文摘
Metabolites of androgenic synthetic growth promoters used at confined animal feeding operations (CAFOs) pose a demonstrated ecological risk. To evaluate the transport of trenbolone acetate (TBA) metabolites from beef cattle CAFOs, rainfall simulation experiments were conducted at the University of California, Davis, research CAFO. Steroid concentrations in solid and aqueous samples from the research CAFO and solids samples from a commercial CAFO were analyzed by gas chromatography-tandem mass spectrometry. The data indicate that 17伪-trenbolone (17伪-TBOH), 17尾-trenbolone (17尾-TBOH), and trendione (TBO), the three primary TBA metabolites, occur in soils and runoff. Soils at the research CAFO contained up to 8.2 (卤1.1) ng/g-dw of 17伪-TBOH and 1.2 (卤0.1) ng/g-dw of 17尾-TBOH, with slightly higher (20 ng/g-dw) 17伪-TBOH concentrations observed in commercial CAFO soils. In simulated runoff, 17伪-TBOH concentrations of 1鈥?50 ng/L and TBO concentrations from 1鈥?70 ng/L were observed. The metabolite 17尾-TBOH intermittently occurred in runoff samples at 5鈥?6 ng/L and may be correlated to anaerobic soils. Metabolite concentrations observed in CAFO runoff correspond to 5鈥?5% of potential maximum steroid concentrations predicted by mass balances. First order transformation rates of 0.028/day (25 day half-life) were estimated for 17伪-TBOH in CAFO soils. Results suggest that ecologically relevant concentrations of TBA metabolites can be mobilized from CAFO surfaces in storm runoff and may lead to receiving water concentrations at or above ecological effects thresholds for a very limited number of discharge scenarios.