ABSTRACT
The weight and the length of the test organism was taken and recorded. The weight of test organism (Tilapia guineensis) was 222.5 ± 2.11 mg while the length was 1.5 ± 0.03 cm. The physicochemical analysis of habitat water was carried out in order to establish if the habitat water can support life. All test organisms were first acclimatized for ten (10) days at room temperature (28 ± 2º̊C). Range finding test was carried out to establish a preliminary working range by obtaining the least concentration that gives no effect and the minimum concentration that gives 100 % death. Acute toxicity tests were carried out with the aquatic organism (Tilapia guineensis) by exposing them to test solutions (SDS and GC) containing various concentrations of the test solutions using the semi – static agitation test procedure as recommended by Department of Petroleum Resources (DPR). The number of test organism decreased with respect to time even at a particular concentration and also decreased as concentration increased. From the result, it was also observed that as % survival decreased with respect to time even at a particular concentration, % mortality increased with respect to time and also % survival decreased while % mortality increased as concentration increased. This could be attributed to the effect of GC and SDS on the test organism since the control did not follow this trend. This showed that the longer the time of exposure, the more the effect of GC and SDS on Tilapia guineensis. A comparative assessment of the two dispersants SDS and GC showed that GC was more toxic to the test organism Tilapia guineensis than SDS at the same concentration. This is because a slight concentration of 0.05 ml/L of GC gave 90 % mortality after 48 h exposure while 100 mg/L SDS gave 100 % mortality at the same duration. Also at 0.05 ml/L GC and 100 mg/L SDS for exposure period of 72 and 96 h, GC and SDS gave same 100 % mortality. Hence gold crew should be treated as more toxic dispersant compared to SDS at various concentrations and exposure time.
TABLE OF CONTENTS
Title
page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table
contents vi
List of
tables x
List of
xi
List of
xii
Abstract xiii
CHAPTER
1: INTRODUCTION
1.1 Background to the study 1
1.2 Statement of problem 2
1.3 Aim and objectives 2
1.4 Justification of the study 3
1.5 Scope and limitations 3
CHAPTER
2: LITERATURE REVIEW
2.1
Oil spill 4
2.2 Impacts on aquatic and
terrestrial wildlife 6
2.2.1 Impacts on vegetation 6
2.2.2 Impacts on benthic organisms 6
2.2.3 Impacts on animals 7
2.2.4 Impacts on people 7
2.3 Dispersants
8
2.3.1 Dispersants and formulations 9
2.3.2 Effectiveness of dispersants 10
2.3.3 Field Trials of dispersants 12
2.3.4 Laboratory tests of
dispersants 13
2.3.5 Impacts of non-dispersed remnants
14
2.3.6 Dispersant use policies in
other countries of the World 15
2.4 Examples
of dispersants 16
2.4.1 Sodium dodecyl sulphate (SDS) 16
2.4.2 Gold crew 18
2.4.2.1 Brief history of gold crew as
oil spill dispersant 18
2.4.2.2 Gold crew: cost effective and
accelerates bioremediation 20
2.5 Toxicity
of dispersants 21
2.5.1 Toxicity of sodium dodecyl 23
2.5.1.1 Morphological changes 24
2.5.2 Toxicity of gold crew 27
2.6 Type of toxicity tests 27
2.6.1 Static and continuous flow or
flow through 29
2.6.2 Bioassay (Toxicity testing) 31
2.6.2.1 Types of bioassay techniques 32
2.7 Dose response relationship 33
2.7.1 Dose effect relationship 34
2.8 Probit analysis 36
2.8.1 Background 36
2.8.2 The Basics of probit analysis 36
2.8.3 Applications of probit
analysis 37
CHAPTER
3: MATERIALS AND METHODS
39
3.1 Materials
39
3.1.1Reagent and chemicals
39
3.1.2 Equipment
39
3.2 Methods
39
3.2.1 Description of experimental location
39
3.2.2 Preparation of stock
solutions
39
3.2.3 Test methods and test concentrations
40
3.2.3.1 Static renewal (semi-static)
test 40
3.3 Sampling and specification of
test animals 40
3.4 Acclimatization and selection of
test organism 41
3.5 Range finding test 41
3.6 Test medium 41
3.7 Physicochemical analysis 39
3. 7.1 pH (APHA 4500 H+) 42
3.7.2 Electrical conductivity 42
3.7.3 Salinity 43
3.7.4 Alkalinity 43
3.7.5 Hardness 44
3.7.6 Total dissolve solid (TDS) 44
3.7.7 Temperature 45
3.7.8 Dissolved oxygen 45
3.8 Acute toxicity test
45
3.8 .1 Steps in carrying out acute
toxicity test include: 45
3.9 Methodology for determination of
acute toxicity 47
3.10 Histological study 48
3.10.1 Process of staining paraffin section
with H and E 50
3.11 Data analysis 51
CHAPTER 4: RESULTS AND
DISCUSSION
52
4.1 Average
weight of test organism 52
4.2 Average
Length of Test Organisms 52
4.3
Physicochemical characteristics of fresh water 52
4.4 The control test organism Tilapia
guineensis result 53
4.5 Result of range finding test for SDS
54
4.6 Result of range finding test for GC 56
4.7 Acute toxicity
of SDS 58
4.8 Acute
toxicity of gold crew 61
4.9
Percentage mortality 64
4.10 Probit
mortality 65
4.11 Lethal
concentration 66
4.12: Histological
analysis of tissues and organs 69
4.12.1 Gill
histology for SDS samples 70
4.11.2 Gill
histology for GC samples after 24 h 71
4.11.3 Gill
histology for GC samples after 72 h 72
4.11.4 Gill
histology for GC samples after 96 h 73
4.11.5 Gill
histology for GC samples after 21 day 74
4.11.6
Muscle histology for SDS samples 75
4.11.7 Muscle histology for GC samples after
24 h 76
4.11.8
Muscle histology for GC samples after 48 h 77
4.11.9
Muscle histology for GC samples after 96 h 78
4.11.10
Muscle histology for GC samples after 21 days 79
4.11.11
Intestinal histology for GC samples 80
4.11.12
Intestinal histology for GC samples 81
CHAPTER 5: CONCLUSION AND
RECOMMENDATIONS 82
5.1
Conclusion 82
5.2 Recommendations 82
REFERENCES 83
APPENDICES 91
LIST OF TABLES
4.1: Some physicochemical characteristics of
fresh water 51
4.2:
Control with fresh water only using fresh water organism Tilapia guineenis 52
4.3: Range finding test of SDS in fresh water
using Tilapia guineensis 53
4.4:
Range finding test of gold crew in fresh water using Tilapia guineensis 55
4.5:
Acute Toxicity of SDS 57
4.6:
Acute Toxicity of Gold Crew 60
4.7: Percentage mortality of SDS on Tilapia guineenis. 62
4.8: Percentage mortality of Gold crew on Tilapia guineensis. 63
4.9:
Probit mortality of SDS on Tilapia
guineensis. 63
4.10:
Probit mortality of Gold Crew on Tilapia
guineenis. 64
4.11: Lethal concentrations (LC50) of
toxicants on Tilapia guineensis 65
4.12: Probit survival Table for Gold Crew 65
LIST OF PLATES
1:
Gill: Control (a), 40mg/L SDS (b), 80mg/L (c) SDS 68
2:
Gill: Control (a), 0.04ml/L (b), 0.05ml/L (c) GC after 24 h 69
3:
Gill: Control (a), 0.04 ml/L (b) GC after 72 h 70
4:
Gill: Control (a), 0.02 ml/L (b)
GC after 96 h 71
5:
Gill: Control (a), 0.02 ml/L (b) GC after 21days 72
6: Muscle: Control (a), 40 mg/L (b) SDS, 80
mg/L (c) SDS 73
7: Muscle: Control (a), 0.05 ml/L (b) GC after
24 h 74
8:
Muscle: Control (a), 0.04 ml/L (b) GC
after 48 h 75
9: Muscle: Control (a), 0.02 ml/L (b) GC after
96 h 76
10: Muscle:
Control, 0.02 ml/L GC after 21days 77
11:
Intestine: Control, 0.04 ml/L GC after
72 h 78
12:
Intestine: Control, 0.02 ml/L GC after
21days 79
LIST OF FIGURES
2.1: Hydrophobic tail and Hydrophilic head of
SDS 8
2.2:
Structures of the different types of dispersants 15
4.1: Percentage Mortality against Time for SDS 58
4.2:
Percentage Mortality against Concentration for SDS 58
4.3:
Percentage Mortality against Time for Gold Crew 61
4.4:
Percentage Mortality against Concentration for Gold Crew 61
4.5: Probit
Mortality graph for LC50 Calculation for SDS 66
4.6: Probit graph for LC50 Calculation
for Gold Crew 66
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND TO THE STUDY
Cleanup
of oil spill is important for the survival of both terrestrial and aquatic organisms.
Oil spill environment can be cleaned up using dispersants. Dispersants are
mostly regarded harmless on the basis of their biodegradability and their
speculated low concentration. But studies on dispersants’ concentration
worldwide reveal the fact that these chemicals are found in concentrations
higher than their supposedly “no- effect concentrations” (Fingas, 2000;
Gonzalez et al., 2012). Therefore,
regarding dispersants as non-pollutants is a mistake. Records of visible surfactant
toxicity are available and its effects on microbes, plants and animals has been
documented (Ostroumov, 2006).
Gold
crew (GC), Sodium dodecyl sulphate (SDS) and other dispersants have been found
to be toxic to plants, animals and microbes. Dispersants from different sources
affect the ecosystem and its inhabitants, the toxicity increasing down the
trophic level. The potential chemical tool for effective management of crude
oil spill in marine environment is dispersants. However, several factors are
considered in deciding whether to use chemical dispersants or not. One of such factor
is temperature which checks the physical effectiveness of the dispersant under
expected conditions of use. The second factor is the toxicity of the dispersed
oil and dispersant to local marine species. A third factor is the effect of
chemical dispersants on the fate of spilled petroleum hydrocarbon products.
Indiscriminate disposal of untreated chemicals including dispersants to the
receiving environment (aquatic system) is a source of contamination and pollution
to the receiving waters. Pollution causes unfavourable changes in the earth’s
physical, biological and chemical
features in such a manner which affects normal environmental processes (Luke
and Odokuma, 2017).
Dispersants
have been used increasingly for household, personal care and industrial
applications. A number of land-based
waste products, notably dispersants, find their way into rivers and seas. Since
the deep water Horizon drilling platform exploded in the Gulf of Mexico on April
20, 2010, British Petroleum (BP), operators of the platforms, has applied about
two million gallons of dispersants, both on the surface and beneath the Gulf
waters. Government agencies have accepted that this amount and the manner in
which dispersants have been applied in the Gulf are unacceptable. It is also
unacceptable on the application of dispersant at the source of the discharge, 1,524
m under the surface of the water.
Through
enhancing the amount of oil that physically mixes into the water column,
dispersants reduce the amount of oil that reaches shoreline habitats. Even although
it is required for in the oil pollution
Act of 1990 (of Mexico) as a tool for minimizing the impact of oil spills,
chemical dispersants are controversial (NRC, 2005) because of the toxicity of
dispersed mixtures and their potential negative impacts on ocean life. Another
point of controversy is that once oil is dispersed in deep water, it cannot be
recovered. Oil, when combined with dispersants in the water column is more
toxic to marine species than either oil or dispersant alone.
The
possible toxicity of surfactants and oil dispersants has given rise to a number
of researches aiming to find new, less toxic compounds. However, despite the
research and the obvious usefulness of these chemicals, the notion that it
exerts a harmless effect on marine life still exists. The toxicity of some
dispersants can be assessed in the framework of studies aimed to assess the
suitability of dispersants and sorbents to be employed for the decontamination
of the aquatic environment after oil pollution (Gonzalez et al., 2012).
1.2 STATEMENT OF PROBLEM
It
has been discovered that the use of concentrated dispersants in containment of
oil spill in the aquatic environment has been a source of environmental concern
due to the toxic nature of these dispersants to aquatic lives. This problem can
be addressed; hence this research is targeted at finding the solution by
obtaining the least concentration of the dispersant that gives no effect on
aquatic lives and the minimum concentration that gives 100 % death after an
exposure period and thereby determining a synergy between the dispersant toxicity
to aquatic lives and the cleanup concentration.
1.3 AIM AND OBJECTIVES
The
aim of this study is to determine effects of various concentrations of two dispersants
(Sodium
dodecyl sulphate (SDS) and Gold crew (GC)) on fresh water Tilapia guineensis.
The
objectives of this study include:
1.
To determine the physicochemical
parameters of habitat water.
2. To carry out toxicity tests of the
dispersants, SDS and GC on Tilapia guineensis.
3. To carry out a histological study on Tilapia guineensis.
4. To
determine the LC50 concentration of each dispersant and probit
analysis on the toxicity tests.
1.4 JUSTIFICATION
The
environmental concern on the use of dispersants is the justification for this
research. It has been discovered that in the bid to get rid of spilled oil on
the surface and subsurface of aquatic environments, aquatic lives have been
destroyed due to high concentration of dispersants used. This challenge which
is contrary to the achievement of a sustainable environment and sustainable
development goals prompted this research. Till
date, there is no conclusive evidence that dispersants are not toxic to aquatic
lives, hence the need for this research. Nigeria has a massive oil spill
problem especially in the Niger Delta Region where vast areas of land and water
are polluted. However, the use of dispersants for the cleanup of polluted water
may be problematic due to the possible toxicity of these dispersants on aquatic
organisms.
1.5 SCOPE AND LIMITATIONS
This
research studies the toxicity of dispersants (Gold crew and SDS) on Tilapia guineensis in aquatic
environment. The effectiveness of dispersants was quantified in controlled
field. The limitations of the research include that it is restricted to only
aquatic environment.
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