Application of Magnetic Gradiometry, Magnetic Susceptibility and Electrical Resistivity Tomography in the Characterisation of the Sunyani Municipal Waste Disposal Site
Abstract
Areas that surround unlined solid waste disposal sites depict high tendencies of being
contaminated with leachate emanating from the waste deposits that in ltrate into the
ground. For that reason, this research seeks to highlight and bring to the attention of
city authorities and interest groups the alarming levels of the anthropogenic impact of
dumped solid waste on the environment especially, when it pertains to the ground and its
water resources using integrated geophysical methods. The integration of three geophysical
methods comprising of magnetic gradiometry, magnetic susceptibility and electrical resistivity
tomography has helped to characterise the SMA waste disposal site mainly due to the unlined
and heterogeneous nature of the waste deposit. The results of both magnetic susceptibility
and gradiometric methods displayed in anomaly maps clearly de ned the physical boundaries
of the waste deposit with an approximate area extent of 82; 650 m2 which is characterised
by high magnetic susceptibilities between 426 105 SI and 9890 105 SI. Also, an average
magnetic intensity value of 32230:74 nT was recorded over the area with values generally
greater than the average measured over the main waste body. They also revealed high
magnetic anomalies sporadically distributed outside the main waste boundaries which are
attributed to indiscriminate deposition and uncontrolled nature of the waste. Similarly, the
ERT sections also revealed zones of leachate contamination and accumulation just beneath
the waste body and migration pathways for leachate were also delineated with low resistivity
signatures up to 43:9
:m. In spite of the success reported herein with the ERT, the research
also revealed that the ERT is less e ective in estimating the thickness of the waste deposit
due to leachate in ltration into the ground beneath it that masks the resistivities of the
top level ground and makes it indistinguishable from the waste body. Having estimated an
approximate waste thickness of about 5 m using ERT, the volume of waste expected to be
reclaimed from the site for remediation purposes is estimated at 413; 250 m3.
Description
A Thesis Submitted to the Department of Physics, Kwame
Nkrumah University of Science and Technology in partial
ful llment of the requirements for the award of the degree
of Master of Philosophy in Geophysics,