Sorption
and Mineral-Promoted Transformation of Synthetic
Hormone Growth Promoters in Soil Systems
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Abstract
This
work examines the fate of synthetic growth promoters (trenbolone
acetate, melengestrol acetate, and zeranol) in sterilized soil systems,
focusing on their sorption to organic matter and propensity for mineral-promoted
reactions. In organic-rich soil matrices (e.g., Pahokee Peat), the
extent and reversibility of sorption did not generally correlate with
compound hydrophobicity (e.g., <i>K</i><sub>ow</sub> values),
suggesting that specific binding interactions (e.g., potentially hydrogen
bonding through C17 hydroxyl groups for the trenbolone and melengestrol
families) can also contribute to uptake. In soils with lower organic
carbon contents (1β5.9% OC), evidence supports sorption occurring
in parallel with surface reaction on inorganic mineral phases. Subsequent
experiments with pure mineral phases representative of those naturally
abundant in soil (e.g., iron, silica, and manganese oxides) suggest
that growth promoters are prone to mineral-promoted oxidation, hydrolysis,
and/or nucleophilic (e.g., H<sub>2</sub>O or OH<sup>β</sup>) addition reactions. Although reaction products remain unidentified,
this study shows that synthetic growth promoters can undergo abiotic
transformation in soil systems, a previously unidentified fate pathway
with implications for their persistence and ecosystem effects in the
subsurface