The Role of Biodiversity and Ecosystem Services in Carbon Sequestration and its Implication for Climate Change Mitigation
Fowzia Ahmed1,2 and ANM Fakhruddin1,3*
1 Department of Environmental Sciences, Jahangirnagar University, Bangladesh
2Department of Environmental Science, Bangladesh University of Professionals, Bangladesh
3Department of Environmental Science, School of Environmental Science and Management, Independent University, Bangladesh (IUB), Bangladesh
Submission: May 03, 2018; Published: May 24, 2018
*Corresponding author: ANM Fakhruddin, Department of Environmental Science, School of Environmental Science and Management, Independent University, Bangladesh (IUB), Bangladesh, Email: fakhruddin@iub.edu.bd
How to cite this article: Fowzia A, ANM Fakhruddin. A Review on Environmental Contamination of Petroleum Hydrocarbons and its Biodegradation. Int J Environ Sci Nat Res. 2018; 11(3): 555811. DOI: 10.19080/IJESNR.2018.11.555811.
Abstract
Petroleum hydrocarbon contamination is one of the major environmental problems resulting from its large scale uses in transportation, industrial, agricultural and other sectors. Accidental releases and workshop seepage of petroleum products are of key concern for the environment. A variety of petroleum hydrocarbons such as crude oil, diesel, gasoline, heavy oil, kerosene etc. are used extensively as energy source, although their contaminations in soil and water have adverse effects. Contamination of soil with petroleum products deteriorates soil’s biochemical and physicochemical properties; it also limits the growth and develop¬ment of plants. Oil spills has devastating effects on marine ecosystems, it hindered oxygen penetration in water which affect marine ecosystem. Petroleum hydrocarbon has several chronic and acute effects on human health. Inhalation, ingestion and dermal contact of these pollutants cause many harmful diseases. Bioremediation is the promising technology for the treatment of these petroleum hydrocarbons since it is cost-effective and environment friendly. Several microorganisms have the capability to grow on it, use it as a sole source of carbon and mineralize it into simpler forms in natural environment. This review provides an overview on the effects of petroleum hydrocarbons on soil, water and human health and degradation of these petroleum hydrocarbons using microorganisms.
Keywords: Petroleum hydrocarbon; Oil spills; Contamination; Adverse effects; Biodegradation
Introduction
Petroleum hydrocarbons are extensively used worldwide as a fuel. Because of its huge demand as an energy source, contamination occurs quite often as a result of exploration, production, maintenance, transportation, storage and accidental release, leading to significant ecological impacts. As the modern civilization developed, it creates pressure on the energy source, especially on petroleum hydrocarbons [1]. Approximately 5.74 million tonnes of oil were lost as a result of tanker incidents from 1970 to 2014 [2]. Workshop seepage is also another source of petroleum hydrocarbon contamination. The presence of various kinds of automobile and machinery vehicles has caused an increase in the use of motor oil. Used motor oils spillage such as diesels or jet fuels contaminate natural environment [3].
Environmental contamination by petroleum hydrocarbon is one of the significant concerns of recent world. It has disastrous and catastrophic consequences, not only on the human beings but also on other biotic components of the ecosystem [4]. When an oil spill occurs, oil floats being less dense than water. It also pollutes air since the most volatile hydrocarbons start to evaporate initially after the oil spills [5]. There are different types of physical and chemical method for the remediation of oil contaminated soil such as burying, evaporation, dispersion, washing etc. Soil vapor extraction, soil washing and incineration are some of the mechanical methods. However, these technologies are expensive and can lead to incomplete decomposition of contaminants [6]. There are also some chemical methods but these are very costly approach to treat oil contaminated sites. Therefore, it is important to develop an innovative, low cost and eco-friendly method for the removal of hydrocarbon contamination from the soil. Bioremediation method is considered to be more economical and safe method for the treatment of hydrocarbon contaminated site [7]. Several microorganisms have the ability to grow on hydrocarbon contaminated soil and they are capable to degrade oil than those microorganisms which grow on non-contaminated sites of oil [8]. This paper provides information on the effects of petroleum hydrocarbon on soil, water and human health and degradation of these petroleum hydrocarbon using microorganisms.
Petroleum Hydrocarbons
Crude Oil
Crude-oils are mainly short-chain hydrocarbons [9], it is composed of complex mixtures of paraffinic, alicyclic and aromatic hydrocarbons and a smaller proportion of nonhydrocarbon compounds such as naphthenic acids, phenols, thiol, heterocyclic nitrogen, sulphur compounds as well as metallo-prophyrins and asphaltenes [10]. Crude oil as a complex mixture is produced by incomplete decomposition of plant and animal biomass over a long time [11]. The carbon content normally is in the range 83-87%, and the hydrogen content varies between 10 and 14%. In addition, varying small amounts of nitrogen, oxygen, sulfur and metals (Ni and V) are found in crude oils [12].
Diesel
Diesel fuels are middle distillates of crude petroleum separated by fractional distillation. Other middle distillates include kerosene and aviation fuel. The carbon number of diesel oil hydrocarbons is between 11 and 25 and the distillation range is between 180 to 380°C. Diesel oil contains 2000 to 4000 hydrocarbons, which cannot be totally separated by gas chromatography [13]. It includes approximately 64% aliphatic hydrocarbons, l-2% olefinic hydrocarbons and 35% aromatic hydrocarbons [14]. It composed of four main structural classes of hydrocarbons [15].
a) n-alkanes or n-paraffins (linear saturated hydrocarbons).
b) isoalkanes or isoparaffins (branched saturated hydrocarbons).
c) cycloalkanes or naphthenes (saturated cyclic alkanes).
d) Aromatics.
Gasoline
Gasoline is a generic term used to describe volatile, inflammable petroleum fuels used primarily in internal combustion engines to power passenger cars and other types of vehic1e, such as buses, trucks, motorbikes and aircraft [16]. In gasoline composition, aromatics amount to about 50% of the total hydrocarbon content. Iso-alkanes amount to about 35% alkanes, alkenes and cycloalkanes are present in minor quantities. Its distillation range is from 30-35°C to 180-200°C [17]. It is a complex mixture of volatile hydrocarbon compounds with a nominal boiling-point range of 50-200°C (USA) or 25- 220°C (Europe) for automotive gasoline. Hydrocarbons are predominantly in the C4-C12 range [18]. Gasoline is very flammable; it catches on fire quite easily, evaporates quickly, and forms explosive mixtures with air. Most people can begin to smell gasoline at 0.25 parts of gasoline per million parts of air (ppm). Gasoline does not dissolve readily in water.
Heavy Oil
Heavy oils are naturally occurring materials which contain hydrocarbons that are synthesized by living organism usually account for less than 20% by weight of the petroleum and petroleum like materials. It is the residue of crude oil distillation and its composition is carbon 88%, hydrogen 10%, sulfur 1%, H2O 0.5%, ash 0.1% by weight, and may contain dispersed solid or semi-solid particles (asphaltenes, minerals and other leftovers from the oil source, metallic particles from the refinery equipment, and some dumped chemical wastes), plus some 0.5% water. It leaves a carbonaceous residue in the tanks, and may have up to 5% of sulfur [19]. The limited constituents of heavy oil that dissolve in water become available for biodegradation when release to the environment. Heavy oils are not readily biodegradable. Heavy oils are also mutagenic.
Kerosene
Kerosene is a liquid mixture of chemicals produced from the distillation of crude oil. Kerosene is a major component (>60%) of aviation (jet) fuels, is used for “oil” central heating systems and can be used as a cleaning agent or solvent [20]. Kerosene contains hydrocarbons C11 to C12. It is flammable and practically insoluble in water [21].
Petroleum Hydrocarbon Contamination
Though social and economic development largely depends on petroleum hydrocarbon as it is a dominant source of energy, it has caused a huge area of contamination and relevant adverse effects [22]. The contamination of petroleum hydrocarbon disseminate from soil, water to human health.
Petroleum Hydrocarbon Contamination on Soil
Petroleum hydrocarbon contamination of soil is a widespread global environmental concern. Oil and fuel spills in soil are among the most extensive and environmentally damaging pollution problems as it is threatening to human health and ecosystems, especially in cold region [23]. Biochemical and physicochemical properties of soil is deteriorated by refinery products and it also limits the growth and develop¬ment of plants [24]. Water and oxygen deficits as well as to shortage of available forms of nitrogen and phosphorus are the main changes of soil properties due to contamination with petroleum-derived substances [25]. Petroleum hydrocarbon contaminated soil causes organic pollution of underground water which restricts it use and causes economic loss, environmental problems and decreases the agricultural productivity of the soil. Microorganisms, plants, animals and humans are facing vulnerable situation because of the toxicity of petroleum hydrocarbons [26]. Soil enzymes are one of the important biotic components which are responsible for soil biochemical reactions. Petroleum hydrocarbon has adverse effects of on soil enzyme activities [27].
Effect of Crude Oil on Soil
Oil spills affect plants by creating conditions which make essential nutrients like nitrogen and oxygen needed for the plant growth unavailable to them [28]. Crude oil contamination at different levels caused significant reduction in the growth of the plant using plant height, fresh weight and leaf area and the effect is proportional to the levels of contamination [29]. Crude oil pollution has also adverse effects on soil fertility and plant production. It could reduce or stop plant growth leading to death as a result of forming a physical barrier and coating the roots [30]. Table 1 shows adverse effects of crude oil contaminated soil in different plant species.
Effect of Diesel on Soil
Diesel oil has a much stronger inhibitory effect on nitrification than petrol (Kucharski et al., 2010). Diesel oil can cause chronic or acute effects in the plants. Interference in the hydric relations of the plants is caused by diesel oil pollution [31]. Table 2 shows the adverse effects of diesel contaminated soil on different plant species.
Petroleum Hydrocarbon Contamination on Water
Petroleum hydrocarbon released in to the sea, normally during transportation, leading to the pollution of several sites, and can eventually reach the coasts. Oil spills ranging from lowlevel discharges to catastrophic accidents threatened coastal environments; large spills commonly are followed by clean-up efforts, but complete containment is rare [32]. As solubility of petroleum hydrocarbon in water is generally low, certain fractions of it float in water and form thin surface films, which will facilitate agglomeration of particles and natural organic matter, and impact on oxygen transfer. Other heavier fractions will accumulate in the sediment at the bottom of the water, which may affect bottom-feeding fish and organisms [33].
Effects of Petroleum Hydrocarbon on Human Health
Effects of Diesel on Human Health
Occupational exposure may potentially occur, during manual filling or discharge operations in petrochemical industry [34]. Occupational exposure to diesel oil has been associated with the following operations: manually handled filling and discharge; marine diesel bunkering involving the manual handling of discharge lines; retailing through filing stations; tank dipping, pipeline and pump repairs, filter cleaning in refineries, distribution terminals and depots; tank inspection, cleaning and repairing; manufacture, repair, servicing and testing of diesel engines or equipment and injection and fuel systems; routine sampling and laboratory handling of diesel oils; and practices in which diesel oils are used as cleaning agents or solvents [35]. Skin exposures may occur whilst refueling domestic vehicles and pulmonary exposure may result from aspiration of liquid during manual siphoning [36]. Table 3 represents acute effects of diesel on human health.
Chronic Effects of Diesel
Prolonged skin exposure to diesel may cause a variety of dermatitic conditions and is generally a result of inadequate or inappropriate use of personal protective equipment. Also hyperkeratosis may be a common feature of regular contact with diesel [37].
a) Diesel does not have a measurable effect on human reproduction or development.
b) There is currently inadequate evidence to link diesel with the incidence of cancer in humans but there is limited evidence for carcinogenicity in animals following prolonged exposure [36].
Effects of Gasoline on Human Health
Gasoline has harmful effect on soil and water as well as human health. Inhaling or swallowing large amounts of gasoline can cause death [38]. Serious lung injury may occur if droplets of gasoline are inhaled (e.g. if vomiting occurs after ingestion). Inhalation may cause headache, dizziness and drowsiness. In some cases, sickness and diarrhea may occur. Gasoline vapour may be irritating to the eyes and lungs. Prolonged skin exposure to gasoline may cause a variety of skin conditions. Long-term exposure to high levels of gasoline is associated with a range of disorders affecting the nervous system [39].
Effects of Kerosene on Human Health
Kerosene is not particularly poisonous. However, if a child or adult accidentally swallows kerosene, medical advice should be obtained immediately as there is a small risk of short-term lung damage if vomiting occurs. Frequent skin exposure may lead to skin damage [36]. Kerosene possesses moderate to high acute toxicity to biota with product-specific toxicity related to the type and concentration of aromatic compounds. Kerosene spills could result in potential acute toxicity to some forms of aquatic life [40].
Bioremediation of Petroleum Hydrocarbon
Petroleum hydrocarbon contamination is highly hazardous to the environment. It has severe impacts on the plants as well as animal ecosystem including human health. Various conventional methods include physical and chemical technique which are costly and caused negative consequences [41]. In such cases, bioremediation is the most effective and it may be defined as any activity encouraging the natural process of degradation of petroleum hydrocarbon [42]. Bioremediation transforms the toxic substances to harmless products such as CO2, H2O and fatty acids [43].
Indigenous microbial communities have an important role in oil contaminant degradation. Once the site is contaminated, the microbial community composition will be greatly changed [44]. Microorganisms involved in the degradation of contaminant increase in their number till the contaminant is present. After the degradation of the contaminant the microbial population decreases itself naturally [45]. The rates of degradation of different classes of organic compounds in petroleum mixture vary widely. The biodegradation of n-alkanes is more rapid (except for the most volatile fraction C5-C9), followed by simple aromatics such as benzene, toluene and xylene-isoalkanes whereas cycloalkanes and aromatics degrade more slowly [46]. Hydrocarbons differ in their susceptibility to microbial attack. The susceptibility of hydrocarbons to microbial degradation can be generally ranked as follows: linear alkanes >branched alkanes >small aromatics >cyclic alkanes. Some compounds, such as the high molecular weight polycyclic aromatic hydrocarbons (PAHs), may not be degraded at all [47].
Most of the oil spillage occurs in the sea during transportation. Several studies have done by many scientists on microbial degradation of hydrocarbon in marine environment. Sutiknowati found that Alcanivorax, Marinobacter and Prosthecochloris are some hydrocarbon degrading bacteria which are found in marine environment [48]. According to Chikere et al. [49] Bacillus, Nocardia, Staphylococcus, Pseudomonas, Flavobacterium, Escherichia, Acinetobacter and Enterobacter. Bacillus spp are isolated from marine sediments of the Niger Delta and they can degrade hydrocarbon. Bacillus spp showed 92.5% degradation of hydrocarbon content during the spillage of Lubricating oil in the water, studied by Gopinath et al. [50] and Dhar et al. [51] studied on the biodegradation of petroleum hydrocarbon of ship breaking yard and found that Fusariumm oniliforme caused the maximum degradation of octane (58%) and diesel (56%), Penicillium corylophilum caused the same of kerosene (40%). Soil contamination also remedy by using microorganisms. In Kuwait, Bacillus subtilis strains are isolated from oil contaminated soil [52]. Crude oil is a complex mixture consisting of aliphatics, aromatics, resins and asphaltenes. It caused potential hazards for the environment. Several studies have been done for the biodegradation of crude oils. Some of them are given in Table 4.
Soil bacteria are capable of adapting to degrade environmental pollutants; some soil types may have indigenous bacteria that are naturally suitable for degradation. But High concentration of diesel can be toxic to microbes and inhibit degradation, so bacterial degradation is possible when the concentration of contaminant is below the threshold of toxicity [53-59]. Lawson studied on diesel utilizing bacteria on contaminated soil [60-65]. They found that six hydrocarbon utilizing bacterial genera, Bacillus, Staphylococcus, Enterobacter, Yersinia, Proteus, and Alcaligenes were present in the soil and the study clearly indicated that Ghanaian soils contain diverse bacterial genera capable of degrading and utilizing diesel oil as carbon source. Biodegradation of diesel oil was performed using a diesel oil-degrading bacterial consortium, in both laboratory and pilot scale experiments by Marquez-Rocha et al. [66]. The concentration of diesel in soil treated with the bacterial consortium was reduced to <15% of the initial concentration, within a period of five weeks in both laboratory (135 to 19.32 g diesel per kg soil) and pilot scale (118 to 17.5g diesel per kg soil). Table 5 shows biodegradation of diesel by using various microorganisms [67-82].
Conclusion
Petroleum hydrocarbons have devastating short-term and long term effects on soil, water as well as human health. Petroleum hydrocarbon contaminated soil affect plant growth, and reduce yield of crop from an agricultural region. Sometimes, agricultural lands become futile because of loss of fertility. Petroleum hydrocarbon contaminated water affect flora and fauna of aquatic ecosystems. Oxygen penetration is hampered and balance of marine ecosystem is ruined. As petroleum hydrocarbon is one of the main sources of fuel in the current world, the use of its products cannot be neglected. Therefore, cleanup of these worst pollutants is mandatory to keep environment safe and sound. However, petroleum hydrocarbon is not readily degradable in natural environment. Various conventional methods include physical and chemical techniques which are expensive and caused negative consequences. In such cases, bioremediation is the most effective and suitable method to remove these pollutants from the environment. A wide variety of microorganisms have the ability to degrade petroleum hydrocarbons and completely mineralize them. Phytoremediation, bioaugmentation, biostimulation etc. are some other useful bioremediation techniques to cleanup petroleum hydrocarbon from the environment.
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