13 research outputs found
Is SPE Necessary for Environmental Analysis? A Quantitative Comparison of Matrix Effects from Large-Volume Injection and Solid-Phase Extraction Based Methods
Environmental analysis by large-volume injection (LVI)
was compared
to solid-phase extraction (SPE) based methods using matrix effects
as a quantitative indicator of analytical signal quality. LVI was
performed by the direct injection of 900 μL of wastewater onto
a high-performance liquid chromatography (HPLC) column while SPE-based
methods utilized octadecyl silane (C18) and hydrophobic-lypophilic
balance (HLB) solid phases to preconcentrate wastewater prior to analysis.
Model analytes from three classes of environmental contaminants were
selected for study including four estrogens (estrone, estradiol, estriol,
and ethinylestradiol), eight perfluoroalkyl carboxylates (C4–C11),
and five perfluoroalkyl sulfonates (C4, C6–C8, and C10). The
matrix effects on analytes were assessed by two approaches (quantitatively
by calculating percent matrix effects and qualitatively with postcolumn
infusions) and compared across LVI- and SPE-based methods at constant
(high and low) analyte-to-matrix mass ratios. The results from this
study demonstrated that the LVI-based method produced analytical signals
of quality similar to the two SPE-based methods. Furthermore, LVI
presented a clear advantage over SPE because it was performed at lower
cost, required fewer materials, involved less labor and eliminated
the analyte loss associated with SPE
Identification of Novel Fluorochemicals in Aqueous Film-Forming Foams Used by the US Military
Aqueous film-forming foams (AFFFs) are a vital tool to
fight large
hydrocarbon fires and can be used by public, commercial, and military
firefighting organizations. In order to possess these superior firefighting
capabilities, AFFFs contain fluorochemical surfactants, of which many
of the chemical identities are listed as proprietary. Large-scale
controlled (e.g., training activities) and uncontrolled releases of
AFFF have resulted in contamination of groundwater. Information on
the composition of AFFF formulations is needed to fully define the
extent of groundwater contamination, and the first step is to fully
define the fluorochemical composition of AFFFs used by the US military.
Fast atom bombardment mass spectrometry (FAB-MS) and high resolution
quadrupole-time-of-flight mass spectrometry (QTOF-MS) were combined
to elucidate chemical formulas for the fluorochemicals in AFFF mixtures,
and, along with patent-based information, structures were assigned.
Sample collection and analysis was focused on AFFFs that have been
designated as certified for US military use. Ten different fluorochemical
classes were identified in the seven military-certified AFFF formulations
and include anionic, cationic, and zwitterionic surfactants with perfluoroalkyl
chain lengths ranging from 4 to 12. The environmental implications
are discussed, and research needs are identified
Discovery and Implications of C<sub>2</sub> and C<sub>3</sub> Perfluoroalkyl Sulfonates in Aqueous Film-Forming Foams and Groundwater
Historically, 3M aqueous film-forming
foams (AFFFs) were released
at U.S. military and civilian sites to extinguish hydrocarbon-based
fuel fires. To date, only C<sub>4</sub>–C<sub>10</sub> homologues
of the perfluoroalkyl sulfonic acids (PFSAs) are documented in 3M
AFFFs. Perfluoroethanesulfonate (PFEtS) and perfluoropropanesulfonate
(PFPrS), two ultra-short-chain PFSAs, were discovered by liquid chromatography
(LC) quadrupole time-of-flight mass spectrometry. Once they were identified,
PFEtS and PFPrS were then quantified in five 3M AFFFs and in one groundwater
sample from each of 11 U.S. military bases by LC tandem mass spectrometry.
Concentrations of PFEtS and PFPrS in the five AFFFs ranged from 7
to 13 mg/L and from 120 to 270 mg/L, respectively. For the groundwater,
PFEtS was quantified in 8 of the 11 samples (11–7500 ng/L)
and PFPrS in all samples (19–63000 ng/L). The high water solubility,
mobility, and detection frequency of these ultra-short-chain PFSAs
indicate that groundwater contaminant plumes may be larger than previously
believed, and their removal by conventional activated carbon will
be challenging
Repeated Aqueous Film-Forming Foams Applications: Impacts on Polyfluoroalkyl Substances Retention in Saturated Soil
Historical
practices at firefighter-training areas involved
repeated
aqueous film-forming foams (AFFFs) applications, resulting in source
zones characterized by high concentrations of perfluoroalkyl and polyfluoroalkyl
substances (PFAS). Repeated applications of AFFF composed of 14 anionic
and 23 zwitterionic perfluoroalkyl substances (PFAS) were conducted
on a single one-dimensional saturated soil column to quantify PFAS
retention. An electrofluorination-based (3M) Milspec AFFF, which was
above the mixture’s critical micelle concentration (CMC), was
at application strength (3%, v/v). Retention and retardation of PFAS
mass increased with each successive AFFF addition, although the PFAS
concentration profiles for subsequent applications differed from the
initial. Greater degree of mass retention and retardation correlated
with longer PFAS carbon–fluorine chain length and charged-headgroup
type and as a function of AFFF application number.
Anionic PFAS were increasingly retained with each subsequent AFFF
application, while zwitterionic PFAS exhibited an alternating pattern
of sorption and desorption. Surfactant–surfactant adsorption
and competition during repeat AFFF applications that are at concentrations
above the CMC resulted in adsorbed PFAS from the first application,
changing the nature of the soil surface with preferential sorption
of anionic PFAS and release of zwitterionic PFAS due to competitive
elution. Applying a polyparameter quantitative structure–property
relationship developed to describe sorption of AFFF-derived PFAS to
uncontaminated, saturated soil was attempted for our experimental
conditions. The model had been derived for data where AFFF is below
the apparent CMC and our experimental conditions that included the
presence of mixed micelles (aggregates consisting of different kinds
of surfactants that exhibit characteristics properties different from
micelles composed of a single surfactant) resulted in overall PFAS
mass retained by an average of 27.3% ± 2.7% (standard error)
above the predicted values. The correlation was significantly improved
by adding a “micelle parameter” to account for cases
where the applied AFFF was above the apparent CMC. Our results highlight
the importance of interactions between the AFFF components that can
only be investigated by employing complex PFAS mixtures at concentrations
present in actual AFFF at application strength, which are above their
apparent CMC. In firefighter-training areas (AFFF source zones), competitive
desorption of PFAS may result in downgradient PFAS retention when
desorbed PFAS become resorbed to uncontaminated soil
Physical and Biological Release of Poly- and Perfluoroalkyl Substances (PFASs) from Municipal Solid Waste in Anaerobic Model Landfill Reactors
A wide
variety of consumer products that are treated with poly-
and perfluoroalkyl substances (PFASs) and related formulations are
disposed of in landfills. Landfill leachate has significant concentrations
of PFASs and acts as secondary point sources to surface water. This
study models how PFASs enter leachate using four laboratory-scale
anaerobic bioreactors filled with municipal solid waste (MSW) and
operated over 273 days. Duplicate reactors were monitored under live
and abiotic conditions to evaluate influences attributable to biological
activity. The biologically active reactors simulated the methanogenic
conditions that develop in all landfills, producing ∼140 mL
CH<sub>4</sub>/dry g refuse. The average total PFAS leaching measured
in live reactors (16.7 nmol/kg dry refuse) was greater than the average
for abiotic reactors (2.83 nmol/kg dry refuse), indicating biological
processes were primarily responsible for leaching. The low-level leaching
in the abiotic reactors was primarily due to PFCAs ≤C8 (2.48
nmol/kg dry refuse). Concentrations of known biodegradation intermediates,
including methylperfluorobutane sulfonamide acetic acid and the <i>n</i>:2 and <i>n</i>:3 fluorotelomer carboxylates,
increased steadily after the onset of methanogenesis, with the 5:3
fluorotelomer carboxylate becoming the single most concentrated PFAS
observed in live reactors (9.53 nmol/kg dry refuse)
Sorption of Fluorotelomer Sulfonates, Fluorotelomer Sulfonamido Betaines, and a Fluorotelomer Sulfonamido Amine in National Foam Aqueous Film-Forming Foam to Soil
During fire-fighter training, equipment
testing, and emergency
responses with aqueous film-forming foams (AFFFs), milligrams per
liter concentrations of anionic, zwitterionic, and cationic per- and
polyfluoroalkyl substances (PFASs) enter the environment. Because
the behavior of zwitterionic and cationic PFASs in the subsurface
is unknown, batch sorption experiments were conducted using National
Foam AFFF, which contains anionic fluorotelomer sulfonates (FtSs),
zwitterionic fluorotelomer sulfonamido betaines (FtSaBs), and cationic
6:2 fluorotelomer sulfonamido amine (FtSaAm). Sorption of the FtSs,
FtSaBs, and 6:2 FtSaAm to six soils with varying organic carbon, effective
cation-exchange capacity, and anion-exchange capacity was evaluated
to determine sorption mechanisms. Due to the poor recovery of the
FtSaBs and 6:2 FtSaAm with published PFAS soil extraction methods,
a new soil extraction method was developed to achieve good (90–100%)
recoveries. The 6:2 FtSaAm was depleted from the aqueous phase in
all but one soil, which is attributed to electrostatic and hydrophobic
interactions. Sorption of the FtSs was driven by hydrophobic interactions,
while the FtSaBs behave more like cations that strongly associate
with the solid phase relative to groundwater. Thus, the sorption mechanisms
of the FtSs, FtSaBs, and 6:2 FtSaAm are more complex than expected
and cannot be predicted by bulk soil properties
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
National Estimate of Per- and Polyfluoroalkyl Substance (PFAS) Release to U.S. Municipal Landfill Leachate
Landfills are the final stage in
the life cycle of many products
containing per- and polyfluoroalkyl substances (PFASs) and their presence
has been reported in landfill leachate. The concentrations of 70 PFASs
in 95 samples of leachate were measured in a survey of U.S. landfills
of varying climates and waste ages. National release of PFASs was
estimated by coupling measured concentrations for the 19 PFASs where
more than 50% of samples had quantifiable concentrations, with climate-specific
estimates of annual leachate volumes. For 2013, the total volume of
leachate generated in the U.S. was estimated to be 61.1 million m<sup>3</sup>, with 79% of this volume coming from landfills in wet climates
(>75 cm/yr precipitation) that contain 47% of U.S. solid waste.
The
mass of measured PFASs from U.S. landfill leachate to wastewater treatment
plants was estimated to be between 563 and 638 kg for 2013. In the
majority of landfill leachate samples, 5:3 fluorotelomer carboxylic
acid (FTCA) was dominant and variations in concentrations with waste
age affected total estimated mass. There were six PFASs that demonstrated
significantly higher concentrations in leachate from younger waste
compared to older waste and six PFAS demonstrated significant variation
with climate
Release of Per- and Polyfluoroalkyl Substances (PFASs) from Carpet and Clothing in Model Anaerobic Landfill Reactors
Discarded carpet and clothing are
potential sources of per- and
polyfluoroalkyl substances (PFASs) in landfill leachate, but little
is known about their release when disposed in landfills. The concentrations
of 70 PFASs in the aqueous phase of anaerobic model landfill reactors
filled with carpet or clothing were monitored under biologically active
and abiotic conditions. For carpet, total PFAS release was greater
in live than abiotic reactors, with an average of 8.5 nmol/L and 0.62
nmol/L after 552 days, respectively. Release in live carpet reactors
was primarily due to 5:3 fluorotelomer carboxylic acid (FTCA –
3.9 nmol/L) and perfluorohexanoic carboxylic acid (PFHxA –
2.9 nmol/L). For clothing, release was more dependent on sample heterogeneity
than the presence of biological activity, with 0.63, 21.7, 2.6, and
6.3 nmol/L for two live and two abiotic reactors after 519 days, respectively.
Release in the clothing reactors was largely due to perfluorooctatonic
carboxylic acid (PFOA), with low relative concentrations of measured
biotransformation precursors (FTCAs). For carpet and clothing reactors,
the majority of PFAS release was not measured until after day 100.
Results demonstrate that carpet and clothing are likely sources of
PFASs in landfill leachate
Combined Experimental and Molecular Simulation Investigation of the Individual Effects of Corexit Surfactants on the Aerosolization of Oil Spill Matter
We report laboratory aerosolization
experiments and classical molecular
dynamics (MD) simulations, with the objective of investigating the
individual effects of the two Corexit surfactants Span 80 (nonionic)
and dioctyl sodium sulfosuccinate (DOSS, ionic), on the aerosolization
of oil spill matter to the atmosphere. Our simulation results show
that Span 80, DOSS, and the oil alkanes <i>n</i>-pentadecane
(C15) and <i>n</i>-triacontane (C30) exhibit deep free energy
minima at the air/seawater interface. C15 and C30 exhibit deeper free
energy minima at the interface when Span 80 is present, as compared
to the situation when DOSS or no surfactants are at the interface.
These results suggest that Span 80 makes these oil hydrocarbons more
likely to be adsorbed at the surface of seawater droplets and carried
out to the atmosphere, relative to DOSS or to the situation where
no surfactants are present. These simulation trends are in qualitative
agreement with our experimental observations in a bubble-column setup,
where larger amounts of oil hydrocarbons are ejected when Span 80
is mixed with oil and injected into the column, as compared to when
DOSS is used. Our simulations also indicate that Span 80 has a larger
thermodynamic incentive than DOSS to move from the seawater phase
and into the air/seawater interface. This observation is also in qualitative
agreement with our experimental measurements, which indicate that
Span 80 is ejected in larger quantities than DOSS. Our simulations
also suggest that DOSS predominantly adopts a perpendicular orientation
with respect to the air/seawater interface at a dispersant to oil
ratio (DOR) of 1:20, but has a slight preference to lie parallel to
the interfaces at a DOR = 1:5; in both cases, DOSS molecules have
their tails wide open and stretched. In contrast, Span 80 has a slight
preference to align parallel to the interfaces with a coiled conformation
at both DOR values