ENVIRONMENTAL MINING IMPACT ON SOILS AROUND THE ABANDONED KGWAKGWE ...

369 Pages·2010·16.98 MB·English

ENVIRONMENTAL MINING IMPACT ON SOILS AROUND THE
ABANDONED KGWAKGWE MANGANESE MINE, BOTSWANA

Ekosse Georges-Ivo Ekosse

Thesis submitted in fulfillment of the requirements for the
Degree

Doctor of Philosophy in Soil Mineralogy

Discipline of Soil Science
School of Agricultural and Environmental Sciences
University of the North
Sovenga
South Africa

April 2004
ENVIRONMENTAL MINING IMPACT ON SOILS AROUND THE
ABANDONED KGWAKGWE MANGANESE MINE, BOTSWANA

Ekosse Georges-Ivo Ekosse

Thesis submitted in fulfillment of the requirements for the
Degree

Doctor of Philosophy in Soil Mineralogy

Discipline of Soil Science
School of Agricultural and Environmental Sciences
University of the North
Sovenga
South Africa

Supervisor: Prof. P. Fouche

April 2004

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DECLARATION OF INDEPENDENT WORK

I, EKOSSE GEORGES-IVO EKOSSE, do hereby declare that this thesis hereby
submitted to the UNIVERSITY OF THE NORTH, SOVENGA, SOUTH AFRICA
for the degree of DOCTOR OF PHILOSOPHY IN SOIL MINERALOGY has not
been previously submitted by me for a degree at any university; that it is my own
work in design and execution, and that all material contained therein has been
duly acknowledged.

………………………………. ………………………..
SIGNATURE OF STUDENT DATE

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DEDICATION

In memory of Anthony Gabriel Litange Ekosse,
My Father, Teacher, Counselor and Mentor

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ACKNOWLEDGEMENTS
I am particularly grateful to my supervisor and Head of the Discipline of Soil
Science and Acting Director of the School of Agricultural and Health Sciences,
University of the North, Prof P.S. Fouche for the tireless academic, technical,
logistical, moral and spiritual support given to me all through out the time the
research project was executed. I also thank Mr. B. Mashatola for academic and
logistical support and assistance with fieldwork. Their timely field visits to the
study site threw more light and directional understanding on the research work. I
am also grateful to other members of staff of the Department of Soil Science,
University of the North who were contributory to my success includes Ms. P.
Shaker, Mr. F. Madiba, and the secretarial staff. The following individuals and
laboratories are acknowledged:
• Mr. G. Rabalone, Faculty of Science, University of Botswana, for
assistance with some aspects related to physico-chemical analyses.
• Prof. B. Vink, Department of Geology, University of Botswana, for
discussions on manganese mineralogy in the Kgwakgwe Mn oxide ore
abandoned mine.
• Dr. A. Jordaan and Mr. S. Coetzee, Electron Microscopy Unit, University
of Botswana, for assistance with some aspects related electron
microscopy.
• Dr. J. C. Ngila, Ms. Nchindo and Mr. Kiptu, Department of Chemistry,
University of Botswana, for assistance with different aspects related to
chemical analyses.
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• Ms. B. Mazibuku, for assistance with some aspects related to Remote
Sensing and GIS skills and maps.
• My team of field assistants (Katlherelo, Simon and John) who assisted
with some aspects of fieldwork.
• Ms. V. Ngole, Department of Environmental Science, University of
Botswana for logistics, moral and technical support.
• Prof. J. S. Nkoma, Department of Physics, University of Botswana, for
moral and academic support.
• Physico-chemical analyses were conducted at the Soils Laboratory,
Department of Environmental Science, University of Botswana.
• Mineralogical tests were performed at the X-Ray Diffraction Laboratory
and the Electron Microscopy Laboratory, both of the Faculty of Science,
University of Botswana.
• Chemical analyses were done at the Chemical Instrumentation
Laboratory, University of Botswana.
• The different software packages used in this study were provided by the
X-Ray Diffraction Laboratory, and the Department of Geology, University
of Botswana.

I cannot list all the individuals, institutions and organizations that have over the
years been a very strong pillar of support for me. Without them I could not have
attained this level of academic pursuit. Of special mention are Prof. H. H. Murray,
Indiana University, Bloomington, USA for teaching me applied clay mineralogy
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and being my mentor, Drs. E and B Morton for the continuous extension of their
right hand of fellowship to me, and Dr. E. Mondoa for a lifelong relationship of
friendship and perpetual support that has spanned from elementary school days.

On the family side, different levels and forms of support and encouragement
were received from Timothy Ekosse, Emmanuel Ekosse and Comfort Ekosse;
Ma Theresa Ekosse, Dr. Mbako Ngombe and all my siblings, the many wonderful
nephews and lovely nieces, and to all my cousins who have identified
themselves with me over the years.

Finally I am most grateful and thankful to God the Father, the Lord Jesus Christ
and the Blessed Holy Spirit for giving to me the strength, finances, knowledge,
courage and the faith to pull through the program. God has been my shield and
my salvation. All Glory goes back to Him!

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ABSTRACT
This research study focuses on environmental mining impact of soils around the
abandoned Kgwakgwe Mn mine in Botswana. The thesis contains five chapters:
introduction, methods and analytical techniques, results, interpretation and
discussions, and conclusions. The physico-chemical properties, mineralogical
identification and characterisation and chemical properties of soils and related
geological materials as well as the chemical properties of the soils and leaves of
plants around the abandoned mine were investigated in order to determine the
mining impact on the surrounding soils. It mentions field research components,
which included observation and sampling of surface soils, related geological
materials and leaves of plants for different laboratory analyses. Methods,
techniques and instrumentation for physico-chemical, mineralogical and chemical
analyses are explained. Physico-chemical properties studied on soil samples
included particle size distribution (PSD), pH, electrical conductivity (EC), soil
colour, and descriptive petrography. Identification of minerals contained in soil
samples which included both < 53 μm and < 4 μm size fractions were performed
employing X-ray powder diffraction (XRPD) techniques. The < 4 μm size
fractions of soil samples were further characterised using the environmental
scanning electron microscope (ESEM) to which was fitted with an X-ray energy
dispersive spectrometer (EDS). Chemical analyses for iron (Fe) and manganese
(Mn) concentration levels in soil and leaf samples were measured with the flame
atomic absorption spectrometer (FAAS). Determination of exchangeable bases
(Na, K, Ca and Mg), cation echange capacity (CEC) and percent base saturation,
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P, Cl, SO and CO concentrations were performed only on the soil samples. The
4 3
exchangeable bases, CEC and percent base saturation were determined using
the ammonium acetate method which included flame photometry for K and Na,
and AAS for Ca and Mg. The Olsen method was applied to determine P
concentrations. Furthermore analyses for Cl and SO were done using ion
4
chromatography, whereas the calcimeter was used to determine CO
3
concentrations. A Quickbird 2.4 m – 2.8 m resolution with zero cloud cover
multispectral standard imagery of the study area was processed to characterise
the vegetation cover. The laboratory results were processed using Geographical
Information Systems (GIS), and Remote Sensing (RS) techniques with the
integrated Land and Water Information System (ILWIS), Geosoft Oasis Montaj
and ArcGIS software packages. Microsoft Excel was used for statistical and
graphical presentation of data analyses. The particle size distribution of soil
samples revealed the average wt % of the soil fractions as follows: the < 4 μm
fraction was between o.3 wt % and 30.58 wt %, and the < 53 μm fraction was
between 11.05 wt % and slightly above 100 wt %. Soil pH ranged from 2.92 to
7.26 with very acidic soils located close to the mine workings. Electrical
conductivity values were significantly low, and the range was from 49.1 μScm-1
to 123.5 μScm-1. Dark brown to reddish brown soil colour was indicative of very
high Fe and Mn levels in the soils. Bulk soil samples consisted of quartz, SiO ;
2
haematite, Fe O ; goethite, Fe+3O(OH); bixbyte, Mn O ; braunite,
2 3 2 3
Mn+2Mn +3SiO ramsdellite, MnO ; pyrolusite, MnO ; cryptomelane,
6 12 2 2
K Mn O ; sanidine, K(Si Al)O ; microcline, KAlSi O ; whereas the < 4 μm
2-x 8 16 3 8 3 8
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fraction was made up of kaolinite, Al Si O (OH) illite, KAl Si AlO (OH) ; and
2 2 5 4 2 3 10 2
muscovite KAl Si AlO (OH) . The range of concentration levels of Fe in soils
2 3 10 2
was from 1116 μg g-1 to 870766 μg g-1 with a mean of 17593 μg g-1 and for Mn in
soils was 35 μg g-1 to 24907 μg g-1 with a mean of 1088 μg g-1. The values for Na
concentration in the soil samples ranged from 0.1 cmol kg-1 to 89.1 cmol kg-1,
c c
with a mean of 0.44 cmol kg-1, and for K concentration in the soil samples values
c
ranged from 0.1 cmol kg-1 to 163.6.1 cmol kg-1, with a mean of 0.82 cmol kg-1.
c c c
The values for Ca concentration in the soil samples ranged from 0.3cmol kg-1 to
c
1139 cmol kg-1, with a mean of 5.68 cmol kg-1, and values for Mg concentration
c c
in the soil samples ranged from 0.3cmol kg-1 to 1655.3 cmol kg-1, with a mean of
c c
8.26 cmol kg-1. The CEC values in the soil samples from the study area ranged
c
from 1.1cmol kg-1 to 29.2 cmol kg-1, with a mean of 8.2 cmol kg-1, and values for
c c c
percent base saturation in the soil samples were from 33.77% to 100 % with a
mean of 82.10 % cmol kg-1. Values obtained for P O in some randomly chosen
c 2 5
soil samples from the study area were from 0.51 mgkg-1 to 6.02 mgkg-1. The
values for Cl concentration in the soil samples ranged from 0.2 mgkg-1 to 11.9
mgkg-1, with a mean of 7.63 mgkg-1, and for SO concentration in the soil
4
samples values ranged from 2.1 mgkg-1 to 47.5 mgkg-1, with a mean of19.36
mgkg-1. The values for CO concentration (measured in terms of CaCO
3 3
equivalent) in the soil samples ranged from 5.1 gkg-1 to 59.1 gkg-1, with a mean

of 40.98 gkg-1. For the leaves, the range of concentration levels of Fe contained
in them was from 101.2 μg g-1 to 3758 μg g-1 with a mean of 637 μg g-1 and for
Mn in leaves, the range was from 26.2 μg g-1 to 3611.5 μg g-1 with a mean of
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