Hélène Blanchoud

Transfer of glyphosate and its degradate AMPA to surface waters through urban sewerage systems.

A study of glyphosate and aminomethyl phosphonic acid (AMPA) transfer in the Orge watershed (France) was carried out during 2007 and 2008. Water samples were collected in surface water, wastewater sewer, storm sewer and wastewater treatment plant (WWTP). These two molecules appeared to be the most frequently detected ones in the rivers and usually exceeded the European quality standard concentrations of 0.1microg L(-1) for drinking water. The annual glyphosate estimated load was 1.9 kg year(-1) upstream (agricultural zone) and 179.5 kg year(-1) at the catchment outlet (urban zone). This result suggests that the contamination of this basin by glyphosate is essentially from urban origin (road and railway applications). Glyphosate reached surface water prevalently through storm sewer during rainfall event. Maximum concentrations were detected in storm sewer just after a rainfall event (75-90 microg L(-1)). High concentrations of glyphosate in surface water during rainfall events reflected urban runoff impact. AMPA was always detected in the sewerage system. This molecule reached surface water mainly via WWTP effluent and also through storm sewer. Variations in concentrations of AMPA during hydrological episodes were minor compared to glyphosate variations. Our study highlights that AMPA and glyphosate origins in urban area are different. During dry period, detergent degradation seemed to be the major AMPA source in wastewater.

Triazines in the Marne and the Seine Rivers (France) Longitudinal Evolution and Flows

The transportation pathways of triazines were investigatedfrom their origins onwards, in the Marne and the Seine rivers(France). According to the 1991 survey, the highest total triazine concentration levels (956 ng L-1) were found in the river Marne: 580 ng L-1 for atrazine and 200 ng L-1 for simazine, in relation with agricultural practices.The total triazine levels reached 829 ng L-1 in the riverSeine. The other triazines remained low, from 5 to 75 ng L-1. The triazine fluxes were 226 and 404 kg for a 118 d period in the Marne and the Seine rivers, respectively. Out of the treatment period, triazine peaks were related to riverflows with a 48 hr delay between the peak and the top of theflood. After herbicide treatment, peak concentrations wereclosely related with the precipitations. Concerning theriver Marne tributaries, highest atrazine concentrationswere found in June, in those which drained the vineyardarea. In January, the concentrations were higher inperiurban areas underlining their contribution to theherbicide inputs in the rivers. On the whole, the ratio oftriazines transported in the two rivers represented 0.2%of the total amount applicated annually on their catchment basins.

Herbicides and nitrogen in precipitation: progression from west to east and contribution to the Marne river (France).

Herbicides and nitrogen fallout were studied in France at six sites from west to east. Atrazine, a herbicide widely used in France and forbidden in some European countries was found. Its fallout was quantified to 400 kg on the river Marne catchment (13 500 km2), an agricultural region located east of Paris. The average fallout contribution to the Marne river contamination was estimated at 20 ng/l from March to August. Independently of the wind direction, only a small part of this atmospheric contamination can reach adjacent countries.

Water, nitrate and atrazine transfer through the unsaturated zone of the Chalk aquifer in northern France

The water quality of the Chalk aquifer is degrading due to fertilizers and pesticides use which are classified as toxic to public health. The study aims to provide a better understanding of the transfer processes in the unsaturated zone of the Chalk aquifer using different environmental tracers (nitrate, atrazine and tritium). The study was conducted in an underground quarry in northern France (St. Martin le Noeud). The quarry provides direct access to the lower part of the unsaturated zone of the Chalk at a depth of 18-30 m. Fifteen sites throughout the quarry display percolation directly from the unsaturated zone. Since percolation intensity is heterogeneous at one site, a comparison was made between the variation of geochemical properties of ten samples from one site and the spatial variation of samples from 15 sites throughout the quarry. Using the Siegel-Tukey and Wilcoxon tests, we found that the variation between the sites is higher than the variation within one site. Therefore, one percolation sample can be used to represent one site. The transfer time of nitrate and atrazine is estimated based on its use in the cultivated fields. Pore water with no contamination indicates water infiltrated before the use of contaminants at the surface, and pore water with a high concentration of contaminants indicates water infiltrated during the use of contaminants at the surface. The transfer time of water molecules is estimated using the time series of tritium. Transfer velocities were computed for each environmental tracer (nitrate, atrazine and tritium) by dividing the estimated transfer time by the depth of each site. Two transfer velocity ranges are determined: (1) <0.32 ± 0.02 m/year and (2) between 0.72 ± 0.14 and 2.15 ± 0.43 m/year, showing most water transfer through the matrix but also a mixture of water with different velocities.