8 research outputs found
Impacts of (Nano)formulations on the Fate of an Insecticide in Soil and Consequences for Environmental Exposure Assessment
The development of
nanopesticides has recently received an increased
level of attention. However, there are very few data about the environmental
fate of these new products, and it is not known whether nanoformulations
can be evaluated within the current pesticide regulatory framework.
Sorption and degradation parameters of the insecticide bifenthrin
were measured in two soils for (i) the pure active ingredient, (ii)
three nanoformulations, and (iii) a commercially available formulation.
In most cases, fate parameters derived for the nanopesticides were
significantly different from those derived for the pure active ingredient
(factors of up to 10 for sorption and 1.8 for degradation), but discrepancies
were not easy to relate to the characteristics of the nanocarriers.
In some cases, differences were also observed between the commercial
formulation and the pure active ingredient (factors of up to 1.4 for
sorption and 1.7 for degradation). In the regulatory context, the
common assumption that formulations do not influence the environmental
fate of pesticide active ingredients after application seems therefore
not always adequate. In the absence of direct measurement, an inverse
modeling approach was successfully applied to evaluate the durability
of the formulations in soil (release half-life ranged between 11 and
74 days). Predicted groundwater concentrations very much depended
on the modeling approach adopted but overall suggest that the nanoformulations
studied could reduce losses to groundwater
Predicting the Sorption of Aromatic Acids to Noncarbonized and Carbonized Sorbents
Approaches based on the octanolâwater
partition coefficient
are commonly used to describe sorption of neutral organic compounds
in environmental systems, but they are not suitable for organic acids,
which can dissociate to form anions. We here investigate the applicability
of an alternative approach based on the pH-dependent distribution
ratio (<i>D</i><sub>OW</sub>) to describe sorption of aromatic
acids to sorbents representing different degrees of carbonization.
Sorption isotherms for four structurally similar acids ((2,4-dichlorophenoxy)Âacetic
acid (2,4-D), 4-chloro-2-15 methylphenoxy)Âacetic acid (MCPA), 4-(2,4-dichlorophenoxy)Âbutanoic16
acid (2,4-DB), and 5-chloro-2-(2,4-dichlorophenoxy)Âphenol (triclosan))
were measured for 15 sorbents: fresh and carbonized wood shavings,
pig manure, sewage sludge, carbon nanotubes, and activated carbon.
Dissociation greatly affected the sorption of all acids. Sorption
coefficients measured in the high pH range indicated that sorption
of the anions ranged over several orders of magnitude and should not
be neglected. Sorption trends for all sorbates and carbonized sorbents
could be very well described by a single regression equation that
included <i>D</i><sub>OW</sub> of the sorbate and the specific
surface area of the sorbent (<i>R</i><sup>2</sup> > 0.89)
How Redox Conditions and Irradiation Affect Sorption of PAHs by Dispersed Fullerenes (nC60)
Surface properties, dispersion state, and sorption behavior
of
carbon-based nanomaterials will change after being released into the
environment. To study these processes, five different scenarios were
considered to probe the impact of changes in surface properties of
dispersed fullerenes (nC60) on their sorption potential due to irradiation
and presence of oxygen. Sorption isotherms of pyrene by nC60 were
determined at environmentally relevant concentrations applying a passive
sampling method. Isotherms of all dispersion scenarios were best fit
with the DubininâAshthakov model. Sorption was strongest for
nC60 kept under anoxic condition. Both the presence of oxygen and
irradiation significantly decreased the sorption capacity of nC60,
while commercially available polyhydroxy fullerenes had the smallest
sorption. In addition, competition for sorption sites was never observed
in multiple sorbate experiments with four polycyclic aromatic hydrocarbons
at small concentration. A strong relationship between sorption coefficients
and hydrophobic properties of sorbates suggests that hydrophobic interactions
are of major importance. The results emphasize that aging of released
fullerenes results in a reduced strength of interactions with nonpolar
compounds and, thus, reduces the impact on the environmental transport
of hydrophobic pollutants
Dispersion State and Humic Acids Concentration-Dependent Sorption of Pyrene to Carbon Nanotubes
Sonication and humic acids (HA) are known to disperse
carbon nanotube
(CNT) suspensions, but potential effects on sorption of chemicals
to CNTs remain poorly understood. We applied a passive sampling method
to investigate the influence of dispersion/aggregation on sorption
of pyrene to CNTs. Sonication broke down CNT aggregates and increased
pyrene sorption affinity by up to 1.39 orders of magnitude. Sorption
surfaces newly exposed by sonication remained available to pyrene
even after reaggregation occurred, suggesting an irreversible effect
of sonication. The presence of HA decreased sorption of pyrene to
CNTs, but at the highest HA concentration investigated (200 mg/L),
sorption affinity was still 1.90 orders of magnitude larger than sorption
of pyrene to HA alone. Specific interactions between pyrene and CNTs
were thus still taking place, in spite of the presence of a HA coating
on the CNTsâ surface. A greater suppression of sorption by
CNTs occurred when the HA addition was combined with a sonication
pretreatment. Sorption isotherm fitting indicated that the maximum
sorption capacity, sorption affinity, and heterogeneity of the CNT
surface were all affected by sonication and the presence of HA at
a concentration as low as 1 mg/L. The present results contribute to
an improved understanding of the sorption behavior of CNTs in both
natural and wastewater systems
Natural Organic Matter Concentration and Hydrochemistry Influence Aggregation Kinetics of Functionalized Engineered Nanoparticles
Understanding the colloidal stability
of functionalized engineered
nanoparticles (FENPs) in aquatic environments is of paramount importance
in order to assess the risk related to FENPs. In this study, gold
nanoparticles (GNPs) of 68 and 43 nm diameter, coated with citrate
and 11-mercaptoundecanoic acid (MUA) respectively, were used as models
of FENPs. Time-resolved dynamic light scattering was employed to investigate
the aggregation kinetics of two types of GNPs. The results show that
without Suwannee river natural organic matter (SRNOM), MUA coating
resulted in greater stability than citrate coating for GNPs. Cations
have a destabilizing effect on both GNPs following the order Ca<sup>2+</sup> â Mg<sup>2+</sup> â« Na<sup>+</sup>; different
anions (Cl<sup>â</sup> and SO<sub>4</sub><sup>2â</sup>) showed no difference in effects. In the fast aggregation regime,
adding SRNOM enhanced the stability of MUA-coated GNPs in both Ca<sup>2+</sup> and Mg<sup>2+</sup> solutions. However citrate-coated GNPs
were only stabilized in Mg<sup>2+</sup> solution but enhanced aggregation
occurred in high Ca<sup>2+</sup> concentration due to interparticle
bridging. For the investigated GNPs and in the presence of SRNOM,
Ca<sup>2+</sup> does not always act as a strong coagulant. This indicates
that for the new materials emerging from the application of nanotechnology
the well-described aggregation mechanisms of colloids in the environment
require a detailed re-examination
Bovine Serum Albumin Adsorption to Iron-Oxide Coated Sands Can Change Microsphere Deposition Mechanisms
Particulate colloids often occur together with proteins
in sewage-impacted
water. Using Bovine Serum Albumin (BSA) as a surrogate for protein
in sewage, column experiments investigating the capacity of iron-oxide
coated sands to remove latex microspheres from water revealed that
microsphere attenuation mechanisms depended on antecedent BSA coverage.
Dual pulse experiment (DPE) results suggested that where all BSA was
adsorbed, subsequent multiple pore volume microsphere breakthrough
curves reflected progressively reduced colloid deposition rates with
increasing adsorbed BSA content. Modeling colloid responses suggested
adsorption of 1 ÎŒg BSA generated the same response as blockage
by between 7.1 Ă 10<sup>8</sup> and 2.3 Ă 10<sup>9</sup> deposited microspheres. By contrast, microsphere responses in DPEs
where BSA coverage of the deposition sites approached/reached saturation
revealed the coated sand maintained a finite capacity to attenuate
microspheres, even when incapable of further BSA adsorption. Subsequent
microsphere breakthrough curves demonstrated the matrixâs colloid
attenuation capacity progressively increased with continued microsphere
deposition. Experimental findings suggested BSA adsorption on the
sand surface approaching/reaching saturation generated attractive
deposition sites for colloids, which became progressively more attractive
with further colloid deposition (filter ripening). Results demonstrate
that adsorption of a single type of protein may either enhance or
inhibit colloid mobility in saturated porous media
Accessibility of Humic-Associated Fe to a Microbial Siderophore: Implications for Bioavailability
Microorganisms in aerobic, circum-neutral
environments are challenged
to acquire sufficient nutrient Fe due to low solubilities of Fe oxides.
To overcome this challenge, many aerobic microbes produce low molecular
weight (MW) organic ligands, or siderophores, with extremely high
Fe-binding affinities. This research expands the existing understanding
of siderophore-mediated Fe acquisition from minerals by examining
the effects of the siderophore desferrioxamine B (DFOB) on Fe removal
from aquatic humic substances (XAD-8-isolated) and other organic matter
(OM) isolates (reverse osmosis, RO; and âtransphilicâ,
XAD-4) from several rivers including the Suwannee River (GA, USA).
Analysis of samples by asymmetrical flow field-flow fractionation
(AsFlFFF) with in-line ICPâMS and UVâvis detectors showed
that Fe was naturally abundant and primarily associated with intermediate
to high MW OM. An excess of DFOB (relative to naturally present Fe)
removed âŒ75% of Fe and shifted the OM MW distribution to lower
MWs, perhaps due to removal of âbridgingâ Fe, although
additional mechanistic study of MW shifts is needed. Removal of other
OM-associated metals (e.g., Al, Cu, Zn) by DFOB was minimal for all
but a few samples. Fe bound to humic substances and other more âtransphilicâ
organic components therefore should be considered readily bioavailable
to aerobic, siderophore-producing microorganisms
Release of TiO<sub>2</sub> Nanoparticles from Sunscreens into Surface Waters: A One-Year Survey at the Old Danube Recreational Lake
Monitoring data are
necessary for the future production of engineered
nanomaterials and the development of regulations for nanomaterials.
Therefore, it is necessary to develop methods that reliably detect
and quantify nanomaterials in real-world systems at expectedly low
concentrations. In this work we tested several methodological approaches
to detect titanium dioxide nanomaterials released from sunscreen products
into the Old Danube Lake (Vienna, Austria), which is heavily used
for recreational activities like bathing and water sports during the
summer season. During a 12-month period suspended particulate matter
(SPM) was collected from the lake and analyzed using a combination
of complementary techniques. By sampling at a location approximately
50 m from the nearest bathing area and at one meter depth from the
water surface, we focused on the potentially mobile fraction of the
released nanoparticles. We were able to identify titanium dioxide
nanoparticles stemming from sunscreens in the suspended matter of
the lake using electron microscopy. Bulk analysis of SPM clearly shows
an increase of Ti-containing particles during the summer season. These
analyses, however, are not able to distinguish sunscreen nanoparticles
from natural Ti-bearing nanoparticles. Therefore, Elemental ratios
of Ti with Al, V, Ga, Y, Nb, Eu, Ho, Er, Tm, Yb, and Ta as determined
by ICPMS and ICPOES, in combination with single particle ICPMS analysis
were applied to establish local background values. The observed mild
increase of Ti elemental ratios, compared to spring background values
indicates that the residence time of released nanomaterials in the
water column is rather short. Overall, the advantages and disadvantages
of the methods used to detect and characterize the nanomaterials are
discussed