Waste disposal has been a serious challenge in Nigerian cities especially as rural-urbanmigration intensifies. While overwhelming scientific evidences abound that global warming istaking a significant toll on the Earth and its occupants, Nigeria is striving to join other countries in mitigating the effects. One way of intensifying the mitigation is through appropriate and environmentally-friendly waste disposal and management. All manners of wastes are usually disposed of without any serious consideration for the environment. Open incineration is a very common means of waste disposal in developing countries. In spite of the meager contributions of this group of nations to industrial growth, open incineration method of waste disposal hugely adds to the problem of climate change. It has been observed that there is the tendency to dispose wastes indiscriminately and in an uncoordinated manner, thereby resulting in unhealthy environment. In this study, a satellite imagery covering Akure and its environs was analysed using ArcView GIS 3.2a to develop a user interface for selecting a waste disposal site with special emphasis on geologically suitable conditions. This study aims at demonstrating the potential and efficiency of using GIS in selecting sites for the storage of biodegradable solid wastes. Results show suitable areas where landfill sites can be safely and aesthetically located within the study area, putting urban growth rate into consideration.

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Salt-water intrusion was reported to be prevalent in some parts of Lagos Island. To addressthis problem, sub-surface geological mapping of the affected area was carried out usinggamma ray and resistivity logs, ditch cutting samples, and geophysical logs of some existingwells in the area. The work aimed at determining the probable origin of saline water as wellas assessing the depth to the saline/fresh water interface. The suite of logs used facilitated thedelineation of the aquifers and the saline/brackish and fresh water interfaces. A complexlithology of alternating sequence of sand and clay deposits was observed up to a depth ofabout 270m. Also, seven aquifer horizons were delineated. The depths ranges to the tops ofthese aquifers are: 3-10m; 40-70m; 60-100m; 110-140m; 150-180m; 178-210m and 212-240m, corresponding to aquifer thicknesses of 15-25m, 15-30m; 10-45m; 20-40m; 10-42m;10-30m and 20-45m respectively. It is also observed that brackish/saline water occurrence isa major feature of the first four aquifer horizons; this implies that freshwater can only beencountered below 126m, unlike on the Lagos mainland where fresh water is encounteredfirst and at a shallower depth. While it is apparent that the aquifers are highly susceptible tosalt-water pollution, anthropogenic and biogenic influences, however, water contained in theupper four aquifers are probably lagoonal in origin and must have retained the salinity thatcharacterized lagoonal environment, while water in the last three aquifers are of fluvialorigin.

A geophysical study of Iwaraja segment of Ifewara-Zungeru fault zone in Nigeria was conducted using remote sensing and geoelectric techniques to analyse and identify the structural elements and fractures. The Omo Forest Reserve area, Abata Egba (along Ondo-Ife highway), and Iwaraja fault zones were selected for the study. Wenner electrode profiling was undertaken at electrode separations of 10, 20 and 30 m on diplines perpendicul-ar to trend of the fault, while Schlumberger electrode configuration was adopted for vertical electrical sounding on points delineated by resistivity profiles. At Omo Forest Reserve, 3 fault signatures of falling resistivity profi-les in uniformly high resistivity environment were identified. Deep fracturing manifested in consistently decrea-sing resistivity values at large electrode separations. At Olode area, 4 signatures were identified. The profiles at Iwaraja area showed the net resistivity decreased in Western direction. The overburden materials were variably thick and underlain by bedrock that had been partially weathered and fractured, but were not infinitely resistive as usually observed in crystalline Precambrian basement complex environment. The study area was characteriz-ed by a series of faults, which were oriented in the North North East - South South West ((NNE-SSW) directio-ns, and inclined towards the East.

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