17 research outputs found
Subsurface Transport Potential of Perfluoroalkyl Acids at Aqueous Film-Forming Foam (AFFF)-Impacted Sites
Subsurface
transport potential of a suite of perfluoroalkyl acids
(PFAAs) was studied in batch sorption experiments with various soils
and in the presence of co-contaminants relevant to aqueous film-forming
foam (AFFF)-impacted sites. Specifically, PFAA sorption to multiple
soils in the presence of nonaqueous phase liquid (NAPL) and nonfluorinated
AFFF surfactants was examined. This study is the first to report on
sorption of perfluorobutanoate (PFBA) and perfluoropentanoate (PFPeA)
(log <i>K</i><sub>oc</sub> = 1.88 and 1.37, respectively)
and found that sorption of these compounds does not follow the chain-length
dependent trend observed for longer chain-length PFAAs. Sorption of
PFBA was similar to that of perfluorooctanoate (PFOA, log <i>K</i><sub>oc</sub> = 1.89). NAPL and nonfluorinated AFFF surfactants
all had varying impacts on sorption of longer chain (>6 CF<sub>2</sub> groups) PFAAs. The primary impact of NAPL was observed in
low <i>f</i><sub>oc</sub> soil (soil A) where Freundlich <i>n</i>-values increased when NAPL was present. Impacts of nonfluorinated
AFFF surfactants varied with surfactant and soil. The anionic surfactant
sodium decyl sulfate (SDS) illicited PFAA chain-length dependent impacts
in two negatively charged soils with varying <i>f</i><sub>oc</sub>. In soil A, <i>K</i><sub>d</sub> values for perfluoroheptanoate
(PFHpA) increased 91% with SDS, whereas values for perfluorodecanoate
(PFDA) increased only 28%. An amphoteric surfactant, <i>n</i>,<i>n</i>-dimethyldodecylamine <i>n</i>-oxide
(AO), had the most notable impact on PFAA sorption to a positively
charged soil (soil C). In this soil, AO oxide significantly increased
sorption for the longer chain PFAAs (i.e., 528% increase in <i>K</i><sub>d</sub> for PFDA). Changes in sorption caused by SDS
and AO may be due to mixed hemimicelle formation, competitive sorption,
or changes to PFAA solubility. Short-chain PFAA behavior in the presence
of NAPL, SDS, and AO was again notable. Co-contaminants generally
increased the sorption of these compounds to all soils. Log <i>K</i><sub>d</sub> values of PFBA in soil A increased 85%, 372%,
and 32% in the presence of NAPL, SDS, and AO, respectively. Use of <i>K</i><sub>d</sub> values to calculate retardation factors (<i>R</i><sub>f</sub>) of PFAAs demonstrates the variability of
co-contaminant impacts on PFAA transport. Whereas NAPL and nonfluorinated
surfactants decreased the sorption of perfluorooctanesulfonate (PFOS)
at lower PFOS concentrations (1 μg/L), they led to increases
in sorption at higher PFOS concentrations (500 μg/L). These
results demonstrate that PFAA groundwater transport will depend on
the solid phase characteristics as well as PFAA concentration and
chain length. Detailed site-specific information will likely be needed
to accurately predict PFAA transport at AFFF-impacted sites
Sorption of Poly- and Perfluoroalkyl Substances (PFASs) Relevant to Aqueous Film-Forming Foam (AFFF)-Impacted Groundwater by Biochars and Activated Carbon
Despite
growing concerns about human exposure to perfluorooctanoate
(PFOA) and perfluorooctanesulfonate (PFOS), other poly- and perfluoroalkyl
substances (PFASs) derived from aqueous film-forming foams (AFFFs)
have garnered little attention. While these other PFASs may also be
present in AFFF-impacted drinking water, their removal by conventional
drinking-water treatment is poorly understood. This study compared
the removal of 30 PFASs, including 13 recently discovered PFASs, from
an AFFF-impacted drinking water using carbonaceous sorbents (i.e.,
granular activated carbon, GAC). The approach combined laboratory
batch experiments and modeling: batch sorption data were used to determine
partition coefficients (<i>K</i><sub>d</sub>) and calibrate
a transport model based on intraparticle diffusion-limited sorption
kinetics, which was used to make forward predictions of PFAS breakthrough
during GAC adsorption. While strong retention was predicted for PFOS
and PFOA, nearly all of the recently discovered polyfluorinated chemicals
and PFOS-like PFASs detected in the AFFF-impacted drinking water were
predicted to break through GAC systems before both PFOS and PFOA.
These model breakthrough results were used to evaluate a simplified
approach to predicting PFAS removal by GAC using compound-specific
retention times on a C18 column (RT<sub>C18</sub>). Overall, this
study reveals that GAC systems for the treatment of AFFF-impacted
sources of water for PFOA and PFOS likely achieve poor removal, when
operated only for the treatment of PFOS and PFOA, of many unmonitored
PFASs of unknown toxicity
Biochar and Activated Carbon for Enhanced Trace Organic Contaminant Retention in Stormwater Infiltration Systems
To assess the effectiveness of biochar
and activated carbon (AC)
for enhanced trace organic contaminant (TOrC) retention in stormwater
infiltration systems, an approach combining forward-prediction modeling
and laboratory verification experiments was employed. Batch and column
tests were conducted using representative TOrCs and synthetic stormwater.
Based on batch screening tests, two commercially available biochars
(BN-biochar and MCG-biochar) and an AC were investigated. The AC exhibited
the strongest sorption, followed by MCG-biochar and BN-biochar. Langmuir
isotherms provided better fits to equilibrium data than Freundlich
isotherms. Due to superior sorption kinetics, 0.2 wt % MCG-biochar
in saturated sand columns retained TOrCs more effectively than 1.0
wt % BN-biochar. A forward-prediction intraparticle diffusion model
based on the Langmuir isotherm adequately predicted column results
when calibrated using only batch parameters, as indicated by a Monte
Carlo uncertainty analysis. Case study simulations estimated that
an infiltration basin amended with F300-AC or MCG-biochar could obtain
sorption-retarded breakthrough times for atrazine of 54 or 5.8 years,
respectively, at a 1 in./h infiltration rate. These results indicate
that biochars or ACs with superior sorption capacity and kinetics
can enhance TOrC retention in infiltration systems, and performance
under various conditions can be predicted using results from batch
tests
Bioaccumulation of Perfluoroalkyl Acids by Earthworms (<i>Eisenia fetida</i>) Exposed to Contaminated Soils
The
presence of perfluoroalkyl acids (PFAAs) in biosolids-amended
and aqueous film-forming foam (AFFF)-impacted soils results in two
potential pathways for movement of these environmental contaminants
into terrestrial foodwebs. Uptake of PFAAs by earthworms (<i>Eisenia fetida</i>) exposed to unspiked soils with varying levels
of PFAAs (a control soil, an industrially impacted biosolids-amended
soil, a municipal biosolids-amended soil, and two AFFF-impacted soils)
was measured. Standard 28 day exposure experiments were conducted
in each soil, and measurements taken at additional time points in
the municipal soil were used to model the kinetics of uptake. Uptake
and elimination rates and modeling suggested that steady state bioaccumulation
was reached within 28 days of exposure for all PFAAs. The highest
concentrations in the earthworms were for perfluorooctane sulfonate
(PFOS) in the AFFF-impacted Soil A (2160 ng/g) and perfluorododecanoate
(PFDoA) in the industrially impacted soil (737 ng/g). Wet-weight (ww)
and organic carbon (OC)-based biota soil accumulation factors (BSAFs)
for the earthworms were calculated after 28 days of exposure for all
five soils. The highest BSAF in the industrially impacted soil was
for PFDoA (0.42 g<sub>oc</sub>/g<sub>ww,worm</sub>). Bioaccumulation
factors (BAFs, dry-weight-basis, dw) were also calculated at 28 days
for each of the soils. With the exception of the control soil and
perfluorodecanoate (PFDA) in the industrially impacted soil, all BAF
values were above unity, with the highest being for perfluorohexanesulfonate
(PFHxS) in the AFFF-impacted Soil A (139 g<sub>dw,soil</sub>/g<sub>dw,worm</sub>). BSAFs and BAFs increased with increasing chain length
for the perfluorocarboxylates (PFCAs) and decreased with increasing
chain length for the perfluoroalkyl sulfonates (PFSAs). The results
indicate that PFAA bioaccumulation into earthworms depends on soil
concentrations, soil characteristics, analyte, and duration of exposure,
and that accumulation into earthworms may be a potential route of
entry of PFAAs into terrestrial foodwebs
Persistence of Perfluoroalkyl Acid Precursors in AFFF-Impacted Groundwater and Soil
Several classes of
polyfluorinated chemicals that are potential
precursors to the perfluorinated carboxylates and sulfonates are present
in aqueous film-forming foams (AFFF). To assess the persistence of
these AFFF-derived precursors, groundwater, soil, and aquifer solids
were obtained in 2011 from an unlined firefighter training area at
a U.S. Air Force Base where AFFF was regularly used between 1970 and
1990. To measure the total concentration of perfluorinated carboxylate
and sulfonate precursors in archived AFFF formulations and AFFF-impacted
environmental samples, a previously developed assay that uses hydroxyl
radical to oxidize precursors to perfluorinated carboxylates was adapted
for these media. This assay was employed along with direct measurement
of 22 precursors found in AFFF and a suite of other poly- and perfluoroalkyl
substances (PFASs). On a molar basis, precursors accounted for 41–100%
of the total concentration of PFASs in archived AFFF formulations.
In the training area, precursors measured by the oxidation assay accounted
for an average of 23% and 28% of total PFASs (i.e., precursors and
perfluorinated carboxylates and sulfonates) in groundwater and solids
samples, respectively. One precursor in AFFF, perfluorohexane sulfonamide
amine, was observed on several highly contaminated soil and aquifer
solids samples, but no other precursors present in AFFF formulations
were detected in any samples at this field site. Suspected intermediate
transformation products of precursors in AFFF that were directly measured
accounted for approximately half of the total precursor concentration
in samples from the training site. The fraction of PFASs consisting
of perfluorinated carboxylates and sulfonates was greater in groundwater
and solid samples than in any archived AFFF formulations, suggesting
that much of the mass of precursors released at the site was converted
to perfluorinated carboxylates and sulfonates. The precursors that
have persisted at this site may generate significant amounts of additional
perfluorinated carboxylates and sulfonates upon remediation of contaminated
groundwater or aquifer solids
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Perfluoroalkyl Acids Inhibit Reductive Dechlorination of Trichloroethene by Repressing Dehalococcoides
The subsurface recalcitrance of perfluoroalkyl
acids (PFAAs) derived
from aqueous film-forming foams could have adverse impacts on the
microbiological processes used for the bioremediation of co-mingled
chlorinated solvents such as trichloroethene (TCE). Here, we show
that reductive dechlorination by a methanogenic, mixed culture was
significantly inhibited when exposed to concentrations representative
of PFAA source zones (>66 mg/L total of 11 PFAA analytes, 6 mg/L
each).
TCE dechlorination, cis-dichloroethene and vinyl chloride production
and dechlorination, and ethene generation were all inhibited at these
PFAA concentrations. Phylogenetic analysis revealed that the abundances
of 65% of the operational taxonomic units (OTUs) changed significantly
when grown in the presence of PFAAs, although repression or enhancement
resulting from PFAA exposure did not correlate with putative function
or phylogeny. Notably, there was significant repression of Dehalococcoides (8-fold decrease in abundance) coupled
with a corresponding enhancement of methane-generating Archaea (a
9-fold increase). Growth and dechlorination by axenic cultures of Dehalococcoides mccartyi strain 195 were similarly
repressed under these conditions, confirming an inhibitory response
of this pivotal genus to PFAA presence. These results suggest that
chlorinated solvent bioattenuation rates could be impeded in subsurface
environments near PFAA source zones
Uptake of Perfluoroalkyl Acids into Edible Crops via Land Applied Biosolids: Field and Greenhouse Studies
The presence of perfluoroalkyl acids
(PFAAs) in biosolids destined
for use in agriculture has raised concerns about their potential to
enter the terrestrial food chain via bioaccumulation in edible plants.
Uptake of PFAAs by greenhouse lettuce (Lactuca sativa) and tomato (Lycopersicon lycopersicum) grown in an industrially impacted biosolids-amended soil, a municipal
biosolids-amended soil, and a control soil was measured. Bioaccumulation
factors (BAFs) were calculated for the edible portions of both lettuce
and tomato. Dry weight concentrations observed in lettuce grown in
a soil amended (biosolids:soil dry weight ratio of 1:10) with PFAA
industrially contaminated biosolids were up to 266 and 236 ng/g for
perfluorobutanoic acid (PFBA) and perfluoropentanoic acid (PFPeA),
respectively, and reached 56 and 211 ng/g for PFBA and PFPeA in tomato,
respectively. BAFs for many PFAAs were well above unity, with PFBA
having the highest BAF in lettuce (56.8) and PFPeA the highest in
tomato (17.1). In addition, the BAFs for PFAAs in greenhouse lettuce
decreased approximately 0.3 log units per CF<sub>2</sub> group. A
limited-scale field study was conducted to verify greenhouse findings.
The greatest accumulation was seen for PFBA and PFPeA in both field-grown
lettuce and tomato; BAFs for PFBA were highest in both crops. PFAA
levels measured in lettuce and tomato grown in field soil amended
with only a single application of biosolids (at an agronomic rate
for nitrogen) were predominantly below the limit of quantitation (LOQ).
In addition, corn (Zea mays) stover,
corn grains, and soil were collected from several full-scale biosolids-amended
farm fields. At these fields, all PFAAs were below the LOQ in the
corn grains and only trace amounts of PFBA and PFPeA were detected
in the corn stover. This study confirms that the bioaccumulation of
PFAAs from biosolids-amended soils depends strongly on PFAA concentrations,
soil properties, the type of crop, and analyte
Extraction and Analysis of Silver and Gold Nanoparticles from Biological Tissues Using Single Particle Inductively Coupled Plasma Mass Spectrometry
Expanded use of engineered nanoparticles
(ENPs) in consumer products
increases the potential for environmental release and unintended biological
exposures. As a result, measurement techniques are needed to accurately
quantify ENP size, mass, and particle number distributions in biological
matrices. This work combines single particle inductively coupled plasma
mass spectrometry (spICPMS) with tissue extraction to quantify and
characterize metallic ENPs in environmentally relevant biological
tissues for the first time. ENPs were extracted from tissues via alkaline
digestion using tetramethylammonium hydroxide (TMAH). Method development
was performed using ground beef and was verified in Daphnia magna and Lumbriculus variegatus. ENPs investigated include 100 and 60 nm Au and Ag stabilized by
polyvynylpyrrolidone (PVP). Mass- and number-based recovery of spiked
Au and Ag ENPs was high (83–121%) from all tissues tested.
Additional experiments suggested ENP mixtures (60 and 100 nm Ag ENPs)
could be extracted and quantitatively analyzed. Biological exposures
were also conducted to verify the applicability of the method for
aquatic organisms. Size distributions and particle number concentrations
were determined for ENPs extracted from D. magna exposed to 98 μg/L 100 nm Au and 4.8 μg/L 100 nm Ag
ENPs. The D. magna nanoparticulate
body burden for Au ENP uptake was 613 ± 230 μg/kg<sub>ww</sub>, while the measured nanoparticulate body burden for D. magna exposed to Ag ENPs was 59 ± 52 μg/kg<sub>ww</sub>. Notably, the particle size distributions determined from D. magna tissues suggested minimal shifts in the
size distributions of ENPs accumulated, as compared to the exposure
media
Black Carbon-Amended Engineered Media Filters for Improved Treatment of Stormwater Runoff
Urban stormwater runoff is a significant driver of surface
water
quality impairment. Recently, attention has been drawn to potential
beneficial use of urban stormwater runoff, including augmenting drinking
water supply in water-stressed areas. However, beneficial use relies
on improved treatment of stormwater runoff to remove mobile dissolved
metals and trace organic contaminants (TrOCs). This study assesses
six engineered media mixtures consisting of sand, zeolite, high-temperature
gasification biochar, and regenerated activated carbon (RAC) for removing
a suite of co-contaminants comprising five metals, three herbicides,
four pesticides, a corrosion inhibitor, six per- and polyfluoroalkyl
substances (PFASs), five polychlorinated biphenyls (PCBs), and six
polycyclic aromatic hydrocarbons (PAHs). This long-term laboratory-scale
column study uses a novel approach to generate reproducible synthetic
stormwater that incorporates catch basin material and straw-derived
dissolved organic carbon. Higher flow conditions (20 cm hr–1), larger sized media (0.42–1.68 mm), and downflow configuration
with outlet control increase the relevance of this study to better
enable implementation in the field. Biochar- and RAC-amended engineered
media filters removed nearly all of the TrOCs in the effluent over
the course of three months of continuous flow (480 empty bed volumes),
while sample ports spaced at 25% and 50% along the column depth provide
windows to observe contaminant transport. Biochar provided greater
benefit to TrOC removal than RAC on a mass basis. This study used
relatively high concentrations of contaminants and low biochar and
RAC content to observe contaminant transport. Performance in the field
is likely to be significantly better with higher biochar- and RAC-content
filters and lower ambient stormwater contaminant concentrations. This
study provides proof-of-concept for biochar- and RAC-amended engineered
media filters operated at a flow rate of 20 cm hr–1 for removing dissolved TrOCs and metals and offers insights on the
performance of biochar and RAC for improved stormwater treatment and
field trials
Single Particle Inductively Coupled Plasma-Mass Spectrometry: A Performance Evaluation and Method Comparison in the Determination of Nanoparticle Size
Sizing engineered nanoparticles in simple, laboratory
systems is
now a robust field of science; however, application of available techniques
to more complex, natural systems is hindered by numerous challenges
including low nanoparticle number concentrations, polydispersity from
aggregation and/or dissolution, and interference from other incidental
particulates. A new emerging technique, single particle inductively
coupled plasma-mass spectrometry (spICPMS), has the potential to address
many of these analytical challenges when sizing inorganic nanoparticles
in environmental matrices. However, to date, there is little beyond
the initial feasibility studies that investigates the performance
characteristics and validation of spICPMS as a nanoparticle sizing
technique. This study compares sizing of four silver nanoparticle
dispersions (nominal diameters of 40, 60, 80, and 100 nm) by spICPMS
to four established sizing techniques: dynamic light scattering, differential
centrifugal sedimentation, nanoparticle tracking analysis, and TEM.
Results show that spICPMS is able to size silver nanoparticles, across
different sizes and particle number concentrations, with accuracy
similar to the other commercially available techniques. Furthermore,
a novel approach to evaluating particle coincidence is presented.
In addition, spICPMS size measurements were successfully performed
on nanoparticles suspended in algal growth media at low concentrations.
Overall, while further development of the technique is needed, spICPMS
yields important advantages over other techniques when sizing nanoparticles
in environmentally relevant media