Biodegradation of Soil Contaminants

Many industrial and other human activities resulted in a widespread contamination of soils with various contaminants. Most of these contaminants are toxic to humans and animals . They reach humans and animals through migration into the atmosphere, groundwater and crops I. The pollution became especially disturbing in the past few decades, when the awareness of thi s problem resulted in the enormous growth of environmental Science and Technolc.gy (S&T). While some of the contaminants can be eas i!y degraded by the soil microflora, other are much more persistent and can remain in soil for decades, continuously contaminating groundwater and/or air. There are many different chemical, physica l and thermal methods for the elimination of recalcitrant soil pollutants such as incineration, vitrification, chemical oxidation, etc2,3 , Unfortunately, most of these methods are expensive and not quite environmentally friendly. The natural capacity of microorganisms to degrade a huge variety of organic and some inorganic compounds, even the most tox ic ones (e.g. cyanides), is the bas is for the microbial methods for degradation (biodegradation) of soil contaminants, or bioremediation . These methods are generally much less expensive than chemical and physical ones. Another very interesting feature of microorganisms is that they are capable of degrading organic substances, which never existed in the nature and were produced only synthetically I. Biodegradation is. in fact , a biocatalytic process of the transformation of soil contaminants into harmless products. The biocatalyst are the microbial cells. The carbon, oxygen, hydrogen, and chlorine atoms in the contaminant molecule are usually converted into inorganic substances such as H 2 0, CO~ , CH4 ' and HC\. The microbial methods for contaminants degradation can be considered as a basis of "green technologies" 4.