Mineralogical and sorption characterization of lateritic soils from Southwestern Nigeria for use as landfill liners.

Lateritic soils are prevalent in the tropical regions, and they are used for various construction purposes including landfill liner applications. However, their contaminant attenuation potentials through sorption and the influence of parent rocks on this property are poorly understood. This study investigates lateritic soils from southwestern Nigeria as barrier to leachate migration in engineered landfills and related waste containment facilities. The lateritic soils were investigated through X-ray diffraction (XRD), geochemical analysis and batch equilibrium sorption test to evaluate the competitive sorption of Mn, Cd, Pb, Cu and Cr which are common in landfill leachates. The XRD analysis shows that the kaolinite and dickite are the dominant clay minerals present in the lateritic soils, implying low desiccation cracking and low shrink-swell behaviour. The geochemical analysis indicate that the lateritic soils are silico-alumino-feruginuous with average major oxide composition of SiO2, Al2O3and Fe2O3 of 50.86 wt%, 29.83 wt% and 14.29 wt%), respectively. Additional oxides with lower abundance include TiO2 (1.55 wt%), Na2O (0.01 wt%), MgO (0.36 wt%), CaO (0.15 wt%) and K2O (1.52 wt%). The lateritic soils contain trace amount of heavy metals with average concentrations of Cd (0.039 ppm), Pb (0.548 ppm), Cr (0.189 ppm), Cu (0.964 ppm), Mn (0.145 ppm). Furthermore, the low abundance of sodium oxide in the lateritic soils indicates that the soil particles are not susceptible to dispersion while the presence of considerable amount of iron and manganese oxides signify its good heavy metal retention. The batch equilibrium sorption analysis shows that the lateritic soils derived from granite-gneiss and charnockite exhibit better sorption potential than those derived from schist and quartzite. This high sorption capacity is intricately related to the presence of goethite in the soils. The sorption of these trace metals onto the lateritic soils follows Langmuir type isotherm and these isotherms deviate from the corresponding desorption isotherms to different degrees indicating various extents of hysteresis. The sorption hysteresis indices for these trace metals range from 0.63 to 0.99 and imply that the trace metals may re-leached to the surrounding soils and groundwater. Thus, it is recommended that landfill liners utilizing these lateritic soils are design as a composite containment facility by integrating compacted soil liners, leachate collection systems and monitoring networks to ensure effective environmental protection.

Antimicrobial activity of bark extracts of Bridelia ferruginea (Euphorbiaceae).

Water and ethanol extracts of Bridelia ferruginea were examined for phytochemical and antimicrobial properties. The extracts, which were tested at a final concentration of 5 mg/ml, produced in vitro antimicrobial activities in assays against hospital strains of Staphylococcus aureus, Candida albicans, Staphylococcus epidermidis, Escherichia coli, Streptococcus lactis, Proteus vulgaris, Proteus mirabilis, Streptococcus pyogenes and Klebsiella sp. The zones of inhibition produced by the extracts in agar diffusion assays against the test micro-organisms ranged from 4 to 20 mm, while the chloramphenicol antibiotic control produced zones that measured 15-36 mm. Preliminary phytochemical analysis of the plant extracts showed the presence of phenols and tannins. Sesquiterpenes, anthroquinones, and saponins were not detected in the extracts. The Gram-negative bacteria appeared to be more susceptible (4-20 mm) to the antimicrobial effect of the extracts than the Gram-positive organisms (4-18 mm).

Bactericidal properties of crude extracts of Mitracarpus villosus.

Mature leaves and inflorescence of Mitracarpus villosus, collected from Niger State, Nigeria, were shade dried over a period of 5 days, ground into fine particles in a Waring blender and extracted individually with hot distilled water and 95% ethanol. The crude extracts obtained were tested for their in vitro antibacterial activities using agar diffusion and tube dilution techniques. The extracts produced zones of inhibition (8-23 mm) against Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Streptococcus faecalis, while Pseudomonas aeruginosa and Proteus mirabilis were not inhibited. The minimum inhibitory concentrations (MIC) of the effective extracts were in the range 0.06-8.0 mg/ml, while the minimum bactericidal concentrations (MBC) were in the range 0.06-32.0 mg/ml. The ethanolic extracts appeared to exert more inhibitory action against the bacteria than the hot water extracts.

Antifungal activities of crude extracts of Mitracarpus villosus (Rubiaceae).

Extracts of Mitracarpus villosus leaves and inflorescences were investigated individually for in vitro antifungal activities by agar-diffusion and tube-dilution techniques. Ethanolic extracts produced definite antifungal activities against Trichophyton rubrum, Microsporum gypseum, Candida albicans, Aspergillus niger and Fusarium solani. The aqueous extracts and the glycerol vehicle control did not inhibit any of the fungi tested. The zones of inhibition produced by the ethanol extracts ranged from 10 to 20.5 mm while ketoconazole control ranged from 9 to 19 mm. The minimum inhibitory concentration of the extracts ranged from 0.50 to 4.0 mg/ml while their minimum fungicidal concentration values ranged from 1 to 8 mg/ml. These results indicate that the extracts were fungistatic at lower concentrations and fungicidal at higher concentrations.

Some factors affecting mother-child relationships following low birthweight delivery in a Nigerian sociocultural environment.

Twenty mothers with low birthweight babies, cared for in neonatal unit and kept in incubators (as index group) and 20 mothers with full-term babies (as control group) were studied to determine the extent of maternal separation and deprivation following delivery and the effects of these on mother-child relationships. The population was prospectively sampled and an interview method using a structured questionnaire, was adopted to obtain the information for the study. The result showed a delayed post-partum contact, negative reactions and some delays in maternal attachment in mothers of premature infants. Nevertheless, some degree of adjustment in the mother-child relationship, as shown by some positive perceptions of the infants, took place 6 months after leaving hospital. Other social and cultural factors that may contribute to the negative reactions of the mothers to premature delivery are highlighted.