Implementation

Asbestos is a useful material made of six different fibrous minerals:

chrysotile, crocidolite, amosite, tremolite, anthophyllite, and actinolite.

These minerals come from mines throughout the world including Nigeria. Asbestos has a very high heat retardant capacity, for which reason it is used in the manufacture of heat insulating products like roofing shingles, automobile brake pads, floor tiles, assorted gaskets, wraps for insulation of heating ducts and water pipes in homes, offices, and other buildings. These inert asbestos-containing products are not dangerous and constitute no hazards to health, but once they are damaged or breached, or during manufacturing processes, they release asbestos dust, which people can inhale. Asbestos dust contains fragmented particles considered hazardous because they can cause lung

problems, including the development of mesothelioma, a form of lung cancer.

On its own, mine dusts are dust emissions from mining activities. The mine dust and also the asbestos dust mix with particles in air, becoming part of what is generally called particulate matter (PM). Particulate matter contain both naturally- occurring particles and emissions from different human activities, including vehicle exhaust, quarrying, wood processing, industrial processes, power stations, farming and biomass burning. Particulate matter is classified into three major classes on the bases of particulate sizes - greater than 10 µm (PM10+), 10 µm and 2.5 µm (PM 2.5). Each of these is associated with health risks for which reason control of asbestos and mine dust is an important component of environmental health practice.

Asbestos dust contains fibres which are made of pathogenic elements like iron and other metals. Crocidolite, one of the most potently carcinogenic components of asbestos, contains up to 29 % iron, which has the capacity to form highly reactive free radicals that damage DNA and eventually trigger cancers in humans and animals. Experiments in vitro demonstrate that iron removal makes the asbestos considerably less hazardous by reducing their potential to generate radicals and to damage DNA. Several fungi species have the capacity to extract iron from crocidolites and are therefore very good candidates for bioremediation of asbestos contaminated land (Figure 1). Fungi species perform this task in several ways. First, species such as Fusarium oxysporum, Mortierella hyalina and Oidiodendron maius, a mycorrhizal fungus, extract iron from crocidolites. Second, some such as the fungal hyphae form a web of thin strands that bind asbestos fibres, making them less liable to escape into the air. Third, fungal chelators modify fibre surfaces in vitro, destroying active sites involved in the triggering of the carcinogenic mechanisms. As a result of these, fungi species, either naturally occurring or genetically-engineered are widely used in the bioremediation of asbestos contaminated sites.

4.0 CONCLUSION

Several pollutants including heavy metals, toxic chemical substances, oil and tar as well as asbestos and mining dust usually cause contamination.

Because of this, steps in effective remediation must begin with determining the type and sources of contamination. Once the type of pollutant is identified and probably the source too, appropriate remediation technologies are chosen. Although, there are several physical and chemical methods of remediating contaminated sites, biotechnology methods are always preferred for several reasons. They are cheaper, simpler and above all more environmentally friendly.

Bioremediation of contaminated sites may involve several methods

EHS 308 BIOTECHNOLOGY

which are either in situ (treatment at the site of contamination) or ex situ (removal of contaminated soil to another site for treatment). The most important in situ methods are asparging, venting, bio-augumentation and phyto-remediation, while the ex situ methods include forms of composting such as windrows, land farming and bio-piling.

Each of these methods uses either resident microorganisms at the site or introduced species which may be naturally-occurring or genetically-engineered. Both naturally- occurring and genetically-engineered species are commercially available in different parts of the world.

5.0 SUMMARY

In this unit, you have learnt about the different biotechnology methods that can be applied to remediate and decontaminate land sites contaminated by different types of pollutants such as oil and heavy metals. You learnt that a piece of land is said to be contaminated when there are substances in, on or under it that actually, or potentially, constitute a hazard to health or the environment. Contaminated land may be restored to its original state using either bio-remediating or non-bio-remediating techniques. However, non-bio-remediating methods are cheaper and more environmentally- friendly.

We discussed several bio-remediating methods on contaminated land . In the next unit, you will learn about the concepts of merits and demerits, i.e. how to determine what constitutes merit and demerit of an action or issue.

6.0 TUTOR-MARKED ASSIGNMENT

1. Describe the concept of land contamination and the process involve in remediation of hydrocarbon polluted soil.

2. Explain six sources of land contamination and their methods of polluting the land.

3. Discuss the role of heavy metals in soil contaminantion.

4. Define the term phyto-remediation and outline its advantages and disadvantages

7.0 REFERENCES/FURTHER READING

“Application of Compost in Bioremediation.” Retrieved from http://www.wrap.org.on 03/09/2012

“Biopile - Energy from waste.” Retrieved from http://www.seventh-generation.de on 31/08/2012.

Brown, W. P. (2012). “Fractional Distillation and of Crude Oil and Uses of Fractions.” Retrieved from http://www.docbrown.info on 04/09/2012.

“Dealing with Land Contamination.” Retrieved from https://www.csduk.com on 31/08/2012.

“Ex Situ Biological Treatment.” Retrieved from http://205.153.241.230/P2_Opportunity_Handbook on 31/8/12).

Miller, J. (2012). “What are the Treatments for Soil Pollution?”

Retrieved from http://www.ehow.com on 31/8/12.

Thapa, B., Ajay Kumar, K. C. & Ghimire, A. (2012). “A Review on Bioremediation of Petroleum Hydrocarbon Contaminants in Soil.” Kathmandu University Journal of Science, Engineering and Technology, 8(1): 164-170.

Turpeinen, R. (2002). “Interactions between Metals, Microbes and Plants – Bioremediation of Arsenic and Lead Contaminated Soils. Academic dissertation in environmental ecology, to be presented, with the permission of the Faculty of Science of the University of Helsinki, for public criticism in Auditorium, Neopoli, Lahti

“What are Examples of Non-biodegradable Material? Retrieved from http://homeguides.sfgate.com on 03/9/12.

Wikipedia (2012). “Groundwater Remediation. Retrieved from http://en.wikipedia.org on 31/8/12.

Wuana, R. A. & Okieimen, F. E. (2011). “Heavy Metals in Contaminated Soils: A Review of Sources, Chemistry, Risks and Best Available Strategies for Remediation.” International Scholarly Research Network Ecology, Volume1, p. 20.

Zeyaullah, M.D, et al. (2009). “Bioremediation: A Tool for Environmental Cleaning.” African Journal of Microbiology Research, 3(6): 310-314.

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