Influence of Soil Properties and Test Conditions on Sorption and Desorption of Testosterone

In this study, batch sorption and desorption experiments were conducted for testosterone using four agricultural soils and five clay minerals. Significant differences in sorption behavior were observed between abiotic and biotic systems. The Freundlich sorption coefficient K-f (mu g/g) / (mu g/mL)(n) ranged from 8.53 to 74.46 for soils and from 35.28 to 1,243 for clays. The maximum sorption capacity (mu g/g) of soils ranged from 25.25 to 440.61 for soils and from 168.46 to 499.84 for clays. Correlation of the sorption model parameters with the soil properties indicated that both clay content and soil organic matter are important variables in predicting testosterone sorption behavior. Observed testosterone desorption from agricultural soils ranged from approximately 14 to 100% after three desorption cycles, and the desorption percentage decreased as the initial testosterone concentration decreased. It was determined that the temperature, ionic strength, water/soil ratio, and soil depth influenced the sorption and desorption of testosterone. Desorption significantly increased with the soil depth (p < 0.05) and with the increase in the water/soil ratio. Temperature had an inverse effect on the sorption capacity of the soils tested. Thermodynamic calculations showed that the enthalpy change (Delta H-0) of the soils tested ranged from 12.9 to 20.7 kJ/mol, indicating a weak interaction between the testosterone and soil. The authors' results suggest that additional studies on how soil particles with different size fractions affect hormones' fate and transport are needed to determine the potential risk of testosterone leaching or runoff. (C) 2015 American Society of Civil Engineers.