INVESTIGATION OF MAGNETOGENIC POLLUTANTS USING ENVIRONMENTAL MAGNETISM TECHNIQUES AND ATOMIC ABSORPTION ANALYSIS IN ABUJA METROPOLIS, NIGERIA
INVESTIGATION OF MAGNETOGENIC POLLUTANTS USING ENVIRONMENTAL MAGNETISM TECHNIQUES AND ATOMIC ABSORPTION ANALYSIS IN ABUJA METROPOLIS, NIGERIA
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Date
2018-07
Authors
JATTO, Solomon Sunday
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Abstract
In this study, the use of environmental magnetism techniques were applied both as a proxy and as a fast and time efficient method to investigate the spatial and vertical distribution of these magnetic grains within some road networks and soils of Abuja. Results from these methods where complimented with Atomic Absorption Spectrometer analysis of some roadside and urban soils of Abuja. The susceptibility test on rock samples and background soil samples within the study area show a low magnetic susceptibility values of about (40.0-120.0) x 10-5SI, with an average of about 112.0 x 10-5SI. The magnetic susceptibility results around the city of Abuja shows magnetic susceptibility enhancement of about (350.0-700.0) x 10-5SI. These values were dominant along the road networks and commercial areas at the surface to a depth of about 30.0cm in soil profiles. The susceptibility also decreases with increasing distance away from roads and commercial places and highly reduced in residential areas of Abuja. The 2D spatial distribution of magnetic susceptibility with depth reveals the pattern theses magnetic grains are distributed in the subsurface. From the profiles obtained, it is evidenced that the anthropogenic boundary is about 20.0-30.0cm of depth. From the field measurements it is observed that the frequency-dependence of magnetic susceptibility (χfd%) values are very low ( 0-5.0%) in most of the areas on the surface soil. Low frequency-dependence susceptibility values indicate that the magnetic properties are predominantly contributed by the coarse multidomian (MD) and stable single domain (SSD) grains of anthropogenic rather than super paramagnetic grains. From the surface map, low frequency-susceptibility is mostly observed in Wuse, Garki and Part of Central districts, these districts have high commercial activities and vehicle movement. In Asokoro district, the frequency-dependence susceptibility is mostly above 6%, this is due to the contribution of the super paramagnetic grains from the parent rocks. At a depth of 30.0 cm, the subsurface map clearly show frequency-dependence susceptibility greater than 6% in almost all the area with exception of few portions. This indicates that, super paramagnetic grains are the main contributors to the magnetic susceptibility at that depth. These super paramagnetic grains are mostly from pedogenic origin rather than anthropogenic source. From most of the samples, magnetite, pyrrhotite and hematite were evidenced in the susceptibility variation with temperature. Atomic Absorption Spectrometer analysis of these soil samples indicates the presence of Iron, Chromium, Lead, Zinc, Cadmium and Nickel in large concentration at the surface soil but decreases with depth. A strong positive correlation exists between concentration of Fe, Pb, and Cd with the spatial magnetic susceptibility measurements. From the research obtained in this study, high magnetic enhancements are attributed to vehicular/industrial activities within the areas and mostly deposited at the surface with the boundary depth between anthropogenic pollutants and pedogenic influenced susceptibility placed at 30.0cm. The frequency-dependence less than 5.0 percent predominantly found near road networks and most of the commercial areas at the surface but almost not all observed at the depth of 30.0cm. These indicate the contribution of vehicular/industrial emission to the deposition of these particles in the environment. The strong correlation between magnetic susceptibility and the concentration of Lead, Iron and Chromium indicates that these heavy metals contribute most of the high magnetic susceptibility observed around Abuja city. From the results obtained here, it is clear only magnetic method can be an effective and efficient tool to map out anthropogenic magnetic pollutants at the surface and at various depths.
Description
A DISSERTATION SUBMITTED TO THE POSTGRADUATE SCHOOL AHMADU BELLO UNIVERSITY (ABU), ZARIA NIGERIA IN PARTIAL FULFILLMENT FOR THE AWARD OF THE DOCTOR OF PHILOSOPHY IN APPLIED GEOPHYSICS DEPARTMENT OF PHYSICS AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
Keywords
INVESTIGATION,, MAGNETOGENIC POLLUTANTS,, ENVIRONMENTAL MAGNETISM TECHNIQUES,, ATOMIC ABSORPTION ANALYSIS,, ABUJA METROPOLIS,, NIGERIA,