Equilibrium Polyethylene Passive Sampling of Soil Gas VOC Concentrations: Modeling, Parameter Determinations, and Laboratory Testing.

The use of low-density polyethylene (PE) sheets as equilibrium passive soil gas samplers to quantify volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene, and xylenes, and chlorinated solvents ( trichloroethene and tetrachloroethene) in unsaturated subsurface environments was evaluated modeling and benchtop testing. Two methods were devised to quantify such VOCs in PE. Key chemical properties, including PE-water () and PE-air () partition coefficients and diffusivities in the PE (), were determined.

Interlaboratory Study of Polyethylene and Polydimethylsiloxane Polymeric Samplers for Ex Situ Measurement of Freely Dissolved Hydrophobic Organic Compounds in Sediment Porewater.

We evaluated the precision and accuracy of multilaboratory measurements for determining freely dissolved concentrations (C ) of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in sediment porewater using polydimethylsiloxane (PDMS) and low-density polyethylene (LDPE) polymeric samplers. Four laboratories exposed performance reference compound (PRC) preloaded polymers to actively mixed and static ex situ sediment for approximately 1 month; two laboratories had longer exposures (2 and 3 months). For C results, intralaboratory precision was high for single compounds (coefficient of variation 50% or less), and for most PAHs and PCBs interlaboratory variability was low (magnitude of difference was a factor of 2 or less) across polymers and exposure methods.

Ex situ determination of freely dissolved concentrations of hydrophobic organic chemicals in sediments and soils: basis for interpreting toxicity and assessing bioavailability, risks and remediation necessity.

The freely dissolved concentration (C) of hydrophobic organic chemicals in sediments and soils is considered the driver behind chemical bioavailability and, ultimately, toxic effects in benthic organisms. Therefore, quantifying C, although challenging, is critical when assessing risks of contamination in field and spiked sediments and soils (e.g.

Investigating the Effect of Bioirrigation on In Situ Porewater Concentrations and Fluxes of Polychlorinated Biphenyls Using Passive Samplers.

Polychlorinated biphenyl (PCB) fluxes from contaminated sediments can be caused by mechanisms including diffusion, bioirrigation, and resuspension, but it is often unclear which mechanisms are important. In the Lower Duwamish Waterway (Seattle, Washington), the presence of abundant benthic macrofauna suggests that porewater bioirrigation may be an important mechanism for PCB transport from the bed into the overlying water column. In this field study, the fluxes of PCBs due to bioirrigation were quantified by using (a) polyethylene (PE) samplers to quantify in situ and ex situ (i.

Performance of passive sampling with low-density polyethylene membranes for the estimation of freely dissolved DDx concentrations in lake environments.

Laboratory and field studies were used to evaluate the performance of low-density polyethylene (PE) passive samplers for assessing the freely dissolved concentrations of DDT and its degradates (DDD and DDE, together referred to as DDx) in an Italian lake environment. We tested commercially available 25 μm thick PE sheets as well as specially synthesized, 10 μm thick PE films which equilibrated with their surroundings more quickly. We measured PE-water partitioning coefficients (K) of the 10 μm thick PE films, finding good correspondence with previously reported values for thicker PE.

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).

Passive sampling of DDT, DDE and DDD in sediments: accounting for degradation processes with reaction-diffusion modeling.

Passive sampling is becoming a widely used tool for assessing freely dissolved concentrations of hydrophobic organic contaminants in environmental media. For certain media and target analytes, the time to reach equilibrium exceeds the deployment time, and in such cases, the loss of performance reference compounds (PRCs), loaded in the sampler before deployment, is one of the common ways used to assess the fractional equilibration of target analytes. The key assumption behind the use of PRCs is that their release is solely diffusion driven.

The atmosphere as a source/sink of polychlorinated biphenyls to/from the Lower Duwamish Waterway Superfund site.

Waterbodies polluted with polychlorinated biphenyls (PCBs) may cause the air in the surrounding area to become PCB-contaminated. Conversely, when a waterbody is located in or near an urban area, the deposition of atmospheric PCBs may act as a low-level, ongoing source of PCB contamination to that water. Distinguishing these situations is necessary to be protective of human populations and to guide efforts seeking to cleanup such aquatic ecosystems.

In situ passive sampling of sediments in the Lower Duwamish Waterway Superfund site: Replicability, comparison with ex situ measurements, and use of data.

Superfund sites with sediments contaminated by hydrophobic organic compounds (HOCs) can be difficult to characterize because of the complex nature of sorption to sediments. Porewater concentrations, which are often used to model transport of HOCs from the sediment bed into overlying water, benthic organisms, and the larger food web, are traditionally estimated using sediment concentrations and sorption coefficients estimated using equilibrium partitioning (EqP) theory. However, researchers have begun using polymeric samplers to determine porewater concentrations since this method does not require knowledge of the sediment's sorption properties.

Steroidal estrogen sources in a sewage-impacted coastal ocean.

Estrogens are known to be potent endocrine disrupting chemicals that are commonly found in wastewater effluents at ng L(-1) levels. Yet, we know very little about the distribution and fate of estrogens in coastal oceans that receive wastewater inputs. This study measured a wide range of steroidal estrogens in sewage-impacted seawater using ultra high performance liquid chromatography (UHPLC) tandem mass spectrometry (MS/MS) together with the method of standard addition.

Adsorption of Organic Compounds to Diesel Soot: Frontal Analysis and Polyparameter Linear Free-Energy Relationship.

Black carbons (BCs) dominate the sorption of many hydrophobic organic compounds (HOCs) in soils and sediments, thereby reducing the HOCs' mobilities and bioavailabilities. However, we do not have data for diverse HOCs' sorption to BC because it is time-consuming and labor-intensive to obtain isotherms on soot and other BCs. In this study, we developed a frontal analysis chromatographic method to investigate the adsorption of 21 organic compounds with diverse functional groups to NIST diesel soot.

Understanding the rates of nonpolar organic chemical accumulation into passive samplers deployed in the environment: Guidance for passive sampler deployments.

Polymeric passive samplers have become a common method for estimating freely dissolved concentrations in environmental media. However, this approach has not yet been adopted by investigators conducting remedial investigations of contaminated environmental sites. Successful adoption of this sampling methodology relies on an understanding of how passive samplers accumulate chemical mass as well as developing guidance for the design and deployment of passive samplers.

Modeling the transport of organic chemicals between polyethylene passive samplers and water in finite and infinite bath conditions.

Understanding the transfer of chemicals between passive samplers and water is essential for their use as monitoring devices of organic contaminants in surface waters. By applying Fick's second law to diffusion through the polymer and an aqueous boundary layer, the authors derived a mathematical model for the uptake of chemicals into a passive sampler from water, in finite and infinite bath conditions. The finite bath model performed well when applied to laboratory observations of sorption into polyethylene (PE) sheets for various chemicals (polycyclic aromatic hydrocarbons, polychlorinated biphenyls [PCBs], and dichlorodiphenyltrichloroethane [DDT]) and at varying turbulence levels.

Polyparameter linear free energy relationship for wood char-water sorption coefficients of organic sorbates.

Black carbons, including soots, chars, activated carbons, and engineered nanocarbons, have different surface properties, but the extent to which these affect their sorbent properties is not known. To evaluate this for an environmentally ubiquitous form of black carbon, biomass char, the surface of a well-studied wood char was probed using 14 sorbates exhibiting diverse functional groups, and the data were fit with a polyparameter linear free energy relationship to assess the importance of the various possible sorbate-char surface interactions. Sorption from water to water-wet char evolved with the sorbate's degree of surface saturation and depended on only a few sorbate parameters: log K(d)L/kg) = [(4.

Predicting bioaccumulation of polycyclic aromatic hydrocarbons in soft-shelled clams (Mya arenaria) using field deployments of polyethylene passive samplers.

Biota-sediment accumulation factors (BSAF), frequently used to predict tissue concentrations of organisms living within and above sediments contaminated with hydrophobic organic chemicals, often produce inaccurate estimates. Hence, freely dissolved porewater concentrations, CW , have also been investigated as predictors of organism tissue concentrations, but they are more difficult to measure than bulk sediment concentrations (used with BSAF). In situ passive sampling methods, however, make it possible to deduce CW with less effort than required to measure the value directly and make it possible to relate CW with tissue concentrations of undisturbed, native organisms.

Validating the use of performance reference compounds in passive samplers to assess porewater concentrations in sediment beds.

Hydrophobic organic compounds (HOCs) like polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) tend to accumulate in sediment beds when they are released into aquatic environments. Due to this buildup of HOCs in the sediment, the highest water concentrations are often in the pore water. Passive samplers can be used in the field (i.

Measuring free, conjugated, and halogenated estrogens in secondary treated wastewater effluent.

Steroidal estrogens are potent endocrine-disrupting chemicals that enter natural waters through the discharge of treated and raw sewage. Because estrogens are detrimental to aquatic organisms at sub-nanogram per liter concentrations, many studies have measured so-called "free" estrogen concentrations in wastewater effluents, rivers, and lakes. Other forms of estrogens are also of potential concern because conjugated estrogens can be easily converted to potent free estrogens by bacteria in wastewater treatment plants and receiving waters and halogenated estrogens are likely produced during wastewater disinfection.

Passive sampling methods for contaminated sediments: scientific rationale supporting use of freely dissolved concentrations.

Passive sampling methods (PSMs) allow the quantification of the freely dissolved concentration (Cfree ) of an organic contaminant even in complex matrices such as sediments. Cfree is directly related to a contaminant's chemical activity, which drives spontaneous processes including diffusive uptake into benthic organisms and exchange with the overlying water column. Consequently, Cfree provides a more relevant dose metric than total sediment concentration.

Hydrophobic meshes for oil spill recovery devices.

Widespread use of petrochemicals often leads to accidental releases in aquatic environments, occasionally with disastrous results. We have developed a hydrophobic and oleophilic mesh that separates oil from water continuously in situ via capillary action, providing a means of recovering spilt oil from surface waters. Steel mesh is dip-coated in a xylene solution of low-density polyethylene, creating a hydrophobic surface with tunable roughness and opening size.

Carbon isotopic (13C and 14C) composition of synthetic estrogens and progestogens.

Rationale: Steroids are potent hormones that are found in many environments. Yet, contributions from synthetic and endogenous sources are largely uncharacterized. The goal of this study was to evaluate whether carbon isotopes could be used to distinguish between synthetic and endogenous steroids in wastewater and other environmental matrices.

Estimating phospholipid membrane-water partition coefficients using comprehensive two-dimensional gas chromatography.

Recent studies have shown that membrane-water partition coefficients of organic chemicals can be used to predict bioaccumulation and type I narcosis toxicity more accurately than the traditional K(OW)-based approach. In this paper, we demonstrate how comprehensive two-dimensional gas chromatography (GC × GC) can be used to estimate such membrane-water partition coefficients (K(PLW)s), focusing in particular on phosphatidyl choline based lipids. This method performed well for a set of 38 compounds, including polycyclic aromatic hydrocarbons, polychlorinated benzenes and biphenyls, and substituted benzenes including some phenols and anilines.

Thermogravimetry-mass spectrometry for carbon nanotube detection in complex mixtures.

In spite of the growth of the carbon nanotube (CNT) industry, there are no established analytical methods with which to detect or quantify CNTs in environmental matrices. Given that CNTs have relatively high thermal stabilities, we investigated the use of thermal techniques to isolate and quantify single wall carbon nanotubes (SWCNTs). Test materials included ten types of commercial SWCNTs, representative biological macromolecules (bovine serum albumin and methylcellulose), soot, natural coastal sediments, and SWCNT-amended sediments.

Comparison of polymeric samplers for accurately assessing PCBs in pore waters.

Assessing the hazard posed by sediments contaminated with hydrophobic organic compounds is difficult, because measuring the freely dissolved porewater concentrations of such low-solubility chemicals can be challenging, and estimating their sediment-water partition coefficients remains quite uncertain. We suggest that more accurate site assessments can be achieved by employing sampling devices in which polymers, with known polymer-water partition coefficients, are used to absorb the contaminants from the sediment. To demonstrate the current accuracy and limitations of this approach, we compared use of three polymers, polydimethylsiloxane, polyoxymethylene, and polyethylene, exposed to a single sediment in two modes, one in which they were exhaustively mixed (tumbled) with the sediment and the other in which they were simply inserted into a static bed (passive).

Multiple alkynes react with ethylene to enhance carbon nanotube synthesis, suggesting a polymerization-like formation mechanism.

Thermal treatments of feedstock gases (e.g., C(2)H(4)/H(2)) used during carbon nanotube (CNT) synthesis result in the formation of a complex mixture of volatile organic compounds and polycyclic aromatic hydrocarbons.

Influence of low oxygen tensions and sorption to sediment black carbon on biodegradation of pyrene.

Sorption to sediment black carbon (BC) may limit the aerobic biodegradation of polycyclic aromatic hydrocarbons (PAHs) in resuspension events and intact sediment beds. We examined this hypothesis experimentally under conditions that were realistic in terms of oxygen concentrations and BC content. A new method, based on synchronous fluorescence observations of (14)C-pyrene, was developed for continuously measuring the uptake of dissolved pyrene by Mycobacterium gilvum VM552, a representative degrader of PAHs.