arundinacea collected from the PCB storage site at Ontario (0.6–200 μg g
À1 of total
PCBs (Aroclor 1254/1260)) ascended as potential PCBs phytoextractors (Åslund
et al. 2007).
Phytofiltration or rhizofiltration This technology involves use of plant roots for
removing chemical species from aqueous wastes. According to United States Environmental Protection Agency (2000), rhizofiltration or phytofiltration can be used
for Zn, Cu, Ni, Cd, Pb and Cr which are principally retained within the roots. Plants
such as mustard, sunflower, spinach, rye, tobacco and corn have been identified as
suitable candidates for infiltration of Pb from water (Mukhopadhyay and Maiti
2010). Abhilash et al. (2009) found maximum Cd content in roots followed by
leaves and peduncle of Limnocharis flava grown in Cd-contaminated water, thus
showing the efficacy of L. flava in phytofiltration of Cd (>93%). Micranthemum
umbrosum was found effective in removing organic As species such as
monomethylarsenic acid (CH 5 AsO 3 ) and dimethylarsenic acid (C 2 H 7 AsO 2 ) from
oxic environment through phytofiltration process (Islam et al. 2017).
Phytovolatilization The technique uses green plants to extract contaminants such
as As, Hg, Se and volatile organic compounds from polluted soils, transform them
into volatile forms and transpire them into the atmosphere from their leaves or stem
(Limmer and Burken 2016; Karami and Shamsuddin 2010). According to
Sakakibara et al. (2010), Pteris vittata was found efficient in remediating about
90% As from soil containing 37% of arsenite and 63% of arsenate. Similarly,
Lepidium latifolium, Artemisia douglasiana, Caulanthus sp., Fragaria vesca and
Eucalyptus globulus were grown in soil contaminated with mercury (450–1605 mg
kg
À1 , where Caulanthus sp. showed a higher proficiency in removing mercury from
soil (emission rate 92.6 ng m
À2 h
À1 ) as compared to other plant species (Wang et al.
2012). Limmer and Burken (2016) highlighted the phytovolatilization efficiency of
several plants, i.e. Eucalyptus sp., Populus sp., Salix sp. and Pine, in remediating
volatile organic compounds in soil.
Phytodegradation or phytotransformation Plants and its associated
microorganisms are involved in uptake, metabolization and degradation of
pollutants especially organic compounds (Ekta and Modi 2018; Thakare et al.
2021). Phytoconversion of Cr (VI) (more toxic) to Cr (III) (less toxic) form using
halophytes was reported by Cacador and Duarte (2015). Some plants are successfully used to decontaminate polluted soil and sludge dumps using root exudates
(Ekta and Modi 2018). Newman and Reynolds (2004) enlisted the plants, i.e.,
Leucaena sp., Populus sp., Brassica sp., Helianthus sp., Secale cereale, Cucurbita
sp., Arabidopsis sp., Bruguiera sp., Kandelia sp., Nicotiana tabacum, Sorghum sp.,
etc. commonly used in phytodegradation of organic pollutants (such as pesticides,
PAHs, PCBs, chlorinated compounds, gasoline additives and de-icing agents)
in soil.
Typically, four main strategies currently exist to augment phytoremediation of
organic as well as inorganic pollutants from soils: (1) use of natural
478
M. Gautam et al.
À1 of total
PCBs (Aroclor 1254/1260)) ascended as potential PCBs phytoextractors (Åslund
et al. 2007).
Phytofiltration or rhizofiltration This technology involves use of plant roots for
removing chemical species from aqueous wastes. According to United States Environmental Protection Agency (2000), rhizofiltration or phytofiltration can be used
for Zn, Cu, Ni, Cd, Pb and Cr which are principally retained within the roots. Plants
such as mustard, sunflower, spinach, rye, tobacco and corn have been identified as
suitable candidates for infiltration of Pb from water (Mukhopadhyay and Maiti
2010). Abhilash et al. (2009) found maximum Cd content in roots followed by
leaves and peduncle of Limnocharis flava grown in Cd-contaminated water, thus
showing the efficacy of L. flava in phytofiltration of Cd (>93%). Micranthemum
umbrosum was found effective in removing organic As species such as
monomethylarsenic acid (CH 5 AsO 3 ) and dimethylarsenic acid (C 2 H 7 AsO 2 ) from
oxic environment through phytofiltration process (Islam et al. 2017).
Phytovolatilization The technique uses green plants to extract contaminants such
as As, Hg, Se and volatile organic compounds from polluted soils, transform them
into volatile forms and transpire them into the atmosphere from their leaves or stem
(Limmer and Burken 2016; Karami and Shamsuddin 2010). According to
Sakakibara et al. (2010), Pteris vittata was found efficient in remediating about
90% As from soil containing 37% of arsenite and 63% of arsenate. Similarly,
Lepidium latifolium, Artemisia douglasiana, Caulanthus sp., Fragaria vesca and
Eucalyptus globulus were grown in soil contaminated with mercury (450–1605 mg
kg
À1 , where Caulanthus sp. showed a higher proficiency in removing mercury from
soil (emission rate 92.6 ng m
À2 h
À1 ) as compared to other plant species (Wang et al.
2012). Limmer and Burken (2016) highlighted the phytovolatilization efficiency of
several plants, i.e. Eucalyptus sp., Populus sp., Salix sp. and Pine, in remediating
volatile organic compounds in soil.
Phytodegradation or phytotransformation Plants and its associated
microorganisms are involved in uptake, metabolization and degradation of
pollutants especially organic compounds (Ekta and Modi 2018; Thakare et al.
2021). Phytoconversion of Cr (VI) (more toxic) to Cr (III) (less toxic) form using
halophytes was reported by Cacador and Duarte (2015). Some plants are successfully used to decontaminate polluted soil and sludge dumps using root exudates
(Ekta and Modi 2018). Newman and Reynolds (2004) enlisted the plants, i.e.,
Leucaena sp., Populus sp., Brassica sp., Helianthus sp., Secale cereale, Cucurbita
sp., Arabidopsis sp., Bruguiera sp., Kandelia sp., Nicotiana tabacum, Sorghum sp.,
etc. commonly used in phytodegradation of organic pollutants (such as pesticides,
PAHs, PCBs, chlorinated compounds, gasoline additives and de-icing agents)
in soil.
Typically, four main strategies currently exist to augment phytoremediation of
organic as well as inorganic pollutants from soils: (1) use of natural
478
M. Gautam et al.