Sorption and degradation of 17ß-estradiol-17-sulfate in sterilized soil-water systems.

To identify abiotic processes that govern the fate of a sulfate conjugated estrogen, 17ß-estradiol-17-sulfate (E2-17S), soil batch experiments were conducted to investigate the dissipation, sorption, and degradation of radiolabeled E2-17S under sterilized conditions. The aqueous dissipation half-lives (DT50) for E2-17S ranged from 2.5 to 9.3h for the topsoil of high organic carbon (OC) content (1.29%), but E2-17S remained at ∼80% of applied dose in the low OC (0.26%) subsoil by 14 d. The non-linear sorption isotherms indicated limited sorption of E2-17S, and the concentration-dependent log KOC values were 2.20 and 2.45 for the topsoil and subsoil, respectively. Additionally, two types of hydroxyl E2-17S (OH-E2-17S and diOH-E2-17S) were found as major metabolites in the aqueous phase, which represented 9-25% and 6-7% of applied dose for the topsoil and subsoil at 14 d, respectively. Free estrogens, 17ß-estradiol (E2) and estrone (E1), were detected from the sorbed phase of the soil-water systems.

Dissipation and transformation of 17ß-estradiol-17-sulfate in soil-water systems.

In the environment, estrogen conjugates can be precursors to the endocrine-disrupting free estrogens, 17ß-estradiol (E2) and estrone (E1). Compared to other estrogen conjugates, 17ß-estradiol-17-sulfate (E2-17S) is detected at relatively high concentrations and frequencies in animal manure and surface runoff from fields receiving manure. To elucidate the lifecycle of manure-borne estrogens and their conjugates in the environment, the fate of radiolabelled E2-17S in agricultural soils was investigated using laboratory batch studies with soils of different organic carbon (OC) content (1.29% for topsoil versus 0.26% for subsoil). E2-17S was found relatively persistent in the aqueous phase throughout the duration of the 14 d experiment. The aqueous E2-17S persisted longer in the subsoil (half-lives (DT50)=64-173 h) than the topsoil (DT50=4.9-26 h), and the aqueous persistence of E2-17S depended on its initial concentration. The major transformation pathway was hydroxylation, yielding mono- and di-hydroxy-E2-17S (OH-E2-17S and diOH-E2-17S). Free estrogens, E2 and E1, were only observed in the sorbed phase of the soil at low concentrations (∼1% of applied dose), which demonstrated that deconjugation and subsequent oxidation had occurred. Although deconjugation was not a major pathway, E2-17S could be a precursor of free estrogens in the environment.

Effects of field-manure applications on stratified 17ß-estradiol concentrations.

The occurrence of the manure-borne estrogen, 17ß-estradiol (E2), was investigated in laboratory and field soils. In the laboratory, E2 was applied to soil to simulate concentrations found in swine (Sus scrofa domestica) manure (5000ngL(-1)). The aqueous-extracted E2 dissipated in the soil by 98% within 1h and was not significantly different from background concentrations (18ng L(-1)) for the duration of the experiment (64h). In the field study, soil cores were taken before and several dates after swine manure application. Equivalent porewater concentrations of water-extractable E2 were determined in 0.15-m increments down to the water table (0.70-2.00m deep). The average frequency of detection for 168 samples was 38% (average=40ng L(-1) porewater equivalents). Eleven days after manure application there was no significant effect on E2 detection frequency or concentration. However, E2 concentrations significantly increased by 6 months after manure application, and appeared to be related to precipitation. Concentrations then returned to original levels by 17 months after manure application. Manure did not have an immediate effect on E2 occurrence due to the capacity of the soil to rapidly sorb E2. However, it appears that soil may act as a long-term reservoir for E2 in the environment, which may be periodically released through desorption.