Soil contamination and its Bioremediation

Introduction

Global industrialization is causing significant harm to life forms due to the release of pollutants like oil hydrocarbons, heavy metals, and pesticides. Remediation of contaminated sites is essential for environmental preservation and urban development. Soil remediation methods include chemical, physical, and biological methods.  Bio-processes such as phyto and bioremediation are mostly used as they are eco-friendly and cost-effective. The choice of in-situ or ex-situ biological remediation techniques depends on environmental conditions, pollutant type, soil composition, removal costs, and treatment time.

Major Soil Contaminants

Soil contamination is the accumulation of harmful substances, chemical compounds, radioactive wastes, salts, or pathogens in soil, negatively impacting ecosystems and human health. Major sources include agricultural residues, byproducts, air pollutants, irrigation, floods, accidental oil spills, inadequate municipal waste management, heavy metals, and hydrocarbon deposition. Sometimes, soil pollution from oil spills is caused by human error or natural disasters. In the America, the main causes include indiscriminate use of fertilizers and pesticides, spills from mining, extraction, and transportation of petroleum products, and open-air garbage dumps. In Eurasia, soil monitoring systems have changed significantly in the past 25 years, with heavy metals and mineral oils being the most common pollutants. So generally, the main sources of soil contamination worldwide include petroleum products, chemical  pesticides, biological warfare and urban waste.

Pollution by Petroleum Derivatives

The petroleum is a fossil. Some of its characteristics include flammable, less dense than water, oily, and foul smelling . It has high energy value, extracted from onshore or offshore. Its color ranges from colorless to black.

Although the crude oil and its derivative brings comfort to human life but it has adverse impacts on environment. The oil products release carbon dioxide gas when used as energy carriers along with other contaminants. This gas is responsible for green house effect. Petroleum hydrocarbons are capable of changing the particle texture, shape and porosity, thus reduce the number of micropores and overall surface. There can be the accumulation of  hydrocarbons in food chain. This will disrupt the physiological and biological in different species, leading to mutagenesis, and impair reproductive ability.

Pollution by Petroleum Derivatives
Pollution by Petroleum Derivatives

 

Heavy Metals

Oil and its derivatives contain heavy metals linked to their carbon chains, which can be introduced into ecosystems through oil spills, burning oil in engines, and thermal power plants. Heavy metals, such as lead, cadmium, chrome, mercury, nickel, copper, zinc, and arsenic, are naturally present in soils and pose a threat to humans and animals. Human activities, such as manufacturing, metallurgy, and waste disposal, contribute to increasing heavy metal concentrations in soils and their harmful effects on humans.

Soil contamination and its Bioremediation
Soil contamination and its Bioremediation

Bioremediation

Bioremediation is a process using living organisms like plants, algae, and microorganisms to remove environmental contaminants. It involves breaking down hydrocarbons into greener products or inorganic compounds. The process is highly efficient but takes weeks or months to complete. Factors influencing bioremediation include pollutant type, environmental conditions, nitrogen and phosphorus sources, temperature, and microbial species. Temperature strongly impact the bioremediation of  hydrocarbons. The optimal temperature for hydrocarbon biodegradation  is effected by climate, site location, and microbial species. Other factors include medium pH, redox potential, moisture content, oxygen availability, soil/water composition, and pollutant solubility have direct effect on bioremediation. However, some hydrocarbons are recalcitrant or slow to biodegrade.

Soil contamination and its Bioremediation
Soil contamination and its Bioremediation

Classification

Bioremediation can be classified as in-situ or ex-situ processes, with ex-situ methods being costlier due to excavation and transport expenses but able to remove more contaminants under controlled conditions. In-situ methods may be unfeasible due to installation costs and control challenges. So the type of contaminant is the main factor in choosing the method.

In-situ Bioremediation

In-situ techniques are classified as

  •  Intrinsic Bioremediation
  • Projected Bioremediation

Ex-Situ Techniques

  • Semi-solid Phase Bioremediation
  • Solid Phase Bioremediation

Conclusion

Pollution is increasing with industrialization. The most effective way to get rid of it and its effects on environment is bioremediation as it is an environmental friendly process.

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