Discerning and Modeling the Fate and Transport of Testosterone in Undisturbed Soil

Authors: FAN, ZHAOSHENG - NORTH DAKOTA STATE UNIVER; CASEY, FRANCIS - NORTH DAKOTA STATE UNIV; Hakk, Heldur; Larsen, Gerald

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2007
Publication Date: 3/1/2007
Citation: Fan, Z., Casey, F.X., Hakk, H., Larsen, G.L. 2007. Discerning and Modeling the Fate and Transport of Testosterone in Undisturbed Soil. Journal of Environmental Quality 36:864-873.

Interpretive Summary: Testosterone is a hormone that is excreted into the environment naturally most extensively by male mammals in their urine and feces. As a hormone testosterone can interfere with other mammalian endocrine systems, and as such it is important to determine its fate once it is excreted. The objective of this study was to achieve a better understanding of the fate and transport of testosterone in agricultural soil to determine its impact on groundwater systems. This was accomplished using experiments where the soil and testosterone in a solution interact (termed batch experiments) and where testosterone in solution is passed over the soil in a column (termed soil column experiments). Rate of degradation of testosterone was determined using various batch experiments. Multiple computer models were used to successfully describe the results generated in the batch experiments where simultaneous degradation and sorption processes were observed. A novel computer modeling method was developed to describe these processes and parameters (e.g., fate and absorption of testosterone) from the data generated in the batch experiments. These batch parameters were then incorporated into a transport model for testosterone, which were used to describe transport of testosterone through undisturbed soil and correlated with the data observed in the soil column experiment. The final computer model resulted in the identification of individual biological (e.g., degradation) and physical (e.g., absorption and transport) processes that simultaneous described the complex fate and transport of testosterone in soil, which then could be used to simulate transport of testosterone under field conditions and provided a reasonable prediction of actual field concentrations.

Technical Abstract: Testosterone is a naturally occurring endocrine disruptor (ED) that is released into the environment from natural and anthropogenic sources. The objective of this study was to achieve a better understanding of the complex fate and transport of this labile compound in undisturbed agricultural soil. This was done using batch and miscible-displacement experiments, and a comprehensive model. Degradation and transformation processes of testosterone were discerned using various batch experiments. Multiple first-order models were used to successfully describe batch experiments where simultaneous degradation and sorption processes occurred. An evolutionary global optimization strategy was used to estimate the process parameters from these batch experiments and provided high confidence in these parameter estimates. The independently determined batch parameters were then incorporated into a solute transport model and used to describe an undisturbed soil column experiment. The final modeling result was a unique identification of individual biological (e.g., degradation) and physical (e.g., sorption and transport) processes that simultaneous combined in the complex fate and transport of testosterone in soil. The estimated parameters and process model from this study were then used to simulate transport of testosterone under field conditions and provided a reasonable prediction of actual field concentrations.