Long-term monitoring of sulfonamide leaching from manure amended soil into groundwater.

Veterinary antibiotics such as sulfonamides are frequently applied in livestock farming worldwide. Due to poor absorption in the animal gut and/or reversible metabolization sulfonamides are excreted in considerable amounts and can subsequently be detected in liquid manure. As manure is utilized for soil fertilization, sulfonamides can enter the environment via this pathway. Water samples taken below an agriculture field in Lower Saxony revealed the permanent entrance of sulfamethazine into groundwater and concentrations up to 100 ng L were determined. During a long-term lysimeter study, nine sulfonamides were applied to two different soil types by using fortified liquid manure. Divert mobilities were found with sulfamethazine und sulfamethoxazole showing the highest detection frequency in water samples taken below both bedrock and sandy soil. Four years after the last application of fortified manure, sulfonamides were still detectable in the leachate. Based on analyses of manure and fermentation residue samples, a permanent input of sulfonamides to the soil can be excluded. Thus, the positive findings must be caused by the antibiotics once applied. Soils fertilized with manure contaminated with sulfonamides can consequently be a long-time source for the transfer of antibiotics into groundwater.