152
uranium may be present as U(IV)-oxide. Due to the very low solubility of U(IV) in
environmental media, it often is present in particulate form (diameter of 0.1 microns
or less) which may confer higher biological toxicity (Tasat et al. 2012). Being reactive in nature, U persistently binds to nucleotides and proteins and affects citrate,
lactate, carbonate, pyruvate and phosphate metabolisms after entering in the body
primarily through inhalation, but also by dermal contact and ingestion (Tasat et al.
2012).
U(VI) is mobile in soil, which exists in solution UO 2
2+
and as soluble carbonate
complexes, like UO 2 CO 3 °, UO 2 (CO 3 ) 3
4−
, (UO 2 ) 2 CO 3 (OH)
3−
, UO 2 (CO 3 ) 2
2−
and plausibly (UO 2 ) 3 (CO 3 ) 6
6−
(Grenthe et al. 1992; Duff and Amrhein 1996). Meinrath et al.
(1996) suggested that U(VI) primarily exits in hydrolysed forms in pH 4.0–7.5,
while vented air may affect clay lattice of the soils creating less transferrable and
solvable forms of U, leading to limited availability to plants (Bunzl et al. 1995;
ANRCP 1998). Sheppard and Thibault (1992) showed that Fe-Mn oxide association
is common in U(VI) spiked soil, where rate of desorption of the element increased
with time.
4 Plant-Based Remediation
Appropriate eco-friendly U remediation technologies for U-contaminated soil and
water are an important research area. Apart from physical and chemical methods,
application of bioremediation, including phytoremediation technology, is useful for
decontamination of U contamination from the environment.
Remediation of organic and inorganic molecules using plant species to achieve
site-specific cleaning is the basis of phytoremediation (Ancient Greek: phyto—
‘plant’ and Latin remedium—‘restoring balance’). This technique is environmentally friendly and cheap in comparison to the conventional instrument and/or
chemical-based environmental restoration processes. Microbial diversity at rhizosphere and plant and its exudates along with soil properties are essential factors for
elemental uptake and accumulation (Gupta et al. 2016a). After the Chernobyl accident in 1986 (UNSCEAR 2010) that caused huge release of radionuclides into the
environment, scientists thought for phytoremediation of contaminated sites. In
1998, PhytoTech, Consolidated Growers and Processors (CGP) and Institute of Bast
Crops (Ukraine) came up with plant industrial hemp (cannabis) for phytoremediation. The process was further developed by USEPA and US Department of Defense
extensive clean- up projects to eliminate toxins and specific metals (Rai and Pal
1999; Gupta et al. 2016a). The elements including toxic cations or oxyanions are
extracted from the soil and are translocated into the above-ground parts of plants
forming less toxic substances (Chatterjee et al. 2012). Processes like exclusion, stabilization, detoxification and partitioning (storing in particular tissues and cell
organelles like cell walls, vacuoles) to a particular metal are strategically characteristics to a plant, which may also develop antistress responses through proteins like
phytochelatins and metallothioneins. In phytoremediation practices, these processes
D. K. Gupta et al.
uranium may be present as U(IV)-oxide. Due to the very low solubility of U(IV) in
environmental media, it often is present in particulate form (diameter of 0.1 microns
or less) which may confer higher biological toxicity (Tasat et al. 2012). Being reactive in nature, U persistently binds to nucleotides and proteins and affects citrate,
lactate, carbonate, pyruvate and phosphate metabolisms after entering in the body
primarily through inhalation, but also by dermal contact and ingestion (Tasat et al.
2012).
U(VI) is mobile in soil, which exists in solution UO 2
2+
and as soluble carbonate
complexes, like UO 2 CO 3 °, UO 2 (CO 3 ) 3
4−
, (UO 2 ) 2 CO 3 (OH)
3−
, UO 2 (CO 3 ) 2
2−
and plausibly (UO 2 ) 3 (CO 3 ) 6
6−
(Grenthe et al. 1992; Duff and Amrhein 1996). Meinrath et al.
(1996) suggested that U(VI) primarily exits in hydrolysed forms in pH 4.0–7.5,
while vented air may affect clay lattice of the soils creating less transferrable and
solvable forms of U, leading to limited availability to plants (Bunzl et al. 1995;
ANRCP 1998). Sheppard and Thibault (1992) showed that Fe-Mn oxide association
is common in U(VI) spiked soil, where rate of desorption of the element increased
with time.
4 Plant-Based Remediation
Appropriate eco-friendly U remediation technologies for U-contaminated soil and
water are an important research area. Apart from physical and chemical methods,
application of bioremediation, including phytoremediation technology, is useful for
decontamination of U contamination from the environment.
Remediation of organic and inorganic molecules using plant species to achieve
site-specific cleaning is the basis of phytoremediation (Ancient Greek: phyto—
‘plant’ and Latin remedium—‘restoring balance’). This technique is environmentally friendly and cheap in comparison to the conventional instrument and/or
chemical-based environmental restoration processes. Microbial diversity at rhizosphere and plant and its exudates along with soil properties are essential factors for
elemental uptake and accumulation (Gupta et al. 2016a). After the Chernobyl accident in 1986 (UNSCEAR 2010) that caused huge release of radionuclides into the
environment, scientists thought for phytoremediation of contaminated sites. In
1998, PhytoTech, Consolidated Growers and Processors (CGP) and Institute of Bast
Crops (Ukraine) came up with plant industrial hemp (cannabis) for phytoremediation. The process was further developed by USEPA and US Department of Defense
extensive clean- up projects to eliminate toxins and specific metals (Rai and Pal
1999; Gupta et al. 2016a). The elements including toxic cations or oxyanions are
extracted from the soil and are translocated into the above-ground parts of plants
forming less toxic substances (Chatterjee et al. 2012). Processes like exclusion, stabilization, detoxification and partitioning (storing in particular tissues and cell
organelles like cell walls, vacuoles) to a particular metal are strategically characteristics to a plant, which may also develop antistress responses through proteins like
phytochelatins and metallothioneins. In phytoremediation practices, these processes
D. K. Gupta et al.