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4A - Integrated ecological and human health risk assessment (MOP/170) Transport of veterinary antibiotics to surface water in a tile drained clay soil. Kay, Paul 1, Blackwell, Paul1, Boxall, Alistair1, 1 Cranfield University, Derby, Derbyshire, UK ABSTRACT- Pharmaceuticals are used in livestock production to prevent disease and treat sick animals, and thus, may be present in manure and slurry as the parent compound and/or metabolites. The environment may therefore be exposed to these substances due to the application of organic fertilisers to agricultural land or deposition by grazing livestock. For other groups of substances that are applied to land (e.g. pesticides), preferential flow in underdrained clay soils has been identified as an extremely important mechanism by which pollution of surface waters can occur. This study was therefore performed to investigate the fate of veterinary antibiotics in a tile drained clay soil. Slurry containing three antibiotics from the sulphonamide, tetracycline and macrolide groups was applied to a 1.5 ha field with a discrete tile drainage catchment over two growing seasons. Sulphachloropyridazine and oxytetracycline, were measured in the soil at up to 1 mg/kg respectively although the sulphonamide degraded rapidly whilst the tetracycline persisted. Subsequently, the two compounds were detected in drainflow at concentrations of 589 and 28 Key words: tile drainage, veterinary medicine, macropores, surface water |
g/l, whilst tylosin was not found in soil or water. Mass losses from the field were however less than 0.5 % of the total applied for each substance. These findings could be explained by the antibiotics′ persistence and sorption characteristics, whilst preferential flow via desiccation cracks and worm channels to the tile drains was found to be the most important route for translocation of the compounds. Therefore, tillage of the soil prior to the second slurry application significantly reduced antibiotic transport by breaking the connectivity of these pathways with the soil surface. Thus, it is evident that processes governing pesticide fate also apply to veterinary antibiotics.