be optimized as the particle size and amount used greatly
modulates the soil physical attributes.
The naturally existing soil iron oxide nanoparticles having average size ranging from 5 to 100 nm, possess reactive
sites with inherent ability to adsorb varieties of organic and
inorganic contaminants through the process like surface
binding (Bigham et al. 2002). The efficiency in rapid
adsorption, minimal chances of secondary contamination,
and ecofriendly nature has fostered the engineered iron oxide
nanoparticles with multiple applications including remediation of contaminated water as well as soil. Some of the
widely applied iron oxide nanomaterials described for
extraction of heavy metals such as copper, chromium,
nickel, lead, arsenic, and zinc are goethite, magnetite,
hematite, and maghemite. Column-based investigation
indicating arsenic immobilization for more than four months
in soil amended with 15% nanomagnetite and 100 µg l
−1
arsenic spiked at a rate of 0.3 ml h
−1 , in contrast to soil
without amendment, has been presented by Shipley et al.
(2011). However, after the elapse of 208 days, a total of
20% arsenic was noticed to be leached from column. The
study further suggested the simultaneous removal of 12
other metals.
The strong reductant nanozero-valent iron (nZVI) had
been synthesized with an objective to degrade the organic
contaminants including pesticides and petrochemical products (Zhang 2003). Intriguingly, nZVI may also serve as an
important material for sequestration of various heavy metals
from terrestrial system. Because of reducing action of nZVI,
metal ions with higher oxidation states like chromium and
uranium are transformed to corresponding lower oxidation
states and reduce the toxicity, as well as solubility and
mobilization in soil environment by the process referred as
reductive immobilization. Numerous studies have shown the
efficiency of nZVI in immobilization of uranium in comparison with reductants including iron fillings, lead sulfide,
and iron sulfide, because of large size conferred by small
size, increased reactivity, and release of reactive iron produced. Reduction of approximately 98% hexavalent chromium to trivalent form assisted by the catalytic activity of
nZVI, leading to reduction in toxicity to soil is demonstrated
by Franco et al. (2009). Similar observation on reductive
immobilization of higher oxidation state chromium (hexavalent) in soil, with the resultant decline in ecotoxicity to
soil, is also documented (Ponder et al. 2000; Xu and Zhao
2007). The application of engineered graphene oxide
nanoparticles as a promising tool in management of heavy
metal contaminated soil responsible for immobilization of
copper, lead, and cadmium, in contrast to mobilization of
arsenic and phosphorus has been reported by Baragaño et al.
(2020). In addition, phosphate and iron sulfide-based
nanomaterials (Liu et al. 2020; Rodríguez-Seijo et al. 2020)
and carbon nanotubes (Liu et al. 2018; Egbosiuba et al.
2020) are also remarkably annotated for possessing
promising potential in removal of heavy metals and organic
contaminants.
The employment of ENPs, although, for reclamation of
contaminated agro-ecosystem is quite attractive, the fate and
toxicity to environmental components must be extensively
investigated for safe application. The behavior of ENPs
incorporated into soil environment is significantly modified
by soil attributes, prevailing environmental conditions as
well as its own size and morphology. The optimization of
dose for different soil types, and different organic and
inorganic contaminants are crucial steps toward application
of ENPs in agro-ecosystems.
6 Conclusion and Future Perspectives
Engineered nanomaterials are continuously gaining importance in varied disciplines like medicine, electronics, environment, and agriculture. The increased applications in
agriculture as nanofertilizers and nanopesticides have
improved the productivity of agro-ecosystem multifolds.
However, the nanoparticle incorporation in food crops,
toxicity to human health, and negative consequences on soil
properties including enzymes, microbial diversity, soil
nutrient cycling, and ecotoxicity to soil dwelling annelids
and arthropods have questioned their application for
enhancing the crop productivity. The employment of ENPs,
therefore, must be based on extensive ecotoxicity appraisal
to beneficial non-target organisms as well as humans
exposed via agronomic crops. In addition to augmentation of
soil productivity, ENPs could be applied for restoration of
ecologically disturbed sites like mining affected cultivable
sites. The soil reclamation using zeolites and iron oxide
nanoparticles, however, is in infant stage, implying further
research work in this direction.
Since the dose of applied ENPs varies according to the
nature of nanoparticles and soil characteristics, deciding
optimum dose so as to minimize the residues left over in
agro-environment is a crucial step and need much experimental work. The techniques for identification and quantification of ENPs should be improved in order to minimize
the impact on natural environment and associated health
hazards. Investigation on sources of nanoparticles, fate, and
transport in soil environment is another area of research for
protection of soil health. Further, there is urgent need to set
the regulatory limits for different nanoparticles currently
being applied in agro-ecosystem to prevent excessive accumulation in soil as well as crop products.
Effect of Engineered Nanoparticles on Soil Attributes …
125
modulates the soil physical attributes.
The naturally existing soil iron oxide nanoparticles having average size ranging from 5 to 100 nm, possess reactive
sites with inherent ability to adsorb varieties of organic and
inorganic contaminants through the process like surface
binding (Bigham et al. 2002). The efficiency in rapid
adsorption, minimal chances of secondary contamination,
and ecofriendly nature has fostered the engineered iron oxide
nanoparticles with multiple applications including remediation of contaminated water as well as soil. Some of the
widely applied iron oxide nanomaterials described for
extraction of heavy metals such as copper, chromium,
nickel, lead, arsenic, and zinc are goethite, magnetite,
hematite, and maghemite. Column-based investigation
indicating arsenic immobilization for more than four months
in soil amended with 15% nanomagnetite and 100 µg l
−1
arsenic spiked at a rate of 0.3 ml h
−1 , in contrast to soil
without amendment, has been presented by Shipley et al.
(2011). However, after the elapse of 208 days, a total of
20% arsenic was noticed to be leached from column. The
study further suggested the simultaneous removal of 12
other metals.
The strong reductant nanozero-valent iron (nZVI) had
been synthesized with an objective to degrade the organic
contaminants including pesticides and petrochemical products (Zhang 2003). Intriguingly, nZVI may also serve as an
important material for sequestration of various heavy metals
from terrestrial system. Because of reducing action of nZVI,
metal ions with higher oxidation states like chromium and
uranium are transformed to corresponding lower oxidation
states and reduce the toxicity, as well as solubility and
mobilization in soil environment by the process referred as
reductive immobilization. Numerous studies have shown the
efficiency of nZVI in immobilization of uranium in comparison with reductants including iron fillings, lead sulfide,
and iron sulfide, because of large size conferred by small
size, increased reactivity, and release of reactive iron produced. Reduction of approximately 98% hexavalent chromium to trivalent form assisted by the catalytic activity of
nZVI, leading to reduction in toxicity to soil is demonstrated
by Franco et al. (2009). Similar observation on reductive
immobilization of higher oxidation state chromium (hexavalent) in soil, with the resultant decline in ecotoxicity to
soil, is also documented (Ponder et al. 2000; Xu and Zhao
2007). The application of engineered graphene oxide
nanoparticles as a promising tool in management of heavy
metal contaminated soil responsible for immobilization of
copper, lead, and cadmium, in contrast to mobilization of
arsenic and phosphorus has been reported by Baragaño et al.
(2020). In addition, phosphate and iron sulfide-based
nanomaterials (Liu et al. 2020; Rodríguez-Seijo et al. 2020)
and carbon nanotubes (Liu et al. 2018; Egbosiuba et al.
2020) are also remarkably annotated for possessing
promising potential in removal of heavy metals and organic
contaminants.
The employment of ENPs, although, for reclamation of
contaminated agro-ecosystem is quite attractive, the fate and
toxicity to environmental components must be extensively
investigated for safe application. The behavior of ENPs
incorporated into soil environment is significantly modified
by soil attributes, prevailing environmental conditions as
well as its own size and morphology. The optimization of
dose for different soil types, and different organic and
inorganic contaminants are crucial steps toward application
of ENPs in agro-ecosystems.
6 Conclusion and Future Perspectives
Engineered nanomaterials are continuously gaining importance in varied disciplines like medicine, electronics, environment, and agriculture. The increased applications in
agriculture as nanofertilizers and nanopesticides have
improved the productivity of agro-ecosystem multifolds.
However, the nanoparticle incorporation in food crops,
toxicity to human health, and negative consequences on soil
properties including enzymes, microbial diversity, soil
nutrient cycling, and ecotoxicity to soil dwelling annelids
and arthropods have questioned their application for
enhancing the crop productivity. The employment of ENPs,
therefore, must be based on extensive ecotoxicity appraisal
to beneficial non-target organisms as well as humans
exposed via agronomic crops. In addition to augmentation of
soil productivity, ENPs could be applied for restoration of
ecologically disturbed sites like mining affected cultivable
sites. The soil reclamation using zeolites and iron oxide
nanoparticles, however, is in infant stage, implying further
research work in this direction.
Since the dose of applied ENPs varies according to the
nature of nanoparticles and soil characteristics, deciding
optimum dose so as to minimize the residues left over in
agro-environment is a crucial step and need much experimental work. The techniques for identification and quantification of ENPs should be improved in order to minimize
the impact on natural environment and associated health
hazards. Investigation on sources of nanoparticles, fate, and
transport in soil environment is another area of research for
protection of soil health. Further, there is urgent need to set
the regulatory limits for different nanoparticles currently
being applied in agro-ecosystem to prevent excessive accumulation in soil as well as crop products.
Effect of Engineered Nanoparticles on Soil Attributes …
125