Heavy metal concentrations and degradation efficiency of total petroleum hydrocarbons on environment in ibeno local government area, akwa ibom state, nigeria

Thesis Overview

<p> </p><p>INTRODUCTION<br>Metal pollutants have been a part of human history since the dawn of civilization. However,<br>toxic metals pollution of the biosphere has intensified rapidly since the onset of the industrial<br>revolution, posing major environmental and health problems1. Recently, environmental<br>scientists have raised concern on the increasing ecological and toxicological problems arising<br>from pollution of the environment. Heavy metals represent an important source of the<br>pollution 2. Heavy metals like As, Pb, Hg, Cd, Co, Cu, Ni, Zn, and Cr are phyto-toxic at all<br>concentrations or above certain threshold levels3. Toxic metals are biologically magnified<br>through the food chain. They infect the environment by affecting soil properties, its fertility,<br>biomass, crops yield and human health3.<br>Heavy metals occur naturally in small quantities in soil though rarely at toxic level,<br>but human activities have raised these to exceptionally high levels at many polluted land and<br>water sites. Soil is a crucial component of rural and urban environments, and in both places,<br>land management is the key to soil quality4. Human endeavours such as technology,<br>industrialization, agriculture, transportation, education, construction, trade, commerce, as<br>well as nutrition have rendered the whole environmental system a “throwing society”. This is<br>true because indiscriminate disposal of wastewater coupled with increasing world population<br>and urbanization have combined to worsen the situation. The use of synthetic products e.g.<br>(pesticides, paints, batteries, industrial waste, and land application of industrial and domestic<br>sludge) can result in heavy metal contamination of urban and agricultural soils.4<br>The extent of soil pollution by heavy metals and metal base ions, some of which are<br>soil micronutrients is very alarming. Ademoroti 5, reported positive linear correlation<br>between cadmium, lead, and nickel contents in the soil and vegetable.<br>Essein et al. 4, observed the trend of mean heavy metals concentrations in Mkpanak a<br>community in the study area as Fe &gt; Zn &gt; Pb &gt; Ni &gt; V &gt; Cd. The mean concentration of iron<br>in the soil was quite high and exceeded the critical toxicity level. The result obtained also<br>showed that the mean concentration of Cd was high and exceeded the lower limit of 0.01 mg<br>kg-1. Also, Osuji et al.6, had earlier reported possible bio-magnification of Ni, V, Pb, Cu and<br>Cd in the area. Industrial wastes are the major sources of soil pollution and originate from<br>mining industries, chemical industries, metal processing and petroleum industries; the wastes<br>include a variety of chemicals like heavy metals.6<br>2<br>While many heavy metals are essential elements at low levels, they can exert toxic<br>effects at concentration higher. Soil receives heavy metals coming from different sources and<br>at the same time acts as a buffer, which controls the movement of these heavy metals to other<br>natural components2.<br>Increase in anthropogenic activities, heavy metals pollution of soil, water and<br>atmosphere represent a growing environmental problem affecting food quality and human<br>health 7 in the Niger Delta region of Nigeria. Nigeria as a major producer and exporter of<br>crude petroleum oil continue to experience oil spill and this exposes the environment to<br>hazards and its effects on agricultural lands as well as on plant growth8. Oil pollution of soil<br>leads to the buildup of essential (Organic carbon, P, Ca, Cu) and non-essential (Mn, Pb, Zn,<br>Fe, Co, Cu) elements in soil and the eventual translocation in plant tissues9. Industrialization<br>coupled with an ever-increasing demand for petrochemicals have resulted in prospecting for<br>more oil wells with consequent pollution of the environment. Causes of oil pollution in<br>Nigeria include discharge from sludge, production test, drilling mud, and spills from<br>pipelines, well blowouts, gas flaring and sabotage10. Oil spills have long effects on soil; an<br>immediate effect of petroleum products in the soil is a depression in population of soil<br>microorganisms. Besides the economic and aesthetic damages caused by oil spills, plants and<br>animals life in both aquatic and terrestrial environment are affected as most life form die<br>rapidly following spillage. Many unique plants and animals’ species have gone into<br>extinction in the Niger Delta regions11.<br>Pollution of the ecosystem by toxic metals during man’s activities poses serious<br>concerns because heavy metals are not biodegradable and are persistent in the ecosystem.<br>Once metals are introduced and contaminate the environment, they will remain for a very<br>long time.11<br>The presence of heavy metals in toxic concentrations can result in the formation of<br>super oxide radicals, hydrogen peroxide (H2O2), hydroxide radicals (OH-), bio-molecules like<br>lipids, protein and nucleic acid. Chromium, Copper and Zinc can induce the activity of<br>various antioxidant enzymes and non-enzymes like ascorbate and glutathione3. Petroleum<br>renders the soil infertile, burns vegetation and kills useful soil organism12.<br>In Nigeria, a study of heavy metals concentration near Warri refinery found three to<br>seven times elevated levels of various heavy metals in the soil13. Although the petroleum<br>industry is by far the largest industrial sub-sector in the Niger Delta, at least eight of the most<br>polluting sub-sectors in Nigeria (steel work, metal fabrication, food processing, textile,<br>refineries and paints manufacturing) operate in the Niger Delta13, 14.<br>3<br>Oil exploration and exploitation have uplifted Nigerian economy leading to rapid<br>development but the impact on the environment is receiving less attention15. One of the major<br>anthropogenic sources of heavy metals enrichment in terrestrial habitats of oil producing area<br>of Nigeria is the frequent spills of crude oil on land and gas flaring 12. Nigerian crude oil is<br>known to contain heavy metals such as Zn, As, Ba, Fe, Pb, Co, Cu, Cr, Ga, Mn, Ni and V.<br>Toxicity of ingested heavy metals has been an important health issue for decades 16.<br>Some species of Brassica (cabbage) are high accumulators of heavy metals in the edible parts<br>of the plants 17 and this can be an important exposure pathway for people who consume<br>vegetable grown in heavy metal contaminated soil 15. The level of heavy metals for examples<br>lead, cadmium and copper where determined in cassava from different location of oil<br>exploration areas of Delta State, Nigeria. The results of different heavy metals have higher<br>values when compared with WHO standard. These metals have damaging effects on the<br>plants themselves and may become hazardous to man and animals. Above certain<br>concentrations and over a narrow range, the heavy metals turn toxic. Moreover, these metals<br>adversely affect natural microbial population leading to disruption of vital ecological<br>processes. Plants can accumulate heavy metals in their tissues and uptake increases generally<br>in plants that are grown in areas with increased soil contamination with heavy metals and<br>therefore, many people could be at risk of adverse health effects from consuming common<br>garden vegetables cultivated in contaminated soil 12.<br>Streit and Strum, and Ruszewski et al 18, 19, classified the exchange of chemicals<br>between soil and plants; they divided the most common method of assessing metal toxicity to<br>plants from soil into three categories:<br>i. monitoring of the presence or absence of specific plant ecotypes and or plant<br>species (indicator plant).<br>ii. measurements of metal concentration in tissues of selected species<br>(accumulative bio-indicators).<br>iii. recording of physiological and biochemical responses (bio-makers) in<br>sensitive bio-indicators.<br>The pollution of rivers, lakes, underground water, bays of oceans, and streams with<br>chemical contaminants (heavy metals, organic and inorganic compounds) has become one of<br>the most critical environmental problems of the century.4 Non-degradable, bio-persistent<br>stock pollutant such as heavy metals and mineral hydrocarbons could get into aquatic<br>environment from a wide range of natural and anthropogenic point sources. In aquatic<br>ecosystems, heavy metals are contained in four reservoirs, namely; the suspended sediment,<br>4<br>the bottom sediment, the surface water and the pore water. Studies have revealed that<br>contaminants in aquatic system are usually in pore water-surface water-sediment dynamic<br>with bottom sediment acting as the major depository of heavy metals5. The questions of<br>heavy metals in water first became an issue only in Sweden and later in Canada.<br>Writing on the impact of economic activities on the environment of the Niger Delta,<br>Agbozu 13, stated that water bodies have been heavily polluted due to the recurring incident<br>of oil spillage. Most micro-populations and invertebrates are eliminated following large-scale<br>spillage, while sub lethal levels of oil following several scale spillages have generally<br>affected aquatic resources.<br>Ibeno Local Government Area is a coastal sub-region characterized by abundant<br>water resources. The absence of potable water supply for domestic use in some parts of Ibeno<br>has compelled the population to rely heavily on natural sources of water supply for domestic<br>uses. The quality of most of these sources of water is doubtful. The study area is one of the<br>coastal area as well as an oil producing area in Akwa Ibom State bordered by the Atlantic<br>ocean and has various environmental problems including pollution of available water<br>resources. There are many types of water sources available for domestic, recreational, fishing<br>and industrial uses. These include ponds, streams, boreholes, lakes, rivers, oceans and rain<br>water, but they are all polluted by human and industrial activities in the area. The<br>anthropogenic and natural phenomena seem to affect water quality in the study area. These<br>include gas flaring, oil spillage, washing wastewater and sludge from industrial processes,<br>poor sanitation, storm surges, salt-water extrusion and intrusion, release of untreated human<br>waste and sewage into waterways.<br>Water pollution occurs when chemical, physical or biological substances exceed the<br>capacity of water body to assimilate or break down the substance that can cause harm to the<br>aquatic ecosystem. Precipitation that reaches the earth’s surface follows two basic pathways;<br>it either flows overhead or soaks into the soil20. Water that flows over the ground is often<br>called run off. The term surface water refers to water flowing in streams and rivers as well as<br>water stored in natural or artificial lakes. Surface water is water that flows or rests on land<br>and is open to atmosphere; lakes, pond, lagoons, rivers, streams, oceans, ditches, man-made<br>impoundments are bodies of surface water 20. Analysis of soil samples from Uyo town by<br>Akaeze 106 disclosed that heavy metals such as lead, copper and iron are present in the soil,<br>these may contaminate soil water, which constitutes the major sources of drinking water 21.<br>Oil spillage and dumping of petroleum effluents on land are common phenomena. Gas flaring<br>also contributes to heavy metals contamination of soil15.<br>5<br>The contamination of the environment by heavy metals is viewed as an international<br>problem because of the effects on the ecosystem in most countries. In Nigeria, the situation is<br>no better by the unethical activities of most industries and because of countries inability to<br>manage industrial wastes with the increasing level of pollution of water bodies.<br>Environmental degradation of the oil rich Niger Delta region has caused a wanton destruction<br>and continuous harm to their health, social and economic consequences for its people, for<br>over a decade. Petroleum refineries produce a wide variety of air and water pollutants and the<br>distillation products of refining and industrialization, intensive agriculture and other<br>anthropogenic activities have led to land degradation, environmental pollution and decline in<br>crop productivity and sustainability. These have been of great concern to human and animal<br>health 22, 23.<br>One of the prominent sources contributing to increased load of soil contamination is<br>the disposal of municipal and industrial wastes. The wastes are either dumped on roadsides or<br>used in landfills. These wastes although useful as sources of nutrients are also sources of<br>carcinogens and toxic metals 23<br>.<br>In the study of the socio-economic impact of oil pollution, Worgu 23 stated that crude<br>oil exploration has had adverse environmental effect on soil, forest and water bodies in host<br>communities in the Niger Delta. All stages of oil exploration impacted negatively on the<br>environment and the greatest single intractable environment problem caused by crude oil<br>exploration in the Niger Delta region is oil spillage. According to Annual reports of the<br>Department of Petroleum Resources (DPR) 1997, over 6,000 spills have been recorded in the<br>40 years of oil exploration in Nigeria with an average of 150 spills per annum. In the period<br>1976 – 1996, 647 incidents occurred resulting in the spillage of 2,369,407.00 barrels of crude<br>oil with only 549,040.38 barrel recovered, while 1,820,410.50 barrels of oil were lost to the<br>ecosystem23. These chemicals if not properly controlled according to guidelines and standards<br>set by regulating agencies like Department of Petroleum Resources, it can pollute the soil and<br>groundwater system in the area where such operation is carried out. Thousands of spills occur<br>across the fragile Niger Delta and have destroyed livelihoods of fishermen and farmers,<br>fouled water sources and polluted the ground and air. The Nigerian government estimates that<br>there were over 7,000 spills, large and small, between 1970 and 2000. That is approximately<br>300 spills a year and some spills have been leaking for years. Vast swathes of the Delta are<br>covered with tar and stagnant lakes of crude. By some estimate, over 13 million barrels of oil<br>have spilled into the Delta. An additional 2,405 spills by all major oil companies in the region<br>6<br>have occurred since 2006. Corroded pipes caused a spill in 2010 that leaked about 232 barrels<br>of crude oil 23.<br>7<br>Table 1: Number of spills, quantity of spills (barrels), and quantity of oil recovered<br>(barrels) and net loss to the environment in barrels between 1976 -1989.<br>Year Number<br>of spills<br>Quantity<br>(barrels)<br>Quantity<br>recovered<br>(barrels)<br>Net loss to the<br>environment<br>(barrels)<br>1976 128 26157.00 7135.00 19021.50<br>1977 104 32879.25 1703 3117675.00<br>1978 154 489294.75 391445.00 97849.75<br>1979 157 64117.13 63482.20 630635.95<br>1980 241 600511.02 42416.23 558094.19<br>1981 238 42722.50 5470.20 37052.30<br>1982 257 42814.00 2171 40669.60<br>1983 173 48351.30 6355.90 41995.40<br>1984 151 40209.00 1644.80 38564.20<br>1985 187 11876.60 1719.30 10157.30<br>1986 155 12905.00 252.00 12358.00<br>1987 129 31866.00 6109.00 25358.00<br>1988 108 9172.00 2153.00 7202.00<br>1989 118 5956.00 2092.55 3830.00<br>Source: Annual report of Department of Petroleum Resources (DPR), 1997191<br>8<br>1.0.1 Statement of the problem<br>The study area (Ibeno Local Government Area) in recent times has received attention<br>owing to considerable stress it has been subjected to through deliberate and or accidental oil<br>spills, blast water discharge, untreated sewage, gas flaring and industrial effluents.<br>Qua Iboe River estuary is the point where petroleum exploration and production (E<br>and P) wastes from the Exxon Mobil Qua Iboe Terminal (QIT) tank farm are transferred to<br>the lower Qua Iboe River estuary and adjourning creeks through two 24 mm diameter pipes.<br>The Exxon Mobil oily sludge dumpsite and flare stack, where gas is flared continuously are<br>in the study area. The study area has a number of oil wells, NNPC pipelines run across and<br>some flow stations situated.<br>Seemingly, most of the terrestrial ecosystem and shorelines in the oil producing<br>communities are under continuous cultivation. After heavy spills of crude oil, soils are<br>usually barren, and may run into low-lying areas with organic soils and natural re-vegetation<br>of the soil generally slow. Depending on the amount of oil in the soil, the soil may remain<br>completely barren for many years. Environmental pollution by the industrial and domestic<br>activities may therefore have far-reaching implication on the agricultural productivity on the<br>area and multiplier effect on the socio-economic wellbeing of the people. At present, there is<br>no report available on the seasonal levels of anthropogenically associated heavy metals in<br>Telfairia occidentalis (fluted pumpkin) a common vegetable cultivated in the study area. In<br>addition, more extensive work is needed on the comparison between the seasonal dynamics<br>of heavy metals levels in soil, plant, sediment and water with local and international<br>guidelines and standards.<br>Also, increase in demand for crude oil and petrochemicals has resulted in exploration<br>for more oil wells with consequent pollution of the environments. This has adversely affected<br>food quality and human health in Niger Delta region of Nigeria. The traditional methods of<br>detection and remediation of environments from contaminants include the use of Atomic<br>Absorption Spectrophotometer (AAS), capping and chemical precipitation for heavy metals<br>in soil and water respectively. In addition, accelerated solvent extraction and application of<br>Tween 80 to degrade total petroleum hydrocarbons (TPHs) in soil are cost prohibiting when a<br>large area is involved. They also affect the biota with resultant adverse effects on human<br>beings. These necessitated the quest for development of alternative, indigenous and ecofriendly<br>green remediation and bio-indicator technologies for controlling and assessing<br>environmental contaminants.<br>9<br>The present study was carried out to determine the existing concentrations of heavy<br>metals in soil, Telfairia occidentalis (fluted pumpkin), water and sediment during wet and dry<br>seasons in Ibeno coastal area. Also, to find bio-indicator properties of Telfairia occidentalis<br>as an indigenous and eco-friendly green tool in detecting heavy metals pollutants in soil of<br>the study area. Furthermore, the present study was conducted to determine the concentration<br>of total petroleum hydrocarbon in the soil of the study area and consequently developed an<br>alternative indigenous and eco-friendly remediation technology for total petroleum<br>hydrocarbon in soil by comparing degradation efficiencies kinetics of natural surfactant<br>(palm bunch ash) and synthetic surfactant (Tween 80).<br>1.0.2 Objectives of the study<br>This research work was designed, to achieve the following objectives:<br>(i) determine seasonal concentrations of heavy metals in soil, sediment, water,<br>and leaves of Telfairia occidentalis,<br>(ii) establish correlation between the amount of the heavy metals in soil and leaves<br>of Telfairia occidentalis,<br>(iii) determine bio-indicator properties of leaves of Telfairia occidentalis,<br>(iv) investigate the amount of total petroleum hydrocarbons (TPHs) in the soil, and<br>(v) compare the degradation efficiencies of the TPHs in the soil amended with<br>palm bunch ash (PBA) and Tween 80.<br>(vi) investigate the effects of palm bunch ash (PBA) and Tween 80 on the<br>physicochemical properties of the soil.<br>10<br>1.0.3 Scope of the study<br>The present study covered the following areas:<br>(i) samples collection and preparation.<br>(ii) determination of heavy metal concentrations, in soil, leaves of Telfairia occidentalis<br>(fluted pumpkin), water and sediment during wet and dry seasons in Ibeno coastal<br>area.<br>(iii) investigation of bioindicator properties of leaves of Telfairia occidentalis (fluted<br>pumpkin)<br>(iv) determination of total petroleum hydrocarbon concentration in soil and investigation<br>of the degradation efficiency kinetics of palm bunch ash and tween 80.<br>(v) verification of the effects of palm bunch ash and Tween 80 on the physicochemical<br>properties of oil polluted soil.</p><p>&nbsp;</p> <br><p></p>