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DETERMINATION OF THE LEVELS OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) AND HEAVY METALS IN SOILS AND PLANT FOOD CULTIVARS FROM SOME OIL EXPLORATION COMMUNITIES OF BAYELSA STATE

DETERMINATION OF THE LEVELS OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) AND HEAVY METALS IN SOILS AND PLANT FOOD CULTIVARS FROM SOME OIL EXPLORATION COMMUNITIES OF BAYELSA STATE

 

ABSTRACT

Soils and vegetation in three selected communities in Bayelsa state were investigated for presence of recalcitrant Polycyclic aromatic hydrocarbons (PAHs) and heavy metals in the soils and edible plant food cultivars Two of the communities, Angiama and Oporoma are crude oil impacted areas having had oil spillage accidents in 2010 and 2008 respectively while Yenagoa a non crude oil impacted area is used as control Physicochemical properties of soils from these study areas were investigated using standard methods, the polycyclic aromatic hydrocarbon (PAHs) in the soil and food cultivars were determined using Gas Chromatography - Mass Spectrophotometer while heavy metals were analysed by Atomic Absorption Spectrophotometer The result of the investigation reveal that oil spillage degrades the soil as revealed by the significant reduction in pH , moisture content and bulk density of soils from Angiama and Oporoma communities compared with Yenagoa Soil from Angiama had the highest percentage (%) organic carbon (440±053%) and total hydrocarbon (84640±1011mg/kg) followed by Oporoma (213±012% and 52000±500mg/kg respectively) and Yenagoa (130±108% and 6220±026mg/kg respectively) The anion levels of soil nitrate (NO3 2-) and phosphate (PO4 3-) were significantly highest in soil residues from Yenagoa than in Angiama and Oporoma while the levels of exchangeable cations (Ca2+, Mg2+, K+,and Na+) were highest in Angiama than in Oporoma and Yenagoa soils The values were significantly different at p<005This suggest that exchangeable cations accompany oil spill High molecular weight recalcitrant PAHs Benzo(a) pyrene, benzo(a) anthracene, Benzo(K) fluoranthene, Benzo(b)fluoranthene were present in both Angiama and Oporoma soil but were not detected in Yenagoa Except for phenanthrene, low molecular weight PAHs were not detected in soil samples from Yenagoa, occurred sparingly in Oporoma but were predominant in Angiama Food cultivars from both Angiama and Oporoma were equally proportionately contaminated with these high molecular weight PAHs The leafy vegetables (pumpkin and scent leaf) were far more contaminated than the tubers (yam and cassava) Heavy metal contaminants of soils and food cultivars mirror exactly the same trend associated with recalcitrant PAHs These results reveal that oil spillage activity is responsible for the preponderance of PAHs and heavy metals in the soils of the Niger Delta It also demonstrates that by the process of natural weathering polluted soils are remedied over time Given the appreciable accumulation of these crude fraction toxicants in food cultivars, it is suggested that the foods remain a major endogenous source of PAHs and heavy metals among the people of the area

 

TABLE OF CONTENTS

Title page ii

Certification iii

Approval iv

Dedication v

Acknowledgement vi

Abstract vii

Table of content viii

List of tables ix

List of figures x

List of Abbreviations xi

 

Chapter One

10 Introduction 1

11 Statement of the problem 2

12 Aims and objectives 3

13 Significant of the study 3

14 Relevance of the study 4

15 Description of the study areas with maps and pollution history 4

 

Chapter Two

20 Literature review 8

21 Occurrence of Polycyclic aromatic hydrocarbons (PAHs) 8

22 List of Polycyclic aromatic hydrocarbons (PAHs) 9

23 Classification of PAHs 10

24 Transport and Partitioning of PAHs 11

241 Vapour pressure 11

242 Henry’s Law 12

243 Solubility 12

244 Octanol water (Kow) and Organic Carbon (Koc) Partition Coefficient 13

25 Health hazards oh PAHs 14

251 Respiratory effect 14

252 Immunological effects 14

253 Reproductive effects 15

254 Developmental effects 15

255 Genotoxic effects 16

256 Cancinogenic effect 18

26 Pollution sources of PAHs 19

261 Air 20

262 Water 20

263 Soil 21

27 Heavy metal contaminants of crude oil 21

271 Lead ( Pb) 22

272 Cadmium (Cd) 24

273 Copper 26

274 Zinc (Zn) 28

275 Iron (fe) 30

276 Nickel (Ni) 31

28 Crude oil spills and the environment 32

29 Recalcitrant PAHs 34

210 Uptake of PAHs and Heavy metals by food crops 35

Chapter Three

30 Materials and Methods 38

31 Materials 38

311 Equipments/Apparatus 38

312 Chemicals and Reagents 38

32 Methods 39

321 Sample collections and preparation 39

3211 Sample collection 39

3212 Sample preparation 40

322 Analytical methods 41

3221 Characterization of soil samples 41

3222 Physicochemical analysis of soil samples 41

3223 Determination of PAHs 45

3224 Determination of heavy metal contaminant 47

3225 Result Analysis 48

 

Chapter Four

40 Results 49

41 Physicochemical properties of soils from polluted areas 49

42 Residual polycyclic aromatic hydrocarbon constituents of soils from the study areas 51

43 Polycyclic aromatic hydrocarbon levels in tuber cultivars from the study areas 53

44 Polycyclic aromatic hydrocarbon levels in plant leaves from the study areas 56

45 The composite pattern of PAHs distribution in soils and plant food cultivars in Yenagoa 59

46 The composite pattern of PAHs distribution in soils and plant food cultivars in Angiama 60

47 The composite pattern of PAHs distribution in soil and plant food cultivars from Oporoma 62

48 Heavy Metal Constituents of soils from the study areas 64

49 Heavy Metal Constituents in tuber cultivars from the study areas 65

410 Heavy Metal Constituents in plant leaves from the study areas 68

411 Composite pattern of heavy metal distribution in soils and food cultivars in Yenagoa 71

412 Composite pattern of heavy metal distribution in soils and food cultivars in Angiama 72

413 Composite pattern of heavy metal distribution in soils and food cultivars in Oporoma 74

 

Chapter five

50 Discussion 66

51 Physicochemical properties of soil from the study areas 66

52 Residual Polycyclic aromatic hydrocarbon constituents of soils from the study areas 67

521 Polycyclic Aromatic hydrocarbon levels in tuber cultivars from the study areas 69

523 Polycyclic Aromatic hydrocarbon levels in plant leave from the study areas 70

53 Heavy metal concentration in soil from the study areas 72

531 Concentrations of Heavy metal in tuber cultivars from the study areas 73

532 Heavy metal concentration in plant leaves from the study areas 73

Conclusion 78

Contribution to knowledge 78

References 79

Appendices 88


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