Trace metals in selected fish species from lakes Awassa and Ziway, Ethiopia

Samples of two fish species (Tilapia Oreochromis niloticus and Catfish Clarias gariepinus) were collected from six sampling stations in Lakes Awassa and Ziway, Ethiopia. The edible portion was separated and placed in a freeze-drying unit until constant mass was obtained. The calculated moisture content of the two fish species obtained from six sites in the two lakes varied from 79.3%–82.5%. An optimal procedure for mineralizing 2.0 g dried and powdered fish muscle required 7.0 hours and consumed 8.0 mL of 70% HNO3, 2.0 mL of 98% H2SO4 and 10 mL of 35% H2O2 under reflux. The accuracy of the optimal procedure was checked by digesting a mixture of standard solutions or spiked fish samples and subsequently determining percent recovery. Recoveries varied from 98.5%–123% in a mixture of standard solutions and from 92.5%–120% in spiked fish samples. Trace metal concentrations in the two fish species were measured by flame atomic absorption spectrometer employing an external calibration graph. Concentrations of trace elements in the fishes ranged (µg element/g dry mass): Zn 23.04–30.92; Fe 19.25–59.75; Cu 1.03–2.78; Mn 1.54–4.46; Cd < 0.24; Pb < 1.66; Ni < 0.99; and Co < 0.71. The maximum levels of trace metals found in edible portion of fishes were far below the thresholds. Hence, without regard to bioavailability, O. niloticus and C. gariepinus may be considered safe for human consumption relative to the analyzed elements. Key words/phrases: Bioindicators of lake pollution, Clarias gariepinus, Oreochromis niloticus, trace metals SINET: Ethiopian Journal of Science Vol.26(2) 2003: 103-11

Sugarcane Bagasse and Orange Peels as Low-Cost Biosorbents for the Removal of Lead Ions from Contaminated Water Samples

The pollution of water by lead (Pb(II)) constitutes a substantial threat to the environment and subsequently to animals and humans. In this study, the efficacy of sugarcane bagasse (SCB) and orange peels (OPS) have been investigated as potential low-cost biosorbents, individually and in a homogeneous combination for the removal of Pb(II) from simulated and real water samples. Biosorbents were characterised using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) coupled to energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), powder X-ray diffraction (pXRD), a zeta potential analyser, and the Brunauer&ndash;Emmett&ndash;Teller (BET) method. Batch adsorption studies were explored under several experimental conditions to optimise the removal efficiency of Pb(II) ions from artificially contaminated aqueous solutions. The pH study revealed optimum removal efficiencies of Pb(II) at pH 7, for SCB and OPS. The optimum contact time for SCB and OPS individually and a homogenous mixture was 60, 120, and 120 min, respectively. The study also revealed that the optimum biosorbent dosage was 0.2, 0.17, and 0.2 g for SCB, OPS, and the homogenous combination of SCB and OPS (1:1). Optimum experimental conditions could achieve up to 100% removal efficiencies for 10 and 20 mg/L of Pb(II) using SCB and OPS, respectively. The potential of the homogenised combination of biosorbents demonstrated 100% removal efficiencies for 10 mg/L of Pb(II). The removal of 10 mg/L of Pb(II) in real water samples remained at 100% for biosorbents individually and the homogenised combination. The reusability performance of SCB, OPS, and the homogenised combination of SCB and OPS presented Pb(II) removal efficiencies above 70% for three adsorption&ndash;desorption cycles