Human exposure to heavy metal toxicity has been linked to the consumption of vegetables grown on polluted soils. The goal of this study was to see how much heavy metals accumulated in the soil, irrigation water, and vegetative sections of lettuce and cabbage planted in Wawan Rafi, Jigawa State, Nigeria. The concentrations of potentially harmful metals in soil, water, and crops are in the order Mn > Pb > Zn > Ni > Cd > Cu, except for lettuce, where Pb was found to be greater than Mn. Furthermore, the majority of the hazardous elements analyzed were below the allowed limit. Nevertheless, the presence of high levels of metals revealed evidence of contamination, which was attributed to human activities. The potential ecological risk index values for lettuce and cabbage are 86.488 and 225.463, respectively, and both are considered safe because the RI values for both lettuce and cabbage are below or within the range of 200 ≤ RI ˂ 400. This implies consumption of these vegetables may not pose a high health risk to the local public when individual heavy metal is considered, but the risk could multiply when all of the heavy metals are considered together.

The environmental problems caused by the excessive usage of fossil fuel, prompted the need for an alternative source of energy. Renewable energy from biodiesel is one of the most promising substitutions of fossil fuel due its environmental-friendliness. In the present work NaOH-modified γ-alumina heterogeneous base catalysts were prepared using wet impregnation method, and characterized by Nitrogen Adsorption Analysis (BET), Fourier Transform Infra-Red (FTIR), X-Ray Powder Diffraction (XRD), basic back titration, and Temperature Programmed Desorption-CO2 (CO2-TPD). The catalysts were tested for the transesterification of rice bran oil with methanol, and the biodiesel product characterized by Fourier Transform Infra-Red-Attenuated Total Reflection (FTIR-ATR) and Nuclear Magnetic Resonance Spectroscopy (NMR) analyses. Catalyst synthesize with 50% NaOH was found to have the highest basic sites and when applied for the transesterification of rice bran oil it gave the highest yield of 81.2%. The high catalytic activity is attributed to the formation of NaAlO2 that is believed to contribute to the basicity of the catalyst.

Mesoporous c-alumina was synthesized by acid extraction of alumina from Kano kaolin using polyoxyethylene (40) stearate (PS) as a surfactant. The synthesized alumina was characterized using X-ray diffraction (XRD), N 2 adsorption-desorption, Fourier transform infra-red spectroscopy (FTIR), field emission scanning electron microscopy attached with energydispersive X-ray (FESEM-EDX), and thermogravimetric analysis (TG-DTA). High-purity mesoporous c-Al 2 O 3 with relatively large surface area and narrow pore size distribution was obtained. For comparison the preparation in the absence of surfactant was also carried out. In this study mesoporous alumina was also obtained even in the absence of the surfactant, however, the addition of PS resulted in modification on physical properties and morphology. The surface area increased from 169.0 m 2 /g to 222.7 m 2 /g, pore size from 4.4 nm to 5.6 nm and pore volume from 0.32 cm 3 /g to 0.45 cm 3 /g. Crystallite size was also found to increase from 2.68 nm to 3.33 nm after the addition of the surfactant. ª 2015 Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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