predicted to be five times higher as compared to water and
air. The major sources of ENPs in soil include sewage sludge
used for agricultural purpose (forecasted annual load of
1.01–2380 µg
−1 engineered nanomaterials (ENMs) kg
−1
year
−1 sludge) (Schwab et al. 2016), increased usage of
novel
pesticides
or
fertilizers’
nanoformulations
(Gardea-Torresdey et al. 2014), wastewater effluents (0.001–
15 ng L
−1 year
−1 ), and atmospheric sources like dry depositions and rainfall (551 µg m
−3 year
−1 ) (Gottschalk et al.
2009; Hendren et al. 2011). In addition, nanotechnology has
been used frequently in the remediation of environmental
pollutants (Cecchin et al. 2017; Lv et al. 2019). The use of
ENPs to remediate pollution also adds NPs to the soil and
the immediate environment. The extensive applications of
NPs in different areas have attracted more attention due to
their potential environmental risks. Hence the research is
increasing for the toxicity of nanomaterials on animals,
plants, and microbes (Lee et al. 2012). So, there is an urgent
need to assess the potential risks of NPs on soil, bacteria,
plants, and the environment.
3 Impact of Engineered Nanoparticles
on Environmental Components
The expeditious use of NPs in cosmetics, drug delivery,
biosensor, electronics, environmental remediation, and
wastewater treatment has an urgent need to evaluate their
impact on soil and microbes present in soil and plants.
Extensive research has shown both positive and negative
impacts of NPs on soil, soil microbes, and plants (Table 1,
Fig. 2). However, there are many challenges and unresolved
issues related to the impact of NPs (Schwab et al. 2016; Lv
et al. 2019). So, it is crucial to understand the biological
effects of different types of ENPs and its long-term environmental consequences. Study reveals that ENPs can have a
toxic effect on living organism including, viruses, bacteria,
fungi, plants (Fig. 3), and animals (Cecchin et al. 2017). The
plants and soil microbes are among the most closely associated biotic components in the environment. Alterations in
soil microbial biomass are a sensitive indicator of changes in
soil properties and health. Therefore, it is essential to explore
the fate and transport of engineered NPs in soil, plants,
animals, and associated environment.
3.1 Impact of Engineered Nanoparticles on Soil
Microbes
The introduction and use of NPs in the environment cause
harm to beneficial microbes such as bacteria, fungi, and
actinomycetes which are involved in plant growth and
development (Kumar et al. 2020). NPs used for different
purposes are directly or indirectly released into the environment. These ENPs accumulate in soil and change their
properties with time. The major impact of ENPs includes
changes in soil enzyme and soil respiration, and ultimately
microbial diversity. TiO 2 NPs decrease soil microbial and
enzymatic activity in the environment (Peng et al. 2015;
Peyrot 2015). Silver (Ag) NPs are produced by many fungi
by both intracellular and extracellular pathways (Bhainsa
and D’Souza 2006). The Ag NPs are effective to certain
pathogenic bacteria such as Syphilis typhus, Vibrio cholera,
Staphylococcus aureus, Pseudomonas aeruginosa (Siddiqi
and Husen 2016). The major mechanism through which
ENPs caused bacterial cell death includes oxidative stress
leading to damage of lipids, proteins, carbohydrates, and
DNA (Table 1). The generation of hydrogen peroxides is
one of the major events responsible for antibacterial activity.
The green NPs synthesized from Allium cepa also have
antibacterial activity (Jini and Sharmila 2020).
The Ag NPs widely used in industrial products are
released in soil having extensive implications. Soil microbial
diversity, biomass, and plant growth is highly affected by
these particles. These ENPs easily cross the cell membrane
and affect the physiology of bacteria and cause cellular
toxicity (Courtios et al. 2019). The ENPs synthesized from
Vitis vinifera (black grapes) have antibacterial activities
against S. aureus, Bacillus cereus, P. aeruginosa, and
Escherichia coli (Kowsalya et al. 2019). Some NPs show
activity against both beneficial as well as harmful microbes.
The Cu NPs release copper ions in the soil which may cause
considerable loss in counts of both beneficial and pathogenic
bacteria (Lofts et al. 2013). The effect of ENPs on microbial
community depends on its types, size, and structure. Inorganic NPs have more toxic effect than organic ones (Frenk
et al. 2013). A decrease in soil enzyme, nitrogen fixation,
and crop productivity occurs due to higher concentration of
ENPs. NPs like TiO 2 generate superoxide and hydroxide
radicals which show strong antibacterial activity (Table 1)
(Peyrot et al. 2014; Xu et al. 2015). NPs cross most biological barriers such as bacterial cell wall and their behaviors
on the cell is unpredictable. Hence, as the production of
ENPs is increasing, soil microbes facing challenges of toxicity and decreasing microbial diversity.
3.2 Impact of Engineered Nanoparticles on Soil
Biophysical Properties
Soil is the main repository of waste products of nanomaterials which are added after use. It is a complex living
system that has different assemblages. The properties of soil
such as size, surface area, charge, mineral composition, and
organic matter are mostly affected by ENPs. NPs may
undergo many transformations in soil and alter its properties
Impact of Engineered Nanoparticles on Microbial Communities, Soil …
203
air. The major sources of ENPs in soil include sewage sludge
used for agricultural purpose (forecasted annual load of
1.01–2380 µg
−1 engineered nanomaterials (ENMs) kg
−1
year
−1 sludge) (Schwab et al. 2016), increased usage of
novel
pesticides
or
fertilizers’
nanoformulations
(Gardea-Torresdey et al. 2014), wastewater effluents (0.001–
15 ng L
−1 year
−1 ), and atmospheric sources like dry depositions and rainfall (551 µg m
−3 year
−1 ) (Gottschalk et al.
2009; Hendren et al. 2011). In addition, nanotechnology has
been used frequently in the remediation of environmental
pollutants (Cecchin et al. 2017; Lv et al. 2019). The use of
ENPs to remediate pollution also adds NPs to the soil and
the immediate environment. The extensive applications of
NPs in different areas have attracted more attention due to
their potential environmental risks. Hence the research is
increasing for the toxicity of nanomaterials on animals,
plants, and microbes (Lee et al. 2012). So, there is an urgent
need to assess the potential risks of NPs on soil, bacteria,
plants, and the environment.
3 Impact of Engineered Nanoparticles
on Environmental Components
The expeditious use of NPs in cosmetics, drug delivery,
biosensor, electronics, environmental remediation, and
wastewater treatment has an urgent need to evaluate their
impact on soil and microbes present in soil and plants.
Extensive research has shown both positive and negative
impacts of NPs on soil, soil microbes, and plants (Table 1,
Fig. 2). However, there are many challenges and unresolved
issues related to the impact of NPs (Schwab et al. 2016; Lv
et al. 2019). So, it is crucial to understand the biological
effects of different types of ENPs and its long-term environmental consequences. Study reveals that ENPs can have a
toxic effect on living organism including, viruses, bacteria,
fungi, plants (Fig. 3), and animals (Cecchin et al. 2017). The
plants and soil microbes are among the most closely associated biotic components in the environment. Alterations in
soil microbial biomass are a sensitive indicator of changes in
soil properties and health. Therefore, it is essential to explore
the fate and transport of engineered NPs in soil, plants,
animals, and associated environment.
3.1 Impact of Engineered Nanoparticles on Soil
Microbes
The introduction and use of NPs in the environment cause
harm to beneficial microbes such as bacteria, fungi, and
actinomycetes which are involved in plant growth and
development (Kumar et al. 2020). NPs used for different
purposes are directly or indirectly released into the environment. These ENPs accumulate in soil and change their
properties with time. The major impact of ENPs includes
changes in soil enzyme and soil respiration, and ultimately
microbial diversity. TiO 2 NPs decrease soil microbial and
enzymatic activity in the environment (Peng et al. 2015;
Peyrot 2015). Silver (Ag) NPs are produced by many fungi
by both intracellular and extracellular pathways (Bhainsa
and D’Souza 2006). The Ag NPs are effective to certain
pathogenic bacteria such as Syphilis typhus, Vibrio cholera,
Staphylococcus aureus, Pseudomonas aeruginosa (Siddiqi
and Husen 2016). The major mechanism through which
ENPs caused bacterial cell death includes oxidative stress
leading to damage of lipids, proteins, carbohydrates, and
DNA (Table 1). The generation of hydrogen peroxides is
one of the major events responsible for antibacterial activity.
The green NPs synthesized from Allium cepa also have
antibacterial activity (Jini and Sharmila 2020).
The Ag NPs widely used in industrial products are
released in soil having extensive implications. Soil microbial
diversity, biomass, and plant growth is highly affected by
these particles. These ENPs easily cross the cell membrane
and affect the physiology of bacteria and cause cellular
toxicity (Courtios et al. 2019). The ENPs synthesized from
Vitis vinifera (black grapes) have antibacterial activities
against S. aureus, Bacillus cereus, P. aeruginosa, and
Escherichia coli (Kowsalya et al. 2019). Some NPs show
activity against both beneficial as well as harmful microbes.
The Cu NPs release copper ions in the soil which may cause
considerable loss in counts of both beneficial and pathogenic
bacteria (Lofts et al. 2013). The effect of ENPs on microbial
community depends on its types, size, and structure. Inorganic NPs have more toxic effect than organic ones (Frenk
et al. 2013). A decrease in soil enzyme, nitrogen fixation,
and crop productivity occurs due to higher concentration of
ENPs. NPs like TiO 2 generate superoxide and hydroxide
radicals which show strong antibacterial activity (Table 1)
(Peyrot et al. 2014; Xu et al. 2015). NPs cross most biological barriers such as bacterial cell wall and their behaviors
on the cell is unpredictable. Hence, as the production of
ENPs is increasing, soil microbes facing challenges of toxicity and decreasing microbial diversity.
3.2 Impact of Engineered Nanoparticles on Soil
Biophysical Properties
Soil is the main repository of waste products of nanomaterials which are added after use. It is a complex living
system that has different assemblages. The properties of soil
such as size, surface area, charge, mineral composition, and
organic matter are mostly affected by ENPs. NPs may
undergo many transformations in soil and alter its properties
Impact of Engineered Nanoparticles on Microbial Communities, Soil …
203