environments and understanding the mechanisms driving microbial activity and
metal metabolic pathways under wide range of extreme climatic conditions need
to be further elucidated before successful and better-controlled site-specific treatments can be undertaken.
12.5.4 Bioremediation of Radionuclides
The extensive use of radioactive materials at research laboratories, industrial sites
and biomedical institutions has produced a great accumulation of radioactive waste.
Fredrickson et al. (2004) reported that about 90 million gallons of high-level
radioactive waste are accumulated across the USA during the World War II. The
occasional disastrous accidents at nuclear facilities such as Chernobyl disaster of
1986 and the Fukushima Daiichi nuclear disaster in 2011 have also caused damage
to the human health and environment issues by generating a large quantity of
radioactive materials or radionuclides in the environment. Most radioactive wastes
are generated by nuclear power plants contributing about 95% of the radioactively
generated from all sources (Ahier and Tracy 1995; Tamponnet and Declerck 2008).
The commonly encountered radionuclides include cobalt-60 (
60 Co), Plutonium-239
(
239 Pu), Radium-226 (
226 Ra), Radon-222 (
222 Rn), Technetium-99 (
99 Tc), Thorium226 (
226 Th) and Uranium-238 (
238 U). Other radionuclides created through nuclear
reactors by means of the splitting of elemental atoms are Thallium-201 (
201 Tl),
Iridium-238 (
238 Ir), Caesium-137 (
137
Cs) and Strontium-90 (
90 Sr) having longer
time to decay (Kumraz et al. 2007).
Radionuclides in the environment are a major human and environmental health
concern. Even a small concentration of radionuclides in the environment can have an
impact for a prolonged period of time due to their long half-life. The impact of these
pollutants is growing with time. Exposure to radionuclides or radiation causes acute
health effects that begin with vomiting, nausea, headaches, and with increased
exposure, fatigue, weakness, fever, dizziness, diarrhoea, fever, blood in stool and
low blood pressure and finally death. Mohner et al. (2006) reported that long-term
exposure to radionuclides leads to high risk of leukaemia, kidney damage an genetic
damage, resulting in lethal problems, even passing to the next generation.
Excavation and shipping to a distant waste disposal location is the most common
means of eradicating soil contaminated with radionuclides. Due to high costs of
physiochemical approaches, bioremediation has been viewed as the ecological
responsible alternative environmentally destructive physical remediation. Microorganisms carry endogenous genetic, biochemical and physiological properties that
make them ideal agents for pollutants remediation in soil and groundwater. Attempts
have been made to develop native or genetically engineered or extremophilic
microbes for the remediation of environmental containments including radionuclides. Extremophiles have been used to remediate radionuclides. Microorganisms
such as Rhodanobacter sp. and Desulfuromusa ferrireducens were observed to be
able to interact with these contaminants which initiate solubility of transformed
314
S. Kaushik et al.
metal metabolic pathways under wide range of extreme climatic conditions need
to be further elucidated before successful and better-controlled site-specific treatments can be undertaken.
12.5.4 Bioremediation of Radionuclides
The extensive use of radioactive materials at research laboratories, industrial sites
and biomedical institutions has produced a great accumulation of radioactive waste.
Fredrickson et al. (2004) reported that about 90 million gallons of high-level
radioactive waste are accumulated across the USA during the World War II. The
occasional disastrous accidents at nuclear facilities such as Chernobyl disaster of
1986 and the Fukushima Daiichi nuclear disaster in 2011 have also caused damage
to the human health and environment issues by generating a large quantity of
radioactive materials or radionuclides in the environment. Most radioactive wastes
are generated by nuclear power plants contributing about 95% of the radioactively
generated from all sources (Ahier and Tracy 1995; Tamponnet and Declerck 2008).
The commonly encountered radionuclides include cobalt-60 (
60 Co), Plutonium-239
(
239 Pu), Radium-226 (
226 Ra), Radon-222 (
222 Rn), Technetium-99 (
99 Tc), Thorium226 (
226 Th) and Uranium-238 (
238 U). Other radionuclides created through nuclear
reactors by means of the splitting of elemental atoms are Thallium-201 (
201 Tl),
Iridium-238 (
238 Ir), Caesium-137 (
137
Cs) and Strontium-90 (
90 Sr) having longer
time to decay (Kumraz et al. 2007).
Radionuclides in the environment are a major human and environmental health
concern. Even a small concentration of radionuclides in the environment can have an
impact for a prolonged period of time due to their long half-life. The impact of these
pollutants is growing with time. Exposure to radionuclides or radiation causes acute
health effects that begin with vomiting, nausea, headaches, and with increased
exposure, fatigue, weakness, fever, dizziness, diarrhoea, fever, blood in stool and
low blood pressure and finally death. Mohner et al. (2006) reported that long-term
exposure to radionuclides leads to high risk of leukaemia, kidney damage an genetic
damage, resulting in lethal problems, even passing to the next generation.
Excavation and shipping to a distant waste disposal location is the most common
means of eradicating soil contaminated with radionuclides. Due to high costs of
physiochemical approaches, bioremediation has been viewed as the ecological
responsible alternative environmentally destructive physical remediation. Microorganisms carry endogenous genetic, biochemical and physiological properties that
make them ideal agents for pollutants remediation in soil and groundwater. Attempts
have been made to develop native or genetically engineered or extremophilic
microbes for the remediation of environmental containments including radionuclides. Extremophiles have been used to remediate radionuclides. Microorganisms
such as Rhodanobacter sp. and Desulfuromusa ferrireducens were observed to be
able to interact with these contaminants which initiate solubility of transformed
314
S. Kaushik et al.