Crude oil spillage on the environment, whether accidental or deliberate, is a significant source of environmental contamination. These spills pose a significant threat to the environment due to the possibility of air, water and soil pollution. Soil which is the essential basis of agricultural resources, food security, global economy and environmental quality is polluted by heavy metals, organic pollutant and petroleum products due to urbanization and industrialisation. This development threatens the ecosystems, surface and groundwater, food safety and human health (Kokyo et al., 2014).
Soil pollution has become a significant environmental issue all over the world and the contaminants ability to gather over time has become toxic to plants and animals. Therefore, for sustainability management and remediation of the contaminated soil, there is great need for effective technologies to be applied said Kokyo et al., (2014). Soil always serves as the location for spillage of oil and in determining the type and extent of environmental contamination, the capacity of the soil compartment to filter, retain or release hydrocarbon is key.
Contamination by hydrocarbon products on water and land has been an issue from the time oil was discovered as fuel in developing countries. However, in most industrialised countries, the treatment and removal of harmful wastes is controlled carefully by variety of policies, regulations, incentive programs and voluntary efforts. The use of petroleum products is increasing due to the increase in different types of machineries and automobiles. The crude oil or petroleum discovery has transformed considerably man’s way of life by improving his life economically and has made available a quick and accessible source of energy.
Products from petroleum, like volatile hydrocarbon mixtures, are part of the main pollutants that pollute the soil. This pollution results from oil spillage, out of service oil distribution, leakage from underground storage tank or waste from other industrial activities. The spill of petroleum products into the soil will be different since these products are comprised of complex mixtures of hydrocarbons with significantly varying vapour pressures and water solubility. The variation in these chemical and physical characteristics will result in variance distribution of released hydrocarbon components in air, soil and water.
The presence of Volatile Organic Compounds (VOCs) in the soil is a threat to groundwater due to their high toxicity and water-soluble nature. Soil contamination is affected by the type of contaminant as well as the soil’s properties therefore, an understanding of the properties of the soil been affected by the petroleum contaminants is a basic step to soil remediation (Al-Duwaisan and Al-Naseem, 2011). Soil behaviour is modified by the presence of oil in the pore space of the soil system as a result of oil spillage and their presence in the soil has resulted in contamination and therefore requires remediation.
The effect of petroleum contaminants on the soil depends on the quantity and concentration of the spilled petroleum. Soil porosity is decreased by the presence of petroleum. This is because its presence tends to forcefully bind the particles of the soil together resulting in the decrease of pores. In petroleum contaminated soil, droplets of oil interfere with the interstices. Petroleum presence in the soil form a covering on the soil surface to prevent the escape of carbon dioxide release by soil’s microbes during respiration.
Remediation as regard to a polluted area is define as the management of the contaminated area to enable the prevention of danger to human health or the environment and restoring all or portion of the area to a beneficial goal.
Some soil remediation methods include:
- Soil flushing
- Molecular and phase separation
- Chemical destruction
- Soil washing
- Vapor extraction
- Electro kinetics and
Successful application of all these methods can be made possible if the physicochemical properties of contaminants and particles of soil are well understood before the selection of any technique. Choosing the most suitable soil and sediment remediation technique rests on the site properties, concentration, kinds of contaminants to be removed and final use of the concentrated medium.