Changes due oil exploration and production have occurred within Cawthorne Channel area from 1986 to 2003. Three satellite image datasets consisting of Landat TM acquired On 19th of December 1986; SPOT 4 of 16th December 1998 and Landsat ETM of 8th January 2003 were used for the study. The satellite image datasets were processed using ISOclass unsupervised classification to generate the various landcover classes. Baseline information was extracted from Natural Colour Composites, LandCover Classification and Normalized Difference Vegetation Index (NDVI) composites, for the three epochs. The statistics of the various classes were then generated for each processed dataset. These statistics were further analyzed to identify the change patterns. Change analysis also involved processing and graphically identifying various landcover types and the changes that have occurred over the years. Normalized Difference Vegetation Index was performed using NDVI processing algorithm for the three epochs to adduce the possible reasons for such changes. From the analysis carried out, it is evident that the landcover classes changed across the three epochs. The water class covered an area of 80.12 km2 in 1986: 85.05 km2 in 1999 and 76.64 km2 in 2003. High mangrove covered an area of about 32.64 km2 in 1986, 77.72 km2 in 1998 and 110.41 km2 in 2003. This could be due to the decrease in low mangrove. Low mangrove covered an area of about 146.96 km2 in 1986, 100.66 km2 in 1998 and 75.41 km2 in 2003. Wet mangrove covered an area of about 25.46 km2 in 1986, 18.57 km2 in 1998 and 19.71 km2 in 2003. The increase in 2003 could be due to the presence of water within the mangrove. Settlements, sand and cloudcover covered an area of about 1.85 km2 in 1986, 5.03 km2 in 1998 and 4.86 km2 in 2003. The decrease in 2003 after the increase in 1998 might be attributed to sand reduction and vegetation growth. Also, orthometric elevation changes are carried out using Global Positioning System (GPS) to ascertain areas where elevation changes (land subsidence) have occurred. The rate of elevation changes (land subsidence) in the study area is at each location of levelling. It varies from 66.67 mm yr-1 to 200.00 mmyr-1, and an average of 86.00 mmyr-1. The elevation changes in this Field are localized only where the measurements are located, and are mainly in river and drenched channels and slopes caused by erosion. This conclusion regarding minimal impacts of hydrocarbon production on elevation changes is based only on orthometric height difference, and not on the reservoir stress changes. Knowledge of the present distribution and area of landcover, elevation changes, as well as information on their changing proportions, is needed by legislators, planners, and State and local governmental officials to determine better land use policy, to project transportation and utility demand, to identify future development pressure points and areas, and to implement effective plans for regional development.
Most problems of soil pollution are associated with large amount of heavy metals deposited on it through disposed waste. This study was carried out to assess heavy metals (Fe, Zn, Pb, Cu and Cd) in soil samples around metal scrap dumps at Araromi vicinities of Akure South Local Government, Ondo State, Nigeria, in order to assess the effects of the dumps on the soils. A total of thirty nine soil samples were taken for laboratory analysis. The soil samples were collected using hand driven stainless steel auger at various depths at the dumpsite, and at various horizontal distances away from the dumpsite including human settlements close to the dumpsite. The heavy metals in the waste soils samples was sequentially extracted and quantified, using atomic absorption spectrometry (AAS). The findings revealed that Iron, Lead, Cadmium and Copper with concentration of 611.7 mg/kg, 200.8 mg/kg, 4.9 mg/kg and 103 mg/kg respectively, all exceeded National Environmental Standards and Regulation Enforcement Agency (NESREA) acceptable limit and index of 2007, except Zinc 229.2 mg/kg The order was Fe>Zn>Pb>Cu>Cd for the study area. A consistent trend showing a decrease in the concentration of toxic metals was observed at increasing depths and distances from dumpsite, which suggest a discontinuation or mitigation of anthropogenic input on the environment.
This study aimed to determine the major elemental oxides in the exposed rock types of the study area, classify these rocks on this basis and establish the relationships between the various elemental constituents and hence predict the mode of origin of the rocks. The study area falls within the south-western part of the reactivated Basement Complex of Nigeria. Field work to collect samples lasted about 21 days. About 13 fresh rock samples from the igneous suite, which range from fine to coarse grains, were collected. Thin sections were cut and petrographic studies carried out, also geochemical analysis of the samples was done at the Activation Laboratories, Ontario, Canada. Field investigation clearly revealed two distinct suite of rocks, which characterises the study area. These are the migmatite gneiss suite and the igneous suite. The migmatite gneiss suite, which consists of the migmatite gneiss and the banded gneiss, is the basement rock of the terrain. While the igneous suite, which is mainly the rocks of the older granitoids, intrude the older migmatite gneiss suite. Petrographic studies showed these igneous suites as having the major igneous rock forming minerals – that is quartz, biotite, plagioclase, orthoclase, and microcline. Also present was zircon and other accessory minerals. Geochemical studies of these rocks enabled their classification into granites, granodiorites, syenites, syenodiorites, and diorites using the plot of Na2O + K2O versus SiO2. Further geochemical evaluation revealed these felsic and intermediate rocks as peraluminous, non-oceanic in origin, ferroan and magnesian mixed, and alkali rich rocks. They were also grouped as within plate granites. A dual source of origin was finally proposed for the rocks based on their geochemical behaviour.
Use of enrichment, ecological risk and contamination factors with geo-accumulation indexes were employed to evaluate the Content of Cd, Cu, and Ni in the soils around Ameka mining area, South of Abakaliki, Nigeria. Ecological risk indices and contamination indexes namely, enrichment factor, geo-accumulation index, degree of contamination, contamination factor and pollution load index were used in the assessment of level of metal contamination in the soils around Ameka mining area, Southern Benue Trough Nigeria. Fifteen (15) soil samples were collected at the depth of 5 cm from various locations for laboratory analysis. From the results, the variation of Cu, Zn and Cd concentrations is controlled by anthropogenic intense agriculture activities. For all sites, concentrations of heavy metal in the soils do not exceed the permissible US EPA standard. From the results the pollution load index values ranged from 0.19 to 0.86 indicating that the soils were moderately contaminated. As for the single-factor pollution, the average values ranging from 0.25 to 6.52 indicate that the potential ecological risk of the metals in the three sampling sites all has low ecological risk level. The ecological risk assessment revealed the possibility of soils being not polluted. The significant spatial variation recorded in the concentrations of some parameters used in characterizing the sediment quality is a reflection of impacts of anthropogenic activity on quality of the mining area. The geo-accumulation index also revealed that the sediments at all stations were practically uncontaminated by heavy metals. The results of all the contamination indexes used agreed well in explaining the contaminated levels and possible sources of the metals present in the mining area samples. This study recommends an immediate plan for analysis of the quality of drinking water and some staple crops grown in the area to determine the levels of these noxious metals and uptake by plants, to be followed by a comprehensive mitigation plan.
Nowadays, Web-based Land Information System is important to learn about the use of Geographic Information Systems and software for our profession. Modern technologies like geo-data processing, earth observation data processing and analysis are needed for Sri Lankan young researchers and students. This research work is dedicated to develop a land information system of Nintavur DSD. One task of the work is to establish a land information database which is based on an Open Source Geographic Information System. Work is starting with acquisition of existing geo-data and information, qualification, maintenance, utilization and transferring of data from Nintavur DSD. The establishment of a land information system for Nintavur DSD will contribute to the National Land Information System of Sri Lanka. The study demonstrates that Land Information Systems can be developed using GIS software as e.g. QuantumGIS, and the Open Source database management system Postgre SQL /Post GIS and Arc GIS.