ABSTRACT
Some agricultural wastes which constitute nuisance to the environment have been found to be rich sources of nutrients. Hence this study evaluated their applicability as bioremediation agents for soils contaminated with spent automobile engine oil. Main plot treatments were 0% (control), 1%, 2%, and 3% spent oil (Sp) applied in a single dose at 0, 12, 24 and 36 Mg/ha respectively. The sub-plot treatments were control (No Amendment = NA), Palm Oil Mill Effluent (PE), Palm Bunch Refuse (PR) and Cassava Peels (CS) applied at 12 Mg/ha each, per year. Treatments were arranged in a split-plot in Randomized Complete Block Design (RCBD) with three replications. Samples were collected from top (0 – 20 cm) and sub (20 – 40 cm) soil at 3, 6, 12, 18, 24, 30 and 36 months and analyzed for aggregate stability, bulk density (BD), soil porosity, saturated hydraulic conductivity (Ks), total hydrocarbon content (THC), heavy metals (Al, Cr, Fe, Pb and Zn) and viable microbial count (VMC). Maize and cowpea were planted in three seasons to evaluate crop response to the treatments. The texture of the soil was sandy loam. The stability of top soil aggregates under wet conditions was observed to have increased with increased spent oil, with mean weight diameter (MWD) values ranging from 1.30 mm – 1.88 mm. Plots under PE and CS organic amendments showed significantly higher stability(P < 0.05) compared to PR amended and the un-amended (NA) soils. Bulk density increased with increasing oil contamination but was restored to control values (1.50 g cm-3) 12 months following amendment with PE and CS. The Ks of the soils decreased from 25cmh-1 (very rapid permeability) before oil contamination to 6cm h-1 (moderately rapid permeability) following contamination but increased to 25cm h-1 (very rapid permeability) following 36 months of organic amendment. Reduction in THC was shown to be achieved not only by biodegradation, as commonly reported by other researchers but also by its combination with loss due to gravity (downward seepage). Reduction in THC in un-amended top (0 – 20 cm) soils was 3 times more by gravity compared to amended plots in which THC reduction was 3 times more on the average by microbial degradation. The PE amended plots reached a peak of 11-fold loss in THC relative to un-amended equivalent. The rate of hydrocarbon degradation was highest in the first 3 months, increasing from 43.0 mg Kg-1 d-1 in un-amended soils to 125.5 mg Kg-1d-1 in PE amended soils. The PE treatment was the most efficient amendment of the three organic amendments applied with remediation efficiency ranging from 19.1–111.3 % compared to PR amendment with the least remediation efficiency ranging from 1.3 – 51.3 %. Increased heavy metal (Al, Fe, Cr, Pb and Zn) concentration in soil followed increased oil contamination. The C/P index values obtained in this experiment were < 1, thereby indicating that the resultant contaminations were within tolerable levels for soil micro-fauna, -flora and higher plants. The population of viable hydrocarbon degrading micro-organisms grew with increase in oil contamination, nutrient and time. Microbial population in amended plots followed the order PE > CS > PR > NA. Viable microbial count declined with soil depth. The 3% oil treatment reduced maize germination from 86% (control) to 41 while it reduced cowpea germination from 92% (control) to 74 %, in the first year. Germination in amended plots was higher than that in un-amended plots, with PE treated plots showing highest germination rate. Increasing oil beyond 1% significantly reduced dry matter yield to between 41.7 % and 83.9 % in maize and to between 2.3 and 8.0 % in cowpea 12 months after contamination. Increased oil contamination led to decrease in leaf area of maize and cowpea plants. Plants grown in amended plots showed significantly larger leaf area compared to those in un-amended plots. Maize yield reduced by 94.7 % and 99.3% in 2 % and 3 % oil treated plots respectively while there was a 70 % cowpea yield decline under 3 % oil. The yield of maize and cowpea in amended plots were between 19.3 – 43.0 % and 1.6 – 32.9 % respectively higher than yield in un-amended plots. All maize plants under 3 % oil showed yield failure except those in plots amended with PE. The crop parameters examined showed that oil had more deleterious effect on the maize than on cowpea plant.
TABLE OF CONTENTS
CHAPTER ONE
- Introduction
CHAPTER TWO:
- LITERATURE REVIEW
- Description of Contaminants
- Contaminant sources
- Properties of spent and crude oil
- Physical and chemical properties of petroleum hydrocarbon
- Petroleum components and their biodegradation
2.6 Properties affecting the fate and transport of organic contaminants in the environment
- Solubility
- Biodegradability
- Effects of petroleum hydrocarbons on soil physical properties
- Effects of petroleum and oil based products on soil chemical properties
- Effects of petroleum hydrocarbon on soil microbial ecology
- Effects of petroleum hydrocarbon on crop development
- The test crops
- Remediation of petroleum Hydrocarbon contaminated soils
- Excavation and off-site disposal
- In-situ soil venting
- In-situ bioremediation
2.12.4 Above ground or in-situ chemical oxidation
- Assessment of petroleum hydrocarbon and heavy metals hazard
- Benzene,toluene,ethyl benzene and xylene
- Poly-Aromatic Hydrocarbons (PAHs)
- Heavy metals
- Micro-organisms in bioremediation
2.15 Properties of the organic amendments
CHAPTER THREE:
3.0 MATERIALS AND METHODS
3.1 Site description
3.2 Field methods
3.2.1 Experimental design
3.2.2 Experimental layout
3.2.3 Field preparations
3.3 Data collection
3.4 Laboratory studies
3.4.1Texture and bulk density
3.4.2 Soil porosity
3.4.3 Mean weight diameter (aggregate stability)
3.4.4 Saturated hydraulic conductivity
3.4.5 Total Hydrocarbon Content (THC)
3.4.6 Heavy metal analysis
3.4.7 Biodegradation rate (hydrocarbon loss)
3.4.8 Remediation Efficiency (R.E)
3.4.9 Microbial count
3.4.10 Determination of Leaf Area Index (LAI) and dry matter yield
CHAPTER FOUR:
4.0 RESULTS AND DISCUSSION
4.1 Soil physical properties
4.1.1 Texture
4.1.2 Soil bulk density
4.1.3 Soil porosity
4.1.4 Aggregate stability (Mean Weight Diameter-Wet and –Dry)
4.1.5 Saturated hydraulic conductivity (Ks)
4.2. Soil chemical properties
4.2.1 Total hydrocarbon content (THC) of soil
4.2.2 Distribution of heavy metals and contaminant/pollution limit (C/P index)
4.3 Biological enhancement
4.4. Effects on crop performance
CHAPTER FIVE
5.0 Summary and Conclusion
CHAPTER ONE
1.0 INTRODUCTION
Pollution caused by petroleum and its derivatives (like spent engine oil) is a prevalent problem in the environment. In Nigeria, however, common forms of pollution come from household wastes, agricultural wastes, gas flaring, oil spills and spent lubricating oil. Spent engine oil, usually obtained after servicing and subsequently draining used oil from automobiles and generator engines, is indiscriminately disposed into gutters, water drains, open vacant plots and farms in Nigeria by auto mechanics and allied artisans with workshops on the road sides and open places (Anoliefo and Vwioko, 2001). The pollution incidence of spent oil in the environment has been shown by Atuanya (1987) to be more widespread than crude oil pollution. Nigeria was reported to account for more than 87 million litres of spent automobile engine oil annually (Anon, 1985), and adequate attention has not been given to its disposal (Anoliefo and Vwioko, 1994).
Furthermore, both crude oil and spent engine oil contain potentially phyto-toxic polycyclic aromatic hydrocarbons (Sharifi, et. al., 2007). Lubricating oil contains heavy metals. However, the proportion and type of these heavy metals increase in the used lubricant depending on the process generating the waste. Edebiri and Nwanokwale (1981) reported that metals present in spent oil were not necessarily the same as those present in the unused lubricants. Whisman et. al., (1974) observed that heavy metals like Vanadium (Va),Lead (Pb),Aluminium (Al),Nickel (Ni) and Iron (Fe) that were below detection in unused lubricant oil showed high values in the used oil. Atuanya (1987) and Agbogidi and Ejemete (2005) noted that oil in soil has deleterious effects on biological, chemical and physical properties of the soil depending on the dose, type of the oil and other factors. Benka-Coker and Ekundayo (1995) and Benka-Coker and Ekundayo (1997) also reported that the microbiological components of soil were usually negatively affected following oil application to the soil. According to Ekundayo et. al., (2001), germination of seeds planted in crude oil polluted soil area is delayed while percentage germination is also significantly affected. Agbogidi (2010) reported poorer germination response of cowpea with increasing dose of spent engine oil. Also, the effects of crude oil on plants according to Sharma et. al., (1980) have been found to include morphological aberration, reduction in biomass and stomata abnormalities while yellowing and dropping of leaves to complete shedding of leaves in areas of heavy pollution have been reported by Opeolu (2000). Crude oil spilled in soils has also been found to inhibit cowpea growth due to impaired water drainage and oxygen diffusion (Amadi et. al., 1993).
Worse still, the natural recovery of oil from polluted soils is slow and communities affected by such problems are denied utilization of their agricultural lands for a long time (Gradi, 1985). The problem is further compounded by the vast number of sites that need to be treated (McGugan et. al., 1995) and coupled with the fact that there are areas of the world (developing countries) that cannot afford expensive remediation. Therefore, bioremediation is now being considered as a viable alternative for this purpose.
Bioremediation has been defined by Madsen (1991) as “a managed or spontaneous process in which biological, especially microbial catalysis, acts on pollutant compounds, thereby remedying or eliminating environmental contamination”. It also refers to the enhancement of the native capability of micro-organisms by the addition of oxygen and nutrients to the soil system to support biological growth and improve the degradation (Catallo and Portier, 1992). Petroleum contaminants which are classified into saturated hydrocarbons, aromatic hydrocarbons and polar organic compounds can be converted by this method to inert or less harmful materials (Ram, et. al., 1993). Though this technology is yet evolving in Nigeria, it will prove most useful in the remediation of spent oil polluted soils. It was observed that the bioremediation process depended on nutrient supply among other factors (Ladousse and Tramier,1991; Leahy and Cowell,1990). This calls for concerted research efforts geared at tapping the fertility potentials of some of the agricultural wastes abundant in the various agro-ecological zones of Nigeria. These wastes can be employed to enhance the nutrient status of polluted soils for remediation in such places.
The south-eastern part of Nigeria falls into the oil palm belt and cassava producing region in the country. Nigeria, with the year 2006 production of 49 million tonnes of cassava, is the largest producer of the crop in the world (NPC, 2008). The processing of these produce, generates quite an enormous quantity of wastes in this area. During the processing of the ripe fruits of oil palm to extract cooking oil, a lot of waste water (Palm Oil Mill Effluent-POME) is generated. Observations show that most of the POME is not treated before discharge into the surrounding environment especially by small scale mills, causing pollution problems. For cassava, its processing results in the production of peels, chaff, fibre and spoilt or otherwise unwanted tubers. A relatively small quantity of peels and unwanted tubers are fed directly to ruminants. However, the much larger remaining proportion of cassava solid wastes are indiscriminately discharged into the environment and amassed as waste dumps on sites where cassava is processed, with increased production of peels and other cassava-derived wastes. This constitutes an enhanced risk of pollution to the environment. There is, therefore, an urgent need to find an alternative productive use of these agricultural wastes. One area of possibility is to investigate the potentials of POME, oil palm bunch refuse and cassava peels as bioremediation tools and by so doing, reduce their nuisance to the environment. Hence this research is aimed at assessing the effectiveness of these wastes for the bioremediation of an Ultisol (in eastern Nigeria), contaminated with waste crank-case oil (spent engine oil). The specific objectives of the study were to:
- Determine the physico-chemical properties of spent oil-contaminated, organic waste amended and control soils.
- Evaluate the applicability of some nutrient supplements as bioremediation technology.
- Assess the toxicity of some spent oil-induced heavy metals to cowpea, maize and soil micro-fauna.
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