The introduction of glyphosate-tolerant (GT) crops is expected to mitigate the environmental contamination by herbicides because glyphosate is less persistent and toxic than the herbicides used on non-GT crops. Here, we compared the environmental balances of herbicide applications for both crop types in three French field trials. The dynamic of herbicides and their metabolites in soil, groundwater and air was simulated with PRZM model and compared to field measurements. The associated impacts were aggregated with toxicity potentials calculated with the fate and exposure model USES for several environmental endpoints. The impacts of GT systems were lower than those of non-GT systems, but the accumulation in soils of one glyphosate metabolite (aminomethylphosphonic acid) questions the sustainability of GT systems. The magnitude of the impacts depends on the rates and frequency of glyphosate application being highest for GT maize monoculture and lowest for combination of GT oilseed rape and non-GT sugarbeet crops. The impacts of herbicide applications on glyphosate-tolerant crops could be higher than expected due to the accumulation of a metabolite of glyphosate in soils.

The introduction of glyphosate-tolerant (GT) crops is expected to mitigate the environmental contamination by herbicides because glyphosate is less persistent and toxic than the herbicides used on non-GT crops. Here, we compared the environmental balances of herbicide applications for both crop types in three French field trials. The dynamic of herbicides and their metabolites in soil, groundwater and air was simulated with PRZM model and compared to field measurements. The associated impacts were aggregated with toxicity potentials calculated with the fate and exposure model USES for several environmental endpoints. The impacts of GT systems were lower than those of non-GT systems, but the accumulation in soils of one glyphosate metabolite (aminomethylphosphonic acid) questions the sustainability of GT systems. The magnitude of the impacts depends on the rates and frequency of glyphosate application being highest for GT maize monoculture and lowest for combination of GT oilseed rape and non-GT sugarbeet crops. The impacts of herbicide applications on glyphosate-tolerant crops could be higher than expected due to the accumulation of a metabolite of glyphosate in soils.

The introduction of glyphosate-tolerant (GT) crops is expected to mitigate the environmental contamination by herbicides because glyphosate is less persistent and toxic than the herbicides used on non-GT crops. Here, we compared the environmental balances of herbicide applications for both crop types in three French field trials. The dynamic of herbicides and their metabolites in soil, groundwater and air was simulated with PRZM model and compared to field measurements. The associated impacts were aggregated with toxicity potentials calculated with the fate and exposure model USES for several environmental endpoints. The impacts of GT systems were lower than those of non-GT systems, but the accumulation in soils of one glyphosate metabolite (aminomethylphosphonic acid) questions the sustainability of GT systems. The magnitude of the impacts depends on the rates and frequency of glyphosate application being highest for GT maize monoculture and lowest for combination of GT oilseed rape and non-GT sugarbeet crops. The impacts of herbicide applications on glyphosate-tolerant crops could be higher than expected due to the accumulation of a metabolite of glyphosate in soils.

In Réunion Island, expanding human populations, urbanization and agriculture during the last 50 years have all contributed to a steady increase in the level of nitrates in drinking water. Various nitrate point sources are responsible for the nitrate contamination around the island including chemical fertilizers, animal effluent applied to pasture and crops, and urban waste such as sewage and domestic waste water. In terms of agricultural fertilizers, pig effluent is the most widely used, but the cumulative effects of slurry applications on soil water and groundwater are unknown. Our objectives were (1) to characterize and follow in situ the fate of nitrogen through the subsurface after application of pig effluent onto a cultivated soil using stable nitrate isotopes, 15N and 18O, and (2) to compare the isotopic signatures of Réunion Island's principal aquifers with results from the experimental site to infer potential contamination sources. The study was conducted on an experimental field site planted with maize in the western part of Réunion Island during the rainy season. A control site with no fertilizer application to the maize was compared with the investigation site which had pig effluent applied once a year. The site which had pig effluent applied over one year had an average maximum surface soil water 15N-NO-3 value of +9.0% at 0.45 m depth. This signature was significantly more enriched in 15N than the corresponding subsurface soil water 15N-NO? 3 value of +3.8%_ at 10 m depth. The control site average maximum surface soil water 15N-NO? 3 value of +3.6%_ at 0.45 m is similar to the subsurface pig effluent application plot. This indicates that nitrates derived from pig effluent have not reached 10 m depth in the subsurface, even though over the last 18 months this site was subjected to two effluent applications, each around 200 kg N ha?1, and more than 1900 mm of rain, more than half of which drains directly into the root zone. This slow migration shows that mobilization of nitrates through cultivated soil can take many tens of years before infiltrating and contaminating the saturated zone situated at several tens, and in places, hundreds of meters depth. On an island-wide scale, an isotopic assessment of nitrates from the experimental site's soil water and other drinking water wells highlights a nitrogenous contaminations derived primarily from urban and/or agriculture via effluent application. (Résumé d'auteur)

International audience | In Réunion Island, expanding human populations, urbanization and agriculture during the last 50 years have all contributed to a steady increase in the level of nitrates in drinking water. Various nitrate point sources are responsible for the nitrate contamination around the island including chemical fertilizers, animal effluent applied to pasture and crops, and urban waste such as sewage and domestic waste water. In terms of agricultural fertilizers, pig effluent is the most widely used, but the cumulative effects of slurry applications on soil water and groundwater are unknown. Our objectives were (1) to characterize and follow in situ the fate of nitrogen through the subsurface after application of pig effluent onto a cultivated soil using stable nitrate isotopes, δ15N and δ18O, and (2) to compare the isotopic signatures of Réunion Island's principal aquifers with results from the experimental site to infer potential contamination sources. The study was conducted on an experimental field site planted with maize in the western part of Réunion Island during the rainy season. A control site with no fertilizer application to the maize was compared with the investigation site which had pig effluent applied once a year. The site which had pig effluent applied over one year had an average maximum surface soil water 15N-${\rm NO}_{3}^{-}$ value of +9.0‰ at 0.45 m depth. This signature was significantly more enriched in 15N than the corresponding subsurface soil water 15N-${\rm NO}_{3}^{-}$ value of +3.8‰ at 10 m depth. The control site average maximum surface soil water 15N-${\rm NO}_{3}^{-}$ value of +3.6‰ at 0.45 m is similar to the subsurface pig effluent application plot. This indicates that nitrates derived from pig effluent have not reached 10 m depth in the subsurface, even though over the last 18 months this site was subjected to two effluent applications, each around 200 kg N ha−1, and more than 1900 mm of rain, more than half of which drains directly into the root zone. This slow migration shows that mobilization of nitrates through cultivated soil can take many tens of years before infiltrating and contaminating the saturated zone situated at several tens, and in places, hundreds of meters depth. On an island-wide scale, an isotopic assessment of nitrates from the experimental site's soil water and other drinking water wells highlights a nitrogenous contamination derived primarily from urban and/or agriculture via effluent application.

In Réunion Island, expanding human populations, urbanization and agriculture during the last 50 years have all contributed to a steady increase in the level of nitrates in drinking water. Various nitrate point sources are responsible for the nitrate contamination around the island including chemical fertilizers, animal effluent applied to pasture and crops, and urban waste such as sewage and domestic waste water. In terms of agricultural fertilizers, pig effluent is the most widely used, but the cumulative effects of slurry applications on soil water and groundwater are unknown. Our objectives were (1) to characterize and follow in situ the fate of nitrogen through the subsurface after application of pig effluent onto a cultivated soil using stable nitrate isotopes, delta15N and delta18O, and (2) to compare the isotopic signatures of Réunion Island's principal aquifers with results from the experimental site to infer potential contamination sources. The study was conducted on an experimental field site planted with maize in the western part of Réunion Island during the rainy season. A control site with no fertilizer application to the maize was compared with the investigation site which had pig effluent applied once a year. The site which had pig effluent applied over one year had an average maximum surface soil water 15N- value of +9.0‰ at 0.45 m depth. This signature was significantly more enriched in 15N than the corresponding subsurface soil water 15N- value of +3.8‰ at 10 m depth. The control site average maximum surface soil water 15N- value of +3.6‰ at 0.45 m is similar to the subsurface pig effluent application plot. This indicates that nitrates derived from pig effluent have not reached 10 m depth in the subsurface, even though over the last 18 months this site was subjected to two effluent applications, each around 200 kg N ha-1, and more than 1900 mm of rain, more than half of which drains directly into the root zone. This slow migration shows that mobilization of nitrates through cultivated soil can take many tens of years before infiltrating and contaminating the saturated zone situated at several tens, and in places, hundreds of meters depth. On an island-wide scale, an isotopic assessment of nitrates from the experimental site's soil water and other drinking water wells highlights a nitrogenous contamination derived primarily from urban and/or agriculture via effluent application.

We present here the effects of ambient ozone (O3)-induced decline in carbon availability, accelerated foliar senescence, and a decrease in aboveground biomass accumulation in the Aleppo pine (Pinus halepensis Mill.). Aleppo pine seedlings were continuously exposed in open-top chambers for 39 months to three different types of O3 treatments, which are as follows: charcoal-filtered air, nonfiltered air (NFA), and nonfiltered air supplemented with 40 ppb O3 (NFA+). Stable carbon isotope discrimination (Δ) and derived time-integrated ci/ca ratios were reduced after an accumulated ozone exposure over a threshold of 40 ppb (AOT40) value from April to September of around 20,000 ppb·h. An AOT40 of above 67,000 ppb·h induced reductions in ribulose-1, 5-biphosphate carboxylase/oxygenase activity, aboveground C and needle N and K concentrations, the C/N ratio, Ca concentrations in twigs under 3 mm, and the aerial biomass, as well as increases in needle P concentrations and phosphoenolpyruvate carboxylase (PEPC) activity and the N and K concentrations in twigs under 3 mm. Macronutrients losses, the limitations placed on carbon uptake, and increases in catabolic processes may be the causes of carbon gain diminution in leaves which was reflected as a reduction in aboveground biomass at tree level. Stimulation of PEPC activity, the consequent decreased Δ, and compensation processes in nutrient distribution may increase O3 tolerance and might be interpreted as part of Aleppo pine acclimation response to O3.

We present here the effects of ambient ozone (O3)-induced decline in carbon availability, accelerated foliar senescence, and a decrease in aboveground biomass accumulation in the Aleppo pine (Pinus halepensis Mill.). Aleppo pine seedlings were continuously exposed in open-top chambers for 39 months to three different types of O3 treatments, which are as follows: charcoal-filtered air, nonfiltered air (NFA), and nonfiltered air supplemented with 40 ppb O3 (NFA+). Stable carbon isotope discrimination (Δ) and derived time-integrated ci/ca ratios were reduced after an accumulated ozone exposure over a threshold of 40 ppb (AOT40) value from April to September of around 20,000 ppb·h. An AOT40 of above 67,000 ppb·h induced reductions in ribulose-1, 5-biphosphate carboxylase/oxygenase activity, aboveground C and needle N and K concentrations, the C/N ratio, Ca concentrations in twigs under 3 mm, and the aerial biomass, as well as increases in needle P concentrations and phosphoenolpyruvate carboxylase (PEPC) activity and the N and K concentrations in twigs under 3 mm. Macronutrients losses, the limitations placed on carbon uptake, and increases in catabolic processes may be the causes of carbon gain diminution in leaves which was reflected as a reduction in aboveground biomass at tree level. Stimulation of PEPC activity, the consequent decreased Δ, and compensation processes in nutrient distribution may increase O3 tolerance and might be interpreted as part of Aleppo pine acclimation response to O3.

Effects of soil properties on the accumulation of metals to wood mice (Apodemus sylvaticus) were evaluated at two sites with different pH and organic matter content of the soil. pH and organic matter content significantly affected accumulation of Cd, Cu, Pb and Zn in earthworms and vegetation. For Cd, Cu and Zn these effects propagated through the food web to the wood mouse. Soil-to-kidney ratios differed between sites: Cd: 0.15 versus 3.52, Cu: 0.37 versus 1.30 and Zn: 0.33-0.83. This was confirmed in model calculations for Cd and Zn. Results indicate that total soil concentrations may be unsuitable indicators for risks that metals pose to wildlife. Furthermore, environmental managers may, unintentionally, change soil properties while taking specific environmental measures. In this way they may affect risks of metals to wildlife, even without changes in total soil concentrations.

Effects of soil properties on the accumulation of metals to wood mice (Apodemus sylvaticus) were evaluated at two sites with different pH and organic matter content of the soil. pH and organic matter content significantly affected accumulation of Cd, Cu, Pb and Zn in earthworms and vegetation. For Cd, Cu and Zn these effects propagated through the food web to the wood mouse. Soil-to-kidney ratios differed between sites: Cd: 0.15 versus 3.52, Cu: 0.37 versus 1.30 and Zn: 0.33–0.83. This was confirmed in model calculations for Cd and Zn. Results indicate that total soil concentrations may be unsuitable indicators for risks that metals pose to wildlife. Furthermore, environmental managers may, unintentionally, change soil properties while taking specific environmental measures. In this way they may affect risks of metals to wildlife, even without changes in total soil concentrations. Soil properties significantly affect accumulation of heavy metals to wood mice so; risks cannot be based on total concentrations.