Development and validation of an acid/alkaline digestion method for efficient microplastic extraction from wastewater treatment plant effluents: Sulfuric acid concentration and contact time do matter.

Accurate analysis of microplastic particles (MPs) in environmental samples requires removal of interferences during sample preparation. Wastewater samples are interference-rich and thus particularly challenging, with concentrated sulfuric acid currently deemed impractical as a reagent. Therefore, this study aimed to establish a straightforward, effective, and safe method employing concentrated sulfuric acid and potassium hydroxide to eliminate interferents from effluent samples obtained from wastewater treatment plants (WWTPs). We found that 80 % sulfuric acid at room temperature with a brief contact time of 5 min was viable through a qualitative spot test involving 37 plastics categorized into three types (I, II, and III) based on their polymer structure's oxygen position. A quantitative assessment revealed that treatments involving H2SO4 and KOH (20 %, 24 h, 48 °C), either separately or in combination, had no discernible physical impact on the overall plastics, except for a subtle one for Type III plastics (e.g., nylon and PMMA) known to be labile under harsh pH conditions. This acid/alkaline digestion (AAD) method, incorporating such conditions for H2SO4 and KOH treatments, yielded a high mass removal efficacy (97.8 ± 2.4 %, n = 13) for eliminating natural particle interferents for primary, secondary, and tertiary effluent samples. Furthermore, the AAD method allowed for the determination of MPs in effluents with high surrogate particle recoveries (e.g., 95.1 % for larger than 500 µm size fraction). This method is readily adaptable to create appropriate protocols for different types of environmental matrices.

The influence of complex matrices on method performance in extracting and monitoring for microplastics.

Previous studies have evaluated method performance for quantifying and characterizing microplastics in clean water, but little is known about the efficacy of procedures used to extract microplastics from complex matrices. Here we provided 15 laboratories with samples representing four matrices (i.e., drinking water, fish tissue, sediment, and surface water) each spiked with a known number of microplastic particles spanning a variety of polymers, morphologies, colors, and sizes. Percent recovery (i.e., accuracy) in complex matrices was particle size dependent, with ∼60-70% recovery for particles >212 µm, but as little as 2% recovery for particles <20 µm. Extraction from sediment was most problematic, with recoveries reduced by at least one-third relative to drinking water. Though accuracy was low, the extraction procedures had no observed effect on precision or chemical identification using spectroscopy. Extraction procedures greatly increased sample processing times for all matrices with the extraction of sediment, tissue, and surface water taking approximately 16, 9, and 4 times longer than drinking water, respectively. Overall, our findings indicate that increasing accuracy and reducing sample processing times present the greatest opportunities for method improvement rather than particle identification and characterization.

How to establish detection limits for environmental microplastics analysis.

Establishing analytical detection limits is crucial. Common methods to do so are suitable only for variables with continuous distributions. Because count data for microplastic particles is a discrete variable following the Poisson distribution, currently-used approaches for estimating the detection limit in microplastics analysis are inadequate. Here we evaluate detection limits with techniques for low-level discrete observations to develop proper approaches for estimating the minimum detectable amount (MDA) in microplastic particle analysis, using blank sample data from an interlaboratory calibration exercise for clean water (representing drinking water), dirty water (ambient water), sediment (porous media) and fish tissue (biotic tissues). Two MDAs are applicable: MDAA to evaluate analytical methods, estimated with replicate blank data; and MDAB for individual sample batches, calculated with a single blank count. For illustrative purposes, this dataset's overall MDAA values were 164 counts (clean water), 88 (dirty water), 192 (sediment), and 379 (tissue). MDA values should be reported on a laboratory-specific basis and for individual size fractions, as this provides more useful information about capabilities of individual laboratories. This is due to wide variation in blank levels, as noted by MDAB values (i.e., among different laboratories) from 14 to 158 (clean water), 9 to 86 (dirty water, 9 to 186 (sediment), and 9 to 247 (tissue). MDA values for fibers were considerably greater than for non-fibers, suggesting that separate MDA values should be reported. This study provides a guideline for estimation and application of microplastics MDA for more robust data to support research activities and environmental management decisions.

Incorporating performance reference compounds in retractable/reusable solid phase microextraction fiber for passive sampling of hydrophobic organic contaminants in water.

Solid phase microextraction (SPME) has been used to measure aqueous-phase hydrophobic organic chemicals (HOCs) in equilibrium passive sampling mode for over two decades. However, determination of the extent of equilibrium has not been well-established for the retractable/reusable SPME sampler (RR-SPME), especially in the field applications. The goal of this study was to establish a method regarding to sampler preparation and data processing to characterize the extent of equilibrium of HOCs on the RR-SPME (100-µm thickness of polydimethylsiloxane (PDMS) coating) by incorporating performance reference compounds (PRCs). A fast (4 h) PRC loading protocol was identified with using a ternary solvent mixture (i.e., acetone-methanol-water mixture (4:4:2, v/v)) to accommodate diverse carrier solvents of the PRCs. The isotropy of the RR-SPME was validated by a paired, co-exposure approach with 12 different PRCs. The aging factors measured with the co-exposure method approximately equal to one, indicating the isotropic behavior was not changed after storage at 15 °C and -20 °C for 28 days. As a method demonstration, the PRC-loaded RR-SPME samplers were deployed in the ocean off Santa Barbara, CA (USA) for 35 days. The PRCs approaching the extents of equilibrium ranged from 20 ± 15.5 % to 96.5 ± 1.5 % and showed a declining trend along with log KOW increase. A generic equation relationship was deduced based on a correlation relationship of desorption rate constant (k2) and log KOW to extrapolate non-equilibrium correction factor from the PRCs to the HOCs. The merit of the present study is manifested by its theory and implement to enable the RR-SPME passive sampler to be utilized in environmental monitoring.

Comparison of two procedures for microplastics analysis in sediments based on an interlaboratory exercise.

Microplastics (MP) are distributed throughout ecosystems and settle into sediments where they may threaten benthic communities; however, methods for quantifying MP in sediments have not been standardized. This study compares two methods for analyzing MP in sediments, including extraction and identification, and provides recommendations for improvement. Two laboratories processed sediment samples using two methods, referred to as "core" and "augmentation", and identified particles with visual microscopy and spectroscopy. Using visual microscopy, the augmentation method yielded mean recoveries (78%) significantly greater than the core (47%) (p = 0.03), likely due to the use of separatory funnels in the former. Spectroscopic recovery of particles was lower at 42 and 54% for the core and augmentation methods, respectively. We suspect the visual identification recoveries are overestimations from erroneous identification of non-plastic materials persisting post-extraction, indicating visual identification alone is not an accurate method to identify MP, particularly in complex matrices like sediment. However, both Raman and FTIR proved highly accurate at identifying recovered MP, with 96.7% and 99.8% accuracy, respectively. Low spectroscopic recovery of spiked particles indicates that MP recovery from sediments is lower than previously assumed, and MP may be more abundant in sediments than current analyses suggest. To our knowledge, likely due to the excessive time/labor-intensity associated with MP analyses, this is the first interlaboratory study to quantify complete method performance (extraction, identification) for sediments, with regards to capabilities and limitations. This is essential as regulatory bodies move toward long-term environmental MP monitoring.

What determines accuracy of chemical identification when using microspectroscopy for the analysis of microplastics?

Fourier transform infrared (FTIR) and Raman microspectroscopy are methods applied in microplastics research to determine the chemical identity of microplastics. These techniques enable quantification of microplastic particles across various matrices. Previous work has highlighted the benefits and limitations of each method and found these to be complimentary. Within this work, metadata collected within an interlaboratory method validation study was used to determine which variables most influenced successful chemical identification of un-weathered microplastics in simulated drinking water samples using FTIR and Raman microspectroscopy. No variables tested had a strong correlation with the accuracy of chemical identification (r = ≤0.63). The variables most correlated with accuracy differed between the two methods, and include both physical characteristics of particles (color, morphology, size, polymer type), and instrumental parameters (spectral collection mode, spectral range). Based on these results, we provide technical recommendations to improve capabilities of both methods for measuring microplastics in drinking water and highlight priorities for further research. For FTIR microspectroscopy, recommendations include considering the type of particle in question to inform sample presentation and spectral collection mode for sample analysis. Instrumental parameters should be adjusted for certain particle types when using Raman microspectroscopy. For both instruments, the study highlighted the need for harmonization of spectral reference libraries among research groups, including the use of libraries containing reference materials of both weathered plastic and natural materials that are commonly found in environmental samples.

Assessing bioaccumulation potential of sediment associated fipronil degradates in oligochaete Lumbriculus variegatus based on passive sampler measured bioavailable concentration.

The degradates of fipronil have equivalent or even more toxicity to non-target aquatic invertebrates. To assess their environmental risks, information of bioaccumulation is required. Currently, little is known about the bioaccumulative property of fipronil degradates in sediment, while it is well known that passive sampler may measure bioavailable concentration (Cfree) which links with the environmental effect more tightly than the total environment concentration. The goal of the present study was to characterize bioaccumulation potential in oligochaete Lumbriculus variegatus for a fipronil degradate sulfide. The sediment organic carbon-water partition coefficient (KOC) was measured with polymethyl methacrylate (PMMA) film passive sampler, and KOC was used to bridge the gap between biota-sediment accumulation factor (BSAF) and bioconcentration factor (BCF). The bioavailable concentration (Cfree)-based KOC values were 5371 ± 152 and 5013 ± 152 (mL/g OC) for fipronil sulfide (FSI) and sulfone (FSO), respectively. Since the two fipronil degradates were produced continuously in sediment by the parent compound, the time-weighted-average (TWA) concentration of FSI in the sediment was estimated from a bioassay with L. variegatus to calculate BSAF value (0.581 ± 0.211 g OC/g lipid) and BCF (3046 ± 1103 or log 3.48 ± 0.16 mL/g). This approach is able to estimate the Cfree-based KOC and BCF values of fipronil degradate in sediment with ongoing degradation of the parent compound.

Quantitative assessment of visual microscopy as a tool for microplastic research: Recommendations for improving methods and reporting.

Microscopy is often the first step in microplastic analysis and is generally followed by spectroscopy to confirm material type. The value of microscopy lies in its ability to provide count, size, color, and morphological information to inform toxicity and source apportionment. To assess the accuracy and precision of microscopy, we conducted a method evaluation study. Twenty-two laboratories from six countries were provided three blind spiked clean water samples and asked to follow a standard operating procedure. The samples contained a known number of microplastics with different morphologies (fiber, fragment, sphere), colors (clear, white, green, blue, red, and orange), polymer types (PE, PS, PVC, and PET), and sizes (ranging from roughly 3-2000 µm), and natural materials (natural hair, fibers, and shells; 100-7000 µm) that could be mistaken for microplastics (i.e., false positives). Particle recovery was poor for the smallest size fraction (3-20 µm). Average recovery (±StDev) for all reported particles >50 µm was 94.5 ± 56.3%. After quality checks, recovery for >50 µm spiked particles was 51.3 ± 21.7%. Recovery varied based on morphology and color, with poorest recovery for fibers and the largest deviations for clear and white particles. Experience mattered; less experienced laboratories tended to report higher concentration and had a higher variance among replicates. Participants identified opportunity for increased accuracy and precision through training, improved color and morphology keys, and method alterations relevant to size fractionation. The resulting data informs future work, constraining and highlighting the value of microscopy for microplastics.

Bioanalytical and chemical-specific screening of contaminants of concern in three California (USA) watersheds.

To broaden the scope of contaminants monitored in human-impacted riverine systems, water, sediment, and treated wastewater effluent were analyzed using receptor-based cell assays that provide an integrated response to chemicals based on their mode of biological activity. Samples were collected from three California (USA) watersheds with varying degrees of urbanization and discharge from municipal wastewater treatment plants (WWTPs). To complement cell assay results, samples were also analyzed for a suite of contaminants of emerging concern (CECs) using gas and liquid chromatography-mass spectrometry (GC- and LC-MS/MS). For most water and sediment samples, bioassay equivalent concentrations for estrogen and glucocorticoid receptor assays (ER- and GR-BEQs, respectively) were near or below reporting limits. Measured CEC concentrations compared to monitoring trigger values established by a science advisory panel indicated minimal to moderate concern in water but suggested that select pesticides (pyrethroids and fipronil) had accumulated to levels of greater concern in river sediments. Integrating robust, standardized bioanalytical tools such as the ER and GR assays utilized in this study into existing chemical-specific monitoring and assessment efforts will enhance future CEC monitoring efforts in impacted riverine systems and coastal watersheds.

Monitoring microplastics in drinking water: An interlaboratory study to inform effective methods for quantifying and characterizing microplastics.

California Senate Bill 1422 requires the development of State-approved standardized methods for quantifying and characterizing microplastics in drinking water. Accordingly, we led an interlaboratory microplastic method evaluation study, with 22 participating laboratories from six countries, to evaluate the performance of widely used methods: sample extraction via filtering/sieving, optical microscopy, FTIR spectroscopy, and Raman spectroscopy. Three spiked samples of simulated clean water and a laboratory blank were sent to each laboratory with a prescribed standard operating procedure for particle extraction, quantification, and characterization. The samples contained known amounts of microparticles within four size fractions (1-20 µm, 20-212 µm, 212-500 µm, >500 µm), four polymer types (PE, PS, PVC, and PET), and six colors (clear, white, green, blue, red, and orange). They also included false positives (natural hair, fibers, and shells) that may be mistaken for microplastics. Among laboratories, mean particle recovery using stereomicroscopy was 76% ± 10% (SE). For particles in the three largest size fractions, mean recovery was 92% ± 12% SD. On average, laboratory contamination from blank samples was 91 particles (± 141 SD). FTIR and Raman spectroscopy accurately identified microplastics by polymer type for 95% and 91% of particles analyzed, respectively. Per particle, FTIR spectroscopy required the longest time for analysis (12 min ± 9 SD). Participants demonstrated excellent recovery and chemical identification for particles greater than 50 µm in size, with opportunity for increased accuracy and precision through training and further method refinement. This work has informed methods and QA/QC for microplastics monitoring in drinking water in the State of California.

Development and field evaluation of the organic-diffusive gradients in thin-films (o-DGT) passive water sampler for microcystins.

The presence of microcystins (MCs) in waterbodies requires a simple and reliable monitoring technique to characterize better their spatiotemporal distribution and ecological risks. An organic-diffusive gradients in thin films (o-DGT) passive sampler based on polyacrylamide diffusive gel and hydrophilic-lipophilic balance (HLB) binding gel was developed for MCs in water. The mass accumulation of three MCs (MC-LR, -RR, and -YR) was linear over 10 days (R2 ≥ 0.98). Sampling rates (2.68-3.22 mL d-1) and diffusion coefficients (0.90-1.08 × 10-6 cm2 s-1) of three MCs were obtained at 20 °C. Two different passive samplers, o-DGT and the Solid Phase Adsorption Toxin Tracking device (SPATT), were co-deployed to estimate MC levels at three lakes in California, USA. Measured total MC concentrations were up to 10.9 µg L-1, with MC-LR the primary variant at a measured maximum concentration of 2.74 µg L-1. Time-weighted average MC concentrations by o-DGT were lower than grab water samples, probably because grab sampling measures both dissolved and particulate phases (i.e., MCs in cyanobacteria). Passive water samplers by design can only measure dissolved-phase MCs, which are considerably less during the cyanobacteria-laden periods observed. Both o-DGT and grab samples gave comparable results for three MC variants at low levels of MCs, e.g., <0.1 µg L-1. o-DGT showed a higher correlation with grab sampling than SPATT did. This study demonstrates that o-DGT can be effectively used for monitoring and evaluation of dissolved MCs in waters.

Scrutinizing surficial sediment along a 600-km-long urban coastal zone: Occurrence and risk assessment of fipronil and its three degradates.

Contamination in the coastal zone is closely linked to urbanization and has become a global issue. The coastal aquatic environment is the terminal sink for many chemicals; however, little is known about the occurrence and variation among habitats as well as integrative toxicity for pesticides, i.e., fipronil, and its three major degradates (-desulfinyl, -sulfide, and -sulfone, fiproles hereafter) in sediments in urban coastlines. In the present study, we report results of a random stratified survey for fiproles in surficial sediments in five embayment habitats (strata) along the Southern California Bight (SCB), USA coastline. Fiproles were present in a small areal extent (6.8%) of the SCB embayment, and detected in 14 out of 174 stations with a total concentration of the four analytes ranging from 0.50 to 17.5 µg/kg dry weight. The area-weighted mean concentrations were 3.16 ± 3.37, 0.584 ± 0.558, 0.071 ± 0.103, and 0.005 ± 0.009 µg/kg in brackish estuaries, estuaries, bays, and marinas, respectively, with the results below the detection limits in ports. Fipronil sulfone had the greatest detection frequency (8.05%) and highest mean concentration (3.24 ± 3.36 µg/kg) among the four compounds. A screening-level deterministic risk assessment for invertebrates found that, region-wide, fiproles generally posed an insignificant to low acute risk to the amphipod Eohaustorius estuarius in 7.36% of the SCB embayment area. In addition, high risk to the midge Chironomus dilutus was found in 77.5% of the fiproles-detectable area in the brackish estuary stratum that is a part of the Los Angeles River. Fipronil sulfone was identified as the major contributor of these effects. The results of this study establish a baseline of occurrence and toxicity potential for fiproles in coastal sediments of southern California.

Transcriptomic response patterns of hornyhead turbot (Pleuronichthys verticalis) dosed with polychlorinated biphenyls and polybrominated diphenyl ethers.

To evaluate the impact of environmental contaminants on aquatic health, extensive surveys of fish populations have been conducted using bioaccumulation as an indicator of impairment. While these studies have reported mixtures of chemicals in fish tissues, the relationship between specific contaminants and observed adverse impacts remains poorly understood. The present study aimed to characterize the toxicological responses induced by persistent organic pollutants in wild-caught hornyhead turbot (P. verticalis). To do so, hornyhead turbot were interperitoneally injected with a single dose of PCB or PBDE congeners prepared using environmentally realistic mixture proportions. After 96-hour exposure, the livers were excised and analyzed using transcriptomic approaches and analytical chemistry. Concentrations of PCBs and PBDEs measured in the livers indicated clear differences across treatments, and congener profiles closely mirrored our expectations. Distinct gene profiles were characterized for PCB and PBDE exposed fish, with significant differences observed in the expression of genes associated with immune responses, endocrine-related functions, and lipid metabolism. Our findings highlight the key role that transcriptomics can play in monitoring programs to assess chemical-induced toxicity in heterogeneous group of fish (mixed gender and life stage) as is typically found during field surveys. Altogether, the present study provides further evidence of the potential of transcriptomic tools to improve aquatic health assessment and identify causative agents.

Promoting the stability and adsorptive capacity of Fe3O4-embedded expanded graphite with an aminopropyltriethoxysilane-polydopamine coating for the removal of copper(ii) from water.

In this study, three magnetic graphites, namely, EGF, GAF, and GFA + KH550, were prepared, which were loaded either with Fe3O4 or with Fe3O4 and PDA or with Fe3O4, PDA, and KH550 onto expanded graphite. ATR-FTIR, XRD, XPS, SEM, TEM, and TGA characterization results showed that EGF, GAF, and GFA + KH550 were successfully prepared. Under the same initial copper concentration, the removal rates of copper ions by EGF, GFA, and GFA + KH550 were 86.2%, 96.9%, and 97.0%, respectively and the hazard index reductions of the three adsorbents were 2191 ± 71 (EGF), 1843 ± 68 (GFA), and 1664 ± 102 (GFA + KH550), respectively. Therefore GFA + KH550 exhibited better removal of Cu(ii) than EGF and GFA, for PDA and KH550 provided more adsorption-active sites like -OH and -NH. Here, the adsorption of GFA + KH550 fitted the pseudo-second-order kinetic and Langmuir models well within the testing range, which means that adsorption occurs on a monolayer surface between Cu(ii) and the adsorption sites. The intraparticle diffusion model and various thermodynamic parameters demonstrated that Cu(ii) was adsorbed on GFA + KH550 mainly via external surface diffusion and that the process was both endothermic and spontaneous. Recycling experiments show that GFA + KH550 has a satisfactory recyclability, and the way of direct recovery by magnets exhibits good magnetic induction. GFA + KH550 was applied in lake water and artificial seawater samples, and exhibited better removal of copper than that in DI water under the same environmental conditions for the existence of macromolecular organic matter. Furthermore, the adsorption capacity of copper ions was not relative to the salinity of water. The application of GFA + KH550 demonstrated the potential for application in water treatment procedures.

Fiproles as a proxy for ecological risk assessment of mixture of fipronil and its degradates in effluent-dominated surface waters.

Environmental risk assessment of complex chemical mixtures has increasingly been prioritized as a management goal, especially in the regulatory sector. Although fipronil and its three degradates (-sulfone, -sulfide and -desulfinyl) have been frequently quantified in waterways, little information is available about the likelihood and magnitude of ecological risk posed by these chemical mixtures - collectively known as fiproles - in surface water. In the present study, a probabilistic risk assessment of mixtures of fipronil and its three degradates was conducted for three effluent-dominated southern California rivers: Los Angeles River (LAR), San Gabriel River (SGR) and Santa Clara River (SCR), California, USA. The assessments, which used fiproles as an integrated proxy, were based on three levels of toxicity endpoints: median lethal concentration (LC50), half-maximal effective concentration (EC50), and lowest observed effect concentration (LOEC), to gain comprehensive assessment information. Probabilistic approaches based on species sensitivity distribution (SSD) and exposure concentration distribution (ECD) were developed with the log-logistic model by pooling the toxicity and occurrence data, respectively. The 5th percentile hazardous concentrations (HC5s) were calculated to be at low parts per billion levels, enabling these values to be used to estimate the chemical-specific benchmarks for components that lack ecotoxicity data. The single substance potentially affected fraction (ssPAF) of fiproles revealed risk levels for the three rivers in descending order: LAR ≥ SGR > SCR. The overall risk probability estimated from the joint probability curve (JPC) by Monte Carlo simulation was 1.13 ±â€¯0.20% (LC50), 9.31 ±â€¯1.46% (EC50), and 6.58 ±â€¯1.43% (LOEC) for the three rivers collectively. These results derived from the fiproles indicates that fipronil and its degradates pose risks to the aquatic organisms in the surface water of the three rivers. The present study provides a methodology for the use of a proxy in the risk assessment of chemical mixtures.

Measuring bioconcentration factors of sediment-associated fipronil in Lumbriculus variegatus using passive sampling techniques.

Fipronil and its degradates have been detected ubiquitously in aquatic environment worldwide, yet little is known about its bioaccumulation potential. The goal of the present study was to measure bioconcentration factor (BCF) of sediment-associated fipronil in a benthic invertebrate, Lumbriculus variegatus using passive sampling techniques. Three passive samplers including polymethyl methacrylate (PMMA) film, poly(dimethylsiloxane) fiber and polyacrylate fiber were evaluated. PMMA film was identified as the preferred method and was applied to determine fipronil log KOC (3.77 ±â€¯0.04). BCF of sediment-associated fipronil in L. variegatus was obtained through measuring freely dissolved concentration (Cfree). Because fipronil degraded in sediment, time weighted average (TWA) Cfree was estimated for calculating BCFTWA (1855 ±â€¯293 mL/g lipid). Fipronil BCF was also measured in a water-only bioaccumulation test of L. variegatus under constant exposure condition. This BCF value (1892 ±â€¯76 mL/g lipid) was comparable with the BCFTWA, validating effectiveness of the passive sampling method for the measurement of sediment Cfree. Fipronil was bioaccumulative in L. variegatus according to the USEPA's criteria. The combination of Cfree and TWA concentration measurements was demonstrated to properly determine BCF value for moderately hydrophobic and degradable chemicals in sediment.

An exponential model based new approach for correcting aqueous concentrations of hydrophobic organic chemicals measured by polyethylene passive samplers.

Although low density polyethylene (PE) passive samplers show promise for the measurement of aqueous phase hydrophobic organic chemicals (HOCs), the lack of a practical and unsophisticated approach to account for non-equilibrium exposure conditions has impeded widespread acceptance and thus application in situ. The goal of this study was to develop a streamlined approach based on an exponential model and a convection mass transfer principle for correcting aqueous concentrations for HOCs deduced by PE samplers under non-equilibrium conditions. First, uptake rate constants (k1), elimination rate constants (k2), and seawater-PE equilibrium partition coefficients (KPEWs) were determined in laboratory experiments for a diverse suite of HOCs with logKow range of 3.4-8.3. Linear relationships between log k2 and logKow, and between log KPEW and logKow were established. Second, PE samplers pre-loaded with 13C-labeled performance reference compounds (PRCs) were deployed in the ocean to determine their k2in situ. By applying boundary layer and convection mass transfer theories, ratio (C) of k2 values in field and laboratory exposures was estimated. This C value was demonstrated a constant that was only determined by water velocities and widths of PE strips. A generic equation with C and logKow as parameters was eventually established for extrapolation of non-equilibrium correction factors for the water boundary layer-controlled HOCs. Characterizing the hydrodynamic conditions indicated the sampler configuration and mooring mode should aim at sustaining laminar flow on the PE surface for optimal mass transfer. The PE estimates corrected using this novel approach possessed high accuracy and acceptable precision, and can be suited for a broad spectrum of HOCs. The presented method should facilitate routine utilization of the PE samplers.

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 (

Enantiomer-specific measurements of current-use pesticides in aquatic systems.

Some current-use pesticides are chiral and have nonsuperimposable mirror images called enantiomers that exhibit identical physical-chemical properties but can behave differently when in contact with other chiral molecules (e.g., regarding degradation and uptake). These differences can result in variations in enantiomer presence in the environment and potentially change the toxicity of pesticide residues. Several current-use chiral pesticides are applied in urban and agricultural areas, with increased potential to enter watersheds and adversely affect aquatic organisms. The present study describes a stereoselective analytical method for the current-use pesticides fipronil, cis-bifenthrin, cis-permethrin, cypermethrin, and cyfluthrin. We show use of the method by characterizing enantiomer fractions in environmental sample extracts (sediment and water), and laboratory-dosed fish and concrete extracts previously collected by California organizations. Enantiomer fractions for most environmental samples are the same as racemic standards (equal amounts of enantiomers, enantiomer fraction = 0.5) and therefore are not expected to differ in toxicity from racemic mixtures typically tested. In laboratory-derived samples, enantiomer fractions are more frequently nonracemic and favor the less toxic enantiomer; permethrin enantiomer fractions range from 0.094 to 0.391 in one type of concrete runoff and enantiomer fractions of bifenthrin in dosed fish range from 0.378 to 0.499. We use enantiomer fractions as a screening tool to understand environmental exposure and explore ways this uncommon measurement could be used to better understand toxicity and risk. Environ Toxicol Chem 2018;37:99-106. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Measuring freely dissolved DDT and metabolites in seawater using solid-phase microextraction with performance reference compounds.

The coupling of disposable solid-phase microextraction (SPME) with performance reference compounds (PRCs) has been recently introduced to measure time-averaged freely dissolved concentrations (Cfree) of hydrophobic organic contaminants in sediments under laboratory conditions. To explore the use of PRC-SPME for in situ sampling in seawater, disposable PDMS fibers (35-µm and 100-µm coating) preloaded with stable isotope labeled analogues as PRCs were deployed at six stations (each with three depths) in the open ocean of the Palos Verdes Shelf (CA, USA) Superfund site for 33d to measure Cfree of DDT and its degradates. The observed values of fractional equilibration (feq) of PRCs were mostly <0.85, suggesting nonequilibrium conditions at the end of deployment. The observed feqs for the samplers varied with compound, sampling station and depth, validating the need for calibration to derive accurate Cfree. The Cfree values of DDE and DDD determined with PRC-SPME were in good agreement with those previously measured by in situ large-volume water sampling or polyethylene devices. The highest Cfree in seawater 5m off the ocean floor was 750pgL-1 for o,p'-DDE, 2170pgL-1 for p,p'-DDE, 24pgL-1 for o,p'-DDD, and 75pgL-1 for p,p'-DDD. Results of this study demonstrated the feasibility and advantages of using disposable PDMS fiber coupled with PRCs for in situ sampling.