Browsing by Author "Asiedu, Obed"
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- ItemImpact of land use on nematode assemblage in three agro-ecological zones of Ghana(NOVEMBER, 2015) Asiedu, ObedUnderstanding the types of biological and nutritional degradations is critical in developing practical soil health management strategies in Ghana. To understand the types of biological and nutritional degradations in disturbed and undisturbed landscapes; and the impact of change in land use on soil physicochemical and biological properties, 90 farms (maize and tomato agro-systems) and nine undisturbed sites were sampled in 2012 and 2013 from the semi-deciduous forest, forest-savannah transition and guinea savannah agro-ecological zones of Ghana for laboratory investigations. Farmers were also interviewed to ascertain prevailing cultivation practices in the study areas. This study used nematode assemblage analysis to determine ecological disturbance (PPI, MI and ΣMI), community diversity (H′, λ, N0 and N1), and soil food web structure (BI, CI, SI and EI). Samples were also analysed for soil pH (H2O), organic carbon (OC) total nitrogen (%N), available nitrogen (NO3-+NH4+), P2O5, K2O5, Ca2+, Mg2+ and effective cation exchange capacity (ECEC) to evaluate the levels of physicochemical degradations. Results from the laboratory analysis of 396 and 99 samples for physicochemical and biological properties respectively, were analysed by Residual Maximum Likelihood (RELM) Linear Mixed Model (VSN International, 2011). Results from the study show that the soils were inherently poor, in terms of plant nutrients and naturally fragile, in terms of soil food web condition which were further worsened by cultivation practices. Most farmers continuously cultivated their fields for over 9 years in the Semi-Deciduous Forest and Forest-Savannah Transition zones yet their cultivation practices, were not directed towards maintaining good soil health. Soils from undisturbed sites of all the three agro-ecological zones recorded significantly higher maturity index (ΣMI) than soils from maize and tomato fields, indicating that the current cultivating practices are disturbing the soil’s ecosystem.
- ItemRemoval of Fluoride from water using Surfactant Modified Synthetic Zeolites(MAY, 2016) Asiedu, ObedAlthough fluoride is beneficial in preventing dental caries, long term consumption of drinking water contaminated with high levels of fluoride (above 1.5 mg/L) could cause teeth mottling. Extreme concentrations may result in severe health conditions such as skeletal fluorosis and even crippling fluorosis. The removal of fluoride from water using synthetic zeolites modified with a cationic surfactant was studied using a batch system. The zeolites employed as adsorbents in the study, zeolite Na-LSX and zeolite Na-LTA, were synthesized from locally available clay materials. A third synthetic zeolite nicknamed zeolite ZR (containing both Na-LSX and Na-LTA phases) was synthesized using only reagent-grade chemicals. Hexadecyltrimethylammonium (HDTMA) bromide surfactant was used to modify the zeolites in order to improve their fluoride removal potential. The X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and Fourier Infrared Spectroscopy (FTIR) techniques used to characterize the zeolites confirmed the surface modification by the HDTMA surfactant molecules. Moreover, the characterization confirmed that the structural integrity of the zeolites remained intact after the surface modification. Varying process conditions including surfactant dosage, modification reaction time and pH of the batch processes were investigated to determine the optimal conditions for fluoride uptake. From the batch experiments, fluoride adsorption was found to be highly pH dependent. Zeolite Na-LSX was found to be the best performing adsorbent at a pH of 5.5. Increase in solution pH from 5.5 to 7.5 significantly reduced fluoride removal efficiency (86 % to 15 %). No appreciable removal was observed above pH of 7.5. The best performing HDTMA surfactant dosage was found to be 5 g surfactant/L for all the zeolite types. Fluoride removal performance of modified zeolites increased with increasing modification reaction time from 2 hours until 24 hours, beyond which performance relatively declined.