14 research outputs found
Characterization and Quantitative Analysis of Single-Walled Carbon Nanotubes in the Aquatic Environment Using Near-Infrared Fluorescence Spectroscopy
Near infrared fluorescence (NIRF) spectroscopy is capable
of sensitive
and selective detection of semiconductive, single-walled carbon nanotubes
(SWNT) using the unique electronic bandgap properties of these carbon
allotropes. We reported here the first detection and quantitation
of SWNT in sediment and biota at environmentally relevant concentrations
using NIRF spectroscopy. In addition, we utilized this technique to
qualitatively characterize SWNT samples before and after ecotoxicity,
bioavailability and fate studies in the aquatic environment. Sample
preparation prior to NIRF analysis consisted of surfactant-assisted
high power ultrasonication. The bile salt sodium deoxycholate (SDC)
enabled efficient extraction and disaggregation of SWNT prior to NIRF
analysis. The method was validated using standard-addition experiments
in two types of estuarine sediments, yielding recoveries between 66
Ā± 7% and 103 Ā± 10% depending on SWNT type and coating used,
demonstrating the ability to isolate SWNT from complex sediment matrices.
Instrument detection limits were determined to be 15 ng mL<sup>ā1</sup> SWNT in 2% SDC solution and method detection limits (including a
concentration step) were 62 ng g<sup>ā1</sup> for estuarine
sediment, and 1.0 Ī¼g L<sup>ā1</sup> for water. Our work
has shown that NIRF spectroscopy is highly sensitive and selective
for SWNT and that this technique can be applied to track the environmental
and biological fate of this important class of carbon nanomaterial
in the aquatic environment
Single-Walled Carbon Nanotube Transport in Representative Municipal Solid Waste Landfill Conditions
Single-walled
carbon nanotubes (SWNTs) are being used in many consumer
products and devices. It is likely that as some of these products
reach the end of their useful life, they will be discarded in municipal
solid waste landfills. However, there has been little work evaluating
the fate of nanomaterials in solid waste environments. The purpose
of this study is to systematically evaluate the influence of organic
matter type and concentration in landfill-relevant conditions on SWNT
transport through a packed-bed of mixed municipal solid waste collectors.
The influence of individual waste materials on SWNT deposition is
also evaluated. Transport experiments were conducted through saturated
waste-containing columns over a range of simulated leachate conditions
representing both mature and young leachates. Results indicate that
SWNT transport may be significant in mature waste environments, with
mobility decreasing with decreasing humic acid concentration. SWNT
mobility in the presence of acetic acid was inhibited, suggesting
their mobility in young waste environments may be small. SWNTs also
exhibited collector media-dependent transport, with greatest transport
in glass and least in paper. These results represent the first study
evaluating how leachate age and changes in waste composition influence
potential SWNT mobility in landfills
Effects of Toxic Leachate from Commercial Plastics on Larval Survival and Settlement of the Barnacle <i>Amphibalanus amphitrite</i>
Plastic pollution represents a major
and growing global problem.
It is well-known that plastics are a source of chemical contaminants
to the aquatic environment and provide novel habitats for marine organisms.
The present study quantified the impacts of plastic leachates from
the seven categories of recyclable plastics on larval survival and
settlement of barnacle <i>Amphibalanus</i> (=<i>Balanus</i>) <i>amphitrite</i>. Leachates from plastics significantly
increased barnacle nauplii mortality at the highest tested concentrations
(0.10 and 0.50 m<sup>2</sup>/L). Hydrophobicity (measured as surface
energy) was positively correlated with mortality indicating that plastic
surface chemistry may be an important factor in the effects of plastics
on sessile organisms. Plastic leachates significantly inhibited barnacle
cyprids settlement on glass at all tested concentrations. Settlement
on plastic surfaces was significantly inhibited after 24 and 48 h,
but settlement was not significantly inhibited compared to the controls
for some plastics after 72ā96 h. In 24 h exposure to seawater,
we found larval toxicity and inhibition of settlement with all seven
categories of recyclable commercial plastics. Chemical analysis revealed
a complex mixture of substances released in plastic leachates. Leaching
of toxic compounds from all plastics should be considered when assessing
the risks of plastic pollution
Results from Screening Polyurethane Foam Based Consumer Products for Flame Retardant Chemicals: Assessing Impacts on the Change in the Furniture Flammability Standards
Flame retardant (FR)
chemicals have often been added to polyurethane
foam to meet required state and federal flammability standards. However,
some FRs (e.g., PBDEs and TDCIPP) are associated with health hazards
and are now restricted from use in some regions. In addition, Californiaās
residential furniture flammability standard (TB-117) has undergone
significant amendments over the past few years, and TDCIPP has been
added to Californiaās Proposition 65 list. These events have
likely led to shifts in the types of FRs used, and the products to
which they are applied. To provide more information on the use of
FRs in products containing polyurethane foam (PUF), we established
a screening service for the general public. Participants residing
in the US were allowed to submit up to 5 samples from their household
for analysis, free of charge, and supplied information on the product
category, labeling, and year and state of purchase. Between February
2014 and June 2016, we received 1141 PUF samples for analysis from
various products including sofas, chairs, mattresses, car seats and
pillows. Of these samples tested, 52% contained a FR at levels greater
than 1% by weight. TrisĀ(1,3-dichloroisopropyl)Āphosphate (TDCIPP) was
the most common FR detected in PUF samples, and was the most common
FR detected in all product categories. Analysis of the data by purchasing
date suggests that the use of TDCIPP decreased in recent years, paralleled
with an increase in the use of TCIPP and a nonhalogenated aryl phosphate
mixture we call āTBPP.ā In addition, we observed significant
decreases in FR applications in furniture products and child car seats,
suggesting the use of additive FRs in PUF may be declining, perhaps
as a reflection of recent changes to TB-117 and Proposition 65. More
studies are needed to determine how these changes in FR use relate
to changes in exposure among the general population
Novel and High Volume Use Flame Retardants in US Couches Reflective of the 2005 PentaBDE Phase Out
Californiaās furniture flammability
standard Technical Bulletin
117 (TB 117) is believed to be a major driver of chemical flame retardant
(FR) use in residential furniture in the United States. With the phase-out
of the polybrominated diphenyl ether (PBDE) FR mixture PentaBDE in
2005, alternative FRs are increasingly being used to meet TB 117;
however, it was unclear which chemicals were being used and how frequently.
To address this data gap, we collected and analyzed 102 samples of
polyurethane foam from residential couches purchased in the United
States from 1985 to 2010. Overall, we detected chemical flame retardants
in 85% of the couches. In samples purchased prior to 2005 (<i>n</i> = 41) PBDEs associated with the PentaBDE mixture including
BDEs 47, 99, and 100 (PentaBDE) were the most common FR detected (39%),
followed by trisĀ(1,3-dichloroisopropyl) phosphate (TDCPP; 24%), which
is a suspected human carcinogen. In samples purchased in 2005 or later
(<i>n</i> = 61) the most common FRs detected were TDCPP
(52%) and components associated with the Firemaster550 (FM 550) mixture
(18%). Since the 2005 phase-out of PentaBDE, the use of TDCPP increased
significantly. In addition, a mixture of nonhalogenated organophosphate
FRs that included triphenyl phosphate (TPP), trisĀ(4-butylphenyl) phosphate
(TBPP), and a mix of butylphenyl phosphate isomers were observed in
13% of the couch samples purchased in 2005 or later. Overall the prevalence
of flame retardants (and PentaBDE) was higher in couches bought in
California compared to elsewhere, although the difference was not
quite significant (<i>p</i> = 0.054 for PentaBDE). The difference
was greater before 2005 than after, suggesting that TB 117 is becoming
a de facto standard across the U.S. We determined that the presence
of a TB 117 label did predict the presence of a FR; however, lack
of a label did not predict the absence of a flame retardant. Following
the PentaBDE phase out, we also found an increased number of flame
retardants on the market. Given these results, and the potential for
human exposure to FRs, health studies should be conducted on the types
of FRs identified here
Chirality Affects Aggregation Kinetics of Single-Walled Carbon Nanotubes
Aggregation kinetics of chiral-specific semiconducting
single-walled
carbon nanotubes (SWNTs) was systematically studied through time-resolved
dynamic light scattering. Varied monovalent (NaCl) and divalent (CaCl<sub>2</sub>) electrolyte composition was used as background solution
chemistry. Suwannee River humic acid (SRHA) was used to study the
effects of natural organic matter on chirally separated SWNT aggregation.
Increasing salt concentration and introduction of divalent cations
caused aggregation of SWNT clusters by suppressing the electrostatic
repulsive interaction from the oxidized surfaces. The (6,5) SWNTs,
i.e., SG65, with relatively lower diameter tubes compared to (7,6),
i.e., SG76, showed substantially higher stability (7- and 5-fold for
NaCl and CaCl<sub>2</sub>, respectively). The critical coagulation
concentration (CCC) values were 96 and 13 mM NaCl in the case of NaCl
and 2.8 and 0.6 mM CaCl<sub>2</sub> for SG65 and SG76, respectively.
The increased tube diameter for (7,6) armchair SWNTs likely presented
with higher van der Waals interaction and thus increased the aggregation
propensity substantially. The presence of SRHA enhanced SWNT stability
in divalent CaCl<sub>2</sub> environment through steric interaction
from adsorbed humic molecules; however showed little or no effects
for monovalent NaCl. The mechanism of aggregationīødescribing
favorable interaction tendencies for (7,6) SWNTsīøis probed
through ab initio molecular modeling. The results suggest that SWNT
stability can be chirality dependent in typical aquatic environment
Identification of Flame Retardants in Polyurethane Foam Collected from Baby Products
With the phase-out of PentaBDE in 2004, alternative flame retardants are being used in polyurethane foam to meet flammability standards. However, insufficient information is available on the identity of the flame retardants currently in use. Baby products containing polyurethane foam must meet California state furniture flammability standards, which likely affects the use of flame retardants in baby products throughout the U.S. However, it is unclear which products contain flame retardants and at what concentrations. In this study we surveyed baby products containing polyurethane foam to investigate how often flame retardants were used in these products. Information on when the products were purchased and whether they contained a label indicating that the product meets requirements for a California flammability standard were recorded. When possible, we identified the flame retardants being used and their concentrations in the foam. Foam samples collected from 101 commonly used baby products were analyzed. Eighty samples contained an identifiable flame retardant additive, and all but one of these was either chlorinated or brominated. The most common flame retardant detected was tris(1,3-dichloroisopropyl) phosphate (TDCPP; detection frequency 36%), followed by components typically found in the Firemaster550 commercial mixture (detection frequency 17%). Five samples contained PBDE congeners commonly associated with PentaBDE, suggesting products with PentaBDE are still in-use. Two chlorinated organophosphate flame retardants (OPFRs) not previously documented in the environment were also identified, one of which is commercially sold as V6 (detection frequency 15%) and contains tris(2-chloroethyl) phosphate (TCEP) as an impurity. As an addition to this study, we used a portable X-ray fluorescence (XRF) analyzer to estimate the bromine and chlorine content of the foam and investigate whether XRF is a useful method for predicting the presence of halogenated flame retardant additives in these products. A significant correlation was observed for bromine; however, there was no significant relationship observed for chlorine. To the authors knowledge, this is the first study to report on flame retardants in baby products. In addition, we have identified two chlorinated OPFRs not previously documented in the environment or in consumer products. Based on exposure estimates conducted by the Consumer Product Safety Commission (CPSC), we predict that infants may receive greater exposure to TDCPP from these products compared to the average child or adult from upholstered furniture, all of which are higher than acceptable daily intake levels of TDCPP set by the CPSC. Future studies are therefore warranted to specifically measure infants exposure to these flame retardants from intimate contact with these products and to determine if there are any associated health concerns
Natural Gas Residual Fluids: Sources, Endpoints, and Organic Chemical Composition after Centralized Waste Treatment in Pennsylvania
Volumes of natural gas extraction-derived
wastewaters have increased
sharply over the past decade, but the ultimate fate of those waste
streams is poorly characterized. Here, we sought to (a) quantify natural
gas residual fluid sources and endpoints to bound the scope of potential
waste stream impacts and (b) describe the organic pollutants discharged
to surface waters following treatment, a route of likely ecological
exposure. Our findings indicate that centralized waste treatment facilities
(CWTF) received 9.5% (8.5 Ć 10<sup>8</sup> L) of natural gas
residual fluids in 2013, with some facilities discharging all effluent
to surface waters. In dry months, discharged water volumes were on
the order of the receiving body flows for some plants, indicating
that surface waters can become waste-dominated in summer. As disclosed
organic compounds used in high volume hydraulic fracturing (HVHF)
vary greatly in physicochemical properties, we deployed a suite of
analytical techniques to characterize CWTF effluents, covering 90.5%
of disclosed compounds. Results revealed that, of nearly 1000 disclosed
organic compounds used in HVHF, only petroleum distillates and alcohol
polyethoxylates were present. Few analytes targeted by regulatory
agencies (e.g., benzene or toluene) were observed, highlighting the
need for expanded and improved monitoring efforts at CWTFs
Discovery of 40 Classes of Per- and Polyfluoroalkyl Substances in Historical Aqueous Film-Forming Foams (AFFFs) and AFFF-Impacted Groundwater
Aqueous film-forming foams (AFFFs),
containing per- and polyfluoroalkyl
substances (PFASs), are released into the environment during response
to fire-related emergencies. Repeated historical applications of AFFF
at military sites were a result of fire-fighter training exercises
and equipment testing. Recent data on AFFF-impacted groundwater indicates
that ā¼25% of the PFASs remain unidentified. In an attempt to
close the mass balance, a systematic evaluation of 3M and fluorotelomer-based
AFFFs, commercial products, and AFFF-impacted groundwaters from 15
U.S. military bases was conducted to identify the remaining PFASs.
Liquid chromatography quadrupole time-of-flight mass spectrometry
was used for compound discovery. Nontarget analysis utilized Kendrick
mass defect plots and a ānontargetā R script. Suspect
screening compared masses with those of previously reported PFASs.
Forty classes of novel anionic, zwitterionic, and cationic PFASs were
discovered, and an additional 17 previously reported classes were
observed for the first time in AFFF and/or AFFF-impacted groundwater.
All 57 classes received an acronym and IUPAC-like name derived from
collective author knowledge. Thirty-four of the 40 newly identified
PFAS classes derive from electrochemical fluorination (ECF) processes,
most of which have the same base structure. Of the newly discovered
PFASs found only in AFFF-impacted groundwater, 11 of the 13 classes
are ECF-derived, and the remaining two classes are fluorotelomer-derived,
which suggests that both ECF- and fluorotelomer-based PFASs are persistent
in the environment
Effects of single-walled carbon nanotubes on the bioavailability of PCBs in field-contaminated sediments
<p>Adsorption of hydrophobic organic contaminants (HOCs) to black carbon is a well-studied phenomenon. One emerging class of engineered black carbon materials are single-walled carbon nanotubes (SWNTs). Little research has investigated the potential of SWNT to adsorb and sequester HOCs in complex environmental systems. This study addressed the capacity of SWNT, amended to polychlorinated biphenyl (PCB)-contaminated New Bedford Harbor (NBH) sediment, to reduce the toxicity and bioaccumulation of these HOCs to benthic organisms. Overall, SWNT amendments increased the survival of two benthic estuarine invertebrates, <i>Americamysis bahia</i> and <i>Ampelisca abdita</i>, and reduced the accumulation of PCBs to the benthic polychaete, <i>Nereis virens</i>. Reduction in PCB bioaccumulation by SWNT was independent of <i>K</i><sub>ow</sub>. Further, passive sampling-based estimates of interstitial water concentrations indicated that SWNT reduced PCB bioavailability. Results from this study suggest that SWNT are a good adsorbent for PCBs and might be useful for remediation in the future once SWNT manufacturing technology improves and costs decrease.</p