Triclocarban and triclosan biodegradation at field concentrations and the resulting leaching potentials in three agricultural soils

This study evaluated the leaching potential of the antimicrobials triclocarban (TCC) and triclosan (TCS) in three agricultural soils using a simple model based on biodegradation and adsorption. The antimicrobials were added to the soils at two moisture levels (10% or 15% w/w) to achieve initial concentrations of 0.05, 0.2, or 2 mg kg−1. The low concentrations (0.05, 0.2 mg kg−1) are more representative of field concentrations, important because previous studies have typically focused on higher initial concentrations. After 100 d, significant residuals of both TCC and TCS occurred under all conditions and first-order degradation half-lives indicated TCC was more resistant to biodegradation. The estimated Kd and Koc values were 193–296 L kg−1 and 18 175–33 991 L kg−1 for TCC and 33–55 L kg−1 and 3968–6310 L kg−1 for TCS. The resulting leaching models indicated these chemicals have a very low leaching potential and are thus unlikely to contaminate groundwater.