Behavior of steroids and veterinary antibiotics in soil: study of transfer and degradation in soil columns.
Résumé
Antibiotics are more and more used for animal treatments and are excreted unchanged. So, these compounds can enter the environment through land application of manure. This phenomenon could induce a resistance to antibiotics in human or animal medicine. Steroids, which are endocrine disruptors are also found in the environment due to animals but also humans wastes. The presence, distribution, fate and impact of veterinary substances and hormones regularly introduced into the soil via land application are far from known and very poorly characterised at the present time. In this context, the project aims at the development of methodologies based on soil columns experiments, in order to characterise the main products of biotic and abiotic transformations and to evaluate the migration and/or retention of selected contaminants and their breakdown products. For this purpose, 45 substances were selected including 11 hormonal steroids, 23 veterinary compounds and 11 other well-known human contaminants. The surface of the columns were first spiked with the different compounds and then regularly watered with artificial rain (0.01 M CaCl2 in distilled water). The leachates were regularly collected and analysed using a multi-residue method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS). Several series of columns were set up for periods ranging between 0 and 30 days. After this, the columns were sectioned into 5 horizons that were analysed using an original method based on a sample extraction by QuEChERS followed by a purification by solid phase extraction and an analysis by LC-MS/MS. Then, the presence and distribution of contaminants in the different horizons and/or leachates were established. The influence of various parameters on this transfer was also examined such as the pluviometry and the composition of soil (clay, loam, sand and organic matter contents).