Sorption and Dissipation of Testosterone, Estrogens, and Their

Aug 8, 2003 - Department of Agronomy and School of Civil Engineering, Purdue University, West Lafayette, Indiana 47907 ... transport, metabolism, bind...
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Environ. Sci. Technol. 2003, 37, 4098-4105

Sorption and Dissipation of Testosterone, Estrogens, and Their Primary Transformation Products in Soils and Sediment L I N D A S . L E E , * ,† T R O Y J . S T R O C K , † A J I T K . S A R M A H , †,‡,§ A N D P . S U R E S H C . R A O †,‡ Department of Agronomy and School of Civil Engineering, Purdue University, West Lafayette, Indiana 47907

Concern over the potential negative ecological effects of steroid hormones from human- and animal-derived wastes has resulted in an increased interest regarding the mobility and persistence of these compounds in the environment. Batch experiments were conducted to examine the simultaneous sorption and dissipation of three reproductive hormones (testosterone, 17β-estradiol, and 17Rethynyl estradiol) in four midwestern U. S. soils and one freshwater sediment. Sorption isotherms were generated by measuring aqueous concentrations and by extracting the sorbed parent chemical or transformation products (e.g., estrone, androstenedione). Apparent sorption equilibrium is reached within a few hours. Measured sorption isotherms for the three parent chemicals and their principal transformation products were generally linear. Average organic carbon normalized sorption coefficients (Koc) resulted in standard deviations of less than 0.2 log units and were consistent with reported aqueous solubilites and octanol-water partition coefficients, indicating hydrophobic partitioning as the dominant sorption mechanism. Large log Koc values (≈3-4) suggest that leaching from soils will be limited, runoff of soil- and land-applied biosolids are the most likely inputs into surface waters, and that a significant fraction of these compounds will be associated with sediments. Half-lives for hormone dissipation in the aerobic soil and sediment slurries estimated assuming pseudo firstorder processes ranged from a few hours to a few days with testosterone having the shortest half-life.

Introduction The detection of natural and synthetic estrogens and androgens in surface waters (1-7) has sparked an interest in the research community and the general public about the potential adverse ecological effects (e.g., endocrine disruption) of these chemicals. Endocrine-disrupting chemicals (EDCs) have been defined as “exogenous agents that interfere with the production, release, transport, metabolism, binding, action, or elimination of the natural hormones in the body [of a human and/or wildlife species] responsible for the * Corresponding author phone: (765)494-8612; fax: (765)496-2926; e-mail: [email protected]. † Department of Agronomy. ‡ School of Civil Engineering. § Current address: Landcare Research NZ Ltd., Private Bag 3127, Hamilton, New Zealand. 4098

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maintenance of homeostasis and the regulation of developmental processes” (8). Research interest in this area was originally stimulated by discovery of chemicals that produced biological responses similar to those of ovarian estrogens (e.g., estradiol), but now includes chemicals with androgenic or anti-androgenic properties as well (9). Exposure to environmental estrogens has been linked to decreased sperm counts, increased testicular, prostate, and breast cancer, and to reproductive disorders in human males (10). Much of the concern with EDCs has focused on industrial or agricultural chemicals; however, relatively large amounts of natural and synthetic reproductive hormones can be introduced into various environmental compartments via several pathways. In addition to the sewage treatment plant (STP) effluent outfalls, large amounts of animal wastes and biosolids applied to agricultural fields might run off into nearby bodies of water or infiltrate through the soil into groundwater. Cattle and poultry manure have been reported as a source of the environmental loadings of 17β-estradiol, testosterone, and trenbolone (10-14). Naturally occurring estrogens include 17β-estradiol (often shortened to “estradiol”) and its most common metabolite and/or precursors: estrone and estriol. Compared to estradiol, the relative potency of estrone and estriol can be 5 and 1000 times smaller depending on the biological assay used (15-18). Synthetic estrogens of interest include 17R-ethynyl estradiol, mestranol, and diethylstilbestrol, which may have higher estrogenic activity than their natural analogues. For example, 17R-ethynyl estradiol has a potency factor of 1.2 relative to 17β-estradiol (15). Although the study of natural and synthetic estrogens and estrogen mimics has received considerable attention, much less effort has been directed at studying the potential endocrine-disrupting effects of androgens such as testosterone and chemical androgen receptor agonists or antagonists. Testosterone is an endogenous steroid hormone that plays an important role in preand post-natal development, sexual differentiation, and normal endocrine function of vertebrates (19). Much of the current research on reproductive hormones is focused on one of three aspects: (1) ecological and human toxicological studies of a broad range of chemicals to identify potential EDCs; (2) new analytical techniques for detecting trace levels (ppb and ppt levels) of potential EDCs in environmental matrixes; and (3) field-monitoring studies attempting to link land application of biosolids, such as manure or sewage sludge, with the presence of reproductive hormones in surface waters. Of the latter, most work has focused on measuring concentrations of either or both estradiol and testosterone in runoff from agricultural fields to which poultry litter had been applied (12, 20-22). In all these studies, significant amounts of 17β-estradiol and/or testosterone were observed in runoff or drainage waters. Finlay-Moore et al. (12), in a field study of a cattle-grazed grassland amended with poultry litter, used an enzyme-linked immunosorbent assay (ELISA) to estimate 17β-estradiol and testosterone concentrations in both runoff water and soil. Runoff concentrations of estradiol and testosterone ranged between 20 and 2330 ng L-1 and 10 to 1830 ng L-1, respectively. After poultry litter application, soil concentrations of estradiol and testosterone were as high as 675 ng kg-1 and 165 ng kg-1, respectively. In the presence of grazing cattle, the presence of grazing cattle did increase levels of testosterone compared to that of control fields (12). The interaction of reproductive hormones with soils and sediments will impact their entry into aquatic systems and their subsequent fate, of which little has been published. Lai 10.1021/es020998t CCC: $25.00

 2003 American Chemical Society Published on Web 08/08/2003

TABLE 1. Properties of Estrogens and Androgens

a Cited by Lai et al. (23). b Sugaya et al. (36). c Calculated by Nuez and Yalkowsky (37). R-cyclodextrin (38). e Measured at 37 °C (39). f Suzuki et al. (40). g Not available.

et al. (23) estimated sorption of 17b-estradiol, estrone, estriol, 17a-ethynyl estradiol, and mestranol onto sediments from the United Kingdom. Larsen et al. (24) evaluated sorption and mobility of 17β-estradiol and testosterone in two soils, a Glyndon silt loam (a Mollisol with 2-3% organic carbon) and a sand. Neither hormone was eluted from the silt loam column after leaching with more than 10 pore volumes of water with 80% and 96% of applied testosterone and 17βestradiol, respectively, retained within the top 5 cm. In the sand column, approximately 90% of both compounds were eluted within two pore volumes. In both studies sorption increased (23) and mobility decreased (24) with increasing organic carbon (OC) content, consistent with hydrophobic sorption mechanisms. With regard to dissipation in soils, Colucci et al. (25, 26) reported dissipation rates between 0.1 and 3 d-1 for 17β-estradiol and 17R-ethynyl estradiol in three agricultural soils from Ontario. In this study, we employed batch equilibration techniques to examine sorption of testosterone by four soils and one freshwater sediment from the midwestern United States as well as 17β-estradiol and 17R-ethynyl estradiol on a subset of these sorbents. After equilibration, the soil and aqueous

d

Solubility from a control tablet comprising estriol and

phases were each extracted and the hormones and transformation products produced were quantified for each phase. This approach allows (1) the construction of isotherms that represent the reversible sorption processes for the parent chemicals and the major transformation byproducts formed during the equilibration period, and (2) initial estimates of parent compound half-lives.

Materials and Methods Chemicals. Testosterone, androstenedione, and 17β-estradiol at >98% purity, and estrone and estriol at >99% purity were obtained from Sigma Chemical, St. Louis, MO. 17R-Ethynyl estradiol at > 98% purity was obtained from Aldrich Sigma Chemical Company, St. Louis, MO. Selected chemical properties are shown in Table 1. Acetonitrile and methanol (Mallinckrodt, Chrom AR HPLC, Phillipsburg, NJ), dichloromethane (Fisher Scientific, Pittsburgh, PA), and calcium chloride dihydrate (CaCl2‚2H2O) (Mallinckrodt) were of greater than 99% purity. Soils. Four soils and one sediment previously used in several other studies and representing a range in texture, pH, and cation exchange capacity (CEC) (Table 2) were VOL. 37, NO. 18, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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TABLE 2. Selected Properties of Soils soil

pH (1:2 H2O)

OC (%)

clay (%)

sand (%)

silt (%)

CEC (cmolc kg-1)

EPA1a EPA14a Bloomfieldb Drummer(1)b Drummer(7)c Torontob

7.3 4.3 6.4 7.2 6.9 4.4

0.22 0.48 0.36 2.91 2.39 1.3

6 64 8 21 ND 20

94 2 81 13 ND 12

0 34 11 66 ND 68

1.1 18.9 4.4 26.5 ND 11

a Means et al. (28). b Li and Lee (27) sampled in 1994. c Sampled in 1998 from the same field as Drummer(1).

selected. Bloomfield, Toronto, and Drummer soils are surface soils from Indiana (27), EPA 14 is a soil from an eroded hillside in southeast Ohio (28), and EPA1 is a freshwater sediment from the Mississippi River north of Monticello, MN (28). Soils had been air-dried, gently crushed to pass a 2-mm sieve, thoroughly mixed, and stored in closed containers at room temperature prior to use. Soil characterization methods are detailed in Li and Lee (27), Lee et al. (29), and Means et al. (28). Sorption Studies. A batch-equilibration method, similar to that described by Li and Lee (1999), was used to measure sorption of 17β-estradiol, 17R-ethynyl estradiol, and testosterone by soils and sediment from aqueous CaCl2 solutions (0.005 M). Sorption isotherms of the parent compounds were measured using at least five initial solution concentrations in duplicate or triplicate ranging from 0.5 to 6.2 mg L-1 for 17β-estradiol, from 1.0 to 5 mg L-1 for 17R-ethynyl estradiol, and from 0.7 to 11 mg L-1 for testosterone. Applied concentrations were selected to ensure a concentration range above the limits of quantification in the solution and sorbed phases for both the parent compounds and expected metabolites. Equilibration times for the sorption isotherms were 24-31, 72, and 42 h for testosterone, 17β-estradiol, and 17R-ethynyl estradiol, respectively. On a subset of soils with 2 or 3 initial solution concentrations in duplicate, sorption and transformation of 17β-estradiol and testosterone were measured over a 4-72 h time frame. Glass centrifuge tubes (40 mL) equipped with Teflon-lined screw-caps were used for all studies. Soil mass (g) to solution volume (mL) ratios were optimized for measuring solution and sorbed concentrations and ranged from 1:35 to 3:35 for the different solutesoil combinations. Soils were weighed into preweighed tubes, single hormone solutions were added, and tubes were capped with Teflon-lined screw caps. Tubes were covered with aluminum foil to minimize photolysis and mixed on an endover-end rotary shaker (30 rpm) at room temperature (22 ( 2 °C). At each sampling time, solution and soil phases in selected tubes were analyzed for hormone concentrations. Sample tubes were centrifuged at 1750g for 30 min and the supernatant was removed for analysis followed by extraction of the soil. Solution residual present in the soil prior to extraction was determined gravimetrically and solute concentration in the residual solution was assumed to be the same as that measured in the bulk supernatant. All experiments included analysis of the hormone concentration in the 0.005 M CaCl2 solution containing no soil (controls) at each sampling time, along with 0.005 M CaCl2 solutions equilibrated with and without soils. Standard deviation of solute concentrations in controls containing no soils was less than 5% for averaged initial concentrations during the various time periods. Both aliquots of the supernatant and the soil after supernatant removal were extracted using dichloromethane (DCM). The supernatant (12-25-mL aliquots) was extracted with 3-5 mL of DCM and the soil was extracted with 5-30 mL of DCM. In both cases, a solvent exchange and 4100

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concentration step was performed by taking known aliquots of DCM, evaporating off the DCM, and redissolving the residual precipitates in methanol for the estrogens and 50: 50 v/v methanol/acetonitrile for testosterone. Solutions were then analyzed using an automated Shimadzu high-performance liquid chromatography (HPLC) system equipped with a UV detector (SPD-10A; λ ) 205, 280, and 245 nm for 17βestradiol, 17R-ethynyl estradiol, and testosterone, respectively), 3-cm C-18 guard column, and a Luna end-capped (C18) reversed-phase column (4.6 × 150 mm, 5µm particles; Phenomenex, Torrance, CA). Injection volumes were 25 µL and the mobile phase was acetonitrile/water at volume ratios of 45/55, 50/50, and 60/40 for 17β-estradiol, 17R-ethynyl estradiol, and testosterone, respectively, and a flow rate of either 1.0 or 1.5 mL min-1 (22 ( 2 °C). Retention times were as follows: 6.7 min for 17β-estradiol and 5.6 min for 17Rethynyl estradiol with a flow rate of 1.5 mL min-1, and 4.4 min for testosterone at a flow rate of 1 mL min-1. External calibration curves were generated to estimate sample concentrations from peak areas and were linear between 10 ug/L and 10 mg/L. Practical on-column limit of quantification (LOQ) was approximately 0.005 mg/L. However, up to a 10fold increase in the LOQ of soil and solution extracts from the sorption studies was achieved from the extraction and concentration steps, thus aqueous-phase and sorbed phase concentrations as low as 5 × 10-4 mg/L and 0.01 mg/kg, respectively, were quantifiable.

Results and Discussion Product Identification and Percent Recoveries. In the estradiol sorption studies with Drummer and EPA1 soils, a major transformation product peak was observed between 10.1 and 10.3 min, which was confirmed to be estrone by matching retention times with an estrone standard as well by post-derivatization GC/MS analysis. In the testosterone sorption studies with all soils, a major chromatographic peak was observed at 3.9 min, which was confirmed to be androstenedione by matching retention times with an androstenedione standard and by LC/MS. A second smaller chromatographic peak was observed at 3.4 min in extracts from the EPA14 and Toronto soils, which we hypothesize to be androsta-4-ene-3-one-16,17-diol; however, no confirmation was made. Concentrations for the compound that eluted at 3.4 min were estimated using the standard curve for the parent compound testosterone. Estrone and androstenedione external standard curves were shown to be nearly identical to those generated for the parent compounds; therefore, assuming the 3.4 min peak has a UV response similar to that of the parent seemed reasonable. The percent recovery of the parent compound and total recovery including quantified transformation products are summarized in Table 3. For 17β-estradiol, percent recoveries are detailed for various equilibration times. For the EPA1 sediment after 12 h of equilibration before significant transformation had occurred essentially all the parent compound was recovered (102% ( 12%). With increasingly longer equilibration, 17β-estradiol recovery decreased, but total recovery of 17β-estradiol and estrone was still high. 17β-estradiol recoveries from the higher organic carbon Drummer soil were much lower (5-18%); however, inclusion of estrone increased recoveries to as much as 77%. Compound mass not recovered may exist as other transformation products or be irreversibly bound to the soil. Colucci et al. (25) reported that only 9-44% of the radiolabel was extractable in microbe-active agricultural soil microcosms with 14Clabeled 17β-estradiol. In autoclaved systems transformation of 14C-labeled 17β-estradiol still occurred with 60-95% of the radiolabel extractable primarily as estrone. Similar to estradiol recoveries, percent recoveries in the testosterone sorption studies increased when androstene-

TABLE 3. Summary of the Parent Compound Recovery (Average ( Standard Deviation) and Total % Recovery (Average ( Standard Deviation) of Parent Plus Quantified Transformation Products

solute/soil

contact time (h)

EPA1 EPA1 EPA1 Drummer(1) Drummer(1) Drummer(1)

12 24-48 72 12 24-48 72

recovery parent compound (%)

17β-Estradiola 102 ( 12 85 ( 9 72 ( 6 18 ( 4 14 ( 1 10 ( 3

EPA1 Bloomfield Drummer(1)

17r-Ethynyl Estradiol 42 71 ( 7 42 65 ( 5 42 55 ( 2

EPA1 EPA14 Bloomfield Toronto Drummer(7)

24 28 31 31 28

total recovery parent + products (%) 102 ( 12 93 ( 8 NDb 77 ( 2 60 ( 3 NDb ND ND ND

Testosteronec 83 ( 6 (72-91)d 84 ( 6 (72-96) 77 ( 8 (64-95) 78 ( 9 (65-95) 90 ( 10 (72-98) 97 ( 8 (90-104) 41 ( 31 (4-81) 92 ( 3 (87-96) 23 ( 7 (14-34) 37 ( 9 (25-50)

a Transformation products include estrone. b Transformation products not determined. c Transformation products include androstenedione and the unidentified 3.3 min HPLC peak. d Range in recovery range from low to high applied concentration.

FIGURE 1. Testosterone recovery (%) and total recovery (%) including transformation products for Toronto soil as a function of initial testosterone concentration applied. dione and the unknown transformation product were included (Figure 1). Contribution of transformation products to the total recovery was within a few percent for all soils except the Toronto soil where a large fraction of testosterone converted to androstenedione. For testosterone, % recovery also increased with increasing initial concentrations as detailed in Table 3. The greatest effect was observed for the Toronto soil where testosterone recovery ranged from 4 to 81% from the lowest to highest applied concentration. However, recoveries increased to greater than 90% with inclusion of androstenedione over the entire range of applied concentrations. In general, relative total recoveries were high for all soils and the sediment. Sorption Isotherms. Sorption isotherms for the parent compounds and transformation products produced during parent compound equilibration were constructed from directly measured sorbed (Cs, µg/g) and solution (Cw, µg/ mL) concentrations. Representative sorption isotherms are shown for testosterone, androstenedione, and the unidentified transformation product observed at the 3.4 min HPLC retention time in Figures 2 and 3; for 17β-estradiol and estrone

TABLE 4. Summary of Sorption Parameters for Multiple-Concentration Isotherms solute/soil EPA1 Drummer(1) average log Koc (SD)a

Kd (L kg-1) 17β-Estradiol 3.56 83.2b

17r-Ethynyl Estradiol EPA1 2.33 Bloomfield 3.91 Drummer(1) 23.4c average log Koc (SD) EPA1 EPA14 Bloomfield Drummer(7) Toronto average log Koc (SD)

Testosterone 4.57 16.0 7.20 42.7d 27.3

Log Koc

R2

3.21 3.46 3.34 (0.18)

0.98 0.90

3.02 3.04 2.91 2.99 (0.07)

0.87 0.88 0.94

3.32 3.52 3.30 3.25 3.32 3.34 (0.10)

0.97 0.96 0.96 0.88 0.98

a SD, standard deviation from averaging log K oc values, given in parentheses. b Freundlich fit: Kf ) 43.4 µg1-N mLN g-1; N ) 0.74; R2 ) c 1N N -1 mL g ; N ) 0.77; R2 ) 1.00. 0.96. Freundlich fit: Kf ) 24 µg d Freundlich fit: K ) 59.1 µg1-N mLN g-1; N ) 0.62; R2 ) 0.98. f

in Figure 4; and for 17R-ethynyl estradiol in Figure 5. Estrone sorption isotherms shown in Figure 4B were constructed using only the data from the 17β-estradiol sorption study where two initial concentrations were applied and measured in both solution and sorbed phases at 12, 24, and 48 h. Chromatographic run times for the 72 and 42 h multipleconcentration sorption isotherms for 17β-estradiol and 17Rethynyl estradiol, respectively, were set too short to capture the peak for estrone. For androstenedione and the unknown transformation product (3.4 min retention time), data plotted are from both the multi-concentration 24-31 h isotherms and sorption measured at multiple times from 3 concentrations of testosterone. Chromatographic peaks at 3.4 min were not observed with the EPA1 sediment or the EPA14 or Toronto soils. Detection of the chromatographic peak for androstenedione formed in the testosterone-EPA14 slurry was sporadic; therefore, androstenedione sorption isotherms could not be generated. In most soil-solute combinations, sorption isotherms for the parent compounds and transformation products were reasonable fit with a zero-intercept linear regression model, which allowed the estimation of OC-normalized partition coefficients (Koc, L kg-1 OC) from linear soil-water distribution coefficients (Kd, L kg-1 soil). Kd and log Koc values, along with average log Koc values and associated standard deviations, are summarized for the parent compounds in Tables 4 and 5, respectively. For Drummer soil, sorption isotherms for all compounds except the unknown testosterone transformation product were sufficiently nonlinear, in which case the isotherms were also fitted to the empirical Freundlich sorption model: S ) Kf CwN where Kf (µg1-N mLN g-1) is the Freundlich sorption coefficient and N (unitless) is a measure of isotherm linearity (N ) 1 is a linear isotherm). Freundlich model fits for sorption by Drummer soils are provided in the footnotes of Tables 4 and 5. Of the soils investigated, the Drummer soil has the highest OC content and the finest texture resulting in a high surface area, which may contribute to additional sorption mechanisms resulting in noticeable sorption nonlinearity. Even with the sorption nonlinearity on Drummer soil, Kf and Kd values were within a few percent for all solutes except 17β-estradiol and androstenedione. Averaging log Koc values resulted in small standard deviations (less than 0.2 log units) indicating that OC is the primary sorption domain for these hormones, similar to what we have observed for several classes of organic chemicals. Also, VOL. 37, NO. 18, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 2. Multiple-concentration sorption isotherms for testosterone from a 24-31-h contact time with Drummer along with a Freundlich model fit, and with Bloomfield, EPA14, and Toronto soils along with linear isotherm fits.

FIGURE 3. Isotherm constructed from measured sorbed and solution phase concentrations during equilibration of testosterone for (A) androstenedione (product of testosterone degradation) on Toronto, Drumm, and Bloomfield soils; and (B) an unidentified transformation product with a 3.4 min chromatographic retention time on Drummer and Bloomfield soils. the magnitude of the log Koc values is consistent with the reported estimates for aqueous solubility and log Kow (Table 1). Casey et al. (30) reported a high correlation between 17βestradiol sorption and soil surface area and cation exchange capacity (CEC), which is inconsistent with the hydrophobic theory and observations for other compounds similar to the hormones. 17β-estradiol has a phenolic group with a pKa of 10.71 (31) that will dissociate under very basic conditions 4102

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(pH > 8.7) forming an organic anion, but it will never be positively charged, which is required for cation exchange. The CEC of organic matter is high, thus soils high in organic matter such as those used by Casey et al. (30) will be high in CEC. In addition, hormone sorption in their studies was estimated by difference, i.e., mass of applied chemical not measured in the solution phase was assumed to be sorbed to the soil. This is particularly problematic for organic chemicals that undergo microbial degradation or surfacedinduced abiotic transformation. Clay and oxide surfaces (which have high surface areas) often catalyze abiotic reactions, which, if interpreted as sorption, will overestimate sorption affinity and can cause spurious correlations with soil properties. For pure clays or oxides, where surface reactivity is not hindered by associations with other soil constituents (e.g., soil organic matter coatings), the extent and rates of abiotic reactions will be greatly enhanced. The similar Freundlich sorption coefficients reported by Casey et al. (30) for 17β-estradiol on pure bentonite clay and a 7.5% organic matter loam soil is most likely a coincidence resulting from combined contribution of sorption and transformation toward the removal of the hormone from solution. Lai et al. (23) also estimated sorption by difference, but contact times were short (1 h) in order to minimize degradation. They reported a high positive correlation between sorption and OC for a series of 17β-estradiol, estrone, estriol, 17R-ethynyl estradiol, and mestranol on 5 sediments ranging in OC from 0.3% to 2.2%. Significant sorption to an iron oxide used as a representative model sediment was also reported, but this may have been an artifact of attributing to sorption mass potentially lost in oxide-catalyzed transformations. Ligand exchange of phenolic molecules to iron and aluminum oxides is also plausible (33). Sorption Kinetics. Also shown in Figure 1 are data for testosterone sorption by Bloomfield soil at three initial concentrations (1.3, 2.4, and 4.5 µg mL-1) and at multiple contact times between 4 and 60 h. Likewise, in Figure 2 are data for 17β-estradiol sorption by Drummer soil from two initial solution concentrations (≈2 and 6 µg mL-1) at shorter contact times of 12, 24, and 48 h. In both cases, the majority of sorption appears to be fast and reversible with data points measured at shorter times falling on the isotherms constructed based on data for longer equilibration times. Therefore, as the parent compound is transformed over time, rapid re-distribution of parent compound is similar to what has been observed by Li and Lee (34). Likewise, transforma-

FIGURE 4. (A) Multiple-concentration sorption isotherm with a Freundlich model fit for 17β-estradiol from a 72-h contact time with Drummer soil along with sorption measurements at shorter equilibration times with two initial concentrations; and (B) isotherms constructed for estrone (a product of 17β-estradiol degradation) from measured sorbed and solution phase concentrations during equilibration of 17βestradiol with Drummer and EPA1 soils.

TABLE 5. Summary of Sorption Parameters for Transformation Products Formed in Multiple-Concentration Isotherms of the Parent Compounds 17β-Estradiol or Testosterone Kd (L kg-1)

solute/soil EPA1 Drummer(1) average log Koc (SD)a

FIGURE 5. Multiple-concentration sorption isotherms (42-h contact time) for 17r-ethynyl estradiol along with the Freundlich model fit for Drummer soil and linear model fits for the Bloomfield and EPA1 soils. tion products are rapidly distributed between the soil and solution phases resulting in isotherms with Koc values consistent with hydrophobic theory similar to that of the parent compounds. In the absence of a direct analysis of both sorbed and solution phases, changes in solution concentration caused by degradation or transformation may be misinterpreted as sorption kinetics. Dissipation Half-Lives. Half-lives (t1/2, d) for the dissipation of the parent compounds in these aerobic soil-water slurries were estimated assuming psuedo-first-order dissipation processes. For two solute-soil combinations, a sufficient number of data points were available to estimate

Toronto Bloomfield Drummer(7) average log Koc (SD) Bloomfield Drummer(7) average log Koc (SD)

Estroneb 3.40 48.1d Androstenedionec 77.3 19.3 142e

Log Koc

R2

3.19 3.22 3.20 (0.02)

0.92 0.87

3.77 3.69 3.69 3.72 (0.05)

0.81 0.91 0.73

Unknown Productc 3.91 3.00 17.1 2.77 2.88 (0.16)

0.87 0.99

a SD, standard deviation from averaging log K oc values, given in parentheses. b From 17β-estradiol-soil equilibration. c From testosterd one-soil equilibration. Freundlich fit: Kf ) 44.8 µg1-N mLN g-1; N ) 0.65; R2 ) 0.968. e Freundlich fit: Kf ) 27.9 µg1-N mLN g-1; N ) 0.51; R2 ) 0.98.

the psuedo-first-order rate constant (k) from a linear regression of ln(Mt/Mi) versus time, where Mi and Mt are the parent compound mass at time zero (applied) and at some later VOL. 37, NO. 18, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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TABLE 6. Summary of Estimated Dissipation Half-Lives (t1/2, d) in Soil-Water Slurries range in t1/2 (d)

soil 17β-Estradiol

4.5-9.7 (6.4a) 0.8-1.1

EPA1 Drummer(1)

17r-Ethynyl Estradiol EPA1 Bloomfield Drummer(1)

4.1-9.6 3.7-6.5 3.1-3.9 Testosterone

EPA1 EPA14 Bloomfield Drummer(2) Toronto

2.1-7.3 1.8-5.3 3.0-6.5 (5.7a) 0.4-0.8 0.3-4.1

a

t1/2 (d) value calculated from k value determined by linear regression of ln(Mt/Mi) versus time where Mi and Mt are the parent compound mass applied and at time t, respectively.

time t, respectively. For all other solute-soil combinations, t1/2 values were calculated from k values estimated from the data for fraction recovery of the parent compound measured at a specific time t as follows: k ) -[ln(Mt/Mi)]/t. Ranges in the dissipation t1/2 values estimated in this manner are summarized in Table 6. Note that the estimated t1/2 values vary from only a few hours to a few days, depending on the type and concentration of the hormone and the soil/sediment type. All hormones exhibited the longest half-lives on the EPA1 sediment, which has the highest sand and the lowest OC content of the sorbents investigated. Shorter half-lives for 17β-estradiol compared to 17R-ethynyl estradiol and the range of estimated t1/2 values observed in our aerobic soilwater slurries is consistent with what was reported by Colucci et al. (25, 26) for degradation in unsaturated agricultural soil microcosms. Environmental Implications. On the basis of the consistency of Koc values among different soils, it may be surmised that hydrophobic partitioning into organic carbon domains of soils and sediments plays a dominant role in sorption of the hormones and the associated transformation products examined here. Large Kd and Koc values indicate that a large mass fraction of the hormone will be associated with the sorbed phase. Also, sorption equilibrium was apparently achieved rapidly (within a few hours), as indicated by the time studies and the reasonable and consistent Koc values obtained for the transformation products. Our data suggest that sorption can lead to significant retardation during leaching in soils, as observed by Larsen et al. (24), minimizing the likelihood of groundwater contamination. However, strong association with the soil can increase the potential for surface runoff losses and surface-water contamination during storm events, as has been observed in field experiments (12). Also, preferential flow of solutes, even those with large Kd values, can cause them to be rapidly transported to subsurface tile drains in agricultural fields and serve as input sources to ditches and streams (35). To assess hormone loads associated with suspended colloids as well as sediment, it would be advantageous for surface-water monitoring programs to periodically measure hormone concentrations in sediments in conjunction with water samples before and after filtering. Short half-lives suggest rapid transformation of the parent chemicals, at least under aerobic conditions. Considering Koc values for the transformation products are also large (same order of magnitude as the parent chemicals), their environmental-phase partitioning and transport are likely to be similar to that of the parent chemicals. Our limited data set 4104

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suggests that accumulation of the primary transformation products is soil dependent; data are not sufficient to propose any soil-property-based prediction. Further work is needed to better elucidate the role of abiotic and microbial processes as well as the effect of soil type and hormone concentration. Given the high affinity of these hormones for soils and their relatively short half-lives, the question arises as to why concentrations, albeit small, are consistently detected in aquatic systems. Two possible explanations are suggested. First, hormone degradation can be nonlinear such that rate constants decrease with diminishing concentrations. Second, with continuous input to receiving waters from either sediments or discharges, the observed concentrations may represent psuedo-steady-state conditions.

Acknowledgments This work was funded in part by the U.S. Environmental Protection Agency National Risk Management Research Laboratory (Cincinnati, OH) under Cooperative Agreement 82811901-0 and the School of Agriculture, Purdue University. A special thanks to Stephen Sassman for general laboratory assistance, analytical methods development, and MS analyses.

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Received for review October 23, 2002. Revised manuscript received June 25, 2003. Accepted June 26, 2003. ES020998T

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