ABSTRACT
This study was carried out to determine the effect of municipal waste disposal on some selected soil physical and chemical properties, heavy metals and micronutrient contents of the soil found in solid waste disposal areas in Abia State, Southeastern Nigeria. Soil samples were collected from three dumpsites and control sites in close proximity to the dumpsites at depths of 0 – 20cm, 20 – 40cm and 40 – 60cm. core samples were also collected for determination of some selected soil physical properties at both the dumpsites and control. Some heavy metal and micronutrients were determined on the soil samples. The results revealed that the analyzed physical properties (sand, clay and total porosity) were higher in the dumpsite than control site while bulk density was higher in the control site than in the dumpsite. Sand, silt and clay distribution between soil depths of 0 – 20cm, 20 – 40cm and 40 – 60cm were similar in the dumpsite and control except for clay content in the control site that increased with depth. The analyzed soil chemical properties (total exchangeable bases, organic carbon, organic matter, effective cation exchange capacity and base saturation) were higher in dumpsite than control but exchangeable acidity was higher in control site than dumpsite. They were all similar in the distribution both in the dumpsite and control site. The soil nutrients that were analyzed (nitrogen, potassium, calcium, magnesium, sodium, copper, zinc, iron and manganese) were all higher in the dumpsite than in the control site with exception of phosphorus that had a reversed case. There was no meaningful variation in depths of the soil nutrient contents. The heavy metal contents (Lead, Cadmium, Chromium and Nickel) were all higher in the dumpsite than in the control site but there was no variation in their distribution by depths both in the dumpsite and control site. From this study, it was observed that dumping of municipal solid waste can influence soil properties, heavy metals and micronutrients.
TABLE OF CONTENTS
Title
page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table
of Contents vi
List
of Tables
viii
List
of Figures ix
Abstract x
CHAPTER 1: INTRODUCTION 1
1.1 Background of the Study 1
1.2
Justification 4
1.3
Objectives of the Study 5
CHAPTER 2: LITERATURE
REVIEW 6
2.1 Overview of Municipal Solid Wastes
Management 6
2.2
Types and Sources of Wastes 8
2.3
Solid Wastes in Nigeria 10
2.4
Components of Solid Wastes 11
2.5
Solid Wastes Management 12
2.6
Soil Properties 15
2.7
Influence of Solid Wastes Disposal on
Soil Properties 17
2.8
Heavy Metal Content of Municipal Solid
Wastes 18
2.9
Influence of Solid Wastes Disposal on
Heavy Metal Contents
of Soils 24
2.10
Effects of Wastes at Dumpsite 28
2.10.1
Soil contamination 28
2.10.2
Ground water contamination 29
2.10.3
Environmental pollution 30
2.10.4
Health of plants, animals and humans 30
2.11 Effects of Municipal Solid Wastes on the
Environment 31
2.12
Effects of Wastes at Dumpsites on Heavy
Metals Content 33
2.13
Critical Limits of Soil Properties and
Heavy Metals in Soil Environment 37
CHAPTER 3: MATERIALS AND
METHODS 39
3.1
The Study Area 39
3.2
Vegetation, Soil, Climate and Relief
of the Study Area 39
3.3
Land Use of the Study Area 40
3.4
Sample Collection and Preparation 41
3.5
Laboratory Analysis 43
3.6
Statistical Analysis 45
CHAPTER 4: RESULTS AND
DISCUSSIONS 46
4.1 Effect of
Municipal Wastes on Soil Physical Properties
46
4.2 Soil
Physical Properties as Influenced by Municipal Wastes 49
4.3 Effect of
Municipal Wastes on Soil Chemical Properties 52
4.4 Distribution
of Soil Chemical Properties
57
4.5 Effects
of Municipal Solid Wastes on Soil Nutrient Contents 62
4.6 Distribution
of Nutrient Contents as Influenced by Municipal Wastes 67
4.7 Effect of
Municipal Wastes on Heavy Metal Contents 74
4.8 Distribution
of Heavy Metals as Influenced by Municipal Wastes 77
CHAPTER 5:
CONCLUSION AND RECOMMENDATIONS 81
5.1 Conclusion 81
5.2 Recommendation 81
References
LIST
OF TABLES
PAGE
2.1: Estimated
and projected volumes of solid wastes generation in some Nigerian cities. 7
2.2: The
percentage volume of wastes generated by the companies in Aba, Abia state. 9
2.3: Nature
of solid wastes depots or dumps in 15 Nigerian cities. 11
2.4: Critical
limits for some of the soil properties. 38
2.5: Critical
limits of selected heavy metals. 38
3.1: Geo-referenced
sampled points of the dumpsites. 42
3.2: Geo-referenced
sampled points of the non-dumpsites 42
4.1: Effect
of municipal wastes on soil physical properties. 47
4.2:
Soil Physical properties of dumpsites and control. 50
4.3: Impact
of municipal wastes on soil chemical properties 53
4.4 Distribution
of soil chemical properties. 58
4.5: Effect
of municipal solid wastes on soil nutrient contents 63
4.6: Distribution
of nutrient contents as influenced by municipal wastes. 68
4.7: Effect
of municipal wastes on heavy metal contents. 75
4.8: Distribution
of heavy metals as influenced by municipal waste 78
LIST
OF FIGURES
PAGES
1: Pictorial
view of dumpsites
8
2:
Diagram of soil sample collection 41
CHAPTER 1
INTRODUCTION
1.1
BACKGROUND OF THE STUDY
Dumpsites are places designated for
dumping of refuse and disposal of municipal solid wastes. In Nigeria, disposal of
solid wastes on open plots of land is a common practice. Solid waste
constitutes mainly waste materials generated from manufacturing processes (e.g)
chips and grits from machines shops, pieces of glass, sawdust, metal scraps,
waste paper, etc., and the
by-products of housekeeping activities and consumption like empty cans and
containers, ashes and fuel residues, wrapping leaves etc (NEST,2012). According
to Chopra et al. (2009), waste dumps
practices are the disposal of solid waste by infilling depressions on land.
These solid wastes are often dumped into excavations, open lands and valleys.
In Abia State and other states in
Nigeria, solid wastes are temporally dumped at designated locations from where the
agency’s (Abia State Environmental Protection Agency (ASEPA)) open-back trucks
gathers them and transports to
dumpsites.
Municipal solid wastes are usually
those useless, unwanted or discarded materials with insufficient liquid content
to be free-flowing (Eddy et al., 2006).
They are by-products of human activities. An estimated 20kg of solid wastes is
generated per capita per annum in Nigeria, equivalent to 2.2 million tonnes a
year, given Nigeria’s 1989 estimated population of 110 million (NEST,2012).
Municipal solid waste volume has continued to increase tremendously in recent
times in Nigeria as a result of increase in population and socio-economic
development (Ukpaka, 2012).
The most difficult environmental
problem that faces our cities today is the problem of solid waste disposal.
Most of these wastes are found in large quantities, deposited either on or
along the road sides, at unapproved areas, open dumpsites in the markets or in
waterways (Tariq et al., 2013). Improper
solid waste management in our various municipalities continues to militate
against concerted efforts towards a healthy environment. The arrangements for
waste disposal in many of the urban areas in Abia State have been insufficient
and also ineffective. The indiscriminate disposal of wastes may result to
contamination of the soil with toxic substances above permissible limits,
contamination of ground water and threat to aquatic lives. Soil and ground
water acidification and nitrification have been linked to waste dumps (Bacud et al., 1994) with resultant
contamination of soil and ground water system by microbial agents (Awomeso et al., 2010).
Increase in population and economic
development may result in corresponding increase in the amount of solid wastes
generated by people. Also, with increase in industrialization, municipal solid
wastes are usually generated in large quantities from industries and commercial
activities, plus human settlements when untreated and improperly disposed, wastes
pose serious threat to health and environment (Singh et al., 2011). Siasu (2008) attributed cancer, heart diseases and
teratogenic abnormalities to ground water contamination via leachate from waste
dumps.
Soil serves as a medium for the
global cycle of nutrients and energy. It plays an ecological role in the
purification, detoxification, and decomposition of wastes and hazardous
materials (Thien et al., 2001). Soil
with its components such as water, air, organic matter, dead and decayed plants
and animals are vital to life on earth.
Heavy metals at higher concentration
can lead to poisoning. Heavy metal poisoning could result, for instance, from
drinking lead contaminated water. Heavy metals contaminations of agricultural
soil have become increasingly serious in sewage area. The toxicity of some of
these metals are related to their availability and specific forms in the soil.
The toxicity of any metal depends on its ligand (Sparke and Gallagher, 2000). Heavy
metals are common components of industrial solid wastes like pieces of glass,
metal scraps, sawdust, rubber, chips and grifts generated in the course of
manufacturing processes. Heavy metals like lead is toxic even at low
concentration and besides other uses; it is used as additive in the production
of petrol. Galadima and Garba (2012) noted that the major heavy metal toxicity
cases in Nigeria were believed to be associated with lead poisoning. They are
mostly severe in young children because their brains and central nervous
systems are still at developmental stage. Zinc and cadmium are from tyre
abrasion, because they are used in the manufacturing of tyres. Nickel and
Chromium are gotten from the wearing of mechanical parts of vehicles. Nickel is
a major component in the production of stainless steels, etc.
Studies have shown that heavy metals
are potentially toxic to crops, animals and humans when contaminated soils are
used in crop production, because heavy metals may be easily accumulated by
plants thereby threatening the growth of crops and subsequently human health
when such crops are consumed (Amadi et al,
2012). Heavy metals contamination of environment is a worldwide phenomenon that
has attracted a great deal of attention. Most farmers resort to the use of
decomposed parts of the dumpsites as manure instead of buying fertilizers,
regardless of the risk of metal toxicity resulting from contamination by solid
waste. Additionally, heavy metals can be introduced through high tension
electricity supply lines, municipal solid wastes and building materials (Smith,
1976).
Economic and commercial activities in
Umuahia and Aba generate immense volume of solid wastes daily. Though Abia State
government provided sites in Umuahia and Aba for disposing and managing the
wastes, the management processes include transportation and disposal of solid
wastes to designated sites. These sites have been in use since 2009, but
unfortunately the standards required of the Umuahia and Aba sites and their
management strategies have not been met thus making this study crucial. Wastes
are being disposed recklessly on the sites without adequate management and
concern for the environment. Due to the uncontrolled dumping and disposal of
solid wastes in these sites and lack of expected management of solid waste in
the area, it is expected that the soil quality will be adversely affected.
This research will examine the
contribution of solid wastes on heavy metal contamination. It is believed that
improper solid waste management might affect the soil especially if they
contain heavy metals. Thus there is an urgent need to investigate the effects
on soil, the extent to which it has influenced the soil quality in the areas
and to know the physicochemical and heavy metals properties of soil in
dumpsites and non-dumpsites of Abia State.
1.2
JUSTIFICATION
Municipal solid waste handling and
disposal is a major environmental problem in Abia State Nigeria. Municipal
wastes in form of concrete debris, plastics, garbage, decayed wood, food
processing plants and others have been simply dumped. The soil has
traditionally been an important medium for waste disposal. Within some limits,
such wastes enhance soil fertility and can improve the physicochemical
properties of soils. When waste management is properly carried out and
carefully monitored to supply the crop fertilizer needs of urban farmers, it
reduces the cost of production. However, lack of effective waste management in
overcrowded modern cities like in Abia State can have substantial negative
effects that include the faecal water ways emitting stench from sewage,
spreading diseases, and harboring vehicles that spew lead exhaust into dust
filled air. The excessive input of unsorted and untreated municipal wastes may
likely lead to changes in soil physicochemical characteristics. These can distort
interrelationships among biophysical and chemical soil functions. It may also
lead to loading of heavy metals in soil and ground water. It is based on this
fact that this study is aimed at determining soil properties, distribution of
heavy metals and micronutrients in municipal waste in Abia State Nigeria.
1.3
OBJECTIVES OF THIS STUDY
The main objective of this study is
to evaluate the impact of municipal wastes on some selected soil properties and
heavy metal contents of soils of selected dumpsites and non-dumpsites in Abia
State.
Specific
objectives include:
1. To
evaluate the effect of municipal wastes at dumpsites on soil properties.
2. To
determine the influence of waste at dumpsites on trace elements contents of
soils.
3. To
determine the distribution of heavy metals in soils used for solid waste
disposal in Abia State.
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