Transfer kinetics of perfluorooctane sulfonate from water and sediment to a marine benthic fish, the marbled flounder (Pseudopleuronectes yokohamae)

The authors investigated the kinetics of transfer of perfluorooctane sulfonate (PFOS) from water, suspended sediment, and bottom sediment to a marine benthic fish, the marbled flounder (Pseudopleuronectes yokohamae). Fish were exposed in 3 treatments to PFOS in combinations of these exposure media for 28 d and then depurated for 84 d. A major part (37–66%) of PFOS in the fish was in the carcass (i.e., whole body minus muscle and internal organs). Three first-order-kinetic models that differed in exposure media, that is, 1) sum of dissolved and particulate phases and sediment; 2) dissolved phase, particulate phase, and sediment; and 3) dissolved phase only, were fitted to the data assuming common rate constants among the treatments. The uptake efficiency of dissolved PFOS at the respiratory surfaces was estimated to be 3.2% that of oxygen, and the half-life of PFOS in the whole body to be 29 d to 31 d. The better fit of models 1 and 2 and the values of the estimated uptake rate constants suggested that the PFOS in suspended and bottom sediments, in addition to that dissolved in water, contributed to the observed body burden of the fish. Based on an evaluation of several possible contributing factors to the uptake of PFOS from suspended and bottom sediments, the authors propose that further investigation is necessary regarding the mechanisms responsible for the uptake. Environ Toxicol Chem 2013;32:2009–2017. © 2013 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc., on behalf of SETAC. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.


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Chemical analysis The chemical analysis of PFOS was performed according to previously reported methods with modifications (water and sediment, [S-1]; fish tissue, [S-2]; fish blood, [S-3, S-4]). The samples were spiked with 13 C 4 -PFOS, and quantification was based on the isotope dilution method.
The dissolved phase (filtrate) was extracted by using SPE (C18). The particulate phase (residue on filter) and dried sediment samples were extracted by sonication in methanol, and the extract was diluted and purified by using SPE (C18) [S-1]. Dissolved phase concentrations were measured for the interstitial water samples.
Whole fish, fish tissues (other than blood), and fish food were homogenized (8000 rpm, 5 min; BLAS-501, Nihonseiki Kaisha Ltd., Tokyo, Japan). A 5-g aliquot (whole fish, muscle, and carcass) of the homogenate or all homogenate (other tissues) was taken, spiked with 5 ng of 13 C 4 -PFOS in 10 µL methanol, and mixed with silica gel. The mixed homogenate was extracted three times with 20% methanol (aq) by using an accelerated solvent extractor (ASE-200, Dionex, Sunnyvale, CA, USA), at 100 °C and 10 MPa. The extracts were combined, diluted with water to a methanol concentration <10%, and then passed through Presep-C Agri connected after Presep-C Alumina. The cartridges were washed with 10 mL of water, Presep-C Alumina was removed, and Presep-C Agri was dried and then eluted with 2 mL of methanol.
The eluate was concentrated to 1 mL under a stream of nitrogen gas.

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A 100 µL aliquot of the whole blood samples was mixed with 1 mL of 0.5 M TBA solution, 2 mL of 0.25 M sodium carbonate buffer, and 5 ng of 13 C 4 -PFOS in 10 µL methanol. The mixed solution was extracted by mixing with 5 mL of MTBE for 1 min, and the MTBE layer was taken after centrifugation (1400×g, 10 min; model 5100, Kubota Manufacturing, Gunma, Japan). The ). An Xterra MS C18 LC column (2.1 mm i.d., 150 mm long, 3.5 µm particle size, Waters) was used for separation at a flow rate of 0.2 mL/min of a binary solvent system of acetonitrile and 10 mmol/L ammonium acetate in water as a mobile phase; starting at 45% acetonitrile for 4 min, ramped linearly to 90% at 10 min, kept at 80% for 3 min, and then dropped to 45%. For the water samples collected on days 84 and 112, a Zorbax Eclipse Plus C18 LC column (2.1 mm i.d., 100 mm long, 1.8 µm particle size, Agilent Technologies) was used for separation at a flow rate of 0.4 mL/min of the mobile phase; starting at 20% acetonitrile for 0.2 min, ramped linearly to 90% at 5 min, kept at 90% for 1 min, and then dropped to 20%.
The Lipid contents were determined gravimetrically using chloroform/methanol (2:1) as the extraction solvent [S-5]. Homogenized samples (5 g) were dehydrated by mixing with anhydrous sodium sulfate and Soxhlet-extracted for 8 h with chloroform/methanol (2:1). The extract was concentrated to 1 to 2 mL and dissolved in 25 mL of petroleum ether. A 10 mL aliquot of the supernatant was taken, the solvent was evaporated, and the residue was dried at 100 °C for 1 h. The lipid content was determined by weighing the residue.
For suspended solids (SS) and dissolved organic carbon (DOC) measurements, the water samples were filtered through pre-combusted glass-fiber filters (GF-75). The residue on the filter was dried at 80 °C overnight, and the mass concentration of SS was obtained gravimetrically. The DOC concentration in the filtrate was measured as the non-purgeable organic carbon by using a total organic carbon analyzer (TOC-5000, Shimadzu Corp., Kyoto, 6/12 Japan) by combustion/non-dispersive infrared gas analysis, after acidification followed by bubbling with nitrogen gas. The organic carbon content in the sediment was measured with a CHN coder (Flash EA 1112, Thermo Electron Co., Waltham, MA, USA) after pretreatment of ground and dried (105 °C × 2 h) sediment with HCl (aq) to remove carbonates.
The particle-size distribution of the sediment was determined without pretreatment by using a laser diffraction particle-size analyzer (SALD-2100, Shimadzu, Kyoto, Japan) on the basis of equivalent sphere diameter and was calculated in terms of volumetric percentages.
7/12 S3 Data quality assurance and quality control Refer to  for data quality assurance and quality control of the analysis of water and sediment samples. Analytical reproducibility of PFOS in the whole fish and fish tissue samples was determined by means of seven replicate analyses of pooled unspiked 5-g samples of fish muscle. The average concentration and CV were 57 ng/g-wet and 8.4%, respectively.
Method recovery was checked by seven replicate analyses of pooled muscle samples spiked at a nominal concentration of 0.80 ng/g. The recovery was satisfactory, 98.4% (SD, 4.2%). PFOS was not detected in the method blank samples (fish and fish tissue, n = 7; blood, n = 3).
Analytical reproducibility and method recovery of blood samples were previously established as follows [S-4]. Based on seven replicate analyses of pooled unspiked 0.5 mL samples of human whole blood, the average concentration and CV were 1.0 ng/mL and 2.0%, respectively.
Method recovery was satisfactory, 95.6% (SD, 3.3%), based on seven replicate analyses of pooled blood samples spiked with a nominal concentration of 8.0 ng/mL of PFOS. 8/12