– Heavy Metal Concentrations and Degradation Efficiency of Total Petroleum Hydrocarbons on Environment in Ibeno Local Government Area, Akwa Ibom State, Nigeria –
ABSTRACT
Heavy metal concentrations and degradation efficiency of total petroleum hydrocarbons (TPHs) on the environment in Ibeno Local Government Area, Akwa Ibom State, Nigeria was investigated. An 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 a corer and clean plastic bottles respectively.
Soil and sediment samples were air-dried, mechanically ground using mortar and pestle, and a 2 mm mesh size was 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; the temperature was later adjusted to 120 oC and heated continuously for 2 h. The mixture was cooled, and 0.2 M HNO3 (10 cm3) was 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 was 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 a 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 labelled A, B, C, and D. Varying concentrations of 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 was 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 a 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 the 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 (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 the soil were within the 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 foodstuff 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 the dry season compared to the wet season except for 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 bioindicator 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
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
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
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 of 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
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 about the increasing ecological and toxicological problems arising from pollution of the environment. Heavy metals represent an important source of pollution 2.
Heavy metals like As, Pb, Hg, Cd, Co, Cu, Ni, Zn, and Cr are phytotoxic 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, fertility, biomass, crops yield and human health3.
Heavy metals occur naturally in small quantities in soil though rarely at a 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
REFERENCES
Bhaskar, R. and Lena, Q. (2005). Tolerance of heavy metals in vascular plants; arsenic hyper accumulation by Chinese braker fern (pterzs vzttatal). Pteridology in the new millennium. Kluwer Academic publisher, Netherlands: pp 397-420
Udosen, E. D. and Awak-Ama, J. J. (2005). The concentration of some toxic metals ions in a tropical ultisol from coastal plain area of Akwa Ibom State, Nigeria. Global J. of pure & Appl. Sci.7(3):427 – 431.
Varsha, M., Niddhi, M. and Anurag, M. (2010). Heavy metals in plants: Phytoremidiation: Plants used to remediate heavy metal pollution. Agr. & Biol. J. of North Am. 7(4):2151 – 7517.
Essien, J. P. and Benson, N. U. (2012). Trend in heavy metals and total hydrocarbon burdens in stub creek, a tributary of Qua Iboe Estuary, Nigeria. Trends. Appl.Sci.Res. 2: 312 – 319.
Ademoroti, C. M. (1996). Pollution by heavy metals. Environmental chemistry and toxicology. Foluder Press Limited, Ibadan, 66p
Osuji, C. L. and Chukwunedum, M. O. (2001). The Ebocha-8 oil spillage fate of associated heavy metals six months after. Petroleum chemistry research group, Department of industrial and pure chemistry, University of Port Harcourt, Choba, Port Harcourt, Nigeria.
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