GEOPHYSICAL AND GEOCHEMICAL INVESTIGATION OF GROUNDWATER CONTAMINATION BY LEACHATE IN UMUEZE- IBEKU, UMUAHIA, SOUTH-EASTERN NIGERIA

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ABSTRACT

Residents of Umueze-Ibeku depend on groundwater abstracted through boreholes for drinking and other domestic purposes. However, the existence of a 15 years old dumpsite having proximity of less than 150m from commercial and private boreholes in the community leaves a lot to be desired. This situation has exposed groundwater in the vicinity to high risk of contamination by leachate from the dumpsite located between Latitude 5.55317⁰ and 5.55344⁰, and Longitude 7.49642⁰ and 7.49650⁰. It is against this background that Geophysical and Geochemical investigation of groundwater contamination by leachate was conducted around the dumpsite to identify the presence of leachate and extent of subsurface contamination. Using the Integrated Geo instrument Services (IGIS) device, Wenner array was deployed to carry out two (2) Electrical Resistivity Tomography (ERT) profiles (one at the dumpsite and the other at a control point). Same device was used to conduct two (2) Vertical Electric Sounding (VES) profiles with Half-Schlumberger (pole dipole) array (one at the dumpsite and the other at a control point). The ERT had a profile length of 100m and an electrode spacing of 5m while the VES had an ABmax of 250m. Res2Dinv software was used to model ERT data, while IPI2WIN was used to process the VES resistivity data. The Geochemical process involved strategic collection of six (6) water samples for analysis at the Soil, Plants and Water Laboratory of the Federal Ministry of Water Resources and Environment, Ahieke, Umuahia, Abia State. Result of Geophysical survey show that a depth of 19.8m was probed by the ERT while VES penetrated a depth of 23.9m at the dumpsite and 31.1m at the control. Presence of leachate with resistivity values ≤ 8.71Ωm and up to 18.8Ωm, having active concentration at between 25m to 75m along the horizontal profile in 2-Dimensions was identified. The identified leachate has penetrated a depth of 11.35m. VES data analyses confirmed the geologic formation which was found to be Bende-Ameki Formation. On the other hand, the lithological unit was seen to be sand, clay and shale. Physicochemical analysis conducted shows that Borehole 6 and stream have Lead (Pb) and Mercury (Hg) concentrations above acceptable limits, while boreholes 1, 5 and stream are hard with stream being highly turbid. However, all water samples are contaminated with more of pathogenic organisms as indicated by the high microbial count and harmful isolates. This can be attributed to drilling of boreholes near residential septic tanks since field experiments have shown that the leachate has not reached the aquifer. It should be noted that from results shown in ERT, leachate will in a short time reach the aquifer to further contaminate the waters as infiltration of the harmful fluid is a continuous process. From literature, harmful effects of pathogenic and metallic contaminants discovered in the sampled boreholes are nervous system disorder, diarrhoea, and lots more. In conclusion, the Umueze dumpsite is a threat to groundwater and human health. Urgent proactive measures such as closure of the dumpsite, mounting of dump stands by Abia State Environmental Protection Agency (ASEPA), treatment of borehole water before use, and strict observance of safe distances of 50ft (borehole to septic tanks) and 1000m (boreholes to dumpsites) are required to forestall future health disasters. This research has provided baseline information for geophysical survey in Umueze-Ibeku.

TABLE OF CONTENTS

Title page i

Declaration ii

Certification iii

Dedication iv

Acknowledgement v

Table of Contents vi

List of Tables x

List of Figures xi

List of Plates xiii

ABSTRACT xiv

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND 1

1.2 STATEMENT OF THE PROBLEM 3

1.3 AIM AND OBJECTIVES 3

1.4 SCOPE OF THE STUDY 4

1.5 JUSTIFICATION OF THE STUDY 4

1.6 DESCRIPTION OF THE STUDY AREA 4

1.6.1 Location of the Study Area 4

1.6.2 The Dumpsite 7

1.6.3 Geology and Hydrogeology 7

1.6.4 Drainage and Topography 10

1.6.5 Climate 10

CHAPTER 2

LITERATURE REVIEW

2.1 OVERVIEW 11

2.2 WATER QUALITY 11

2.2.1 Water Quality Standards 12

2.3 OPEN DUMPSITES 16

2.4 GROUNDWATER CONTAMINANTS 17

2.5 DARCY’S LAW AND GROUNDWATER MOVEMENT 18

2.5.1 Darcy’s Law 18

2.5.2 Fundamental Transport Processes 19

2.5.2.1 Advection 19

2.5.2.2 Diffusion 19

2.5.2.3 Dispersion 20

2.5.3 Aquifer Properties 20

2.5.3.1 Hydraulic Conductivity 20

2.5.3.2 Permeability 22

2.5.3.3 Porosity 22

2.5.3.4 Transmissivity 23

2.6 DUMPSITE LEACHATE 24

2.7 ELECTRICAL RESISTIVITY TOMOGRAPHY 24

2.7.1 ERT Survey Techniques 26

2.7.1.1 Wenner Array 26

2.7.1.2 Schlumberger Array 27

2.7.1.3 Wenner-Schlumberger Array 28

2.7.1.4 Dipole-Dipole Array 29

2.7.1.5 Pole-dipole Array 29

2.7.1.6 Pole-pole Array 31

PHYSICOCHEMICAL PROPERTIES IN DETERMINING

2.8 GROUNDWATER QUALITY 33

2.8.1 Turbidity 34

2.8.2 Total Dissolved Solids 34

2.8.3 pH 34

2.8.4 Electrical Conductivity 34

2.8.5 Total Hardness, Carbonates, Calcium and Magnesium 35

2.8.6 Total Colliform Count 35

2.8.7 Lead 36

2.8.8 Mercury 36

2.8.9 Sulphates 37

2.8.10 Nitrates 37

2.8.11 Chlorides 38

2.8.12 Iron and Manganese 38

2.8.13 Zinc 38

CHAPTER 3

MATERIALS AND METHODS

3.1 MATERIALS 39

3.1.1 The Resistivity Data Measuring Instrument 39

3.1.2 Field crew 41

3.2 METHODS 41

3.2.1 Reconnaissance and Pre-survey Activities 41

3.2.2 Electrical Imaging and Field Data Acquisition 42

3.2.3 Pole Dipole (Half Schlumberger) Vertical Electric Sounding (VES) 43

3.2.5 Geochemical Data Acquisition 43

3.2.5.1 Sample Borehole Water Collection 44

3.3 PRECAUTIONARY MEASURES 45

CHAPTER 4

RESULTS AND DISCUSSION

4.1 RESULTS 47

4.1.1 Result of Electrical Resistivity Tomography (ERT) 47

4.1.2 Result of Vertical Electrical sounding (VES) 54

4.1.3 GPS Coordinates, Elevations and Maps 57

4.1.4 Result of Physicochemical Analysis of water samples 60

4.2 DISCUSSION 70

4.2.1 Findings from ERT and VES 70

4.2.2 Findings from Physicochemical Analysis 71

4.2.3 Identified contaminants and human health implication 74

CHAPTER 5

CONCLUSION AND RECOMMENDATIONS

5.1 CONCLUSION 75

5.2 RECOMMENDATIONS 76

5.3 CONTRIBUTION OF THIS RESEARCH TO KNOWLEDGE 78

REFERENCES 79

APPENDICES 84

LIST OF TABLES

Table 1.1 Major landmarks in Umueze 4

Table 2.1 Permissible Limits/ Standards for Drinking water quality 14

Table 2.2 Limits for substances and Characteristics affecting the acceptability of Groundwater for Domestic use

Table 2.3 Microbiological limits for Groundwater 15

Table 2.4 Conductivity values of geologic materials 22

Table 2.5 Range of values of Porosity 23

Table 2.6 Comparison of performance of electrode arrays 32

Table 2.7 Resistivity Values of Rocks and Subsurface Materials 33

Table 4.1 ERT Data at the Dumpsite 48

Table 4.2: ERT Data at Control Point 51

Table 4.3 Data Table of VES Analysis/ Modelling 56

Table 4.4 GPS Coordinates and Elevation of landmarks in the study area 57

Table 4.5 Result of Physicochemical Analysis of Borehole/ Stream water samples

Table 4.6 Summary of identified Contaminants and Human Health Implication

LIST OF FIGURES

Fig. 1.1 Map of Abia State showing Umuahia North LGA 5

Fig. 1.2 Map of Umuahia North LGA showing Umueze-Ibeku (the Study Area) 5

Fig. 1.3 Location Map of Umueze-Ibeku showing the dumpsite and Water Sample

Fig. 1.4 Geologic Map of the study area 9

Fig. 2.1 Wenner Array 26

Fig. 2.2 Schlumberger Array 27

Fig. 2.3 Wenner-Schlumberger Array 28

Fig. 2.4 Dipole-Dipole Array 29

Fig. 2.5 Pole-Dipole Array 30

Fig. 2.6 Pole-Pole Array 31

Fig. 3.1 Pole-Dipole Array 43

Fig. 4.1 Dumpsite ERT Model 50

Fig. 4.2 Control ERT Model 53

Fig. 4.3 Dumpsite VES 54

Fig. 4.4 Control VES 55

Fig. 4.5 Pseudo and Geoelectric Cross Sections 55

Fig. 4.6 Elevation Contour Map of Umueze-Ibeku 58

Fig. 4.7 3D Surface Map of Umueze-Ibeku 58

Fig. 4.8 Grid Map of Umueze-Ibeku showing Flow Direction 59

Fig. 4.9 Turbidity Contour Map 62

Fig. 4.10 Turbidity Concentration Chart 62

Fig. 4.11 Total Hardness Contour Map 63

Fig. 4.12 Total Hardness Concentration Chart 64

Fig. 4.13 Mercury Contour Map 65

Fig. 4.14 Mercury Concentration Chart 65

Fig. 4.15 Lead Contour Map 66

Fig. 4.16 Lead Concentration Chart 66

Fig. 4.17 Manganese Contour Map 67

Fig. 4.18 Manganese Concentration Chart 68

Fig. 4.19 Microbial Count Concentration Chart 69

Fig. 4.20 Temperature Contour Map 84

Fig. 4.21 Electrical Conductivity Contour Map 84

Fig. 4.22 Total Dissolved Solids Contour Map 85

Fig. 4.23 Dissolved Oxygen Contour Map 85

Fig. 4.24 Nitrate Contour Map 86

Fig. 4.25 Phosphate Contour Map 86

Fig. 4.26 Chlorine Contour Map 87

Fig. 4.27 Calcium Contour Map 87

Fig. 4.28 Magnesium Contour Map 88

Fig. 4.29 Sulphate Contour Map 88

Fig. 4.30 Iron Contour Map 89

Fig. 4.31 Zinc Contour Map 89

LIST OF PLATES

Plate 1 The Umueze-Ibeku Dumpsite 90

Plate 2 IGIS Device operator monitoring readings 90

Plate 3 Setting up of ERT Profile around the dumpsite 91

Plate 4 Researcher during the field activity 91

Plate 5 Group photograph of field crew 92

Plate 6 Taking of readings by researcher with guidance from Supervisor 92

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND

Water is needed for sustenance of human life and existence (WHO, 2008). Adequate supply of quality water is a major prerequisite of everyday activity and a major requirement for any sustainable development programme (Igboekwe et al., 2012). It is an important landscape element which is mobile and chemically active, being in continuous motion through the earth crust (Akankpo and Igboekwe, 2011).

In the world over, ground and surface water are the major sources of water for domestic, agricultural and industrial uses. Ground water is majorly accessed through water boreholes and deep wells while surface is accessed in rivers, streams, ponds, reservoirs, etc. Groundwater abstraction has gained significant acceptability in Nigeria due to the increasing need for potable water, particularly in places where there is limited access to rivers and streams (Coker, 2012). It is common knowledge that greater percentage of groundwater comes from rainfall into the earth. This is because, a part of the rainwater flows as run-off into rivers, streams, and as surface water while other part filters into the sub surface to be explored as groundwater from springs and wells (Alabi et al., 2010). According to Anomoharam (2013), 53% of mankind depends on groundwater as source of drinking water.

Nevertheless, the relevance of water for domestic use is dependent on its quality. The ‘looming water crisis’ according to Zaporozec et al., (2002) has become a serious concern to tshe international community. They noted that the World Water Council presented the ‘World Water Vision’ at the Second World Water Forum and Ministerial Conference at The Hague in March 2000. It unveiled the fact that about 1.2 billion persons lack access to potable water, with half of the earth’s inhabitants lacking good sanitation’.

Poor management of solid wastes has led to the emergence of landfills and refuse dumpsites which are as a result of efforts to dispose-off domestic and industrial wastes - a condition that has created serious environmental concerns. Solid waste disposal in the open environment is a popular and age long practice of managing waste. However in recent times, several of such sites have been closed, while some are still in operation (Akinbile and Yusoff, 2011; and Magda and Gaber, 2015). The disposal of these wastes in dumpsites and landfills results in decomposition of degradable substances and further chemical reactions in the presence of water to produce more toxic compounds which sips as leachate into the ground. Dumpsite leachate is made up of groups of contaminants (organic matter, inorganic compounds and heavy metals). The main potential natural impact related with landfill leachate is pollution of groundwater (Maiti et al., 2016).

When Leachate infiltrates and permeates into the ground, it dissolves into groundwater (Akankpo and Igboekwe, 2011; and Maiti et al., 2016), rendering the water unhealthy for human consumption and other domestic purposes. However, the degree of contamination of groundwater due to leachate permeation depends on various variables like chemical composition of leachate, precipitation, depth and distance of the well from the contamination source (Rajkumar et al., 2012).

Access to groundwater can be through drilling of borehole and or digging of water wells. In Nigeria and Abia state in particular, boreholes have become a major source of drinking water. As such the need to protect groundwater quality is of prime importance to the well being of man.

1.2 STATEMENT OF THE PROBLEM

The existence of a 15 years old dumpsite having proximity of less than 150m from commercial and private boreholes in Umueze-Ibeku leaves a lot to be desired. This situation has exposed groundwater in the vicinity to high risk of contamination by leachate from the dumpsite. Considering the effect of a contaminated commercial water source on the populace cum possible outbreak of diseases and epidemic within the catchment including its short and long term implications, it becomes expedient for an in-depth understanding of the likelihood of subsurface water pollution due to leachate within the vicinity and environs of the dumpsite.

1.3 AIM AND OBJECTIVES

The aim of this study is to investigate Groundwater contamination by leachate in Umueze- Ibeku.

The research objectives include

a. Carry out Electrical Resistivity Tomography Survey.

b. Carry out Vertical Elecctrical Sounding.

c. Take water samples from boreholes around dumpsite.

d. Carry out physicochemical and pathogenic analysis of water samples.

e. Determine health implication of consuming borehole water containing contaminants identified in objective d.

1.4 SCOPE OF THE STUDY

This study is limited to the use of Electrical Resistivity Tomography (ERT), Vertical Electrical Sounding (VES), physicochemical and pathogenic analysis only.

1.5 JUSTIFICATION OF THE STUDY

This research became necessary to ascertain the quality of the groundwater and invariably its suitability for drinking and other domestic uses, towards ensuring the protection of the health of users and determine levels of pollution. The information will be of great importance to the community leaders and relevant authorities including policy makers, since such research has not been carried out in the area.

1.6 DESCRIPTION OF THE STUDY AREA

Basic and fundamental description of the study area and location are as presented below:

1.6.1 Location of the Study Area

The study area is Umueze-Ibeku located between Latitude 5.54608⁰ and 5.56128⁰ and Longitude 7.49625⁰ and 7.49822⁰. The dumpsite of interest is located at a gully head between Latitude 5.55317⁰ and 5.55344⁰ and Longitude 7.49642⁰ and 7.49650⁰, with elevations of between 135m and 130m above mean sea level along the Umueze-Agbor- Ubani road.

Major landmarks in Umueze are as presented in the table below.

Table1.1: Major landmarks in Umueze

Location	Latitude (⁰)	Longitude (⁰)	Elevation (m)
Rich Vision table water	5.55033	7.49586	141
St Andrews Methodist Church	5.55153	7.49689	144
Umueze Community Hall	5.55369	7.49703	131
Penile Montessori Academy	5.55383	7.49633	132

Fig. 1.1: Map of Abia State showing Umuahia North LGA

Fig. 1.2: Map of Umuahia North LGA showing Umueze-Ibeku (the Study Area)

Fig. 1.3: Location Map of Umueze-Ibeku showing the dumpsite and Water Sample

The Dumpsite

The Umueze dumpsite which is at the gully head finds its bearing on Latitude 5.55556 and Longitude 7.50556 with an elevation of 139m above sea level; it is a heap of solid wastes which has accumulated for over 15 years. As stated in the statement of the problem, it was a community initiative to halt the active movement of the fast growing Umueze-Emede Chain gully which is about 20m (to the left) from a three storey building and 2m (to the right) from another residential building, with other buildings southwards between 10m to 20m. The waste disposal began from dumping into the ravine until it became a mound at the gully head.

Considering the fact that average distance of the dumpsite to any point in the community is less than 1000m (NIS minimum standard), the dumpsite hence threatens all existing boreholes in the community.

1.6.2 Geology and Hydrogeology

Bende-Ameki and Benin Formation constitute the major geologic formation of Abia State, Nigeria. According to Igboekwe and Cyril, (2011) & Chikezie et al., (2007), the Bende- Ameki Formation of Eocene to Oligocene age consists of unconsolidated fine-medium- coarse-grained cross-bedded sands occasionally pebbly with localized clay and shale.

Umueze is located in Ibeku, Umuahia, South-eastern Nigeria. The Ibeku pedon for the most part is a layered soil framed on shipped dregs of sandstone source happening over materials of weathered clay shale which underlies the region (Chikezie et al., 2007). Nnokwe et al., (2014) in their work, noted that sandstone unit is also a major constituent of the Bende-Ameke formation. They further remarked that the formation has sandy shale at very low shallow depth with underlying shale beyond 30m depth. Umueze as a community located in Ibeku is therefore underlain by the Bende Ameke formation. Communities in Ibeku in the words of Chikezie et al. (2007) are characterized by heavily chiselled valleys as a result of differential disintegration of sandstone and shale that constitute the geologic formation.

The groundwater production within Bende-Ameki and Benin geologic formations is appreciably good (Igboekwe and Amo-Uhegbu, 2014; & Okonkwo and Renteria, 2017). As expressed by Igboekwe and Amo-Uhegbu (2014), the high permeability of Benin Formation, the overlying lateritic earth, the eroded cap of this rock strata and the underlying clay shale member of Bende-Ameki series provide the hydrogeological condition favouring the aquifer formation in the area.

Fig. 1.4: Geologic Map of the Study Area

1.6.3 Drainage and Topography

Umuahia has low to moderately high plain topography. General surface elevation ranged between 110 to 178m contours above sea level (Okonkwo and Renteria, 2017; and Chikezie et al., 2007). This corroborates the elevation of Umueze (the study area) which is within 113m to 174m above mean sea level.

The drainage pattern is dendritic with tributaries generally in a southern direction (Okonkwo and Renteria, 2017). The risk of groundwater contamination is high in places with the dendritic drainage pattern. This is principally due to the fact that water courses are connected hence pollution at a point can easily be transmitted to other points.

1.6.4 Climate

The climate is tropical with two distinct seasons, the rainy season and the dry season. The wet season starts from April and continues into October whereas the harmattan begins from November to March. The rains get to its peak of 300–400mm in June through September and decreases to 0.0-1.0mm from December to January (Okonkwo and Renteria, 2017). The Annual rainfall is between 1250 and 2000 mm (Igboekwe and Cyril, 2011). The dry season is marked by the cold dry weather from the Sahara Desert. During this period, which begins in November and runs through January a dry and dust laden wind blows from the Sahara Desert (Okonkwo and Renteria, 2017).

It therefore shows that there is at least 7 months of intense rainfall. This implies a high volume of rainwater infiltrating and soaking the waste materials for increased production of leachate whose percolation rate thus increases in the presence of much water, a fact confirmed by Rajkumar et al., (2012). This further increases the period of sustained high concentration of leachate contamination in the water within the year; hence the villagers (users of affected borehole water) are exposed to prolonged consumption of polluted water.

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