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4D - Veterinary Medecine (MO13/11) Binding of veterinary pharmaceuticals to humic acids studied by non-depletive equilibrium SPME. Gebbink, Wouter1, Laak, Thomas1, Hermens, Joop1, Tolls, Johannes1, 1 Utrecht University - Institute for Risk Assessment Sciences, Utrecht, NL, The Netherlands ABSTRACT- Agricultural soils are the predominant sink compartment for veterinary medicines due to the use of manure as fertilizer. Manure is rich in particulate and dissolved organic matter. Binding of veterinary pharmaceuticals to dissolved organic matter can lead to increased mobility of these chemicals such that they are more mobile than predicted from batch-sorption experiments with soils. Here we evaluate whether binding to dissolved organic carbon (DOC)is relevant for the soil transport properties of veterinary medicines. To that end, we employed DOC from different sources i.e. Aldrich humic acid, Suwannee river fulvic acids natural and humic acids derived from pig manure in non-depletive equilibrium solid-phase microextraction experiments. Our results show that oxytetracycline and flumequine, two antibiotics, sorb strongly to Aldrich humic acid. The respective values of KDOC range around 105 L/kgDOC. Sorption to the fulvic acid is weaker for both compounds and hardly measurable for the pig manure derived humic acid. Employing the DOC sorption coefficient in a simple mass balance model the effect of the presence of DOC on the mobility of the veterinary medicines in unsaturated soil is shown to be negligible for all scenarios, indicating that DOC mediated transport does not lead to accelerated leaching from soil. Hence, this process can be considered of limited relevance for environmental transport processes. Key words: dissolved organic carbon, veterinary medicines, soil, transport |
