International audience | A soil column leaching experiment was used to gain insight into the long-term metal immobilization capacity of cyclonic ashes (CAH) compared to lime (LIME). Twenty six years of rainfall were simulated. Initially, all amended soils were brought to an equal soil pH. This was done to obtain optimal conditions for the detection of metal immobilization mechanisms different from just a pH effect. During the simulation period, soil pH in all treatments decreased in parallel. However, the evolution of metal mobility and phytoavailability showed a clearly distinct pattern. The strong reduction in metal immobilizing efficiency observed in the lime treatment at the end of the simulation period was much less pronounced, or even absent, in the CAH treatments. Moreover, metal accumulation in plants grown on the CAH amended soil was significantly lower compared to the untreated and the lime treated soil. CAH + SS treatment delivered the strongest reductions in metal mobility and bioavailability. In a soil column leaching experiment, simulating 26 years of rainfall, application of cyclonic ashes resulted in a more durable metal immobilization compared to lime.

A soil column leaching experiment was used to gain insight into the long-term metal immobilization capacity of cyclonic ashes (CAH) compared to lime (LIME). Twenty six years of rainfall were simulated. Initially, all amended soils were brought to an equal soil pH. This was done to obtain optimal conditions for the detection of metal immobilization mechanisms different from just a pH effect. During the simulation period, soil pH in all treatments decreased in parallel. However, the evolution of metal mobility and phytoavailability showed a clearly distinct pattern. The strong reduction in metal immobilizing efficiency observed in the lime treatment at the end of the simulation period was much less pronounced, or even absent, in the CAH treatments. Moreover, metal accumulation in plants grown on the CAH amended soil was significantly lower compared to the untreated and the lime treated soil. CAH + SS treatment delivered the strongest reductions in metal mobility and bioavailability.

[Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAU [TR2_IRSTEA]BELCA | This study reports on the occurrence and behaviour of six pesticides and one metabolite in a small stream draining a vineyard catchment. Base flow and flood events were monitored in order to assess the variability of pesticide concentrations according to the season and to evaluate the role of sampling frequency on the evaluation of fluxes estimates. Results showed that dissolved pesticide concentrations displayed a strong temporal and spatial variability. A large mobilisation of pesticides was observed during floods, with total dissolved pesticide fluxes per event ranging from 5.7*10-3 g/Ha to 0.34 g/Ha. These results highlight the major role of floods in the transport of pesticides in this small stream which contributed to more than 89% of the total load of diuron during August 2007. The evaluation of pesticide loads using different sampling strategies and method calculation, showed that grab sampling largely underestimated pesticide concentrations and fluxes transiting through the stream.

This study reports on the occurrence and behaviour of six pesticides and one metabolite in a small stream draining a vineyard catchment. Base flow and flood events were monitored in order to assess the variability of pesticide concentrations according to the season and to evaluate the role of sampling frequency on the evaluation of fluxes estimates. Results showed that dissolved pesticide concentrations displayed a strong temporal and spatial variability. A large mobilisation of pesticides was observed during floods, with total dissolved pesticide fluxes per event ranging from 5.7 × 10−3 g/Ha to 0.34 g/Ha. These results highlight the major role of floods in the transport of pesticides in this small stream which contributed to more than 89% of the total load of diuron during August 2007. The evaluation of pesticide loads using different sampling strategies and method calculation, showed that grab sampling largely underestimated pesticide concentrations and fluxes transiting through the stream. This work brings new insights about the fluxes of pesticides in surface water of a vineyard catchment, notably during flood events.

[Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAU | The purpose of this work is to assess the effectiveness of two grass covers (buffer zone and grass-covered inter-row), to reduce pesticide leaching, and subsequently to preserve groundwater quality. Lower amounts of pesticides leached through grass-cover soil columns (2.7e24.3% of the initial amount) than the bare soil columns (8.0e55.1%), in correspondence with their sorption coefficients. Diuron was recovered in higher amounts in leachates (8.9e32.2%) than tebuconazole (2.7e12.9%), in agreement with their sorption coefficients. However, despite having a sorption coefficient similar to that of diuron, more procymidone was recovered in the leachates (10.2e55.1%), probably due to its facilitated transport by dissolved organic matter. Thus even in this very permeable soil, higher organic matter contents associated with grass-cover reduce the amount of pesticide leaching and limit the risk of groundwater contamination by the pesticides. The results of diuron and tebuconazole transfer through undisturbed buffer zone soil columns are in agreement with field observations on the buffer zone.

The purpose of this work is to assess the effectiveness of two grass covers (buffer zone and grass-covered inter-row), to reduce pesticide leaching, and subsequently to preserve groundwater quality. Lower amounts of pesticides leached through grass-cover soil columns (2.7-24.3% of the initial amount) than the bare soil columns (8.0-55.1%), in correspondence with their sorption coefficients. Diuron was recovered in higher amounts in leachates (8.9-32.2%) than tebuconazole (2.7-12.9%), in agreement with their sorption coefficients. However, despite having a sorption coefficient similar to that of diuron, more procymidone was recovered in the leachates (10.2-55.1%), probably due to its facilitated transport by dissolved organic matter. Thus even in this very permeable soil, higher organic matter contents associated with grass-cover reduce the amount of pesticide leaching and limit the risk of groundwater contamination by the pesticides. The results of diuron and tebuconazole transfer through undisturbed buffer zone soil columns are in agreement with field observations on the buffer zone.

In the context of pesticide pollution in hydrosystem, limiting pesticide transfer from agricultural plot to surface waterbodies appears to be crucial. Two constructed wetlands were tested at both pilot scale of an experimental constructed wetland and field scale of the outfall of a subsurface drained watershed. Tracer experiment and pesticide mass balance studies allowed us to assess the dissipation potential of a subsurface flow constructed wetland. At field scale, climatic parameters water and pesticide's flows in and out have been measured and monitored. We also recorded the conditions of implementation since we were very closed to real conditions. For this purpose inquiries addressing the various actors were carried out by sociologists. The results of the performance regarding pesticide's dissipation are given mentioning that efficiency is strongly linked to pesticide properties and hydrological transfer period (from 20 to 90% of pesticide removal). Sociologic approaches and amenities assessments have revealed unsuspected relations of the farmers with the society and the environment, and vice versa. The implementations have resulted of a co-construction where each actor had personal involvement. Even if co-construction should be a driving line, solutions for appropriate incentives and land reallocation tools should be fought with politics and authorities in order to facilitate further realisations.

[Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAU [TR2_IRSTEA]TED | International audience | In the context of pesticide pollution in hydrosystem, limiting pesticide transfer from agricultural plot to surface waterbodies appears to be crucial. Two constructed wetlands were tested at both pilot scale of an experimental constructed wetland and field scale of the outfall of a subsurface drained watershed. Tracer experiment and pesticide mass balance studies allowed us to assess the dissipation potential of a subsurface flow constructed wetland. At field scale, climatic parameters water and pesticide's flows in and out have been measured and monitored. We also recorded the conditions of implementation since we were very closed to real conditions. For this purpose inquiries addressing the various actors were carried out by sociologists. The results of the performance regarding pesticide's dissipation are given mentioning that efficiency is strongly linked to pesticide properties and hydrological transfer period (from 20 to 90% of pesticide removal). Sociologic approaches and amenities assessments have revealed unsuspected relations of the farmers with the society and the environment, and vice versa. The implementations have resulted of a co-construction where each actor had personal involvement. Even if co-construction should be a driving line, solutions for appropriate incentives and land reallocation tools should be fought with politics and authorities in order to facilitate further realisations.