Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/18/2010
Publication Date: 6/1/2011
Citation: Fan, Z., Casey, F.X., Hakk, H., Larsen, G.L., Khan, E. 2011. Sorption, fate, and mobility of sulfonamides in soils. Water, Air, and Soil Pollution. 218(1):49-61. Interpretive Summary: Sulfonamides (SAs) are one of the most commonly used veterinary antibiotics. Sulfonamides have relatively high polarity and water solubility, which results in weak sorption affinity to soil particles and high mobility in soil. The objective of this study was to investigate and model the behavior of SAs in soil-water systems using [14C]sulfamethazine (SMZ). Sulfamethazine was considered a prototype for the fate and transport of all SAs, because all SAs have similar physicochemical properties and identical biodegradability. The miscible-displacement experiments showed that 33-70% of SMZ was degraded within 6 h to two polar metabolites (PM1 and PM2) during transport in the soil columns, both of which were detected in column effluent and soil column extracts. The batch experiments indicated that there were strong relationships between the sorption of PM1 from SMZ and various soil fractions, especially organic matter. Sorption of PM1 was greater than that of parent SMZ. A chemical non-equilibrium model was successfully used to describe the experimental data. Processes such as preferential flow (due to cracks, worm holes, or plant debris found in field soils) or particulate-facilitated transport might provide the dominant transport pathways for rapid transport of SAs through soil.
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.