This Critcal Review evaluates passive sampler uptake of hydrophobic organic contaminants (HOCs) in water column and interstitial water exposures as a surrogate for organism bioaccumulation. Fifty-seven studies were found where both passive sampler uptake and organism bioaccumulation were measured and 19 of these investigations provided direct comparisons relating passive sampler uptake and organism bioaccumulation. Polymers compared included low-density polyethylene (LDPE), polyoxymethylene (POM), and polydimethylsiloxane (PDMS), and organisms ranged from polychaetes and oligochaetes to bivalves, aquatic insects, and gastropods. Regression equations correlating bioaccumulation (C) and passive sampler uptake (C) were used to assess the strength of observed relationships. Passive sampling based concentrations resulted in log-log predictive relationships, most of which were within one to 2 orders of magnitude of measured bioaccumulation. Mean coefficients of determination (r) for LDPE, PDMS, and POM were 0.68, 0.76, and 0.58, respectively. For the available raw, untransformed data, the mean ratio of C and C was 10.8 ± 18.4 (n = 609). Using passive sampling as a surrogate for organism bioaccumulation is viable when biomonitoring organisms are not available. Passive sampling based estimates of bioaccumulation provide useful information for making informed decisions about the bioavailability of HOCs.

No abstract

Fluorine nuclear magnetic resonance (19F-NMR) spectroscopy has been shown to be a powerful tool capable of quantifying the total per- and polyfluoroalkyl substances (PFAS) in a complex sample. The technique relies on the characteristic terminal −CF3 shift (−82.4 ppm) in the alkyl chain for quantification and does not introduce bias due to sample preparation or matrix effects. Traditional quantitative analytical techniques for PFAS, such as liquid chromatography–mass spectrometry (LC-MS) and combustion ion chromatography (CIC), contain inherent limitations that make total fluorine analysis challenging. Here, we report a sensitive 19F-NMR method for the analysis of total PFAS, with a limit of detection of 99.97 nM, or 50 μg/L perfluorosulfonic acid. To demonstrate the capabilities of 19F-NMR, the technique was compared to two commonly used methods for PFAS analysis: total oxidizable precursor (TOP) assay and LC-high resolution MS analysis for targeted quantification and suspect screening. In both cases, the 19F-NMR analyses detected higher total PFAS quantities than either the TOP assay (63%) or LC-MS analyses (65%), suggesting that LC-MS and TOP assays can lead to underreporting of PFAS. Importantly, the 19F-NMR detected trifluoroacetic acid at a concentration more than five times the total PFAS concentration quantified using LC-MS in the wastewater sample. Therefore, the use of 19F-NMR to quantify the total PFAS in highly complex samples can be used to complement classic TOP or LC-MS approaches for more accurate reporting of PFAS contamination in the environment.

Low‐density polyethylene sheets are used as passive samplers for aquatic environmental monitoring to measure the freely dissolved concentration (Cfree) of hydrophobic organic contaminants (HOCs). Freely dissolved HOCs in water will partition into the polyethylene until a thermodynamic equilibrium is achieved; that is, the HOC's activity in the passive sampler is the same as its activity in the surrounding environment. One way to evaluate the equilibrium status or estimate the uptake kinetics is by using performance reference compounds (PRCs). A fractional equilibrium (feq) can be determined for target HOCs, under the assumption that PRC desorption from the passive sampler occurs at the same rate as for the unlabeled target HOCs. However, few investigations have evaluated how effectively and accurately PRCs estimate target contaminant Cfree under in situ conditions. In the present study, polyethylene passive samplers were preloaded with 6 13C‐labeled polychlorinated biphenyls (PCBs) as PRCs; deployed in New Bedford Harbor, Massachusetts, USA; and collected after 30‐, 56‐, 99‐, and 129‐d deployments. Using this unique temporal sampling design, PRC results from each deployment were fit to a diffusion model to estimate the Cfree of 27 PCB congeners and compare the results between the different deployment times. Smaller PCBs had variable concentrations over the 4 deployments, whereas mid–molecular weight PCBs had consistent Cfree measurements for all deployments (relative standard deviation <20%). High–molecular weight PCBs had the largest Cfree estimates after 30 d; these estimates and their standard deviations decreased with longer deployment times. These findings suggest that when targeting PCBs with more than 6 chlorines or contaminants with a log octanol–water partition coefficient ≥6.5, a deployment time longer than 30 d may be prudent. Environ Toxicol Chem 2020;39:1165–1173. © 2020 SETAC

Performance reference compounds (PRCs) are often added to passive samplers prior to field deployments to provide information about mass transfer kinetics between the sampled environment and the passive sampler. Their popularity has resulted in different methods of varying complexity to estimate mass transfer and better estimate freely dissolved concentrations (C ) of targeted compounds. Three methods for describing a mass transfer model are commonly used: a first-order kinetic method, a nonlinear least squares fitting of sampling rate, and a diffusion method. Low-density polyethylene strips loaded with PRCs and of 4 different thicknesses were used as passive samplers to create an array of PRC results to assess the comparability and reproducibility of each of the methods. Samplers were deployed in the water column at 3 stations in New Bedford Harbor (MA, USA). Collected data allowed C comparisons to be performed in 2 ways: 1) comparison of C derived from one thickness using different methods, and 2) comparison of C derived by the same method using different thicknesses of polyethylene. Overall, the nonlinear least squares and diffusion methods demonstrated the most precise results for all the PCBs measured and generated C values that were often statistically indistinguishable. Relative standard deviations (RSDs) for total PCB measurements using the same thickness and varying model types ranged from 0.04 to 12% and increased with sampler thickness, and RSDs for estimates using the same method and varying thickness ranged from 8 to 18%. Environmental scientists and managers are encouraged to use these methods when estimating C from passive sampling and PRC data. Environ Toxicol Chem 2018;37:2089-2097. Published 2018 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.