Technical Abstract: Sulfonamides (SAs) are one of the broadly used antibiotics in domestic animal operations and have a notable potential of entering the environment through animal manure management practices. In this study, sulfamethazine (SMZ) was used as a prototype to study the sorption, fate, and transport of SAs in soil-water systems using batch and miscible-displacement experiments. Sulfamethazine was degraded to two polar metabolites (PM1 and PM2), both of which were detected in column effluent and soil column extracts. The batch experiments indicated that the linear sorption partitioning coefficient (Kd) values for PM1 ranged from 7.5 to 206.2 L kg-1. Strong relationships between the sorption of PM1 and various soil fractions and organic matter were also observed. The miscible-displacement experiments showed that 33-70% of SMZ was degraded within 6 h during transport in the soil columns. Also, 69-99.7% of SMZ and PM1 and PM2 were recovered in the effluents suggesting their high mobility. Also, the simultaneous degradation, sorption, and transport of SMZ and PM were described using a two-site chemical nonequilibrium fate and transport model, using the Kd values obtained from the batch experiments. The parameters of this model were uniquely estimated using a global optimization strategy, the stochastic ranking evolutionary strategy.