ABSTRACT
This study investigates the concentration of heavy metals (Zn, Pb, Cd and As) in the soil and leachate from the unlined dumpsite at Ubakala, Umuahia South L.G.A, Abia State, Nigeria. Soil samples from different layers; 0-15cm, 15-30cm and 30-45cm, were collected from three sampling locations, PA, PB. PC and a control site 300M away from the dumpsite, PD. Leachate samples were also collected from leachate pools at the three sampling locations; A, B, C. The soil and leachate samples were analysed using Atomic Absorption Spectrophotometer, SPECTRA AA100. The mean concentration of heavy metals for soil samples across the three sampling locations of the dumpsite ranged from; 7.68±0.10 to 12.40±0.20mg/kg for Zinc, 0.60±0.10 to 3.29±0.10mg/kg for Lead, 0.60±0.10 to 9.45±0.20mg/kg for Cadmium and Arsenic ND (not detected). The mean concentrations for leachate samples across the three sampling locations of the dumpsite ranged from; 0.049±0.001 to 0.061±0.001mg/L for Zinc, 0.023±0.001 to 0.056±0.001mg/L for Lead, 0.037±0.001 to 0.050±0.002mg/L for Cadmium, and Arsenic (ND) not detected. The mean concentration of the heavy metals in the soil sample from the control site ranged from 0.34±0.19 to 1.13±0.03mg/kg for Zinc, 0.74±0.05 to 1.45±0.14mg/kg for Lead, 0.33±0.09 to 1.70±0.07mg/kg for Cadmium and Arsenic was not also detected. The concentrations of heavy metals in the soil and leachate samples display the following decreasing trend Zn˃ Cd˃ Pd. From the results, it was found that the mean concentrations of the heavy metals in the soil of the control site was significantly (p≤0.05) lower than their concentrations in the dumpsite soil and there were also significant differences in the heavy metal concentrations among the three sampling locations PA, PB and PC of the dumpsite, indicating uneven distribution of heavy metals across the dumpsite.. There is high mobility of the heavy metals down the soil profile (as the mean concentrations increased down the soil depth) which indicates possible underground water contamination. The results of this work have revealed that the mean concentration of heavy metals investigated in the soil samples were within the maximum tolerable levels proposed for agricultural soil by WHO (1993) with the exception of cadmium which was higher than the maximum tolerable limits (0.02-0.5mg/kg), while the heavy metals found in leachate were exceeding the allowable limits for Nigerian Standard for Drinking Water Quality set by SON (2007) except for Zinc which is within the allowable limit. These observations suggest that there is tendency of accumulation of these metals in the future as the dumpsite represents a significant source of heavy metal contamination of soil and underground water.
TABLE
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of Contents vi
List of Tables
x
List of Figures xi
List of Plates xii
Abstract
xiii
CHAPTER 1:INTRODUCTION
1.1
Background of the Study 1
1.2
Statement of Problem
4
1.3
Project Site 5
1.4
Aims and Objectives
5
1.5
Scope and Limitation
6
1.6 Significance of the Study
6
CHAPTER 2: LIERATURE REVIEW
2.1 Heavy metals
7
2.1.1 Metal toxicity
7
2.1.2 Heavy metal definitions 8
2.2 Sources of Heavy Metals
9
2.2.1 Cadmium
10
2.2.2 Mercury
11
2.2.3 Lead 12
2.2.4 Arsenic
13
2.2.5 Zinc
14
2.2.6 Nickel
15
2.2.7 Chromium
15
2.3 Environmental and Health Impacts of the
Heavy Metals 16
2.3.1 Cadmium
16
2.3.2 Mercury 17
2.3.3 Lead
18
2.3.3.1 Effects
on soils 18
2.3.3.2Effects
on plants
18
2.3.3.3Effects
on human health 19
2.3.4 Arsenic
19
2.3.5 Chromium
20
2.3.6 Nickel
21
2.4 Review of some Studies on Heavy Metals Contaminations 22
2.5 Atomic Absorption Spectroscopy (AAS) 25
2.5.1 Principles of atomic absorption spectroscopy 26
2.5.2 Theory of atomic absorption
spectrophotometry 27
2.5.3 Schematic diagram of an atomic absorption
spectrometer 28
2.5.4
Advantages of AAS 28
2.5.5
Disadvantages of using AAS
29
2.6
Atomic Emission Spectroscopy
29
2.6.1
Atomic emission spectroscopy principle 30
2.7 Soil
31
2.8 Properties of Soil
32
2.8.1 Soil clay minerals
32
2.8.2 Soil organic matter
32
2.8.3 Soil pH 33
2.8.4 Oxidation and reduction in the soil
34
2.8.5 Soil texture and structure 34
2.8.6 Soil profile
35
2.9 Factors Influencing Metal Availability in
Soils 36
2.10 Leachate 37
CHAPTER 3: MATERIALS AND
METHODS
3.1 Equipment and Laboratory Wares
39
3.2 Reagents and Chemicals
39
3.3 Study Area
40
3.4 Sampling 43
3.4.1
Sample collection
43
3.4.2
Sample preparation
46
3.5 Acid Digestion for Heavy Metal Analysis in
Soil samples 46
3.6 Acid Digestion for Heavy Metals Analysis
in Leachate Samples 46
3.7 Preparation of Stock Solutions for the
Analysis
47
3.8 Preparation of Heavy Metal Standards for Analysis 47
3.9 AAS Analysis of Samples
48
3.10 Determination of pH 48
3.11 Determination of Electrical Conductivity 48
3.12 Statistical Methods of Analysis
48
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Results
50
4.1.1 Physicochemical parameters of soil sample (pH
and EC) 50
4.1.2 Physicochemical parameters of leachate
samples (pH and EC) 52
4.1.3 Heavy metal concentrations in the soil
samples 52
4.1.4 Heavy metal concentration in the leachate
samples 52
4.1.5 Illustration on statistical data analysis for
soil and leachate (mean±SD)
56 4.2 Discussion
68
CHAPTER 5: CONCLUSION AND RECOMMENDATION
5.1 Conclusion
73
5.2 Recommendation
73
References 75
Appendices
83
LIST OF TABLES
3.1:
Sampling locations coordinates 44
4.1: Results of physicochemical parameters of the
soil samples;
soil pH and EC (µS/cm).
53 4.2:
Results of physicochemical parameters of the leachate samples; pH and
EC. 53 4.3: Mean
concentrations of heavy metals in the soil (mg/kg) 54 4.4: Mean
concentrations of heavy metals in dumpsite leachate (mg/L). 55 4.5: Two-way Analysis of Variance of zinc
concentrationin the soil of dumpsite
and control 57 4.6:
Two-way Analysis of Variance of lead concentration in the soil of
dumpsite
and control site
58
4.7: Two-way Analysis of Variance of cadmium
concentration in the soil of
dumpsite and control site 59 4.8:
One-way Analysis of Variance of zinc concentration in leachate samples 60 4.9:
One-way Analysis of Variance of lead concentration in leachate samples 61
4.10: One-way Analysis of Variance of cadmium
concentration in leachate samples 62 4.11:
Range of trace metals concentrations in the soil accepted by WHO (mg/kg) 63
4.12: Nigerian standard for drinking water quality; metals
maximum allowable
limits for drinking water set by NIS
and approved by SON (2007) 64
LIST
OF FIGURES
2.1: Schematic
diagram of an atomic absorption spectrometer 28
2.2: Layers
of asoil profile 35
3.1:
Map of the study area 41
4.1: The
plot of mean concentration of Zinc(mg/kg) down the soil depths
in the dumpsite. 65
4.2: The plot of mean concentration of Lead
(mg/kg) down the soil depth
in the dumpsite 66
4.3: The plot of mean concentration of cadmium
(mg/kg) down the soil
depth in the dumpsite 67
4.4: Mean
concentration of heavy metals (mg/L) in the leachate across
the sampling locations A, B and C
67
LIST OF PLATES
2.1: An open
dumpsite showing generated leachate. 38
3.1: Front view; Sampling site at Ubakala
dumpsite, Umuahia South
L.G.A,Abia
State.
42
3.2: Soil sampling using soil auger
45
CHAPTER 1
INTRODUCTION
1.1
BACKGROUND OF THE
STUDY
Dumpsites are and
will remain a necessary and important component of managing solid waste
(Heimlich, 2000). Dumping is a process of waste management by which solid
wastes are separated from homes, offices, industries, farmlands, commercial
areas etc and are kept in designated
places where they are treated and properly handled in other not to affect the
environment and public health. Municipal solid waste is an unavoidable
by-product of human activity. Population and economic growth have lead to
massive amount of solid waste creation by dwellers of the urban areas
(Karishnamurti and Naidu, 2003). Urban solid waste is usually generated from
human settlement, industries and commercial activities (Sing et al., 2011).
A modern dump site
is a well engineered, well constructed and well controlled land disposal site
for non-hazardous waste, which makes use of the latest science and technology to
protect the environment and public health from heavy metal contamination,
hazardous gases such as methane and carbon(iv)oxide, and air pollution (bad
odours). This is achieved by employing the engineering principles to border the
solid waste to the smallest practical area, installation of a bottom line for
leachate collection and an underlying pipe for collection and pumping of dump
site gases.
Unfortunately, in
developing countries this kind of dumpsite is farfetched, open dumpsites are
commonly practiced, due to the low budget for waste disposal and
non-availability of trained man power. Open dumping of municipal solid waste is
a common practice in Nigeria. It is a process of dumping municipal waste in a
manner that affects the environment by contaminating the soil with heavy metals
due the absence of bottom liner and thisposes a threat to public health. Open
dumping constitutes a serious risk to underground water resources and soil.
Heavy metals contamination of soil may cause adverse effect on human health,
animals and soil productivity. (Smith et
al.,1996).
The municipal
dumping site located at Ubakala, Umuahia South L.G.A, along Umuahia-Aba express
way, Abia State is a typical example of an open dump site. Umuahia is a
non-industrial city and waste generated
in the city comprise largely of bio-degradable materials from markets, farms,
schools, offices and household such as garbage ,plastic etc. These solid wastes contain some amount of heavy metals, which
are considered to be one of the major sources of pollution in the terrestrial
and aquatic environment. (Koomen et al., 1990).
Over the last couple
of years, heavy metals have considerably damage of soil quality and fertility
in consequence of increased environmental pollution from industrial,
agricultural and municipal sources (Adriano, 1986). Metals cause physiological disorders in soils
as absorption through the root system consequently retards plants growth and
deprives it of vigour (Moustakas et al.,
1996). Waste carries different metals which are then transferred to plants by
different ways (Voutsa et al.,1996).
Improper disposal of metal containing
materials and human waste tend to impact on heavy metal load of dumpsites
soils. Consequently, dumpsite soils and leachates most often contain pronounced
level of heavy metals. Terry (1999) and NVSWC (2008) have described the
existence of heavy metals in soils as one of the greatest environmental
problems that hamper agriculture in developing countries. Crops grown on such
soils will no doubt contain high accumulation of heavy metals. Consumption of food
containing heavy metals (Cd, As, Pb ,Hg,and Fe) by humans and animals
predisposes the consumer to serious health hazards. Cadmium causes painful
osteomalacia (bone disease), destruction of red blood cells and kidney damage
leading to renal failure in human beings while lead (Pb) could lead to mental
relapse, disruption of the biosynthesis of haemoglobin and anaemia; a rise in
blood pressure, kidney damage etc
(Odoh, 2011). Toxic metals can have health impacts on plants and animals and
have been involved in causing alarge number of afflictions. (Sayadi and
Torabi,2009).
Many incidents of
heavy metal contamination in aquatic environment have increased the awareness
about heavy metal toxicity (Upendra, 2006 ). Among these are the Minamata
tragedies due to mercury poisoning and “Itai-Itai”disease in Japan due to
cadmium toxicity is well known (Upedra, 2006). In Zamfara State, Nigeria, lead
poisoning were recently reported which lead to the death of several people and
animals as a result of lead contamination of water bodies and environments (Isah,
2009).
However, municipal
solid waste can be reused as organic fertilizer or for soil amendment after
biological transformation (Marrios, 2004), but the heavy metal contained in it
and its product have challenged its beneficial use (Azeez, 2011). According to
Zhang et al. (2008), studies on the
occurrence and distribution of heavy metals in municipal solid waste could
assist policy makers and management authorities in eliminating the major
contaminant sources. This will effectively modify municipal solid waste (MSW)
collection, handling, treatment and disposal practices (Zhang et al., 2008). In most advanced and some
developing countries, several physical and chemical sorting methods
(hydrolysis, glycolysis and hydroglycolysis) have been used in sorting of waste
prior to disposal. The sorting of waste is done with automated machines and equipment;
however, these advanced MSW sorting techniques are not available in most
developing countries including Nigeria. The manner at which waste accumulates
in the dumpsites due to unavailability of these modern technologies has led to
environmental and health implications. Therefore, there is urgent need to
implement alternative ways of monitoring and managing the effects of MSW
disposal in the country.
Traditionally,
people cultivate a variety of crops in some temporarily abandoned section of
the dumpsite. Also, farmers from nearby areas often collect “soil” from the
dumpsite to be used as compost on the farms. This is of the general belief that
natural fertility of the soil from a waste dumpsite is high (Amusa et al., 2005). However, many fall victim
of heavy metal consumption due to lack of adequate information on the status of
heavy metals in the dump sites as this serve as point of entry of heavy metals
into the food chain and human body. Therefore, it is important to evaluate the
extent of soil accumulation of heavy metals, their mobility in soil and
relative amount in dumpsites.
This study is therefore designed to evaluate
the level of heavy metals (arsenic, lead, cadmium and zinc) contamination of
soil and leachate of municipal open dumpsite located at Ubakala in Umuahia
South Local Government Area of Abia State.
1.2 STATEMENT
OF THE PROBLEM
Human environmental
pollution is increasing as a result of indiscriminate dumping of municipal
waste on water and land and more especially for the practice of open dumping
system of waste disposal. There are therefore serious problems posed to the
environment and public health. The municipal solid waste contain large amount
of heavy metals which are considered to be one of the major sources of pollution
in the terrestrial and aquatic environments (Koomen et al., 1990)
Heavy metal deposition
has significant effects on the general ecology of the environment. In Nigeria,
many people are being exposed to these heavy metals by their several and long
contact with them. The heavy metals can enter the food chain as a result of
their uptake by food crops. They can also enter the water through deposition of
the industrial waste, through agricultural run-off waters or through run-off
leachate from dumpsites.
Dumpsites, therefore
is one major source of heavy metals through the production of leachate; a
liquid that percolates through the dump during decomposition. This leachate has
high concentration of heavy metals and is the main contaminant of soil,
groundwater and surface water.
1.2
PROJECT SITE
The project site is at Ubakala Municipal
dumpsite in Umuahia South Local Government Area of Abia State. It lies within
the South-eastern part of Niger Delta Basin, between longitudes 7°22’ and
7°33’E and latitudes 5°26’and 5°34’N. It is within the subequatorial climatic
belt characterized by two major seasons. The wet and dry season starts in April
and ends in September with a peak in June and July while the dry season lasts
from October to March. Rainfall is high in the area, with an annual average of
about 400cm. Relative humidity is also high and generally are over 70%, while
mean annual temperature is about 27°C. A lot of commercial activities including
some small scale industries go on in Umuahia. These activities together with
unrestricted population growth leads to the generation of high volume of solid
and liquid waste which invariably contain some heavy metals.
1.3
AIM AND OBJECTIVES OF THE STUDY
The
aim of this study is to investigate the concentrations and distribution of
heavy metals (Zn, Pb, Cd, As) in the soils and leachate samples from Ubakala
dumpsite, Umuahia South L.G.A of Abia State Nigeria.
This
aim will be achieved through the following objectives:
·
Random
sampling of soil and leachate samples from the dumpsite and soil samples from
the control site (a farm land 300 m from the dumpsite).
·
Assessment
of the physicochemical parameters(pH and electrical conductivity) of the soil
and leachate samples
·
Determination
of the heavy metal; Zinc, Lead, Cadmium and Arsenic concentrations in the soil
and leachate samples.
·
Compare
and contrast the heavy metals concentration in the soil samples of the dumpsite
and control site.
·
Comparison
of results with recommended limits
·
Making
appropriate recommendations.
1.5
SCOPE AND LIMITATION
The scope of this
study is wide, ranging from collection of samples, digestion, determination of
pH and electrical conductivity and the use of Atomic Absorption
Spectrophotometer (AAS) to determine the heavy metals. The data of this project
work focuses on the municipal dumpsite at Ubakala, Umuahia South L.G.A, Abia
State.
1.6
SIGNIFICANCE OF THE STUDY
The
results of this research work will show;
·
The
level of accumulation of some heavy metals (Zn, Pb, Cd, As) in soil and
leachate of the dumpsite at Ubalaka, Umuahia South L.G.A, Abia State,
·
The mobility of these metals down the soil profile,
·
Possible
waste dumps protection.
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