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An overlooked issue for field application of in situ performance reference compound (PRC) calibration methods is the validity of the assumption that both the sorption of a target compound and desorption of its corresponding PRC follow the first-order kinetics with the same rate constants under stagnant conditions. In the present study, disposable polydimethylsiloxane fibers of 2 sizes (7 and 35 µm) impregnated with 8 13C-labeled or deuterated PRCs were statically deployed into different marine sediments, from which the kinetics for sorption of the target compounds and desorption of the PRCs were characterized. Nonsymmetrical profiles were observed for exchange of the target analytes and their corresponding PRCs in sediment under stagnant conditions. The hysteretic desorption of PRCs in the kinetic regime may be ascribed to the low chemical potential between the fiber and sediment porewater, which reflects the inability of water molecules to rapidly diffuse through sediment to solvate the PRCs in the aqueous layer around the fiber surface. A moderate correlation ( r = 0.77 and r = 0.57, p < 0.05 for both regressions) between the PRC-calibrated equilibrium concentrations of 1,1-dichloro-2,2-bis-(chlorophenyl) ethylene ( p, p′-DDE) and polychlorinated biphenyl (PCB)-153 and the lipid normalized levels in worms ( Neanthes arenaceodentata) was obtained in co-exposure tests under simulating field conditions, probably resulting from slightly overestimated bioavailability because of the hysteretic desorption of PRCs and toxic effects. Environ Toxicol Chem 2016;35:1978-1985. © 2015 SETAC [ABSTRACT FROM AUTHOR]

Solid-phase microextraction (SPME) has often been used to estimate the freely dissolved concentration ( Cfree) of organic contaminants in sediments. A significant limitation in the application of SPME for Cfree measurement is the requirement for attaining equilibrium partition, which is often difficult for strongly hydrophobic compounds such as DDT. A method was developed using SPME with stable isotope-labeled analogues as performance reference compounds (PRCs) to measure Cfree of DDT and metabolites (DDTs) in marine sediments. Six 13C-labeled or deuterated PRCs were impregnated into polydimethylsiloxane (PDMS) fiber before use. Desorption of PRCs from PDMS fibers and absorption of DDTs from sediment were isotropic in a range of sediments evaluated ex situ under well-mixed conditions. When applied to a historically contaminated marine sediment from a Superfund site, the PRC-SPME method yielded Cfree values identical to those found by using a conventional equilibrium SPME approach (Eq-SPME), wherease the time for mixing was reduced from 9 d to only 9 h. The PRC-SPME method was further evaluated against bioaccumulation of DDTs by Neanthes arenaceodentata in the contaminated sediment with or without amendment of activated carbon or sand. Strong correlations were consistently found between the derived equilibrium concentrations on the fiber and lipid-normalized tissue residues for DDTs in the worms. Results from the present study clearly demonstrated the feasibility of coupling PRCs with SPME sampling to greatly shorten sampling time, thus affording much improved flexibility in the use of SPME for bioavailability evaluation. Environ Toxicol Chem 2013;32:1946-1953. © 2013 SETAC [ABSTRACT FROM AUTHOR]

A passive water sampler with low-density polyethylene (LDPE) as the sorbent phase was built and field-tested for sensing freely dissolved concentrations of hydrophobic organic compounds (HOCs) in fresh and coastal water. Based on the measured LDPE-water partition coefficients ( Kpew) of 12 polycyclic aromatic hydrocarbons (PAHs) and dichlorodiphenyltrichloroethane (DDT) and its seven metabolites, the detection limits with the passive sampler containing 10-g LDPE ranged from 0.04 to 56.9 pg/L in the equilibrium sampling mode. Furthermore, the utility of the passive sampler in measuring dissolved HOC concentrations in open waters was examined through a comparison with solid-phase extraction combined with liquid-liquid extraction (SPE-LLE) and poly(dimethyl)siloxane (PDMS) coated fiber samplers. The total concentrations of PAHs (3.8-16 ng/L) obtained by the passive sampler were lower than those (87.7-115.5 ng/L) obtained through SPE-LLE. This large difference was probably attributable to slower water exchange in and out of the passive sampler as time progressed because of blockage by algae in eutrophia reservoirs and high dissolved organic carbon contents resulting in higher-than-expected PAH concentrations by SPE-LLE. Furthermore, the concentrations and compositional profiles of DDXs (sum of p,p′-DDT, p,p′-DDD, p,p′-DDE, o,p′-DDT, o,p′-DDD, o,p′-DDE, and p,p′-DDMU) at site A obtained by the passive sampler agreed with the results obtained with the PDMS-coated fibers, suggesting that the passive sampler was able to reasonably quantify dissolved HOCs in seawater. Environ. Toxicol. Chem. 2012; 31: 1012-1018. © 2012 SETAC [ABSTRACT FROM AUTHOR]

The coefficients of partitioning (Kpew) between low-density polyethylene (LDPE) film (50-mm thickness) and water for 23 polybrominated diphenyl ether (PBDE) congeners were determined based on a regression analysis of sorption kinetics over an extended exposure period (up to 365 d). A curvilinear relationship between log Kpew and log KOW (octanol–water partition coefficient) was obtained for the target BDE congeners with the turning point at log KOW approximately 8. Previously obtained dietary uptake efficiencies of BDE congeners in common carp (Cyprinus carpio) were also found to relate curvilinearly to log KOW. In addition, fieldmeasured relative abundances of BDE-209 compiled from previous investigations conducted in the Pearl River Delta of South China were significantly (p<0.001) higher in abiotic samples (n¼79 from 11 matrices) than in biotic samples (n¼73 from 12 matrices), suggesting the likelihood for reduced bioavailability of BDE-209 in certain biota. Finally, a molecular-scale analysis indicated that the curvilinear relationship between log Kpew and log KOW can be attributed to the energy barrier that a molecule has to overcome as it attempts to diffuse into the LDPE structure, which can become significant for larger molecules. Similarly, the reduced bioavailability of BDE-209 in many biological species can be regarded as a reflection of the magnitude of molecular interactions between cell membranes and BDE-209. [ABSTRACT FROM AUTHOR]