Co-occurrence of veterinary antibiotics and fecal source markers in Brittany superficial waters: an experimental study

International audienceBackground and objectivesAfter absorption by human or animals, pharmaceuticals compounds are excreted either in their free, conjugated or metabolized form in soil and water. The dissemination of those compounds through water resources can lead to antibiotic resistance and could have health effects on living organisms. Numerous studies attest the contamination of various aquatic environments by pharmaceutical compounds, including water resources. The two major contaminations sources are : i) the localized release by industrial and municipal wastewater treatment plants ; ii) non-point dispersion through soil amendment using animal manure or release from animal pastures or by individual septic tanks (Sarmah et al. 2006 ; Ruhoya et Daughton, 2008). Prerequisite of any assessment of the health risks induced by these emerging contaminants requires identification of the contamination sources, close quantification of the input to the water environmental compartment, while developing knowledge on the chemical speciation and fate of the residues once released in the environment. Some residues found in waters may have a mixed origin (human and animal), such as some hormones or antibiotics that can be used indifferently (Kemper, 2008). Identification of the source relies then on co-tracers specifics to humans or animals (Murata et al., 2011). This is particularly important in area of intensive livestock activities such as Brittany, region in the North-West part of France, with mixed watershed. We propose to evaluate by experimentation in laboratory the co-persistence of veterinary pharmaceuticals and fecal markers (fecal stanols) in water from agricultural watershed. Fecal stanols associated with usual bacterial indicators of fecal contamination are microbial source tracking markers used to distinguish among human, bovine and porcine fecal contamination in water (Jardé et al., 2007 ; Gourmelon et al., 2010 ; Jeanneau et al., 2011 ; Derrien et al., 2012).Methods and resultsExperimental study has been carried out at the laboratory scale to evaluate the persistence of veterinary antibiotics and fecal indicators and markers (E.coli and fecal stanols) during 21 days. Microcosms of freshwater have been inoculated with pig slurry contaminated by sulfadiazine, sulfamethazine and oxytetracycline. The microcosms were maintained under aerobic conditions with constant mixing and at constant temperature (20°C ± 1 °C). These experiments were conducted in darkness to avoid heterogeneous lighting due to the turbidity of the system. Antibiotics concentration, E.coli and fecal stanols were quantified in microcosms at the starting day and on days 1, 2, 3, 8, 15 and 21.Discussion and conclusionDecay rates and the length of time to obtain a reduction of 50% of the initial inoculums (T1/2) were calculated for E.coli, fecal stanols and antibiotics in the microcosms inoculated with pig slurry. T1/2 was lower for E.coli (1.2 days) than for fecal stanols (between 3.4 to 4.6 days depending on the stanol) and antibiotics (between 2.2 days for oxytetracycline to 7 days for sulfamides). Among antibiotics, the persistence of oxytetracycline is similar to that of fecal stanols and lower than persistence of sulfamides. These differences might be linked to different sorption properties of tetracycline and sulfamides. Fecal stanols seem to co-occur with tetracycline in water samples and might be useful to track sources of pharmaceuticals contamination at the watershed scale. al., 2007 ; Gourmelon et al., 2010 ; Jeanneau et al., 2011 ; Derrien et al., 2012)

Co-occurrence of veterinary antibiotics and fecal source markers in Brittany superficial waters: an experimental study

International audienceBackground and objectivesAfter absorption by human or animals, pharmaceuticals compounds are excreted either in their free, conjugated or metabolized form in soil and water. The dissemination of those compounds through water resources can lead to antibiotic resistance and could have health effects on living organisms. Numerous studies attest the contamination of various aquatic environments by pharmaceutical compounds, including water resources. The two major contaminations sources are : i) the localized release by industrial and municipal wastewater treatment plants ; ii) non-point dispersion through soil amendment using animal manure or release from animal pastures or by individual septic tanks (Sarmah et al. 2006 ; Ruhoya et Daughton, 2008). Prerequisite of any assessment of the health risks induced by these emerging contaminants requires identification of the contamination sources, close quantification of the input to the water environmental compartment, while developing knowledge on the chemical speciation and fate of the residues once released in the environment. Some residues found in waters may have a mixed origin (human and animal), such as some hormones or antibiotics that can be used indifferently (Kemper, 2008). Identification of the source relies then on co-tracers specifics to humans or animals (Murata et al., 2011). This is particularly important in area of intensive livestock activities such as Brittany, region in the North-West part of France, with mixed watershed. We propose to evaluate by experimentation in laboratory the co-persistence of veterinary pharmaceuticals and fecal markers (fecal stanols) in water from agricultural watershed. Fecal stanols associated with usual bacterial indicators of fecal contamination are microbial source tracking markers used to distinguish among human, bovine and porcine fecal contamination in water (Jardé et al., 2007 ; Gourmelon et al., 2010 ; Jeanneau et al., 2011 ; Derrien et al., 2012).Methods and resultsExperimental study has been carried out at the laboratory scale to evaluate the persistence of veterinary antibiotics and fecal indicators and markers (E.coli and fecal stanols) during 21 days. Microcosms of freshwater have been inoculated with pig slurry contaminated by sulfadiazine, sulfamethazine and oxytetracycline. The microcosms were maintained under aerobic conditions with constant mixing and at constant temperature (20°C ± 1 °C). These experiments were conducted in darkness to avoid heterogeneous lighting due to the turbidity of the system. Antibiotics concentration, E.coli and fecal stanols were quantified in microcosms at the starting day and on days 1, 2, 3, 8, 15 and 21.Discussion and conclusionDecay rates and the length of time to obtain a reduction of 50% of the initial inoculums (T1/2) were calculated for E.coli, fecal stanols and antibiotics in the microcosms inoculated with pig slurry. T1/2 was lower for E.coli (1.2 days) than for fecal stanols (between 3.4 to 4.6 days depending on the stanol) and antibiotics (between 2.2 days for oxytetracycline to 7 days for sulfamides). Among antibiotics, the persistence of oxytetracycline is similar to that of fecal stanols and lower than persistence of sulfamides. These differences might be linked to different sorption properties of tetracycline and sulfamides. Fecal stanols seem to co-occur with tetracycline in water samples and might be useful to track sources of pharmaceuticals contamination at the watershed scale. al., 2007 ; Gourmelon et al., 2010 ; Jeanneau et al., 2011 ; Derrien et al., 2012)

New molecular evidence for surface and sub-surface soil erosion controls on the composition of stream DOM during storm events

International audienceStorm events are responsible for more than 60 % of the export of dissolved organic matter (DOM) from head-water catchments due to an increase in both the discharge and concentration. The latter was attributed to changing water pathways inducing the mobilization of DOM from the surface soil horizons. Recent molecular investigations have challenged this view and hypothesized (i) a contribution of an in-stream partition of organic matter (OM) between eroded particles and the dissolved fraction and (ii) the modification of the composition of soil DOM during storm events. To investigate these assumptions, soil solutions in the macro-pores, surface runoff and stream outlet were sampled at high frequency during three storm events in the Kervidy– Naizin catchment, part of the French critical zone observatory AgrHyS. The molecular composition of the DOM was analysed by thermally assisted hydrolysis and methylation (THM) with tetramethylammonium hydroxide (TMAH) coupled to a gas chromatograph and a quadrupole mass spectrometer. These analyses highlighted a modification of the DOM composition in soil solution controlled by the water-table dynamic and pre-event hydrological conditions. These findings fit with the mechanism of colloidal and particulate destabilization in the soil macroporosity. The different behaviour observed for lignins, carbohydrates and fatty acids highlights a potential chemical segregation based on their hydrophobicity. The composition of surface runoff DOM is similar to the DOM composition in soil solution and could be generated by the same mechanism. The DOM composition in both soil solution and surface runoff corresponds to the stream DOM composition observed during storm events. On the basis of these results, modifications of the stream DOM composition during storm events seem to be due to surface and sub-surface soil erosion rather than in-stream production