Degradation and metabolite formation of estrogen conjugates in an agricultural soil


    loading  Checking for direct PDF access through Ovid

Abstract

Graphical abstractHighlightsExplore degradation mechanisms of both sulfate and glucuronide conjugates.Investigate the transformation metabolites by applying collision-induced dissociation mass spectrometry coupled with gas chromatography—mass spectrometry.Ring B unsaturated estrogens and their sulfate conjugates were tentative proposed as new metabolites.Estrogen conjugates are precursors of free estrogens such as 17ß-estradiol (E2) and estrone (E1), which cause potent endocrine disrupting effects on aquatic organisms. In this study, microcosm laboratory experiments were conducted at 25 °C in an agricultural soil to investigate the aerobic degradation and metabolite formation kinetics of 17ß-estradiol-3-glucuronide (E2-3G) and 17ß-estradiol-3-sulfate (E2-3S). The aerobic degradation of E2-3G and E2-3S followed first-order kinetics and the degradation rates were inversely related to their initial concentrations. The degradation of E2-3G and E2-3S was extraordinarily rapid with half of mass lost within hours. Considerable quantities of E2-3G (7.68 ng/g) and E2-3S (4.84 ng/g) were detected at the end of the 20-d experiment, particularly for high initial concentrations. The major degradation pathway of E2-3G and E2-3S was oxidation, yielding the primary metabolites 17ß-estrone-3-glucuronide and 17ß-estrone-3-sulfate, respectively. Common metabolites were E2, the second primary metabolite, and E1, the secondary metabolite. Additionally, ring B unsaturated estrogens and their sulfate conjugates were tentatively proposed as minor metabolites. The persistence of E2-3G and E2-3S (up to 20 d) suggests that the high rate of application of conjugated estrogen-containing substances could be responsible for the frequent detection of free estrogens in surface and subsurface water.

    loading  Loading Related Articles