, downstream). The control soil samples were collected from the farm land at the vicinity placed out of the effluent points. The water samples were collected in plastic containers from five different points in 0.75 km distances. Soil samples also collected from the proximate of the effluent samples collected at the depth of 0-10 cm and 10-20 cm. The physico-chemical analysis for metallic parameters was determined using Graphite furnace atomic absorption spectrometer and atomic absorption spectrophotometer. The determined parameters were like: pH, Electrical conductivity (EC), Biological Chemical Demand (BOD), Chemical Oxygen Demand (COD) and Total Dissolve Solids (TDS) and for heavy metals namely: Cd, Cr, Cu, Fe, Pb, and Zn. The concentrations of analyzed parameters shows decreasing from S₁–S₅ except TDS, Cu, Fe and Zn, that was recorded less than the maximum allowable limits. Fe and Zn recorded more than the maximum allowable limit in all sampling sites. The concentrations of Cr in sample S₁, S₂ and S₃ in both depths recorded more than the maximum allowable limit. In the analysis result the concentration of Fe in all samples also recorded higher than the maximum allowable limit (50,000 mg kg-¹). The concentration of Cd, Cu, Pb and Zn in all samples recorded under the maximum the guideline for total soil. Generally the concentrations all metals observed decreasing from sample S₁(near the effluent out let,) S₅ (near the Koka lake) in both depths of 0-10 cm and 10-20 cm. The control soil sample in both depths were recorded less than the maximum allowable limit. The pH of soil samples in both depths were relatively constant throughout the sampling sites.

Keywords: Contamination, Ejersa, Ethiopia, Heavy metals, Soil, Surface water and Tannery.