ABSTRACT
Heavy metal concentrations and degradation efficiency of total petroleum hydrocarbons
(TPHs) on environment in Ibeno Local Government Area, Akwa Ibom State, Nigeria was
investigated. Experimental design method was adopted for this study. Fifteen composite
samples each of soil, leaves of Telfairia occidentalis, sediment and water were collected in
December 2012 and June 2013. The sediment and water samples were collected using corer
and clean plastic bottles respectively. Soil and sediment samples were air dried, mechanically
ground using mortar and pestle, and 2 mm mesh size obtained for further analysis. The soil
and sediment samples (1.0 g) each were weighed into Kjeldahl flasks. Aqua regia (15 cm3)
was added, swirled to mix and kept overnight. The flasks were heated on a hot plate to 50 oC
for 30 min; temperature was later adjusted to 120 oC and heated continuously for 2 h. The
mixture was cooled, and 0.2 M HNO3 (10 cm3) added. The resulting mixture was filtered with
a Whatman no. 541 filter paper. The filtrate was transferred into a 50 cm3 standard flask and
made up to the mark with 0.2 M HNO3. The leaves samples were washed with de-ionized
water, dried to constant weight in an oven at 105 oC, pulverized and 2 mm mesh size obtained
for further analysis. The ground leaves were digested with 1.0 cm3 concentrated HClO4, 5
cm3 concentrated HNO3 and 0.5 cm3 concentrated H2SO4 in 50 cm3 Kjeldahl flask. Each
water sample (10 cm3) was digested with 2 cm3 concentrated HNO3. Concentrations of the
heavy metals were determined using AAS Unicam 939 model. The soil samples (150 g) each
were transferred into four (4) plastic buckets labeled A, B, C and D. Varying concentrations
palm bunch ash (PBA) (0.0 g, 50.0 g), Tween 80 (50.0 g) and PBA + Tween 80 (25.0 g) each
were added to A, B, C, and D, where A served as control. Portions (5 g each) of A, B, C and
D were weighed into standard flasks, 25 cm3 of xylene added and shaken, NaCl (5 g) was
added and left for 72 h. The liquid portion was decanted into a separatory funnel, corked and
shaken. The xylene layer was transferred into 100 cm3 centrifuge tube containing 5 g of
Na2SO4 and agitated for 15 min, the absorbance of the solution was measured at 425 nm and
used for calculating concentrations of TPHs. Concentrations of TPHs were determined at 20
days intervals for 60 days. The data were analyzed on the basis of first order kinetic model
InC = InCo- kt. Heavy metal concentrations (mg kg-1) during dry season were, soil: Fe (15.15
± 5.91), Mn (10.36 ±3.18), Cd (0.23±0.31 ), V (0.17 ± 0.29), Ni (0.19 ± 0.05), leaves of
Telfairia occidentalis: Mn (7.73 ± 3.06), Fe (5.93±1.28), V (0.16±0.26), Cd (0.21 ± 0.16), Ni
(0.02 ± 0.01), sediment: Fe (22.18 ± 14.82), Mn (9.67±2.75), V (3.39±3.30), Ni (2.18±0.78),
Cd (0.48 ± 0.75), and water: Mn (2.80±0.93), V (1.53±1.42), Ni (1.50 ± 1.53), Fe (0.86 ±
0.25), Cd (0.27±0.21), During wet season, soil: Fe (12.09±4.98), Mn (9.66 ± 2.18), Ni
(0.05±0.03), V (0.04±0.01), Cd (0.04±0.02); leaves of Telfairia occidentalis: Mn (7.75±3.76),
Fe (5.96±4.07), V (0.21±0.09), Cd (0.19±0.06), Ni (0.03±0.06), sediment: Fe (23.28±0.24),
Mn (9.45±2.63), V (3.31±3.34), Ni (1.94±1.48), Cd (0.48±0.74), and water: Mn (3.13 ±
0.79),V (1.88 ±1.45), Ni (1.45 ±1.04), Fe(1.05 ± 0.25), Cd (0.10 ± 0.13), were obtained. The
correlation coefficients were: V (0.556), Ni (0.376), Cd (-0.043), Pb (0.856), Mn (0.813), Co
xx
(0.255), Zn (- 0.193), Fe (- 0.383), and V (-0.419), Ni (- 0.355), Cd (0.248), Pb (0.745), Mn
(0.974), Co (- 0.022), Zn (0.886) and Fe (-0.384) for dry and wet seasons respectively. The
mean concentration of TPHs in the soil was 14.55±0.01 mg kg1. Degradation efficiencies
obtained were PBA (86.69 %), PBA + Tween 80 (85.63 %), Tween 80 (76.70 %), and control
(5.40 %). The rates of degradation (mg kg-1 day-1) ranged from 2.70×10-2 to 1.30×10-2;
5.00×10-1 to 2.18×101; 2.49×10-1 to 1.84×10-1 and 4.67×10-1 to 2.09×10-1 for A, B, C and D
respectively. k ranged from 2.09 × 10-2 to 2.78 × 10-2, 3.79×10-2 to 5.81×10-2, 2.78×10-2 to
2.09×10-2, 5.13×10-2 to 3.23×10-2 for A, B, C and D respectively. Concentrations of heavy
metals in wet and dry seasons were variables. The concentrations of all the investigated
heavy metals in soil were within permissible range as recommended by DPR, but higher than
the reference soil samples. Mean concentrations of some of the investigated heavy metals
(Ni, V, Pb, Zn and Co) in leaves of Telfairia occedentalis were within the normal range of
WHO and FME standards for vegetables and food stuff except Cd, Fe and Mn. The
concentrations of Ni, V, Cd, Pb, and Mn in water were higher than WHO and DPR standards.
Also, the concentrations of Mn, Ni, Pb, and Zn in sediment were higher in dry season
compared to wet season except Fe, V and Co. Concentrations of Fe were the highest in all
the seasons; sediment retained the highest concentrations of heavy metals. Telfairia
occidentalis can be used as a resident indigenous plant bio indicator for monitoring
anthropogenic influenced V, Pb, Mn and Zn in the soil of the study area. Degradation
efficiency of TPHs were as follows: PBA (86.69 %) > PBA + tween 80 (85.63 %) > tween 80
(76.70 %) > control (5.40 %). The rate of degradation of TPHs decreased as the
concentrations of the surfactants decreased with time.
TABLE OF CONTENTS
Chapter one
Introduction – – – – – – 1
Statement of problem – – – – – – 8
Objectives of the study – – – – 9
Scope of the study – – – – – – – 10
Chapter Two
Review of related literature – – – – – – 11
Heavy metals – – – – – – – 11
Heavy metals in sediment – – – – – – – 11
Heavy metals in water – – – – – – – 13
Heavy metals in Soil – – – – – – – 14
Sources of heavy metal pollutants in soil – – – – – 16
Individual element – – – – – – 18
Vanadium – – – – – – 18
Sources of vanadium – – – – – – – 18
Vanadium in human being – – – – – – – 19
Vanadium in plant and soil – – – – – – – 20
Health importance of vanadium – – – – – – 20
Effects of vanadium on experimental animals and human beings – 21
Cadmium – – – – – – 21
Sources of cadmium in the environment – – – – – – 22
Uses of cadmium – – – – – – 22
Cadmium in soil – – – – – – 22
Cadmium in plant – – – – – – 23
Effects of cadmium in human beings – – – – – – 25
Lead – – – – – – 25
Uses of lead – – – – – – – 25
Sources of lead in the environment – – – – – – 26
Lead in soil – – – – – – 26
viii
Lead in plant – – – – – – – 27
Toxicity of lead – – – – – – 28
Zinc – – – – – – 29
Zinc in the environment – – – – – – – 29
Zinc in fossil fuels – – – – – – – – 29
Zinc in plant – – – – – – – – – 29
Toxicity of zinc – – – – – – 31
Cobalt – – – – – – – 32
Cobalt in soil – – – – – – – 32
Cobalt chemistry affecting availability to plant – – – – 32
Uses and toxicity of cadmium- – – – – – – 33
Nickel – – – – – – – 34
Physical properties of nickel – – – – – – – 34
Nickel in aquatic environment – – – – – – 34
Effect of nickel in plant – – – – – – – 35
Nickel in soil – – – – – – – – – 36
Human exposure to nickel – – – – – – – 38
Telfairia occidentalis (fluted pumpkin) – – – – – 39
Telfairia occidentalis as an environmental bio-indicator
for Monitoring of heavy metals soil ecosystem – – – – 41
Types of bio-indicators – – – – – – – 42
Soil electrical conductivity – – – – – – – 44
Soil pH – – – – – – – – – 46
Biodegradation of total petroleum hydrocarbons in soil – – – – 46
Chemical composition of palm bunch ash (PBA) – – – – 51
Tween 80 – – – – – – 52
Chemical structure of Tween 80 – – – – – – 53
Chapter Three
Study design and methodology – – – – – – 54
ix
Niger Delta – – – – – – 54
Map of the study area – – – – – – 55
The study area (Qua Iboe Coastal Area) – – – – – 56
Geographical description – – – – – – 56
Climate – – – – – – 56
Geology and hydrogeology – – – – – – – 57
Soil – – – – – – – – – – 57
Socio-economic characteristics – – – – – – 57
Sampling program design – – – – – – – 58
Sampling procedure for soil – – – – – – – 59
Precaution to avoid being exposed to contaminants – – – – 59
Analytical procedure for the soil/sediment samples preparation – – 60
Preparation of aqua regia – – – – – – – 60
Sample collection (fluted pumpkin) – – – – – – – 60
Sample preparation: leaves of fluted pumpkin – – – – – 61
Analytical procedure for fluted pumpkin sample – – – – 61
Experimental – – – – – – – 61
Samples collection procedures: sediment and water – – – – 62
Sample preparation for water – – – – – – – 62
Analytical procedure for sediment – – – – 62
Experimental procedure for determination of electrical
Conductivity and pH of the soil – – – – – 63
Determination of total petroleum hydrocarbons – – – 64
Materials and apparatus – – – – – – – 64
Samples collection and preparation — – — – – – 64
Preparation of soil and surfactant mixture – – – – – 66
Analysis of the soil for total petroleum hydrocarbons – – – 66
Statistical analysis – – – – – – 70
Chapter Four
Results and discussion – – – – – – 71
Results of extractable heavy metals concentration
in soil, fluted pumpkin, sediment, and water – – – – – 71
Results physicochemical properties of soil – – – – – 86
x
Seasonal dynamics of individual element – – – – – 95
Nickel (Ni) – – – – – – – – 95
Vanadium (V) – – – – – – – — 100
Cadmium (Cd) – – – – – – – – 104
Lead (Pb) – – – – – – — – – 110
Manganese (Mn) – – – – – – – – 115
Iron (Fe) – – – – – – – – – 119
Zinc (Zn) – – – – – – – – – 123
Cobalt (Co) – – – – – – – – – 127
Degradation efficiency kinetics of (TPHs)
by palm bush ash and Tween 80 – – – – – 130
Effects natural surfactant palm bush ash (PBA) and
synthetic surfactant Tween 80 on physicochemical
properties of the soil – – – – – – 150
Correlation coefficient (r) between extractable
Heavy metals in soil Telfairia occidentalis – – – – 151
Leaves of Telfairia occidentalis (Fluted pumpkin) as bio-indicator – – 154
Dry and wet season’s variation between concentrations
of heavy metals in soil, fluted pumpkin, water and sediment – – 156
Relationship between concentrations of heavy metals
in the fifteen sampling locations – – 165
Electrical conductivity and pH – – – – – – 176
Chapter Five
Conclusion – – – – – – – – – 183
Contributions to knowledge – – – – – – – 184
Recommendations – – – – – – – – 185
References – – – – – – – – – 186
Appendix – – – – – – – – – 202
CHAPTER ONE
INTRODUCTION
Metal pollutants have been a part of human history since the dawn of civilization. However,
toxic metals pollution of the biosphere has intensified rapidly since the onset of the industrial
revolution, posing major environmental and health problems1. Recently, environmental
scientists have raised concern on the increasing ecological and toxicological problems arising
from pollution of the environment. Heavy metals represent an important source of the
pollution 2. Heavy metals like As, Pb, Hg, Cd, Co, Cu, Ni, Zn, and Cr are phyto-toxic at all
concentrations or above certain threshold levels3. Toxic metals are biologically magnified
through the food chain. They infect the environment by affecting soil properties, its fertility,
biomass, crops yield and human health3.
Heavy metals occur naturally in small quantities in soil though rarely at toxic level,
but human activities have raised these to exceptionally high levels at many polluted land and
water sites. Soil is a crucial component of rural and urban environments, and in both places,
land management is the key to soil quality4. Human endeavours such as technology,
industrialization, agriculture, transportation, education, construction, trade, commerce, as
well as nutrition have rendered the whole environmental system a “throwing society”. This is
true because indiscriminate disposal of wastewater coupled with increasing world population
and urbanization have combined to worsen the situation. The use of synthetic products e.g.
(pesticides, paints, batteries, industrial waste, and land application of industrial and domestic
sludge) can result in heavy metal contamination of urban and agricultural soils.4
The extent of soil pollution by heavy metals and metal base ions, some of which are
soil micronutrients is very alarming. Ademoroti 5, reported positive linear correlation
between cadmium, lead, and nickel contents in the soil and vegetable.
Essein et al. 4, observed the trend of mean heavy metals concentrations in Mkpanak a
community in the study area as Fe > Zn > Pb > Ni > V > Cd. The mean concentration of iron
in the soil was quite high and exceeded the critical toxicity level. The result obtained also
showed that the mean concentration of Cd was high and exceeded the lower limit of 0.01 mg
kg-1. Also, Osuji et al.6, had earlier reported possible bio-magnification of Ni, V, Pb, Cu and
Cd in the area. Industrial wastes are the major sources of soil pollution and originate from
mining industries, chemical industries, metal processing and petroleum industries; the wastes
include a variety of chemicals like heavy metals.6
2
While many heavy metals are essential elements at low levels, they can exert toxic
effects at concentration higher. Soil receives heavy metals coming from different sources and
at the same time acts as a buffer, which controls the movement of these heavy metals to other
natural components2.
Increase in anthropogenic activities, heavy metals pollution of soil, water and
atmosphere represent a growing environmental problem affecting food quality and human
health 7 in the Niger Delta region of Nigeria. Nigeria as a major producer and exporter of
crude petroleum oil continue to experience oil spill and this exposes the environment to
hazards and its effects on agricultural lands as well as on plant growth8. Oil pollution of soil
leads to the buildup of essential (Organic carbon, P, Ca, Cu) and non-essential (Mn, Pb, Zn,
Fe, Co, Cu) elements in soil and the eventual translocation in plant tissues9. Industrialization
coupled with an ever-increasing demand for petrochemicals have resulted in prospecting for
more oil wells with consequent pollution of the environment. Causes of oil pollution in
Nigeria include discharge from sludge, production test, drilling mud, and spills from
pipelines, well blowouts, gas flaring and sabotage10. Oil spills have long effects on soil; an
immediate effect of petroleum products in the soil is a depression in population of soil
microorganisms. Besides the economic and aesthetic damages caused by oil spills, plants and
animals life in both aquatic and terrestrial environment are affected as most life form die
rapidly following spillage. Many unique plants and animals’ species have gone into
extinction in the Niger Delta regions11.
Pollution of the ecosystem by toxic metals during man’s activities poses serious
concerns because heavy metals are not biodegradable and are persistent in the ecosystem.
Once metals are introduced and contaminate the environment, they will remain for a very
long time.11
The presence of heavy metals in toxic concentrations can result in the formation of
super oxide radicals, hydrogen peroxide (H2O2), hydroxide radicals (OH-), bio-molecules like
lipids, protein and nucleic acid. Chromium, Copper and Zinc can induce the activity of
various antioxidant enzymes and non-enzymes like ascorbate and glutathione3. Petroleum
renders the soil infertile, burns vegetation and kills useful soil organism12.
In Nigeria, a study of heavy metals concentration near Warri refinery found three to
seven times elevated levels of various heavy metals in the soil13. Although the petroleum
industry is by far the largest industrial sub-sector in the Niger Delta, at least eight of the most
polluting sub-sectors in Nigeria (steel work, metal fabrication, food processing, textile,
refineries and paints manufacturing) operate in the Niger Delta13, 14.
3
Oil exploration and exploitation have uplifted Nigerian economy leading to rapid
development but the impact on the environment is receiving less attention15. One of the major
anthropogenic sources of heavy metals enrichment in terrestrial habitats of oil producing area
of Nigeria is the frequent spills of crude oil on land and gas flaring 12. Nigerian crude oil is
known to contain heavy metals such as Zn, As, Ba, Fe, Pb, Co, Cu, Cr, Ga, Mn, Ni and V.
Toxicity of ingested heavy metals has been an important health issue for decades 16.
Some species of Brassica (cabbage) are high accumulators of heavy metals in the edible parts
of the plants 17 and this can be an important exposure pathway for people who consume
vegetable grown in heavy metal contaminated soil 15. The level of heavy metals for examples
lead, cadmium and copper where determined in cassava from different location of oil
exploration areas of Delta State, Nigeria. The results of different heavy metals have higher
values when compared with WHO standard. These metals have damaging effects on the
plants themselves and may become hazardous to man and animals. Above certain
concentrations and over a narrow range, the heavy metals turn toxic. Moreover, these metals
adversely affect natural microbial population leading to disruption of vital ecological
processes. Plants can accumulate heavy metals in their tissues and uptake increases generally
in plants that are grown in areas with increased soil contamination with heavy metals and
therefore, many people could be at risk of adverse health effects from consuming common
garden vegetables cultivated in contaminated soil 12.
Streit and Strum, and Ruszewski et al 18, 19, classified the exchange of chemicals
between soil and plants; they divided the most common method of assessing metal toxicity to
plants from soil into three categories:
i. monitoring of the presence or absence of specific plant ecotypes and or plant
species (indicator plant).
ii. measurements of metal concentration in tissues of selected species
(accumulative bio-indicators).
iii. recording of physiological and biochemical responses (bio-makers) in
sensitive bio-indicators.
The pollution of rivers, lakes, underground water, bays of oceans, and streams with
chemical contaminants (heavy metals, organic and inorganic compounds) has become one of
the most critical environmental problems of the century.4 Non-degradable, bio-persistent
stock pollutant such as heavy metals and mineral hydrocarbons could get into aquatic
environment from a wide range of natural and anthropogenic point sources. In aquatic
ecosystems, heavy metals are contained in four reservoirs, namely; the suspended sediment,
4
the bottom sediment, the surface water and the pore water. Studies have revealed that
contaminants in aquatic system are usually in pore water-surface water-sediment dynamic
with bottom sediment acting as the major depository of heavy metals5. The questions of
heavy metals in water first became an issue only in Sweden and later in Canada.
Writing on the impact of economic activities on the environment of the Niger Delta,
Agbozu 13, stated that water bodies have been heavily polluted due to the recurring incident
of oil spillage. Most micro-populations and invertebrates are eliminated following large-scale
spillage, while sub lethal levels of oil following several scale spillages have generally
affected aquatic resources.
Ibeno Local Government Area is a coastal sub-region characterized by abundant
water resources. The absence of potable water supply for domestic use in some parts of Ibeno
has compelled the population to rely heavily on natural sources of water supply for domestic
uses. The quality of most of these sources of water is doubtful. The study area is one of the
coastal area as well as an oil producing area in Akwa Ibom State bordered by the Atlantic
ocean and has various environmental problems including pollution of available water
resources. There are many types of water sources available for domestic, recreational, fishing
and industrial uses. These include ponds, streams, boreholes, lakes, rivers, oceans and rain
water, but they are all polluted by human and industrial activities in the area. The
anthropogenic and natural phenomena seem to affect water quality in the study area. These
include gas flaring, oil spillage, washing wastewater and sludge from industrial processes,
poor sanitation, storm surges, salt-water extrusion and intrusion, release of untreated human
waste and sewage into waterways.
Water pollution occurs when chemical, physical or biological substances exceed the
capacity of water body to assimilate or break down the substance that can cause harm to the
aquatic ecosystem. Precipitation that reaches the earth’s surface follows two basic pathways;
it either flows overhead or soaks into the soil20. Water that flows over the ground is often
called run off. The term surface water refers to water flowing in streams and rivers as well as
water stored in natural or artificial lakes. Surface water is water that flows or rests on land
and is open to atmosphere; lakes, pond, lagoons, rivers, streams, oceans, ditches, man-made
impoundments are bodies of surface water 20. Analysis of soil samples from Uyo town by
Akaeze 106 disclosed that heavy metals such as lead, copper and iron are present in the soil,
these may contaminate soil water, which constitutes the major sources of drinking water 21.
Oil spillage and dumping of petroleum effluents on land are common phenomena. Gas flaring
also contributes to heavy metals contamination of soil15.
5
The contamination of the environment by heavy metals is viewed as an international
problem because of the effects on the ecosystem in most countries. In Nigeria, the situation is
no better by the unethical activities of most industries and because of countries inability to
manage industrial wastes with the increasing level of pollution of water bodies.
Environmental degradation of the oil rich Niger Delta region has caused a wanton destruction
and continuous harm to their health, social and economic consequences for its people, for
over a decade. Petroleum refineries produce a wide variety of air and water pollutants and the
distillation products of refining and industrialization, intensive agriculture and other
anthropogenic activities have led to land degradation, environmental pollution and decline in
crop productivity and sustainability. These have been of great concern to human and animal
health 22, 23.
One of the prominent sources contributing to increased load of soil contamination is
the disposal of municipal and industrial wastes. The wastes are either dumped on roadsides or
used in landfills. These wastes although useful as sources of nutrients are also sources of
carcinogens and toxic metals 23
.
In the study of the socio-economic impact of oil pollution, Worgu 23 stated that crude
oil exploration has had adverse environmental effect on soil, forest and water bodies in host
communities in the Niger Delta. All stages of oil exploration impacted negatively on the
environment and the greatest single intractable environment problem caused by crude oil
exploration in the Niger Delta region is oil spillage. According to Annual reports of the
Department of Petroleum Resources (DPR) 1997, over 6,000 spills have been recorded in the
40 years of oil exploration in Nigeria with an average of 150 spills per annum. In the period
1976 – 1996, 647 incidents occurred resulting in the spillage of 2,369,407.00 barrels of crude
oil with only 549,040.38 barrel recovered, while 1,820,410.50 barrels of oil were lost to the
ecosystem23. These chemicals if not properly controlled according to guidelines and standards
set by regulating agencies like Department of Petroleum Resources, it can pollute the soil and
groundwater system in the area where such operation is carried out. Thousands of spills occur
across the fragile Niger Delta and have destroyed livelihoods of fishermen and farmers,
fouled water sources and polluted the ground and air. The Nigerian government estimates that
there were over 7,000 spills, large and small, between 1970 and 2000. That is approximately
300 spills a year and some spills have been leaking for years. Vast swathes of the Delta are
covered with tar and stagnant lakes of crude. By some estimate, over 13 million barrels of oil
have spilled into the Delta. An additional 2,405 spills by all major oil companies in the region
6
have occurred since 2006. Corroded pipes caused a spill in 2010 that leaked about 232 barrels
of crude oil 23.
7
Table 1: Number of spills, quantity of spills (barrels), and quantity of oil recovered
(barrels) and net loss to the environment in barrels between 1976 -1989.
Year Number
of spills
Quantity
(barrels)
Quantity
recovered
(barrels)
Net loss to the
environment
(barrels)
1976 128 26157.00 7135.00 19021.50
1977 104 32879.25 1703 3117675.00
1978 154 489294.75 391445.00 97849.75
1979 157 64117.13 63482.20 630635.95
1980 241 600511.02 42416.23 558094.19
1981 238 42722.50 5470.20 37052.30
1982 257 42814.00 2171 40669.60
1983 173 48351.30 6355.90 41995.40
1984 151 40209.00 1644.80 38564.20
1985 187 11876.60 1719.30 10157.30
1986 155 12905.00 252.00 12358.00
1987 129 31866.00 6109.00 25358.00
1988 108 9172.00 2153.00 7202.00
1989 118 5956.00 2092.55 3830.00
Source: Annual report of Department of Petroleum Resources (DPR), 1997191
8
1.0.1 Statement of the problem
The study area (Ibeno Local Government Area) in recent times has received attention
owing to considerable stress it has been subjected to through deliberate and or accidental oil
spills, blast water discharge, untreated sewage, gas flaring and industrial effluents.
Qua Iboe River estuary is the point where petroleum exploration and production (E
and P) wastes from the Exxon Mobil Qua Iboe Terminal (QIT) tank farm are transferred to
the lower Qua Iboe River estuary and adjourning creeks through two 24 mm diameter pipes.
The Exxon Mobil oily sludge dumpsite and flare stack, where gas is flared continuously are
in the study area. The study area has a number of oil wells, NNPC pipelines run across and
some flow stations situated.
Seemingly, most of the terrestrial ecosystem and shorelines in the oil producing
communities are under continuous cultivation. After heavy spills of crude oil, soils are
usually barren, and may run into low-lying areas with organic soils and natural re-vegetation
of the soil generally slow. Depending on the amount of oil in the soil, the soil may remain
completely barren for many years. Environmental pollution by the industrial and domestic
activities may therefore have far-reaching implication on the agricultural productivity on the
area and multiplier effect on the socio-economic wellbeing of the people. At present, there is
no report available on the seasonal levels of anthropogenically associated heavy metals in
Telfairia occidentalis (fluted pumpkin) a common vegetable cultivated in the study area. In
addition, more extensive work is needed on the comparison between the seasonal dynamics
of heavy metals levels in soil, plant, sediment and water with local and international
guidelines and standards.
Also, increase in demand for crude oil and petrochemicals has resulted in exploration
for more oil wells with consequent pollution of the environments. This has adversely affected
food quality and human health in Niger Delta region of Nigeria. The traditional methods of
detection and remediation of environments from contaminants include the use of Atomic
Absorption Spectrophotometer (AAS), capping and chemical precipitation for heavy metals
in soil and water respectively. In addition, accelerated solvent extraction and application of
Tween 80 to degrade total petroleum hydrocarbons (TPHs) in soil are cost prohibiting when a
large area is involved. They also affect the biota with resultant adverse effects on human
beings. These necessitated the quest for development of alternative, indigenous and ecofriendly
green remediation and bio-indicator technologies for controlling and assessing
environmental contaminants.
9
The present study was carried out to determine the existing concentrations of heavy
metals in soil, Telfairia occidentalis (fluted pumpkin), water and sediment during wet and dry
seasons in Ibeno coastal area. Also, to find bio-indicator properties of Telfairia occidentalis
as an indigenous and eco-friendly green tool in detecting heavy metals pollutants in soil of
the study area. Furthermore, the present study was conducted to determine the concentration
of total petroleum hydrocarbon in the soil of the study area and consequently developed an
alternative indigenous and eco-friendly remediation technology for total petroleum
hydrocarbon in soil by comparing degradation efficiencies kinetics of natural surfactant
(palm bunch ash) and synthetic surfactant (Tween 80).
1.0.2 Objectives of the study
This research work was designed, to achieve the following objectives:
(i) determine seasonal concentrations of heavy metals in soil, sediment, water,
and leaves of Telfairia occidentalis,
(ii) establish correlation between the amount of the heavy metals in soil and leaves
of Telfairia occidentalis,
(iii) determine bio-indicator properties of leaves of Telfairia occidentalis,
(iv) investigate the amount of total petroleum hydrocarbons (TPHs) in the soil, and
(v) compare the degradation efficiencies of the TPHs in the soil amended with
palm bunch ash (PBA) and Tween 80.
(vi) investigate the effects of palm bunch ash (PBA) and Tween 80 on the
physicochemical properties of the soil.
10
1.0.3 Scope of the study
The present study covered the following areas:
(i) samples collection and preparation.
(ii) determination of heavy metal concentrations, in soil, leaves of Telfairia occidentalis
(fluted pumpkin), water and sediment during wet and dry seasons in Ibeno coastal
area.
(iii) investigation of bioindicator properties of leaves of Telfairia occidentalis (fluted
pumpkin)
(iv) determination of total petroleum hydrocarbon concentration in soil and investigation
of the degradation efficiency kinetics of palm bunch ash and tween 80.
(v) verification of the effects of palm bunch ash and Tween 80 on the physicochemical
properties of oil polluted soil.
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