Speciation of chromium in soils near Sheba Leather Industry, Wukro Ethiopia

A study on speciation of chromium in soils near Sheba Leather Industry was performed by Flame Atomic Absorption (FAAS) after selective extraction of Cr(VI) using the EPA 3060A method, and oxidizing the Cr(III) residue in the soils with HNO3 and H2O2. The extraction method was evaluated using the spiking method with satisfactory results (recoveries>95% and RSDs<5%). The limit of detection (LOD) for Cr(VI) based on three times the standard deviations of the blank (for n=5) was 0.56 µg g(-1). Statistical evaluation indicated that the comparison of the sum of the concentrations of chromium species to that of the total concentration of chromium do not show any difference at 95% level of confidence. Besides, no statistically significant difference at 95% confidence level was observed between the UV-vis spectrophotometry and FAAS results for Cr(VI). However, it is observed that selective extraction of Cr(VI) using EPA 3060A and subsequent determination by FAAS is simple and faster compared to the other method. Furthermore, for comparison and as control two soil samples collected from a distance of about 2 km from the main Industry and effluent stream. The results indicate that higher total chromium content was observed in soils collected from the target area. Nevertheless, the maximum concentrations of Cr(VI) found in soil samples collected around Sheba Leather Industry was 9.9 µg g(-1) and are within the acceptable level of 10 µg g(-1) in accordance with the WHO.