TABLE OF CONTENTS
Title Page ———————————————————————————————-i
Declaration ——————————————————————————————-ii
Certification —————————————————————————————–iii
Dedication ——————————————————————————————-iv
Acknowledgement ———————————————————————————–v
Abstract ———————————————————————————————-vi
Table of Contents ———————————————————————————viii
List of Tables ————————————————————————————–xii
List of Figures ————————————————————————————-xiii
List of Appendices ——————————————————————————-xiv
Chapter One
Introduction
1.1 Background to the study ——————————————————————-1
1.2 Research Problem ————————————————————————–2
1.3 Justification ———————————————————————————-4
1.4 Aims and Objectives ———————————————————————-13
1.5 Scope and Limitation of the Study ——————————————————13
Chapter Two
Literature Review
2.1 Pollution of Aquatic Sediments ———————————————————15
2.2 Heavy Metals in Aquatic Sediments —————————————————16
2.3 Effect of Physiochemical Parameters on Heavy Metals Mobility ——————17
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2.4 Bioavailability of Heavy Metals in Aquatic Sediments ——————————19
2.5 Effect of Heavy Metal on Aquatic Environment ————————————-20
2.6 Fractionation of Heavy Metals in River Sediment ———————————–22
2.7 Effect of Industrial Effluent on Aquatic Environment ——————————-25
2.8 Principle of Atomic Absorption Spectrophotometry ———————————26
2.8.1 Wavelength and slit width of measurement ——————————————-27
Chapter Three
Materials and Methods
3.1 Materials ————————————————————————————28
3.1.1 Apparatus/Equipment ——————————————————————–28
3.1.2 Reagents ————————————————————————————29
3.1.3 Preparation of Reagent Solution———————————————————30
3.1.3.1 Stock Solutions —————————————————————————-30
3.1.3.2 Standard Working Solutions ————————————————————-31
3.1.3.3 Other Solutions —————————————————————————-32
3.1.4 Study Area ———————————————————————————33
3.1.5 Description of Sampling Sites ———————————————————–34
3.1.6 Samples collection ————————————————————————37
3.1.7 Sample Pre-Treatment ——————————————————————–37
3.2 Methods ————————————————————————————38
3.2.1 Determination of Physicochemical Parameters of Sediment ————————38
3.2.1.1 Determination of pH ———————————————————————-38
3.2.1.2 Organic Matter Determination ———————————————————-38
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3.2.1.3 Particle Size Distribution —————————————————————-39
3.2.1.4 Chloride ————————————————————————————40
3.2.1.5 Sulphate – Sulphur ———————————————————————–40
3.2.1.6 Nitrate – Nitrogen ————————————————————————-41
3.2.1.7 Nitrite – Nitrogen ————————————————————————-42
3.2.1.8 Phosphate – Phosphorus —————————————————————–42
3.2.2 Digestion of Sample ———————————————————————-43
3.2.3 Quality Assurance ————————————————————————-43
3.2.3.1 Treatment of Glass wares, Sample Containers and Crucibles ———————-43
3.2.3.2 Preparation of Multi element Standard Solution (MESS) —————————44
3.2.3.3 Spiking Experiment ———————————————————————–44
3.2.4 Sequential extraction ———————————————————————45
3.2.5 Calibration Curve ————————————————————————-47
3.2.6 Statistical Analysis ————————————————————————48
Chapter Four
Results and discussions
4.1 Methods Validation —————————————————————49
4.2 Sediment physicochemical parameters —————————————–49
4.3 Total Heavy Metal Content in Sediment —————————————61
4.4 Sequential Extraction ————————————————————-66
Chapter Five
Conclusion and Recommendation
5.1 Conclusion ——————————————————————————85
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5.2 Recommendation ——————————————————————–86
References ——————————————————————————————-87
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background to the study
Rivers have been used by man since the dawn of civilization as a source of water,
food, transport, defensive barrier, power, to drive machinery and as means of disposal of
waste. Advancement in the level of industrialization has led to even more waste discharge
in the form of effluents containing heavy metals into our aquatic environment (Warren,
1981). In fact Industrial discharges have been identified as a major component of water
pollution (DWAF and WRF, 1995; Morrison et al., 2001 and Nasruallah et al., 2006).
Although water is commonly employed as a pollution indicator by heavy metals,
sediment can also provide a deeper insight into the long term pollution state of the water
body. Hence, the use of sediments as indicator of heavy metals pollution has been a
major environmental focus especially in the last decade (Ikem et al., 2003).
Heavy metals are one of the main pollution factors in aquatic systems because
some metals are persistent and potentially dangerous to biota. The metals are transported
by particulate matter to the sediment and this is not necessarily the final fate of metallic
species because a fraction of these can be released to the water column when the
physicochemical conditions have changed (Jaime et al., 2003). Hence, the behaviour and
concentration of heavy metals in sediment can play a relevant role in detecting sources,
degree of pollution and distribution mechanism in aquatic environment.
Kano holds about 70% of Nigeria’s tanning industries and most of them are
located in Challawa Industrial Estate (World Bank, 1995 and Faboya, 1997). The
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effluents from the tanneries in this Industrial Estate are channeled into drains which end
up into the Challawa River untreated.
The treatment and processing of animal hides and skins can be a source of
considerable environmental impact. Discharged waste water contains pollutants from the
hide’s products, from their decomposition and from the tanning process. According to
Birle and Lock (1998), the immediate environmental threat posed by the presence of
large number of tanneries which discharge substantial quantities of chromium salts and
numerous other toxins into the rivers are of major concern.
Therefore, the need to assess the state and quality of Challawa river sediment in
terms of its metallic load becomes imperative since the direct transfer of chemicals from
sediments to organisms is now considered to be a major route of exposure for many
species (Zoumis et al., 2001).
1.2 Research Problem
The Kano environment covers an area extending between latitudes 120
40’
E and
100
30’E and longitude 70
40’N and 90
30’N. Kano is a booming industrial establishment
comprising of chemical and cosmetics industries, tanneries, textile and food processing
factories which release waste water untreated into rivers. This led to the deterioration of
aquatic system (Bichi, 2000). Industrial survey showed sixty (60) industries in Kano
discharge untreated effluents into rivers (Dada, 1997).
The Challawa River flows eastwards stranding the region south-west of Kano
municipality and draining into Lake Chad via Hadejia River. Its main tributary is Kano
River; others include River Jatau, Goronyo, Shinar, Takawani, Dawaza and Toba. On
17
either side of the river lies an extensive dulating to flat plain. The discharges from
Challawa Industrial Estate are mostly from tannery and textile industries. The Challawa
Dam supplying water to Kano municipality is located some 75km upstream from the
point where tanneries discharge their effluents into the Challawa River.
River Challawa is an important river in Kano state. The river is used for various
human activities including washing, fishing, farming and drinking. The domestic water
supply for the area comes from this River. Some peasant farmers along the course of the
river also use the water from the river to irrigate their food crops, especially vegetables
during the dry season. This river receives untreated municipal waste and waste water
from the Challawa Industrial areas as shown in Fig 1.1 -1.8.
River sediments are important sinks for various pollutants like pesticides and
heavy metals and also play a significant role in the remobilization of contaminants in
aquatic systems under favorable conditions and in interactions between water and
sediment. (Ikem et al., 2003)The release of heavy metals from sediment into the water
body and consequently to fish will depend on the chemical fractionation and other factors
such as sediment pH and other physical and chemical characteristics of the aquatic
system (Morgan and Stumm 1991).However, in sediments, heavy metals can be present
in various chemical forms and generally exhibit different physical and chemical
behaviour in terms of chemical interaction, mobility, bioavailability and potential
toxicity. These species include: exchangeable, carbonate bound, iron-manganese oxide
bound, organic matter bound and silicate or residual bound species.
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It is therefore necessary to identify and quantify the forms in which a metal is
present in the sediments of Challawa River to gain a more precise understanding of the
potential and actual impacts of the operations in the river.
1.3 Justification
The many human activities in the last decade have increased the metal mobility in
the environment. Heavy metals are one of the main pollution factors in aquatic systems
because some metals are persistent and potentially dangerous to biota.
The total metal concentration in sediment is relevant; nevertheless, the
bioaccumulation, availability, reactivity, mobility and toxicity are determined by the
metal chemical form thus making a chemical fractionation study necessary.
Most of the past investigations on River Challawa concentrate on total metal
concentration in river water (Bichi, 2000), sediment (Akan et al., 2007) and farmland
food crops along the bank (Abdullahi et al., 2008; Awode et al., 2008). There is no
literature information yet on the chemical fractionation of heavy metals in bottom
sediment of River Challawa. There is, therefore, the need to determine the speciation or
fractionation of heavy metals in the bottom sediment of River Challawa in order to
answer the following questions arising from the unregulated discharge of untreated
tannery effluents into River Challawa :
(i) What are the levels of heavy metals- zinc, copper, cadmium, chromium
and lead in the sediments of River Challawa?
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Figure 1.1 A Picture Showing Effluent Discharge Pathway into River Challawa from Textile and Chemical Industries
20
Figure 1.2 A Picture Showing Human Activities in River Challawa
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Figure 1.3 A Picture Showing Effluent Discharge Pathway into River Challawa from Tannery Industries
22
Figure 1.4 Picture Showing Effluent Discharge Pathway into R
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