The soil fate and transport of agricultural antibiotics is of significant concern in relation to the prevalence of antibiotic resistant bacteria. The solid–liquid partitioning co-efficient (Kd) is of high importance in understanding and modeling the transport of antibiotics in soil. Ideally, such Kd determinations should be made “in-situ” under realistic soil conditions, particularly moisture content. Such an approach offers many potential advantages over traditional batch systems. Of the antibiotic classes, the sulfonamides are of particular interest in environmental fate and transport studies due to their demonstrated potential for high mobility. Using sulfadiazine as a model sulfonamide compound, we have developed a system for measuring in-situ Kd values under realistic soil moisture contents. Importantly, the system uses only stainless steel and Teflon components; thereby mitigating adsorptive losses. In-situ Kd values are being determined over time for a range of soil conditions, including varying organic matter contents, ionic strengths, and clay contents; these values will be reported and compared with those determined using the traditional batch approach. Knowledge relating to the solid–liquid partitioning and degradation of sulfadiazine will be used to interpret its leaching behavior through large stainless steel soil columns. Data on the redistribution of surface-applied sulfadiazine throughout the soil columns, and on its presence in pore and leachate water, will be presented. The water/solute transport model Hydrus-1D is being used to simulate the soil column behavior of sulfadiazine and to illustrate the importance of accurate Kd values for correctly simulating sulfadiazine fate and transport. Anticipated future research in this area will also be presented; this will relate to the potential bioavailability and plant uptake of sulfadiazine and other antibiotic compounds.

Fate and transport of the agricultural antibiotic sulfadiazine in soil

254th National Meeting (2017)

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