Transport of Antibiotics in Soil and Their Potential for Ground-Water Contamination

Abstract

Two classes of antibiotics, sulfamethazines and tetracylines, are commonly added to animal feed (swine and poultry) in subtherapeutic dosesg as growth-promoting agents and are excreted subsequently by the animals. This practice is used extensively in large confined animal-feeding operations, which are common in the United States. The large volumes of wastewater generated from these operations are applied on fields to recycle the dissolved nitrogen and phosphorus from animal feeds back into the soil to trap nutrients and increase soil fertility. During this process, however, the antibiotics that are still present in the wastewater are also applied to soil leading to potential infiltration of these compounds to shallow ground water. Recent measurements of sulfamethazine and tetracyclines by liquid chromatography/mass spectrometry have documented that these compounds are present in swine wastewater at concentrations of 100 µg/L or more, Thus, soil-column experiments with antibiotics are being carried out to determine the relative potential for transport, of these two classes of compounds to ground water. The relationship of chemical structure, pKa, and solubility will be discussed in light of the soil-column distribution coefficients for these classes of compounds and their various isometric forms. On the basis of compound structure, it is hypothesized that the sulfamethazines (acidic antibiotics) are transported more rapidly through soil to ground water than the tetracyclines (basic antibioties).

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Thurman, E.M., and Lindsey, M.E., 2000, Transport of antibiotics in soil and their potential for ground-water contamination [abst.] in Global Environmental Issues in the 21st Century: Problems, Causes and Solutions--Proceedings of the Third SETAC World Congress, May 21-25, 2000, Brighton, United Kingdom: Society of Environmental Toxicology and Chemistry, p. 199.

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