Environ. Sci. Technol. 2008, 42, 8446–8451
Relationships between Desorption Intervals and Availability of Sediment-Associated Hydrophobic Contaminants Y U Y A N G , †,‡ W E S L E Y H U N T E R , ‡ S H U T A O , † A N D J A Y G A N * ,‡ Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China, and Department of Environmental Sciences, University of California, Riverside, California 92521
Received July 7, 2008. Revised manuscript received September 11, 2008. Accepted September 15, 2008.
Availability is an important factor regulating the fate and toxic effects of hydrophobic organic compounds (HOCs) in soil and sediment. Many methods have been proposed for measuring HOC availability, but ambiguity exists in the selection of methods or method conditions. In this study, using pyrethroid insecticides as model HOCs, we measured their desorption kinetics from black carbon (BC)-amended sediments and used comprehensivestatisticalanalysistounderstandthedependence of the derived parameters on desorption intervals. Fitting of data from Tenax-aided depletive desorption to a three-phase model gave estimates of 11-13, 28-33, and 57-60% pyrethroid distribution in the rapid (Frapid), slow (Fs), and very slow (Fvs) desorption fractions, respectively. The desorbed fraction after 24 h, or F24h, essentially equaled to Frapid, while the desorbed fraction after 6 h (F6h) was only about half of Frapid, suggesting that the practice of using F6h in lieu of Frapid would lead to inaccurate assessment of availability. In contrast, Pearson correlation coefficients for the desorbed fractions and uptake into polydimethylsiloxane (PDMS) fibers decreased with increasing desorption intervals, with F6h giving the most agreeable measurements. Therefore, while Frapid estimated from depletive desorption reflects the total chemical accessibility, desorbed fractions after short intervals likely provide a measure for the immediate availability, much like PDMS fibers. The use of desorbed fractions after short intervals (e.g., F6h) to approximate Frapid may give estimates substantially different from Frapid and therefore should be avoided.
Introduction Surveys worldwide have revealed ubiquitous sediment contamination by hydrophobic organic compounds (HOCs) (1, 2). Many HOCs may pose risks to human health, through bioaccumulation and food chain transfers, and to nontarget organisms such as benthic invertebrates, due to acute and chronic toxicity (3, 4). However, it is increasingly known that bioaccumulation or toxic effects of HOCs are not directly related to the total chemical concentration, because sediment properties and contact time, among other factors, alter the availability of sediment-associated HOCs (5, 6). The accurate * Corresponding author e-mail:
[email protected]. † Peking University. ‡ University of California. 8446
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estimation of contaminant availability is essential for predicting the fate and risk of HOCs. Over the last 2 decades, an array of chemical methods has been proposed for measuring contaminant availability. However, there often exists ambiguity in method definitions (7, 8), leaving open the question of the soundness of method or method condition selection in some cases. Bioavailability, as articulated by Reichenberg and Mayer (9), is often presented with competing concepts (10, 11). Availability in some processes (e.g., biodegradation) is related to accessibility (12), while in other processes (e.g., baseline or acute aquatic toxicity) it is regulated by chemical activity such as the freely dissolved concentration (Cfree) (6). Failure to recognize differences in measurement goals has sometimes led to the arbitrary selection of methods or method conditions (9). This is exemplified in the use of Tenax-aided depletive desorption in deriving the rapid desorption fraction, Frapid, as an estimate of availability (13, 14). As shown by Cornelissen et al. (15), a single-step desorption, depending on the interval used, could under- or overestimate Frapid. Kukkonen et al. (16) also observed a poor exchangeability between Frapid and desorption after 6 h (F6h) or 24 h (F24h) for predicting bioaccumulation of select HOCs in sediments. However, the use of F6h in lieu of Frapid occurred in other studies (for example, refs 17-21), often with justification based on simple correlation analysis. The main objectives of this study were to use the strongly hydrophobic pyrethroids (Kow ≈ 106) as model HOCs to evaluate potential biases in using the desorption approach and to demonstrate the importance of defining method conditions when using chemical techniques for estimating availability of sediment-associated HOCs.
Materials and Methods Chemicals and Materials. Pyrethroids including bifenthrin (BF) (purity, 98.8%), fenpropathrin (FN) (99.7%), λ-cyhalothrin (LCY) (98.7%), cis-permethrin (CPM) (97.0%), transpermethrin (TPM) (97.0%), cyfluthrin (CF) (92.0%), cypermethrin (CP) (95.1%), and esfenvalerate (ES) (98%) were obtained from FMC (Princeton, PA), Bayer CropScience (Stilwell, KS), Syngenta (Bracknell, Berks, UK), Valent (Walnut Creek, CA), or Chem Service (West Chester, PA). Tenax TA (60-80 mesh) was obtained from Supelco (Bellefonte, PA). Charcoal (Agrocoir, Laguna Niguel, CA) was used as a representative black carbon (BC) to amend into the sediment. All other chemicals or solvents used were of gas chromatography (GC) or analytical reagent grade. Sediment Spike and Equilibration. The sediment was sampled from the top 10 cm in San Diego Creek, located near Irvine, CA, wet sieved through 2 mm, and stored at 4 °C before use. The total organic carbon (OC) and BC contents of the sediment were 1.5 and 0.03%, respectively. Background levels of the pyrethroids in the sediment were analyzed in a previous study (25). The sediment contained 1.3 µg/kg BF and 2.5 µg/kg CF. These values were far below the spiked concentration (1.0 mg/kg) and were considered negligible for this study. The sediment was spiked with BF, FN, LCY, CPM, TPM, CF, CP, and ES by adding the chemicals in 2.0 mL of acetone into a 1.9-L glass jar, evaporating the acetone in a fume hood, and mixing with 200 g (dry weight) of sediment. The calculated initial concentration was 1 mg/kg for each pyrethroid. The spiked sediment samples were thoroughly mixed with a stainless steel spatula. A 30-g aliquot of the spiked sediment was transferred to a 100-mL glass jar and amended with charcoal at 0 (control), 0.38, 0.75, and 1.5% (dry weight basis) to generate a series of sediments 10.1021/es801876z CCC: $40.75
2008 American Chemical Society
Published on Web 10/22/2008
with a gradient of OC contents. The BC-amended sediment samples were mixed for 1 h on a horizontal shaker at about 100 rpm after the sample jars were closed with Teflon-lined caps. Deionized water containing sodium azide (200 mg/L) was used to adjust the water-to-sediment ratio to about 1:1 (w/w) and to sterilize the system. The spiked sediments were capped and equilibrated in the dark at room temperature for 26 d. Tenax Desorption Experiment. The desorption kinetics of pyrethroids from the treated sediments was measured with a method similar to that described in Xu et al. (21). After 26 d equilibration, 1.0-g aliquots (in triplicates) were removed from each sediment and transferred to a 50-mL Teflon centrifuge tube. Tenax beads (0.05 g) and 20 mL of sodium azide solution (200 mg/L) were added into the centrifuge tube. Samples were shaken on a horizontal shaker at about 100 rpm at room temperature. Tenax beads were renewed after desorption intervals of 1, 2, 6, 10, 24, 48, 96, 144, 192, 240, and 312 h and 100 d. Tenax beads were separated from the sediment slurry by centrifugation at 10 000 rpm for 20 min. The supernatant was transferred to a glass funnel fitted with a Whatman No. 41 filter paper (Whatman, Maidstone, UK). Tenax beads were collected and rinsed thoroughly with deionized water. New Tenax beads (0.05 g) and 20 mL of sodium azide solution (200 mg/l) were added again to the same sediment sample. The kinetics up to 312 h were used to construct the desorption curve and used for estimating Frapid, Fs, and Fvs. The measurements after 100 d were used to validate the derived relationship for predicting phase distribution after a prolonged equilibration time. Three replicates were used. Tenax beads were extracted by sonication using 5 mL of acetone-hexane mixture (1:1, v/v) in 20 mL glass scintillation vials three consecutive times. The sonication was conducted for 5 min in 3-s pulse mode by a high-intensity ultrasonic processor (Sonic 550, Fisher). Extracts from the same sample were combined and filtered through a Whatman No. 41 filter paper into a 100-mL round-bottom flask. The extract was evaporated to about 1 mL on a vacuum rotary evaporator. The final residue was analyzed on GC using deltamethrin as an internal standard. Pyrethroids were analyzed on an Agilent 6890N GC with an electron capture detector (Agilent Technologies, Wilmington, DE) and a HP-5MS (30 m × 0.25 mm × 0.25 µm; Agilent Technologies). The oven temperature was initially held at 80 °C for 1.00 min, ramped at 30 °C/min to 160 °C, and followed by ramping at 3 °C/min to a final temperature 300 °C (held for 20 min). Method recoveries for the Tenax desorption experiment were from 74.7 to 94.8% (21). Decachlorobiphenyl was added to 20% of the samples as a surrogate, and the recoveries of the surrogate was 87 ( 11%. Desorption kinetics data were fitted to a three-phase firstorder equation, which consists of rapid, slow, and very slow desorption fractions (15, 21), using SigmaPlot 10.0 (San Jose, CA) St/S0 ) Frape-krapt + Fslowe-kslow + Fvse-kvst
(1)
where St and S0 (µg/kg) are concentrations of pyrethroids in the sediment after desorption time t (h) and before desorption, respectively, Frap, Fslow, and Fvs are fractions of pyrethroids in the rapid, slow, and very slow desorption pools before desorption, respectively, and krap, kslow, and kvs are the rate constants for the rapid, slow, and very slow desorption fractions, respectively. Polydimethylsiloxane (PDMS) Fiber Uptake Experiment. The use of PDMS-coated fibers for detecting Cfree has been reported for pyrethroids and other HOCs (22-24). Studies showed that concentrations detected by PDMS fibers for pyrethroids in sediment, sediment porewater, or surface water containing dissolved organic matter (DOM) were
TABLE 1. Mean Regression Parameters from Fitting the Tenax-Aided Desorption Data of Pyrethroids in Sediments Amended with Black Carbon (BC) at Different Levels to a Three-Phase First-Order Model (eq 1)a BC (%)
Frapid
Krapid (h-1)
Fslow
Kslow (h-1)
Fvs
Kvs (h-1)
0 0.37 0.75 1.5
0.13 0.12 0.11 0.14
0.072 0.090 0.072 0.059
0.29 0.33 0.29 0.28
7.9E-3 6.2E-3 8.4E-3 6.4E-3
0.59 0.56 0.60 0.57
6.8E-12 9.9E-11 1.1E-05 2.9E-11
a Frapid, Fs, and Fvs are the rapid, slow, and very slow desorption fractions, respectively, and Krapid, Ks, and Kvs are the corresponding rate constants.
closely correlated with uptake (24) or acute toxicity (6) to water-column invertebrates (e.g., Ceriodaphnia dubia and Daphnia magna) and benthic invertebrates (e.g., Chironomus tentans) (25). In this study, uptake of pyrethroids into PDMS fibers was determined under the same sediment and treatment conditions as in the above Tenax desorption experiment. Briefly, a 1.0-g aliquot (dry weight) of 26-d-aged sediment was equilibrated with a 1-cm-long PDMS fiber (430 µm glass core with 35 µm PDMS coating, Polymicro Technologies, Phoenix, AZ) in a 20-mL glass scintillation vial after addition of 0.87 mL of 200 mg/L NaN3 solution. The sample vials were capped and rolled at 30 rpm at room temperature for 48 h. All samples consisted of three replicates. After equilibration, fibers were wiped clean and sonicated twice in 100 µL of acetone for 5 min to extract the accumulated pesticides. The extracts were dried under a stream of nitrogen gas and redissolved in 100 µL of hexane for analysis on GC. Statistical Analysis. Correlation analysis was performed using SPSS 10.0 (SPSS, Chicago, IL) to determine the relationship between the desorbed fractions and the uptake into PDMS fibers. Desorption intervals were classified on the basis of the hierarchical cluster analysis using SPSS.
Results and Discussion Desorption Kinetics of Pyrethroids in Sediments. Plots of the ratio of St over S0 against desorption interval t showed different desorption kinetics for the different treatments (Figure S1, Supporting Information). The overall desorption kinetics consisted of an initial rapidly declining stage, followed by a transitional phase and then by a very slowly declining stage. Differences among the different pyrethroid compounds were more obvious than for sediments with different BC contents. For the same sediment, desorption of CPM was the slowest, while BF was the fastest at 312 h. This difference may be attributable to the different molecular volumes, given that CPM has the lowest molecular volume (351.5 Å3) while BF has the highest value (437.3 Å3). When averaged across the different BC amendment rates, after desorption for 6 h, 3.6, 13.8, 4.0, 1.9, 3.9, 6.8, 5.8, and 3.5% of BF, FN, LCY, CPM, TPM, CF, CP, and ES, respectively, were desorbed from the sediments. After 312 h, the remaining residue fractions in all sediments ranged from 52 to 82%, which were comparable to those found for BF, CF, FN, and LCY (50-70%) from sediments that were equilibrated for 40 d in a previous study (21). The change of St/S0 over t showed a good fit to the threephase model. The derived krapid, kslow, and kvs were (5.9-9.0) × 10-2, (6.2-8.4) × 10-3, and 6.8 × 10-12 to 1.1 × 10-5 h-1, respectively. Overall, 11-14, 28-33, and 56-60% of the pyrethroids were present in the rapid, slow, and very slow desorption fractions, respectively (Table 1). The derived Frapid values for pyrethroids were comparable to those obtained for PAHs and PCBs. For instance, 8-31% of PAHs were found to be in Frapid for six field sediments (15). Earlier studies VOL. 42, NO. 22, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 1. Correlation between predicted and observed remaining residue fractions of pyrethroids in BC-amended sediments after 100 d of desorption. Prediction was from the relationship derived using desorption data up to 312 h, and the dashed line represents the 1:1 ratio. Symbols represent measurements for different pyrethroids in the same sediment or the same pyrethroid compound in different sediments. Bars represent standard deviations of three replicated measurements. (Mean and standard deviation are presented.) suggested that Frapid reflected the pool of contaminant attached to the outer regions of sediment aggregates and could be used as an indicator for the bioaccessible fraction of sediment- or soil-associated HOCs (12, 19, 26). Semple et al. (7) further defined the bioaccessible fraction as that which is able to cross an organism’s cellular membrane. Cuypers et al. (27) demonstrated a 1:1 relationship between biodegradation of PAHs in sediments and the accessibility measured from Tenax- or cyclodextrin-aided desorption. Therefore, results from the present study suggest that after only 26 d of contact time, less than 15% of the residual pyrethroids in the sediments were potentially bioavailable or accessible for long-term processes such as biodegradation. The validity of the above derived relationship was assessed for the same samples subjected to 100-d desorption. From Figure 1, the relationship derived from the 312-h sequential desorption experiments accurately predicted the remaining residue fractions following 100 d of continuous desorption (Figure 1). For instance, the observed residue fractions of BF in sediment with 0 and 1.5% BC were 45 ( 2 and 44 ( 2%, while the predicted values were 44 and 39%, respectively. The Pearson correlation coefficient for the relationship between predicted and observed values was 0.96 (P < 0.001), while the slope was 0.77 (R 2 ) 0.92, P < 0.001). In previous studies where Tenax beads were used for assessing desorption kinetics, only relatively short intervals up to 400 h were used (15, 21), and studies using a longer desorption interval are rare (28). The above results provided evidence that desorption kinetics based on data within 312 h of desorption may be extrapolated to a much longer duration to predict long-term desorption trends of HOCs. A single, short desorption interval, usually 6 h, has often been used in previous studies to derive F6h as an approximation of Frapid for soil- or sediment-associated HOCs (17-21). In the current study, there were good correlations between Frapid and the desorbed fraction after any single interval up to 48 h (Pearson correlation coefficient ) 0.92-0.96, P < 0.01) (Figure 2). However, even though the correlation was good, F6h and F10h were significantly smaller than Frapid (P < 0.01). The slopes of regression lines for Frapid and F6h, F10h, F24h, or F48h were 0.55, 0.72, 0.99, and 1.10, respectively. These results clearly indicated that if a single-step desorption were used to approximate Frapid, 24 h would be the optimal interval, while F6h would be an underestimate of Frapid. Correlations between Fvs and the remaining residue fractions of pyrethroids after 144 h were analyzed in a similar manner. Results showed that the remaining residue fractions after 144 or 312 h of desorption were closely correlated with 8448
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Fvs. However, the remaining residue fractions after 144 h were significantly greater than Fvs (slope ) 1.22 ( 0.16, P < 0.01), whereas the remaining residue fraction after 312 h was similar to Fvs (slope ) 1.08 ( 0.09). This observation suggests that the remaining residue fraction after 312 h was a good indicator for Fvs or the sequestered pool of pyrethroids in sediments. Hierarchical cluster analysis was further performed on the desorption kinetics data (Figure S2, Supporting Information). The results were generally in agreement with the above observations. Desorption time intervals were classified into two main groups consisting of before and after 48 h, respectively. Therefore, the desorption kinetics may be separated into three different stages. The rapid desorption fraction was mainly desorbed before 48 h, the slow desorption fraction was desorbed between 48 and 312 h, and the very slow desorption fraction was mainly desorbed after 312 h (Figure S2, Supporting Information). In a number of studies, it was suggested that F6h could be used in lieu of Frapid, because the estimation of Frapid requires repetitive steps and is extremely time-consuming (17-21). For instance, F6h was used as an index for Frapid when the availability of HOCs including hexachlorobiphenyl, DDE, permethrin, chlorpyrifos, and phenanthrene to Lumbriculus variegatus was studied (19). However, the justification for using single time point F6h over Frapid was often less than rigorous. Cornelissen et al. (15) showed that, on average, F6h was about half Frapid, and the ratio of F6h to Frapid varied from 0.38 to 8.11 for PCBs, suggesting that physicochemical properties of HOCs influence the relationship. Shor et al. (28) showed that F24h was the best quantitative indicator for Frapid of PAHs in field-aged sediments, but the conclusion was reached by using a two-phase mass transfer model instead of the more commonly used three-phase first-order model. The largely variable contact times and different sources of the compounds in the field samples used in the study also left open questions for the conclusion. Results from the present study clearly showed that while it is feasible to use the desorbed fraction from a single interval to approximate Frapid, the optimum interval is 24 h for pyrethroids. Comparison of Tenax Desorption with Uptake into PDMS Fiber. Polydimethylsiloxane (PDMS) fibers were used in a number of previous studies to detect Cfree of HOCs, including pyrethroids, because diffusion of HOCs into the PDMS phase is considered a selective process (22, 29). Close dependence was consistently found for pyrethroids between their accumulation into PDMS fibers and uptake by aquatic invertebrates including C. tentans and D. magna or acute toxicity to C. tentans and C. dubia (6, 24, 25, 30). In this study, good correlations were found between the uptake into PDMS fibers and the desorbed fraction of pyrethroids after any interval within 48 h as well as Frapid (P < 0.01) (Figure 3). In general, FN appeared to have enhanced desorption as well as accumulation into PDMS compared to the rest of pyrethroids, while desorption of LCY was somewhat suppressed in relation to its uptake into PDMS, suggesting an influence of chemical characteristics. However, when the correlation between uptake into PDMS fibers and the desorbed fractions was analyzed as a function of desorption intervals, it is clear that R 2 decreased with increasing desorption time, from about 0.90 to 0.19 (Figure S3, Supporting Information). The Pearson correlation coefficients for the relationship between the content in PDMS fibers and the desorbed fractions increased slightly to a peak value of around 0.94 after 6 h and then decreased quickly with increasing desorption interval to about 0.42 after 312 h (Figure 4). Therefore, although F6h was a poor estimate for Frapid, it gave the most similar measurement to SPME (or Cfree).
FIGURE 2. Comparisons between desorbed fractions after short desorption intervals (e48 h) and the rapid desorption fraction Frapid for seven pyrethroids in BC-amended sediments. The dashed lines represent the 1:1 ratio. Symbols represent measurements for different pyrethroids in the same sediment or the same pyrethroid compound in different sediments. Bars represent standard deviations of three replicated measurements. (Mean and standard deviation are presented.)
FIGURE 3. Correlation between pyrethroids short-interval desorption fractions (e48 h) or Frapid and uptake into PDMS fibers in BC-amended sediments. Symbols represent measurements for different pyrethroids in the same sediment or the same pyrethroid compound in different sediments. Bars represent standard deviations of three replicated measurements. (Mean and standard deviation are presented.) Many methods for measuring contaminant availability in soil or sediment are based on the principle of desorption, which includes the use of Tenax and cyclodextrin for trapping the desorbed fraction (15, 31, 32). In some cases, a weak solvent or combination of solvents is also used in place of
water (33). The use of a depletive desorption procedure is considered to give estimates of bioavailability, in the context of bioaccessibility, or the contaminant availability for longerterm processes, such as biodegradation or bioaccumulation of relatively stable HOCs (9, 15). However, nondepletive VOL. 42, NO. 22, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 4. Dependence of Pearson correlation coefficients between the desorbed fraction of pyrethroids and uptake into PDMS fibers on the desorption intervals in BC-amended sediments. The inset box shows the trend of Pearson correlation coefficient with time in a shorter scale up to 60 h. desorption measurements have also been used as a simplified alternative to the depletive desorption approach, mainly to overcome the need for lengthy, tedious operations, as in the use of F6h in lieu of Frapid. As shown in this study, when a single step is used, the exact duration of the desorption interval is critical because of the time-dependent nature of desorption. A long interval may result in a desorbed fraction larger than Frapid, while too short of an interval may lead to significant underestimations. Therefore, the use of 6 h as a convenient time interval should be avoided if the measurement goal is Frapid. On the other hand, desorbed fractions after short time intervals may represent similar measurements as Cfree and may be valuable for predicting bioavailability for short-term processes such as phase partition, diffusion, uptake by small organisms, and acute invertebrate toxicity (14, 19). Again, due to the time dependence of desorption, the exact duration of such an interval is critical and should be experimentally determined. An unnecessarily long interval may give overestimations of Cfree and should be avoided. For instance, while You et al. (19) showed that the lipid-normalized accumulated concentrations of HOCs in L. variegatus were almost identical to F6h, the 14-16 h Tenax extracted amounts of DDTs were around 1.5 times the accumulation in earthworms in another study (13). It is unknown, however, if the exact duration of such an interval depends on the type of HOCs or the sample matrices, and this should be further investigated.
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Acknowledgments This study was supported by the China Scholarship Council to Y.Y. We thank FMC, Bayer CropScience, Valent, and Sygenta for providing chemical standards used in this study.
Supporting Information Available Desorption kinetics of pyrethroids from BC-amended sediments, cluster analysis of desorption intervals, and time ranges for desorption occurring at rapid, slow, and very slow rates, and correlation between the uptake into PDMS fibers and desorbed amounts of pyrethroids showing dependence of correlation coefficient R 2 on desorption intervals. These materials are available free of charge via the Internet at http:// pubs.acs.org.
Literature Cited (1) Metre, P. C. V.; Mahler, B. J. Trends in hydrophobic organic contaminants in urban and reference lake sediments across the United States, 1970-2001. Environ. Sci. Technol. 2005, 39, 5567–5574. (2) Lohmann, R.; Breivik, K.; Dachs, J.; Muir, D. Global fate of POPs: Current and future research directions. Environ. Pollut. 2007, 150, 150–165. (3) Eljarrat, E.; Caixach, J.; Rivera, J.; De Torres, M.; Ginebreda, A. Toxic potency assessment of non- and mono-ortho PCBs, PCDDs, PCDFs, and PAHs in northwest Mediterranean sedi8450
9
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(17)
(18)
(19)
(20)
(21)
(22)
(23)
ments (Catalonia, Spain). Environ. Sci. Technol. 2001, 35, 3589– 3594. Kelly, B. C.; Ikonomou, M. G.; Blair, J. D.; Morin, A. E.; Gobas, F. A. P. C. Food web-specific biomagnification of persistent organic pollutants. Science. 2007, 317, 236–239. Luthy, R. G.; Aiken, G. R.; Brusseau, M. L.; Cunningham, S. D.; Gschwend, P. M.; Pignatello, J. J.; Reinhard, M.; Traina, S. J.; Weber, W. J.; Westall, J. C. Sequestration of hydrophobic organic contaminants by geosorbents. Environ. Sci. Technol. 1997, 31, 3341–3347. Xu, Y.; Spurlock, F.; Wang, Z.; Gan, J. Comparison of five methods for measuring sediment toxicity of hydrophobic contaminants. Environ. Sci. Technol. 2007, 41, 8394–8399. Semple, K. T.; Doick, K. J.; Jones, K. C.; Burauel, P.; Craven, A.; Harms, H. Defining bioavailability and bioaccessibility of contaminated soil and sediment is complicated. Environ. Sci. Technol. 2004, 38, 228A–231A. Birdwell, J.; Cook, R. L.; Thibodeaux, L. J. Desorption kinetics of hydrophobic organic chemicals from sediment to water: A review of data and models. Environ. Toxicol. Chem. 2007, 26, 424–434. Reichenberg, F.; Mayer, P. Two complementary sides of bioavailability: Accessibility and chemical activity of organic contaminants in sediments and soils. Environ. Toxicol. Chem. 2006, 25, 1239–1245. Kraaij, R.; Mayer, P.; Busser, F. J. M.; Bolscher, M. V.; Seinen, W.; Tolls, J. Measured pore-water concentrations make equilibrium partitioning worksA data analysis. Environ. Sci. Technol. 2003, 37, 268–274. Selck, H.; Palmqvist, A.; Forbes, V. E. Uptake, depuration, and toxicity of dissolved and sediment-bound fluoranthene in the polychaete, Capitella sp I. Environ. Toxicol. Chem. 2003, 22, 2354–2363. Cornelissen, G.; Rigterink, H.; Ferdinandy, M. M. A.; Van Noort, P. C. M. Rapidly desorbing fractions of PAHs in contaminated sediments as a predictor of the extent of bioremediation. Environ. Sci. Technol. 1998, 32, 966–970. Morrison, D. E.; Robertson, B. K.; Alexander, M. Bioavailability to earthworms of aged DDT, DDE, DDD, and dieldrin in soil. Environ. Sci. Technol. 2000, 34, 709–713. Landrum, P. F.; Robinson, S. D.; Gossiaux, D. C.; You, J.; Lydy, M. J.; Mitra, S.; Ten Hulscher, T. E. M. Predicting bioavailability of sediment-associated organic contaminants for Diporeia spp. and Oligochaetes. Environ. Sci. Technol. 2007, 41, 6442–6447. Cornelissen, G.; Rigterink, H.; TenHulscher, D. E. M.; Vrind, B. A.; VanNoort, P. C. M. A simple Tenax extraction method to determine the availability of sediment-sorbed organic compounds. Environ. Toxicol. Chem. 2001, 20, 706–711. Kukkonen, J. V. K.; Landrum, P. F.; Mitra, S.; Gossiaux, D. C.; Gunnarsson, J.; Weston, D. The role of desorption for describing the bioavailability of select polycyclic aromatic hydrocarbon and polychlorinated biphenyl congeners for seven laboratoryspiked sediments. Environ. Toxicol. Chem. 2004, 23, 1842–1851. Van Noort, P. C. M.; Cornelissen, G.; Ten Hulscher, T. E. M.; Belfoid, A. Influence of sorbate planarity on the magnitude of rapidly desorbing fractions of organic compounds in sediment. Environ. Toxicol. Chem. 2002, 21, 2326–2330. Moermond, C. T. A.; Zwolsman, J. J. G.; Koelmans, A. A. Black carbon and ecological factors affect in situ biota to sediment accumulation factors for hydrophobic organic compounds in flood plain lakes. Environ. Sci. Technol. 2005, 39, 3101–3109. You, J.; Landrum, P. F.; Lydy, M. J. Comparison of chemical approaches for assessing bioavailability of sediment-associated contaminants. Environ. Sci. Technol. 2006, 40, 6348–6353. Moermond, C. T. A.; Roessink, I.; Jonker, M. T. O.; Meijer, T.; Koelmans, A. A. Impact of polychlorinated biphenyl and polycyclic aromatic hydrocarbon sequestration in sediment on bioaccumulation in aquatic food webs. Environ. Toxicol. Chem. 2007, 26, 607–615. Xu, Y. P.; Gan, J.; Wang, Z. J.; Spurlock, F. Effect of aging on desorption kinetics of sediment-associated pyrethroids. Environ. Toxicol. Chem. 2008, 27 (6), 1293–1301. Mayer, P.; Vaes, W. H. J.; Wijnker, F.; Legierse, K. C. H. M.; Kraaij, R. H.; Tolls, J.; Hermens, J. L. M. Sensing dissolved sediment porewater concentrations of persistent and bioaccumulative pollutants using disposable solid-phase microextraction fibers. Environ. Sci. Technol. 2000, 34, 5177–5183. Ter Laak, T. L.; Barendregt, A.; Hermens, J. L. M. Freely dissolved pore water concentrations and sorption coefficients of PAHs in spiked, aged, and field-contaminated soils. Environ. Sci. Technol. 2006, 40, 2184–2190.
(24) Hunter, W.; Xu, Y. P.; Spurlock, F.; Gan, J. Using disposable polydimethylsiloxane fibers to assess the bioavailability of permethrin in sediment. Environ. Toxicol. Chem. 2008, 27, 568– 575. (25) Yang, W. C.; Hunter, W.; Spurlock, F.; Gan, J. Bioavailability of permethrin and cyfluthrin in surface waters with low levels of dissolved organic matter. J. Environ. Qual. 2007, 36, 1678–1685. (26) Cornelissen, G.; Van Noort, P. C. M.; Govers, H. A. J. Desorption kinetics of chlorobenzenes, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls: Sediment extraction with Tenax and effects of contact time and solute hydrophobicity. Environ. Toxicol. Chem. 1997, 16, 1351–1357. (27) Cuypers, C.; Pancras, T.; Grotenhuis, T.; Rulkens, W. The estimation of PAH bioavailability in contaminated sediments using hydroxypropyl-beta-cyclodextrin and Triton X-100 extraction techniques. Chemosphere 2002, 46, 1235–1245. (28) Shor, L. M.; Rockne, K. J.; Taghon, G. L.; Young, L. Y.; Kosson, D. S. Desorption kinetics for field-aged polycyclic aromatic hydrocarbons from sediments. Environ. Sci. Technol. 2003, 37, 1535–1544.
(29) Jonker, M. T. O.; Van Der Heijden, S. A.; Kreitinger, J. P.; Hawthorne, S. B. Predicting PAH bioaccumulation and toxicity in earthworms exposed to manufactured gas plant soils with solid-phase microextraction. Environ. Sci. Technol. 2007, 41, 7472–7478. (30) Yang, W. C.; Spurlock, F.; Liu, W. P.; Gan, J. Y. Effects of dissolved organic matter on permethrin bioavailability to Daphnia species. J. Agric. Food. Chem. 2006, 54, 3967–3972. (31) Reid, B. J.; Stokes, J. D.; Jones, K. C.; Semple, K. T. Nonexhaustive cyclodextrin-based extraction technique for the evaluation of PAH bioavailability. Environ. Sci. Technol. 2000, 34, 3174– 3179. (32) Rhodes, A. H.; Carlin, A.; Semple, K. T. Impact of black carbon in the extraction and mineralization of phenanthrene in soil. Environ. Sci. Technol. 2008, 42, 740–745. (33) Tang, J. X.; Alexander, M. Mild extractability and bioavailability of polycyclic aromatic hydrocarbons in soil. Environ. Toxicol. Chem. 1999, 18, 2711–2714.
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