Title: Sorption and metabolism of 17ß-estradiol-17-sulfate in sterilized soil-water systems Authors
|Bai, Xuelian -|
|Casey, Francis -|
|Desutter, Thomas -|
|Oduor, Peter -|
|Khan, Eakalak -|
Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 16, 2014
Publication Date: N/A
Interpretive Summary: Endocrine disrupting estrogens are commonly found in lake, river, and well waters. Farm animals and wildlife typically eliminate estrogens as non-toxic, water-soluble conjugates, not as the parent estrogen. Our research has investigated how and why the parent estrogens appear in surface and groundwaters when they are excreted mainly as conjugates. We previously demonstrated that estrogen conjugates dissolved in water were transported through soil, and a measurable amount was eventually converted back to parent (unconjugated) estrogens. For this study, we hypothesized that microbes and a healthy microbial environment were necessary before this conversion could occur in soil. Using soils devoid of microbial activity we demonstrated that active microbial populations were not an important factor in the conversion of estrogen-conjugates to parent estrogens. Instead, we learned that this transformation of estrogen conjugates in soil/water systems might involve soil minerals to promote this reaction. Our findings suggested that the transport of unconjugated estrogens derived from estrogen conjugates into ground or surface waters would occur to the same degree in most soil types regardless of the biological activity or organic matter content. Eliminating the introduction of estrogens into the environment from animal wastes would necessitate their destruction prior to manure field application.
Technical Abstract: Significant amounts of manure-borne estrogens are eliminated as conjugates, which can be hydrolyzed in the environment to release endocrine disrupting free estrogens. Compared to other estrogen conjugates, 17ß-estradiol-17-sulfate (E2-17S) is more stable and persistent in manure storage systems and in manure-applied agricultural fields. In this study, batch experiments were conducted on sterilized, agricultural topsoil (0–6 cm) and subsoil (18–24 cm) to investigate the dissipation, sorption, and degradation of radiolabeled E2-17S. The aqueous phase dissipation half-lives (DT50) for E2-17S ranged from 2.5 to 9.3 h for the topsoil, but ~80% of the applied E2-17S dose remained in the subsoil at the conclusion of the experiments. Non-linear sorption isotherms of E2-17S indicated limited sorption. The concentration-dependent log KOC values were 2.20 and 2.45 for the topsoil and subsoil, respectively. Additionally, E2-17S was transformed by hydroxylation in the aqueous phase, which, represented 9-25% and 6-7% of applied dose in the topsoil and subsoil, respectively, at the end of the batch experiments. Free estrogens (17ß-estradiol and estrone) were only detected in the sorbed phase. These results demonstrated that E2-17S underwent complex metabolic pathways under abiotic conditions; and that sorption and hydroxylation were the predominant processes governing the aqueous dissipation of E2-17S.