18 research outputs found
Nanoparticle interactions with co-existing contaminants: joint toxicity, bioaccumulation and risk
<p>With their growing production and application, engineered nanoparticles (NPs) are increasingly discharged into the environment. The released NPs can potentially interact with pre-existing contaminants, leading to biological effects (bioaccumulation and/or toxicity) that are poorly understood. Most studies on NPs focus on single analyte exposure; the existing literature on joint toxicity of NPs and co-existing contaminants is rather limited but beginning to develop rapidly. This is the first review paper evaluating the current state of knowledge regarding the joint effects of NPs and co-contaminants. Here, we review: (1) methods for investigating and evaluating joint effects of NPs and co-contaminants; (2) simultaneous toxicities from NPs co-exposed with organic contaminants, metal/metalloid ions, dissolved organic matter (DOM), inorganic ligands and additional NPs; and (3) the influence of NPs co-exposure on the bioaccumulation of organic contaminants and heavy metal ions, as well as the influence of contaminants on NPs bioaccumulation. In addition, future research needs are discussed so as to better understand risk associated with NPs-contaminant co-exposure.</p
Physiological and Biochemical Changes Imposed by CeO<sub>2</sub> Nanoparticles on Wheat: A Life Cycle Field Study
Interactions
of <i>n</i>CeO<sub>2</sub> with plants have
been mostly evaluated at seedling stage and under controlled conditions.
In this study, the effects of <i>n</i>CeO<sub>2</sub> at
0 (control), 100 (low), and 400 (high) mg/kg were monitored for the
entire life cycle (about 7 months) of wheat plants grown in a field
lysimeter. Results showed that at high concentration <i>n</i>CeO<sub>2</sub> decreased the chlorophyll content and increased catalase
and superoxide dismutase activities, compared with control. Both concentrations
changed root and leaf cell microstructures by agglomerating chromatin
in nuclei, delaying flowering by 1 week, and reduced the size of starch
grains in endosperm. Exposed to low concentration produced embryos
with larger vacuoles, while exposure to high concentration reduced
number of vacuoles, compared with control. There were no effects on
the final biomass and yield, Ce concentration in shoots, as well as
sugar and starch contents in grains, but grain protein increased by
24.8% and 32.6% at 100 and 400 mg/kg, respectively. Results suggest
that more field life cycle studies are needed in order to better understand
the effects of <i>n</i>CeO<sub>2</sub> in crop plants
Carbonaceous Nanomaterials Have Higher Effects on Soybean Rhizosphere Prokaryotic Communities During the Reproductive Growth Phase than During Vegetative Growth
Carbonaceous
nanomaterials (CNMs) can affect agricultural soil
prokaryotic communities, but how the effects vary with the crop growth
stage is unknown. To investigate this, soybean plants were cultivated
in soils amended with 0, 0.1, 100, or 1000 mg kg<sup>–1</sup> of carbon black, multiwalled carbon nanotubes (MWCNTs), or graphene.
Soil prokaryotic communities were analyzed by Illumina sequencing
at day 0 and at the soybean vegetative and reproductive stages. The
sequencing data were functionally annotated using the functional annotation
of prokaryotic taxa (FAPROTAX) database. The prokaryotic communities
were unaffected at day 0 and were altered at the plant vegetative
stage only by 0.1 mg kg<sup>–1</sup> MWCNTs. However, at the
reproductive stage, when pods were filling, most treatments (except
1000 mg kg<sup>–1</sup> MWCNTs) altered the prokaryotic community
composition, including functional groups associated with C, N, and
S cycling. The lower doses of CNMs, which were previously shown to
be less agglomerated and thus more bioavailable in soil relative to
the higher doses, were more effective toward both overall communities
and individual functional groups. Taken together, prokaryotic communities
in the soybean rhizosphere can be significantly phylogenetically and
functionally altered in response to bioavailable CNMs, especially
when soybean plants are actively directing resources to seed production
Enhanced Formation of Silver Nanoparticles in Ag<sup>+</sup>‑NOM-Iron(II, III) Systems and Antibacterial Activity Studies
This work reports the role of iron
redox pair (Fe<sup>3+</sup>/Fe<sup>2+</sup>) in the formation of naturally
occurring silver nanoparticles
(AgNPs) in the aquatic environment. The results showed that Fe<sup>3+</sup> or Fe<sup>2+</sup> ions in the mixtures of Ag<sup>+</sup> and natural organic matter enhanced the formation of AgNPs. The
formation of AgNPs depended on pH and types of organic matter. Increase
in pH enhanced the formation of AgNPs, and humic acids as ligands
showed higher formation of AgNPs compared to fulvic acids. The observed
results were described by considering the potentials of redox pairs
of silver and iron species and the possible species involved in reducing
silver ions to AgNPs. Dynamic light scattering and transmission electron
microscopy measurements of AgNPs revealed mostly bimodal size distribution
with decrease in size of AgNPs due to iron species in the reaction
mixture. Minimum inhibitory concentration of AgNPs needed to inhibit
the growth of various bacterial species suggested the role of surfaces
of tested Gram-positive and Gram-negative bacteria. Stability study
of AgNPs, formed in Ag<sup>+</sup>-humic acid/fulvic acids-Fe<sup>3+</sup> mixtures over a period of several months showed high stability
of the particles with significant increase in surface plasmon resonance
peak. The environmental implications of the results in terms of fate,
transport, and ecotoxicity of organic-coated AgNPs are briefly presented
Cerium Biomagnification in a Terrestrial Food Chain: Influence of Particle Size and Growth Stage
Mass-flow modeling of engineered nanomaterials (ENMs) indicates
that a major fraction of released particles partition into soils and
sediments. This has aggravated the risk of contaminating agricultural
fields, potentially threatening associated food webs. To assess possible
ENM trophic transfer, cerium accumulation from cerium oxide nanoparticles
(nano-CeO<sub>2</sub>) and their bulk equivalent (bulk-CeO<sub>2</sub>) was investigated in producers and consumers from a terrestrial
food chain. Kidney bean plants (Phaseolus vulgaris var. red hawk) grown in soil contaminated with 1000–2000
mg/kg nano-CeO<sub>2</sub> or 1000 mg/kg bulk-CeO<sub>2</sub> were
presented to Mexican bean beetles (Epilachna varivestis), which were then consumed by spined soldier bugs (Podisus maculiventris). Cerium accumulation in plant
and insects was independent of particle size. After 36 days of exposure
to 1000 mg/kg nano- and bulk-CeO<sub>2</sub>, roots accumulated 26
and 19 μg/g Ce, respectively, and translocated 1.02 and 1.3
μg/g Ce, respectively, to shoots. The beetle larvae feeding
on nano-CeO<sub>2</sub> exposed leaves accumulated low levels of Ce
since ∼98% of Ce was excreted in contrast to bulk<i>-</i>CeO<sub>2</sub>. However, in nano-CeO<sub>2</sub> exposed adults,
Ce in tissues was higher than Ce excreted. Additionally, Ce content
in tissues was biomagnified by a factor of 5.3 from the plants to
adult beetles and further to bugs
Cerium Oxide Nanoparticles Impact Yield and Modify Nutritional Parameters in Wheat (Triticum aestivum L.)
The implications of engineered nanomaterials
on crop productivity
and food quality are not yet well understood. The impact of cerium
oxide nanoparticles (<i>n</i>CeO<sub>2</sub>) on growth
and yield attributes and nutritional composition in wheat (Triticum aestivum L.) was examined. Wheat was cultivated
to grain production in soil amended with 0, 125, 250, and 500 mg of <i>n</i>CeO<sub>2</sub>/kg (control, <i>n</i>CeO<sub>2</sub>-L, <i>n</i>CeO<sub>2</sub>-M, and <i>n</i>CeO<sub>2</sub>-H, respectively). At harvest, grains and tissues
were analyzed for mineral, fatty acid, and amino acid content. Results
showed that, relative to the control, <i>n</i>CeO<sub>2</sub>-H improved plant growth, shoot biomass, and grain yield by 9.0%,
12.7%, and 36.6%, respectively. Ce accumulation in roots increased
at increased <i>n</i>CeO<sub>2</sub> concentration but did
not change across treatments in leaves, hull, and grains, indicating
a lack of Ce transport to the above-ground tissues. <i>n</i>CeO<sub>2</sub> modified S and Mn storage in grains. <i>n</i>CeO<sub>2</sub>-L modified the amino acid composition and increased
linolenic acid by up to 6.17% but decreased linoleic acid by up to
1.63%, compared to the other treatments. The findings suggest the
potential of nanoceria to modify crop physiology and food quality
with unknown consequences for living organisms
Targeting Metal Impurities for the Detection and Quantification of Carbon Black Particles in Water via spICP-MS
Carbon black (CB) is a nanomaterial with numerous industrial
applications
and high potential for integration into nano-enabled water treatment
devices. However, few analytical techniques are capable of measuring
CB in water at environmentally relevant concentrations. Therefore,
we intended to establish a quantification method for CB with lower
detection limits through utilization of trace metal impurities as
analytical tracers. Various metal impurities were investigated in
six commercial CB materials, and the Monarch 1000 CB was chosen as
a model for further testing. The La impurity was chosen as a tracer
for spICP-MS analysis based on measured concentration, low detection
limits, and lack of polyatomic interferences. CB stability in water
and adhesion to the spICP-MS introduction system presented a challenge
that was mitigated by the addition of a nonionic surfactant to the
matrix. Following optimization, the limit of detection (64 μg/L)
and quantification (122 μg/L) for Monarch 1000 CB demonstrated
the applicability of this approach to samples expected to contain
trace amounts of CB. When compared against gravimetric analysis and
UV–visible absorption spectroscopy, spICP-MS quantification
exhibited similar sensitivity but with the ability to detect concentrations
an order of magnitude lower. Method detection and sensitivity was
unaffected when dissolved La was spiked into CB samples at environmentally
relevant concentrations. Additionally, a more complex synthetic matrix
representative of drinking water caused no appreciable impact to CB
quantification. In comparison to existing quantification techniques,
this method has achieved competitive sensitivity, a wide working range
for quantification, and high selectivity for tracing possible release
of CB materials with known metal contents
Targeting Metal Impurities for the Detection and Quantification of Carbon Black Particles in Water via spICP-MS
Carbon black (CB) is a nanomaterial with numerous industrial
applications
and high potential for integration into nano-enabled water treatment
devices. However, few analytical techniques are capable of measuring
CB in water at environmentally relevant concentrations. Therefore,
we intended to establish a quantification method for CB with lower
detection limits through utilization of trace metal impurities as
analytical tracers. Various metal impurities were investigated in
six commercial CB materials, and the Monarch 1000 CB was chosen as
a model for further testing. The La impurity was chosen as a tracer
for spICP-MS analysis based on measured concentration, low detection
limits, and lack of polyatomic interferences. CB stability in water
and adhesion to the spICP-MS introduction system presented a challenge
that was mitigated by the addition of a nonionic surfactant to the
matrix. Following optimization, the limit of detection (64 μg/L)
and quantification (122 μg/L) for Monarch 1000 CB demonstrated
the applicability of this approach to samples expected to contain
trace amounts of CB. When compared against gravimetric analysis and
UV–visible absorption spectroscopy, spICP-MS quantification
exhibited similar sensitivity but with the ability to detect concentrations
an order of magnitude lower. Method detection and sensitivity was
unaffected when dissolved La was spiked into CB samples at environmentally
relevant concentrations. Additionally, a more complex synthetic matrix
representative of drinking water caused no appreciable impact to CB
quantification. In comparison to existing quantification techniques,
this method has achieved competitive sensitivity, a wide working range
for quantification, and high selectivity for tracing possible release
of CB materials with known metal contents
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Agglomeration Determines Effects of Carbonaceous Nanomaterials on Soybean Nodulation, Dinitrogen Fixation Potential, and Growth in Soil
The potential effects of carbonaceous
nanomaterials (CNMs) on agricultural plants are of concern. However,
little research has been performed using plants cultivated to maturity
in soils contaminated with various CNMs at different concentrations.
Here, we grew soybean for 39 days to seed production in soil amended
with 0.1, 100, or 1000 mg kg<sup>–1</sup> of either multiwalled
carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs), or carbon
black (CB) and studied plant growth, nodulation, and dinitrogen (N<sub>2</sub>) fixation potential. Plants in all CNM treatments flowered
earlier (producing 60% to 372% more flowers when reproduction started)
than the unamended controls. The low MWCNT-treated plants were shorter
(by 15%) with slower leaf cover expansion (by 26%) and less final
leaf area (by 24%) than the controls. Nodulation and N<sub>2</sub> fixation potential appeared negatively impacted by CNMs, with stronger
effects at lower CNM concentrations. All CNM treatments reduced the
whole-plant N<sub>2</sub> fixation potential, with the highest reductions
(by over 91%) in the low and medium CB and the low MWCNT treatments.
CB and GNPs appeared to accumulate inside nodules as observed by transmission
electron microscopy. CNM dispersal in aqueous soil extracts was studied
to explain the inverse dose–response relationships, showing
that CNMs at higher concentrations were more agglomerated (over 90%
CNMs settled as agglomerates >3 μm after 12 h) and therefore
proportionally less bioavailable. Overall, our findings suggest that
lower concentrations of CNMs in soils could be more impactful to leguminous
N<sub>2</sub> fixation, owing to greater CNM dispersal and therefore
increased bioavailability at lower concentrations
Evidence of Translocation and Physiological Impacts of Foliar Applied CeO<sub>2</sub> Nanoparticles on Cucumber (<i>Cucumis sativus</i>) Plants
Currently, most of the nanotoxicity
studies in plants involve exposure
to the nanoparticles (NPs) through the roots. However, plants interact
with atmospheric NPs through the leaves, and our knowledge on their
response to this contact is limited. In this study, hydroponically
grown cucumber (<i>Cucumis sativus</i>) plants were aerially
treated either with nano ceria powder (<i>n</i>CeO<sub>2</sub>) at 0.98 and 2.94 g/m<sup>3</sup> or suspensions at 20, 40, 80,
160, and 320 mg/L. Fifteen days after treatment, plants were analyzed
for Ce uptake by using ICP-OES and TEM. In addition, the activity
of three stress enzymes was measured. The ICP-OES results showed Ce
in all tissues of the CeO<sub>2</sub> NP treated plants, suggesting
uptake through the leaves and translocation to the other plant parts.
The TEM results showed the presence of Ce in roots, which corroborates
the ICP-OES results. The biochemical assays showed that catalase activity
increased in roots and ascorbate peroxidase activity decreased in
leaves. Our findings show that atmospheric NPs can be taken up and
distributed within plant tissues, which could represent a threat for
environmental and human health