Stereoselective Degradation of Estradiol and Trenbolone Isomers in Alluvial Sediment.

Stereoisomers of estradiol (E2) or trenbolone (TB) can occur together in the environment receiving human or livestock wastes. However, the effect of their co-occurrence on persistence has not been well elucidated. A sandy and a silt loam sediment were used to establish microcosms with α- and β-isomers of E2 or TB spiked individually and together. Sediments were sampled periodically and analyzed for E2 and TB isomers and their transformation products using derivatization gas chromatography-mass spectrometry. Results showed that stereoselective degradation was significant for E2 in both sediments and TB in the sandy sediment with β-isomers decaying more rapidly than α-isomers. In the sandy sediment containing limited natural organic carbon and nutrients, co-occurrence of both isomers of either E2 or TB decreased the dissipation rates. In the silt loam sediment with abundant organic matter and nutrients, the decay rates of both isomers were not changed in the presence of the other isomer. Estrone (E1) and trendione (TD) were detected as primary metabolites of E2 and TB isomers, respectively. The formation and decay profiles of E1 were similar in both sediments with 92-100% of E2 transformed to E1. The TD profiles were different across sediments with ∼100% of TB transformed to TD except in the sandy sediment where 51-60% of 17α-TB was converted to TD. These results indicate that the transformation processes of steroid hormone are stereoselective in sediment and co-occurrence of stereoisomers can prolong steroid persistence and thus pose greater environmental risk.