Two thirds of the earth is water and one third is land or soil. Oil spills affect both. Spills on land obviously impact on the soil around the site and may impact on ground water and surface waters, like rivers and lakes.
Likewise, spills at sea, such as the 2010 Deepwater Horizon disaster, may contaminate soil and water miles away from the sites. On December 24, 2011, many Nigerian newspapers reported the oil spillage at Bonga, an oil creek in the Niger-Delta region of Nigeria. It was not long after this was reported that another report came regarding an oil spill in a nearby creek.
The spill which the Shell Nigeria Exploration and Production Company (SNEPCO) said happened during a routine export operation to transfer crude oil from Bonga’s Floating Production Storage and Offloading (FPSO), has lead to the complete shutdown of the company’s 200,000 barrel per day (bpd) Bonga facility, about 120 kilometers off the coast of the west African nation. The loss accounted for about 35,000 barrels of crude oil on the Niger-Delta marine body, which is about 1.1 million litres of crude oil spilled into the environment. The latest spill, considered to be one of the worst in ten years, came four months after a major United Nations study said it could take Shell and other oil companies 30 years and about $1 billion to clean up. Photo courtesy of Mazen Saggar / UNEP ©
In August last year, Shell admitted responsibility for two major spills in the Bodo region of the Delta that took place in 2008, but has yet to pay compensation. Satellite images of the spill area indicated that it covered more than 923 square kilometers. Over the years, cases of oil spillage in the Delta region have not been treated with the urgency they demanded, as oil companies, particularly the multinationals, continued their activities without much scrutiny by the authorities.
The serious environmental damage caused by frequent oil spills and their impact on human and marine lives made living in the Delta region a harrowing experience. Besides the health hazards to human lives, farmlands are often destroyed and left unsuitable for vegetation. This is why the recent spillage should be taken very seriously by government. The activities of the National Oil Spill Detection and Response Agency (NOSDRA) are unclear here, because so far there is nothing to indicate it is living up to its mandate. Meanwhile, damage caused by oil companies in the course of their activities in Nigeria and other developing countries appears to get little notice by the international community, compared to similar situations in other parts of the world.
For instance, when a similar incident occurred in the Gulf of Mexico from a damaged BP oil rig in the United States last year, it attracted global attention, forcing prompt action by the company in the cleanup exercise that followed, as well as payment of compensation to fishermen. There is the added fear that the cleanup exercise at the Bonga fields would not be judiciously carried out because of longstanding corruption that has developed in the oil industry over the years. Coming on the heels of the agitation for the passage of the Petroleum Industry Bill that is pending before the National Assembly, the current spillage should be an eye opener for the government to take stringent measures to curtail further occurrences.
On January 16, 2012, there was a fire on the Chevron Nigeria Limited (CNL) oil well located at its Funiwa gas field offshore Bayelsa State in Nigeria. At the time of going to press, this fire was still burning. The National Oil Spill Detection and Response Agency (NOSDRA) had noted that the reason for not putting out the fire since is because Funiwa field is still leaking raw gas and until the point of leakage is found and plugged, the fire wouldn’t be stopped for health and environmental reasons. According to Reuters data, Bonga accounts for ten percent of monthly oil flows from OPEC member Nigeria, the continent’s largest exporter of crude oil.
For the scientists, our interest is not the economic (oil revenue generation) implications, but the adverse effect the oil has on the water-soil-atmosphere continuum – our environment.
Before spelling out the soil scientific methodologies in testing for the said adverse effects, let’s succinctly look at the environmental issues generally in the Niger – Delta of Nigeria as they relate to the petroleum industry.
Environmental issues in the Niger – Delta of Nigeria
The Delta covers 20,000 km² within wetlands of 70,000 km² formed primarily by sediment deposition. Home to 20 million people and 40 different ethnic groups, this floodplain makes up 7.5 percent of Nigeria’s total land mass. It is the largest wetland and maintains the third largest drainage basin in Africa.
The Delta’s environment can be broken down into four ecological zones: coastal barrier islands, mangrove swamp forests, freshwater swamps and lowland rainforests. This incredibly well endowed ecosystem contains one of the highest concentrations of biodiversity on the planet, in addition to supporting abundant flora and fauna, arable terrain that can sustain a wide variety of crops, lumber or agricultural trees, and more species of freshwater fish than any ecosystem in West Africa.
The region could experience a loss of 40 percent of its inhabitable terrain in the next 30 years as a result of extensive dam construction in the region. The carelessness of the oil industry has also precipitated this situation, which can perhaps be best encapsulated by a 1983 report issued by the Nigerian National Petroleum Corporation (NNPC), long before popular unrest surfaced: “We witnessed the slow poisoning of the waters of this country and the destruction of vegetation and agricultural land by oil spills which occur during petroleum operations. But since the inception of the oil industry in Nigeria, more than 25 years ago, there has been no concerned and effective effort on the part of the government, let alone the oil operators, to control environmental problems associated with the industry.”
Extent of the problem
Apart from the estimated amount of oil spilled into the environment as a result of the Bonga spill, the Nigerian government recorded the losses and adverse effects caused by the oil industry in the past. The Department of Petroleum Resources (DPR) estimated that 1.89 million barrels of petroleum were spilled into the Niger – Delta between 1976 and 1996 out of a total of 2.4 million barrels spilled in 4,835 incidents (approximately 220,000 cubic metres). A UNDP report states that there have been a total of 6,817 oil spills between 1976 and 2001, which account for a loss of three million barrels of oil, of which more than 70 percent was not recovered.
Most of these spills occurred offshore (69 percent), a quarter was in swamps and six percent spilled on land. In the early 2000s, it seemed more spills were due to sabotage than by accidents. The Nigerian National Petroleum Corporation places the quantity of petroleum jettisoned into the environment yearly at 2,300 cubic metres, with an average of 300 individual spills annually. Because this amount does not take into account ‘minor’ spills, however, the World Bank argues that the true quantity of petroleum spilled into the environment could be as much as ten times the officially claimed amount.
The largest individual spills include the blowout of a Texaco offshore station which in 1980 dumped an estimated 400,000 barrels (64,000 m3) of crude oil into the Gulf of Guinea and Royal Dutch Shell’s Forcados terminal tank failure, which produced a spillage estimated at 580,000 barrels (92,000 m3). In 2010 Baird reported that between nine and 13 million barrels have been spilled in the Niger – Delta since 1958. One source even calculates that the total amount of petroleum in barrels spilled between 1960 and 1997 is upwards of 100 million barrels (16,000,000 m3).
Oil spillage has a major impact on the ecosystem into which it is released. Immense tracts of the mangrove forests, which are especially susceptible to oil have been destroyed. An estimated five to ten percent of Nigerian mangrove ecosystems have been wiped out either by settlement or by oil. The rainforest which previously occupied some 7,400 km² of land has disappeared as well.
Spills in populated areas often spread out over a wide area, destroying crops and aquacultures through contamination of the groundwater and soils. The consumption of dissolved oxygen by bacteria feeding on the spilled hydrocarbons also contributes to the death of fish. In agricultural communities, often a year’s supply of food can be destroyed. Because of the careless nature of oil operations in the Delta, the environment is growing increasingly uninhabitable.
People in the affected areas complain about health issues including breathing problems and skin lesions; many have lost basic human rights such as health, access to food, clean water and their ability to work.
The invasion of water hyacinth is another problem caused by oil spillage. Water hyacinth is an invasive species that was introduced into Africa as an ornamental plant, and which thrives in polluted environments.Water hyacinth can completely clog the waterways in which it grows, making it nearly impossible for fishing boats to navigate. In recent years it has found its way into the Niger River, choking out both sunlight and oxygen to the marine organisms that live there. When a species such as water hyacinth makes its way into the ecosystem, it competes with native plants for sunlight, diminishing energy resources within the marine environment.
The soil impact
Oil spills can have several detrimental effects on soil. Soil contaminated with oil has characteristics that render it less useful to human beings in most cases. Oil pollution in the environment has been a major source of concern to the people living in the crude oil rich areas. Oil pollution due to a spill could take place in water or on land. Crude oil pollution on land depends on a number of factors which include the permeability of the soil, adsorption properties of the soil and the partition coefficient.
Soil scientific methodologies for testing the adverse effects of oil spillage on soils
Various methods have been used by researchers to find out how adversely crude oil spillage alters the physico chemical properties of soils. Properly conducted research on this subject matter requires the expertise of an experienced soil scientist or environmental scientist. A study was conducted by Uzoije and Agunwamba to find out the behaviour of selected physical and chemical properties of soils of the Niger – Delta region in relation to varying rates of crude oil pollution.
They collected crude oil samples from three selected oil wells of Qua Iboe, Brass River and Bonny respectively, and carried out a sorption test by mixing the various characterised soil samples with the hydrocarbon-determined crude oil samples, and the mixture was shaken for five hours to establish adequate mixture and sorption process. Soil samples, crude oil samples and the crude oil contaminated soils collected after each sorption process were analysed in the laboratory using routine and special analytical techniques.
The results showed corresponding increases in values of some selected physiochemical properties of the soil (bulk density and organic matter) with increases in sorption time, hydrocarbon concentrations of various crude oil samples and volumes of the crude oil applied during sorption process, while an inverse relationship was observed for porosity values. Details of the routine and special laboratory analytical techniques they employed are highlighted below.
The soil samples were collected from four different points of Niger-Delta South Eastern Nigeria. The soils of the area are from coastal plain sands (benin formation) of the Oligocene-Miocene geological era. The area has a low land geomorphology and is of humid, tropical climate with an average annual rainfall of about 2,500mm and mean annual temperature range of between 26 to 29° C.
It is situated within the highly depleted rainforest vegetation, characterised by varieties of vegetal forms, although dominated by trees and shrubs. Frequent oil spillages are reported in the study area due to oil pipe rupture occasioned by pressure, aging and sabotage. Residents cultivate on the soils of the area for arable crops.
Soils that are not affected by crude oil spill were collected from the four different sampling sites using the free survey technique of soil scientists. Each site was designated as A, B, C and D. On each site, soil samples were randomly collected at ten points making a total of 40 soil samples. These soil samples were sieved with a 2mm sieve and air dried in readiness for various laboratory analyses. Crude oil samples were also collected from three different oil wells which included Brass oil, Qua Iboe and Bonny light. The crude oil samples were designated as A, B and C, respectively.
Characterisation of the soils
The soils were characterised by determining in the laboratory some physical and chemical properties of the soils. The analyses carried out were: • Particle Size Distribution: the relative distribution of the size group of soil particles and it was analysed using a process called mechanical analysis, and measured by using the hydrometer • Bulk Density: a measure of mass of the soil relative to its volume • Porosity: the measure of pore spaces in a soil, calculated from the bulk density values • Percentage Soil Organic Matter: consists of a wide range of organic (carbonaceous) substances in various stages of decomposition.
It was determined by a wet digestion method in which the soil is digested in an excess of chromic acid with titration of the unused oxidant The soil types analysed for this study were classified according to their particle size distribution, bulk density, percentages of organic matter and porosity. Soil sample C had the highest percentage of sand while sample D had the least percentage of sand. In terms of percentage of clay, sample D had the highest value with sample C having the lowest. Soil sample B had the highest percentage of silt while sample C had the lowest silt percentage. Bulk density and percentages of organic matter of various soil samples showed a direct relationship with the percentage of clay of the corresponding soil samples. Porosity showed the inverse trend.
Crude oil characterisation
The three crude oil samples were subjected to total hydrocarbon analysis using Gas Chromatographic (GC) method to determine total hydrocarbon contents of each crude oil sample. Density and viscosity of the crude oil samples were also determined using ASTM (American Society for Testing and Materials) methods.
The materials used as adsorbent media were soils of different textural characteristics and the three types of crude oil of known concentrations were used as liquid substances. The predetermined textural characteristics of the four types of soil were air dried and 50g of soil sample A was put into an 800ml conical flask with 100ml of a particular crude oil sample, say sample (A) of a known initial total hydrocarbon concentration. These were shaken in a mechanical shaker for five hours.
Thereafter, a sample of the adsorbent (soil) was collected for analysis of bulk density, porosity and organic carbon at regular intervals of one month, for five months. The effects of varying the volume of crude oil at 400ml, 500ml and 600ml with contact time of one through to five months were studied. The experiment was repeated with the two other oil samples, B and C, and the three other types of soil samples B, C and D.
Effects of sorption on the soil properties
Soil sorption of crude oil seems to have profound effects on the soil properties analysed for this study. Uzoije and Agunwamba reported that soil properties such as the bulk density, organic matter content and porosity were appreciably influenced. They further reported that the apparent effects on the mentioned physiochemical properties of various soil samples could be attributed to three basic reasons: the crude oil samples, applied volume of various crude oil samples and the constitution of various soils used in the study.
The bulk density of the soil increased linearly with time of sorption. As the time of sorption increased more of the hydrocarbons adsorbed and distributed on the soil matrix, thereby adding to its mass and consequently to density values. The bulk density of the various soils varied with different crude oil samples and various crude oil volumes used for the sorption process. According to Uzoije and Agunwamba10 values of the bulk density and percentage organic matter varied linearly with sorption time, but porosity values decreased as the crude oil sorption process on various soil matrices progressed.
The constitution of various crude oil samples has appreciable influence on the selected soil physical and chemical properties after the sorption process. Crude oil samples with low hydrocarbon made lesser impact on the bulk density, percentage organic matter and porosity values of the soil samples, and vice-versa. Volumes of the crude oil samples applied during the process also had impact on the soil properties. The higher the applied crude oil volume, the higher the bulk density and percentage organic matter values.
1. Quoted in Greenpeace International’s Shell Shocked, 11 2. Vidal, John (2010-05-30). Nigeria’s agony dwarfs the Gulf oil spill. The US and Europe ignore it. The Observer. http://www.guardian.co.uk/world/2010/may/30/oil-spills-nigeria-niger-delta-shell. Retrieved July 27, 2010. Government’s national oil spill detection and response agency (NOSDRA) says that between 1976 and 1996 alone, more than 2.4m barrels. 3. Shell And The N15bn Oil Spill Judgement Debt. The Daily Independent (Lagos). 2010-07-19. http://www.independentngonline.com/DailyIndependent/Article.aspx?id=17332. Retrieved 27 July 2010. 4. Niger Delta Human Development Report. UNDP. 2006. p 76. http://hdr.undp.org/en/reports/nationalreports/africa/nigeria/name,3368,en.html. Retrieved 19 June 2011. 5. Bronwen Manby: The Price of Oil Human Rights Watch. 1999. Retrieved November 9, 2007. 6. Perception and Reality: Assessing Priorities for Sustainable Development in the Niger River Delta (Moffat and Linden). 7. Dr PC Nwilo and O T Badejo: Impacts of Oil spills along the Nigerian coast The Association for Environmental Health and Sciences, 2001. 8. Baird J (July 26, 2010). Oil’s Shame in Africa. Newsweek: 27. 9. Fuggle, RF: Africa Environment Outlook Lake Victoria: A Case Study of Complex Interrelationships, pg 75-85. United Nations Environment Programme, 2004. 10. Nudelman, NS, IS Rios and O Katusich, 2002. Fate of the oil residuals in Patagonian soils effects of the environmental exposure time. J Environ. Assessment Remediation, 3: 1-8. 11. AP Uzoije and JC Agunwamba, 2011. Physiochemical Properties of Soil in Relation to Varying Rates of Crude Oil Pollution. Journal of Environmental Science and Technology, 4: 313-323.
Published: 01st Jun 2012 in AWE International