6 research outputs found
Calculating the Diffusive Flux of Persistent Organic Pollutants between Sediments and the Water Column on the Palos Verdes Shelf Superfund Site Using Polymeric Passive Samplers
Passive samplers were deployed to
the seafloor at a marine Superfund
site on the Palos Verdes Shelf, California, USA, and used to determine
water concentrations of persistent organic pollutants (POPs) in the
surface sediments and near-bottom water. A model of Fickian diffusion
across a thin water boundary layer at the sediment-water interface
was used to calculate flux of contaminants due to molecular diffusion.
Concentrations at four stations were used to calculate the flux of
DDE, DDD, DDMU, and selected PCB congeners from sediments to the water
column. Three passive sampling materials were compared: PE strips,
POM strips, and SPME fibers. Performance reference compounds (PRCs)
were used with PE and POM to correct for incomplete equilibration,
and the resulting POP concentrations, determined by each material,
agreed within 1 order of magnitude. SPME fibers, without PRC corrections,
produced values that were generally much lower (1 to 2 orders of magnitude)
than those measured using PE and POM, indicating that SPME may not
have been fully equilibrated with waters being sampled. In addition,
diffusive fluxes measured using PE strips at stations outside of a
pilot remedial sand cap area were similar to those measured at a station
inside the capped area: 240 to 260 ng cm<sup>–2</sup> y<sup>–1</sup> for <i>p,p</i>′-DDE. The largest
diffusive fluxes of POPs were calculated at station 8C, the site where
the highest sediment concentrations have been measured in the past,
1100 ng cm<sup>–2</sup> y<sup>–1</sup> for <i>p,p</i>′-DDE
Aggregation, Sedimentation, Dissolution, and Bioavailability of Quantum Dots in Estuarine Systems
To
understand their fate and transport in estuarine systems, the aggregation,
sedimentation, and dissolution of CdSe quantum dots (QDs) in seawater
were investigated. Hydrodynamic size increased from 40 to 60 nm to
>1 mm within 1 h in seawater, and the aggregates were highly polydispersed.
Their sedimentation rates in seawater were measured to be 4–10
mm/day. Humic acid (HA), further increased their size and polydispersity,
and slowed sedimentation. Light increased their dissolution and release
of dissolved Cd. The ZnS shell also slowed release of Cd ions. With
sufficient light, HA increased the dissolution of QDs, while with
low light, HA alone did not change their dissolution. The benthic
zone in estuarine systems is the most probable long-term destination
of QDs due to aggregation and sedimentation. The bioavailability of
was evaluated using the mysid Americamysis bahia. The 7-day LC50s of particulate and dissolved QDs were 290 and 23
μg (total Cd)/L, respectively. For mysids, the acute toxicity
appears to be from Cd ions; however, research on the effects of QDs
should be conducted with other organisms where QDs may be lodged in
critical tissues such as gills or filtering apparatus and Cd ions
may be released and delivered directly to those tissues
Detection and Quantification of Graphene-Family Nanomaterials in the Environment
An increase in production
of commercial products containing graphene-family
nanomaterials (GFNs) has led to concern over their release into the
environment. The fate and potential ecotoxicological effects of GFNs
in the environment are currently unclear, partially due to the limited
analytical methods for GFN measurements. In this review, the unique
properties of GFNs that are useful for their detection and quantification
are discussed. The capacity of several classes of techniques to identify
and/or quantify GFNs in different environmental matrices (water, soil,
sediment, and organisms), after environmental transformations, and
after release from a polymer matrix of a product is evaluated. Extraction
and strategies to combine methods for more accurate discrimination
of GFNs from environmental interferences as well as from other carbonaceous
nanomaterials are recommended. Overall, a comprehensive review of
the techniques available to detect and quantify GFNs are systematically
presented to inform the state of the science, guide researchers in
their selection of the best technique for the system under investigation,
and enable further development of GFN metrology in environmental matrices.
Two case studies are described to provide practical examples of choosing
which techniques to utilize for detection or quantification of GFNs
in specific scenarios. Because the available quantitative techniques
are somewhat limited, more research is required to distinguish GFNs
from other carbonaceous materials and improve the accuracy and detection
limits of GFNs at more environmentally relevant concentrations
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
Toxicity, Bioaccumulation, and Biotransformation of Silver Nanoparticles in Marine Organisms
The toxicity, bioaccumulation, and
biotransformation of citrate
and polyvinylpyrrolidone (PVP) coated silver nanoparticles (NPs) (AgNP-citrate
and AgNP-PVP) in marine organisms via marine sediment exposure was
investigated. Results from 7-d sediment toxicity tests indicate that
AgNP-citrate and AgNP-PVP did not exhibit toxicity to the amphipod
(<i>Ampelisca abdita</i>) and mysid (<i>Americamysis
bahia</i>) at ≤75 mg/kg dry wt. A 28-d bioaccumulation
study showed that Ag was significantly accumulated in the marine polychaete <i>Nereis virens</i> (<i>N. virens</i>) in the AgNP-citrate,
AgNP-PVP and a conventional salt (AgNO<sub>3</sub>) treatments. Synchrotron
X-ray absorption spectroscopy (XAS) results showed the distribution
of Ag species in marine sediments amended with AgNP-citrate, AgNP-PVP,
and AgNO<sub>3</sub> was AgCl (50–65%) > Ag<sub>2</sub>S
(32–42%)
> Ag metal (Ag<sup>0</sup>) (3–11%). In <i>N virens</i>, AgCl (25–59%) and Ag<sub>2</sub>S (10–31%) generally
decreased and, Ag metal (32–44%) increased, relative to the
sediments. The patterns of speciation in the worm were different depending
upon the coating of the AgNP and both types of AgNPs were different
than the AgNO<sub>3</sub> salt. These results show that the AgNP surface
capping agents influenced Ag uptake, biotransformation, and/or excretion.
To our knowledge, this is the first demonstration of the bioaccumulation
and speciation of AgNPs in a marine organism (<i>N. virens</i>)
Advancing the Use of Passive Sampling in Risk Assessment and Management of Sediments Contaminated with Hydrophobic Organic Chemicals: Results of an International Ex Situ Passive Sampling Interlaboratory Comparison
This work presents the results of an international interlaboratory comparison on ex situ passive sampling in sediments. The main objectives were to map the state of the science in passively sampling sediments, identify sources of variability, provide recommendations and practical guidance for standardized passive sampling, and advance the use of passive sampling in regulatory decision making by increasing confidence in the use of the technique. The study was performed by a consortium of 11 laboratories and included experiments with 14 passive sampling formats on 3 sediments for 25 target chemicals (PAHs and PCBs). The resulting overall interlaboratory variability was large (a factor of ∼10), but standardization of methods halved this variability. The remaining variability was primarily due to factors not related to passive sampling itself, i.e., sediment heterogeneity and analytical chemistry. Excluding the latter source of variability, by performing all analyses in one laboratory, showed that passive sampling results can have a high precision and a very low intermethod variability