THE CONCENTRATIONS OF PAHs AND BTEX IN SOIL AND TUBER CROPS (COCOYAM AND CASSAVA) IN BODO-GOKANA, NIGERIA

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ABSTRACT

The study evaluated polycyclic aromatic hydrocarbons, benzene, toluene, ethylbenzene and xylene in tuber crops (Cocoyam and Cassava) harvested from oil spilled soil. This was done through gas chromatographic technique. The result showed that the concentration of PAHs in soils from the study area (0.004 mg/kg) were significantly higher than the value in the control sample (0.0002mg/kg) and WHO limit of 0.0001mg/kg. The BTEX level in the soil sample was <0.001 mg/kg and was same value as the value of the control sample (<0.001), which were not up to the WHO limit of 0.01mg/kg.   The results indicate that cocoyam and cassava had 0.001mg/kg concentration of PAHs and <0.001mg/kg for BTEX. Benzene, toluene, ethylbenzene and xylene (BTEX) were not significant in all samples. It was concluded that PAHs were present in the soil, cocoyam and cassava samples and that BTEX (benzene, toulene, ethylbenzene and xylene) was not significant from crude oil impacted community of Bodo in Rivers state. It was recommended that stakeholders in the oil industry to enact and enforce laws on effective control of rate of crude oil spillages and pipelines vandalization on farmlands, which devastate crops planted,

 

CHAPTER ONE

1.0 INTRODUCTION

Crude oil  is a mixture of a very large number of different hydrocarbons; the most commonly found molecules are alkanes (paraffins), cycloalkanes (naphthenes), aromatic hydrocarbons, or more complicated chemicals like asphaltenes. The alkanes, also known as paraffins, are saturated hydro-carbon with straight or branched chains which contain only carbon and hydrogen and have the general formula CnH2n+2. They generally have from 5 to 40 carbon atoms per molecule, although trace amounts of shorter or longer molecules may be present in the mixture.

Activities of oil prospecting and other industries resulting in pollution through gas flares, constant oil spills and industrial effluence which affect both aquatic and terrestrial ecosystems, with destruction of forest and farmland is alarming (Dambo, 2000).

Environmental degradation of the oil rich region has caused a wanton destruction and continuous harm to their health, social and economic consequences for its people, for over three decades. Petroleum refineries produce a wide variety of air and water pollutants and hazardous solid wastes. The specific means of pollutants varies and processes involved. Frequently emitted pollutants include all the distillation products of refining and rapid 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 (Worgu, 2000). One of the prominent sources contributing to increased load of soil contamination is the disposal of municipal and industrial wastes. These wastes are either dumped on road sides or used as landfills, while sewage is used for irrigation. These wastes although useful as a source of nutrient are also source of carcinogens and toxic metals. Other industrial activities that take place include those from these industrial activities, pollute the air, water and soil, endangering the environment as they ultimately find their way into food chain,  in small doses. These accumulate and across trophic levels to pose serious health hazards to man (Pickering et al., 2000).

1.1   BACKGROUND OF STUDY

Many researchers have studied the effects of crude oil and gas pollution on crop farms in Nigeria and other parts of the world (Ekundayo et al., 2001; Achuba, 2006; Aade- Ademilua and Mbamalu, 2008; Ibemesim, 2010; Al- Qahtani, 2011).

Ekundayo et al., (2001) studied the effects of crude oil spillage on growth and yield of maize (Zea mays L.) in soil of Midwestern Nigeria. Their results showed that in crude oil polluted soils, germination was delayed and the germination percentage was significantly affected by oil pollution. Growth was poor in polluted soils using parameters such as plant height, stem girth, ear height and leaf area at four weeks after planting, leaf area at maturity and average length of primary roots as growth indicators. Grain yield was significantly reduced by as much as 98.6, 96.5 and 58.3% for pre-plant, five weeks after planting and seven weeks after planting treatments, respectively.

Achuba (2006), studied the effect of crude oil contaminated soil at various sublethal concentrations (0.25, 0.5, 1.0 and 2%) on the growth and metabolism of cowpea (Vigna unguiculata) seedlings. The results showed that crude oil induced environmental stress in the seedlings.

Aade–Ademilua and Mbamalu, (2008) investigated the growth and development of French beans (Phaseolus vulgaris L. var. Ife Brown) under petrol and diesel oil polluted water irrigation in Ijora – Lagos, Nigeria. The results showed that the seeds germinated at the same time and rate when compared with the control. The heights of plants treated with the polluted water were significantly higher than those of the control plants but the former plants had little or no sprawl. There was significant increase in the growth of treated plants in terms of total area and dry weight during vegetative stage but the growth of the plants decreased significantly during flowering stage due to early leaf senescence. The study concluded that an overflow of the polluted water on plant vegetation overtime would endanger the growth and development of plants.

The knowledge of the impact of crude oil pollution on crop production would permit an insight into clear interrelation between socio-economic factors, health and economic welfare of farmers.

Crude oil and petroleum are complex mixtures of several polycyclic aromatic compounds and other hydrocarbons (Domask, 1984). Mangrove forests have fallen to the toxicity of oil spills, the rainforest has fallen to the axe of oil companies, wild life and game have been driven away and farmlands have been rendered infertile with gross implication on the right to adequate food (Pyagbara, 2007; Omofonmwam and Odia, 2009). During oil spills the process of photosynthesis which enhances plant diversity is impaired since the process is reduced because spilled crude have a high absorbance property of UV light which makes plant leaves not to photosynthesis and thus die leading to biodiversity loss (Nwilo and Olusegun, 2007).

Cassava is a source of flour called garri and of toasted starch granules normally called tapioca. It can be processed into maconi.

Cocoyam (Colocasia esculenta) is thought to be native to Southern India and Southeast Asia, but is widely naturalized. It is a perennial, tropical plant primarily grown as a root vegetable for its edible starchy corm, and as a leaf vegetable. Generally, crude oil is toxic to crops, due to the presence of PAHs taken up from soil spilled with oil (Heintz et al., 1999). This is because, PAHs exposed to solar UV radiation can generate O2 through photosensitization (Babu et al., 2002) whereby toxic PAH quinones are produced.

1.2   STATEMENT OF PROBLEM

The most profound and adverse impact of oil pollution is environmental pollution with far reaching implications on all other aspects of traditional lifestyles and livelihood of the people among which is the total loss of biodiversity and destruction of habitats largely due to soil degradation and persistence of recalcitrant hydrocarbon constituents in water bodies, soil and tuber cultivars.

The contamination of soil, water, air and groundwater with crude oil (hydrocarbon) or crude oil based products, is among the most common negative effects of the industrial society. It is a fact we must live with as long as the prospect for oil and gas prevails. Hence, the need for the evaluation of crude oil pollution on tuber crops (Cocoyam and Cassava) harvested from oil spill area as well as the polluted soil of the area in Bodo community.

1.3   AIM AND OBJECTIVES OF THE STUDY

AIM

To determine polycyclic aromatic hydrocarbons, benzene, toluene, ethylbenzene and xylene in tuber crops (Cocoyam and Cassava) harvested from oil spilled soil.

OBJECTIVES

1) To determine the level of PAHs taken up by tuber crops under this study.

2) To determine the correlation between PAHs, benzene, ethylbenzene, toluene and xylene in tuber crops under this study and crude oil polluted soil.

3) To determine the presence of PAHs and BTEX in crude oil polluted soil.

4) To compare the result with WHO standards for food.

1.4   SCOPE OF STUDY

This study covers the assessment of polycyclic aromatic hydrocarbons, benzene, toluene, ethylbenzene and xylene as a determinant for the impact of crude oil pollution on tuber crops harvested in oil spill area of Bodo community. This will be done using the gas chromatographic technique of analyzing organic substances.

1.5   SIGNIFICANCE OF THE STUDY

This study will review the level of PAHs and Benzene, Toluene, Ethylbenzene and Xylene ingested by the tuber crops harvested from the soil contaminated by crude oil.

 

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