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Fate and transformation of an estrogen conjugate and its metabolites in agricultural soils
- Shrestha, Suman L., Casey, Francis X. M., Hakk, Heldur, Smith, David J., Padmanabhan, G.
- Environmental science & technology 2012 v.46 no.20 pp. 11047-11053
- agricultural soils, animal production, biodegradation, chemical residues, conjugated estrogens, endocrine-disrupting chemicals, environmental fate, estrone, farms, groundwater, hydrophobicity, oxidation, secondary metabolites, soil organic matter, sorption, steroid hormones, swine, topsoil, toxicity
- Estrogens are naturally produced steroid hormones that are constantly being eliminated by many life forms, including production animals. An important form of release of estrogens is as water-soluble conjugates, which are not toxic, but may readily be hydrolyzed back to parent estrogens, which are known endocrine disruptors. To identify the fate of a conjugated estrogen in an agricultural soil, batch experiments were conducted with a prototypic estrogen conjugate, i.e. 17B-estradiol-3-glucuronide (E2-3G). While some conjugate oxidation of E2-3G to estrone-3-glucuronide (E1-3G) was observed (7-8%), the primary dissipation pathway of the conjugate was the biological hydrolysis of E2-3G and E1-3G to the estrogens 17B-estradiol (E2) and estrone (E1). Hydrophobic sorption of E2 and E1 to soil was then the dominant feature for the fate of E2-3G. Depending on soil organic matter content, E2-3G persisted for 1–14 d in the aqueous layer, which was much longer than previous studies on E2 or E1 (generally <24 h). Biodegradation rate constants of E2-3G were smaller in the low organic content subsoil (0.01–0.02 h-1) compared to high organic content topsoil (0.2–0.4 h-1). Separate field observations confirmed laboratory results in that relatively high concentrations of the conjugated E2-3G were detected in groundwater (425 ng L-1) near a swine farm that fertilizes with manure. This study provided evidence that conjugated estrogens may be a significant source of endocrine disrupting estrogens in surface and groundwater.