Sylvain Payraudeau

Pesticide risk mitigation by vegetated treatment systems: a meta-analysis.

Pesticides entering agricultural surface waters threaten water quality and aquatic communities. Recently, vegetated treatment systems (VTSs) (e.g., constructed wetlands and vegetated ditches) have been proposed as pesticide risk mitigation measures. However, little is known about the effectiveness of VTSs in controlling nonpoint source pesticide pollution and factors relevant for pesticide retention within these systems. Here, we conducted a meta-analysis on pesticide mitigation by VTSs using data from the scientific literature and the European LIFE ArtWET project. Overall, VTSs effectively reduced pesticide exposure levels (i.e., the majority of pesticide retention performances was >70%). A multiple linear regression analysis of 188 retention performance cases identified the two pesticide properties, organic carbon sorption coefficient value and water-phase 50% dissipation time, as well as the VTS characteristics overall plant coverage and hydraulic retention time for targeting high efficacy of pesticide retention. The application of a Tier I risk assessment (EU Uniform Principle) revealed a higher toxicity reduction for hydrophobic and nonpersistent insecticides compared with less sorptive and not readily degradable herbicides and fungicides. Overall, nearly half (48.5%) of all pesticide field concentrations ( = 130) failed Tier I standard risk assessment at the inlet of VTSs, and 29.2% of all outlet concentrations exceeded conservative acute threshold levels. We conclude that VTSs are a suitable and effective risk mitigation strategy for agricultural nonpoint source pesticide pollution of surface waters. Further research is needed to improve their overall efficacy in retaining pesticides.

Removal of pesticide mixtures in a stormwater wetland collecting runoff from a vineyard catchment

Wetlands can collect contaminated runoff from agricultural catchments and retain dissolved and particle-laden pesticides. However, knowledge about the capacity and functioning of wetland systems with respect to the removal of pesticides is very limited. Here we show that stormwater wetlands can efficiently remove pesticides in runoff from vineyard catchments during the period of pesticide application, although flow and hydrochemical conditions of the wetland largely vary over time. During the entire agricultural season, the inflowing load of nine fungicides, six herbicides, one insecticide and four degradation products was 8.039g whereas the outflowing load was 2.181g. Removal rates of dissolved loads by the wetland ranged from 39% (simazine) to 100% (cymoxanil, gluphosinate, kresoxim methyl and terbuthylazine). Dimethomorph, diuron, glyphosate, metalaxyl and tetraconazole were more efficiently removed in spring than in summer. More than 88% of the input mass of suspended solids was retained, underscoring the capability of the wetland to trap pesticide-laden particles via sedimentation. Only the insecticide flufenoxuron was frequently detected in the wetland sediments. Our results demonstrate that stormwater wetlands can efficiently remove pesticide mixtures in agricultural runoff during critical periods of pesticide application, although fluctuations in the runoff regime and hydrochemical characteristics can affect the removal rates of individual pesticides.

Use and fate of 17 pesticides applied on a vineyard catchment

Non point source (NPS) pollution may degrade water quality and is of concern to water quality managers and environmental risk regulators whose responsibility it is to monitor the status of water bodies. There are many methods of evaluating the impact on a water body from NPS pollution, but one of the most important, effective, and unfortunately expensive methods is to monitor the quality of water flowing from a particular catchment. The flux of 17 pesticides from a small (42.7 ha) agricultural (vineyard) catchment in the Alsatian piemont (France) was systematically monitored over 4 years (2003–2006) from June to September. A metrological station is located within the catchment area and run-off of 58 run-off events was monitored throughout. A water sample for pesticide analyses was collected every 8 m3 of run-off. Detailed information regarding pesticide application was obtained from voluntary surveys submitted annually to active farmers of the studied catchment. There was considerable climatic variation among years. However, variability of the total load of pesticides exported yearly from the catchment was low. Some 78% of the total pesticide applications in the catchment were herbicides and glyphosate was the most used herbicide with annual application ranging from 18 to 61 kg. The run-off coefficient was low (less than 2%), but the frequency of determination was high for some pesticides such as the fungicide dimetomorph (72%) and the herbicides diuron (98%) and glyphosate (100%). The pesticide export coefficients were below 1% of the applied amount, and often below 0.1%. Every water sample exceeded the EU drinking water limit of 0.1 ug L−1.

Transport and attenuation of dissolved glyphosate and AMPA in a stormwater wetland.

Glyphosate is an herbicide used widely and increasingly since the early 1990s in production of many crops and in urban areas. However, knowledge on the transport of glyphosate and its degradation to aminomethylphosphonic acid (AMPA) in ecosystems receiving urban or agricultural runoff is lacking. Here we show that transport and attenuation of runoff-associated glyphosate and AMPA in a stormwater wetland differ and largely vary over time. Dissolved concentrations and loads of glyphosate and AMPA in a wetland receiving runoff from a vineyard catchment were assessed during three consecutive seasons of glyphosate use (March to June 2009, 2010 and 2011). The load removal of glyphosate and AMPA by the wetland gradually varied yearly from 75% to 99%. However, glyphosate and AMPA were not detected in the wetland sediment, which emphasises that sorption on the wetland vegetation, which increased over time, and biodegradation were prevailing attenuation processes. The relative load of AMPA as a percentage of total glyphosate increased in the wetland and ranged from 0% to 100%, which indicates the variability of glyphosate degradation via the AMPA pathway. Our results demonstrate that transport and degradation of glyphosate in stormwater wetlands can largely change over time, mainly depending on the characteristics of the runoff event and the wetland vegetation. We anticipate our results to be a starting point for considering degradation products of runoff-associated pesticides during their transfer in wetlands, in particular when using stormwater wetlands as a management practice targeting pesticide attenuation.

Modelling pesticides transfer to surface water at the catchment scale: a multi-criteria analysis

The demand for operational tools at a catchment scale is growing to assess both the sustainability of agricultural practices and the efficiency of mitigation measures on pesticide transfer to surface water. Here a literature review of 286 investigations highlights the large number of indicators and hydrochemical models developed at the catchment scale. Given this large number of indicators and models, the choice is difficult for potential users. Therefore, this article proposes a multi-criteria analysis applied to ten existing tools including physically based and conceptual models, indicators and multi-agent systems. We found the following major points: (1) Indicators and conceptual models are the most popular approaches to assess the transfer of pesticides to surface water at the catchment scale due to a trade-off between environmental relevance and adaptation to user’s needs. (2) The latest indicators developed are inferred from the results of conceptual or physically based models to combine the strengths of each approach. (3) Only a handful of physically based models have addressed both flow and pesticide transport at the catchment as affected by the internal heterogeneity of the system. However, it is only physically based models that can simulate the impact of changes to the catchment. Physically based models integrate feedbacks between hydrological and chemical processes not possible from conceptual models or indicators alone. (4) The ability of models to assess the pesticide loads both in the dissolved and particulate phases is a key issue not properly addressed by many indicators or models. A key way forward is the integration of erosion processes with the fate of pesticide adsorbed to these particles. (5) At the catchment, the hydrological connectivity is perhaps the primary hydrological variable required to correctly assess rapid flow processes as surface runoff and associated pesticide transfer. This in turn implies using tools that explicitly represent the connectedness of surface and/or sub-surface water pathways including mitigation measures to correctly assess the risk of pesticide transfer.

Kresoxim methyl deposition, drift and runoff in a vineyard catchment

Surface runoff and spray drift represent a primary mode of pesticide mobilisation from agricultural land to ecosystem. Though pesticide drift has mainly been studied at small scale (<1 ha), pesticide transports by drift and runoff have rarely been compared in the same agricultural catchment. Here kresoxim methyl (KM) drift during foliar application was evaluated in a vineyard catchment (Rouffach, Alsace, France), and KM deposition on non-target surfaces was compared to KM runoff. KM was detected on 55% of the collectors and concentration reached 18% of the applied dose (i.e. 1.5 mg m(-2)). Our results indicated that KM soil deposition greatly varied in space and time. The total KM soil deposition in the vineyard plots was estimated by four different interpolation methods (arithmetic mean, Thiessen method, inverse weighting distance and ordinary kriging) and ranged between 53 g and 61 g (5.8 and 6.6% of the total mass applied). The amount of KM drifted on roads was 50 times larger than that in runoff water collected at the outlet of the catchment. Although KM application was carried out under regular operational and climatic conditions, its deposition on non-target surfaces may be significant and lead to pesticide runoff. These results can be anticipated as a starting point for assessing pesticide deposition during spray application and corresponding pesticide runoff in agricultural catchments.

Evaluation of an operational method for the estimation of emissions of nitrogen compounds for a group of farms

The aim of this article is to evaluate a practical method for estimating nitrogen emissions on the scale of a group of farms, to be used in Life Cycle Assessment (LCA). The method rests on the estimation of nitrogen inputs and outputs to calculate the surplus of the annual nitrogen balance on the scale of a farm. The different gaseous nitrogen losses (NH3, NO, N2O, N3) are then estimated for each livestock or cropping system. The leaching losses in the form of NO3 are assumed to correspond to the surplus of the apparent nitrogen balance to which are added the atmospheric depositions, minus the gaseous losses. The feasibility of this method was studied on 24 farms in the Naizin catchment area (Brittany, France). An analysis of the sensitivity of NO3 estimates to different parameters used to calculate gaseous losses was carried out. Lastly the robustness of the NO3 estimates was examined by comparing them with measurements of NO3 collected within this catchment area.

High frequency monitoring of pesticides in runoff water to improve understanding of their transport and environmental impacts

Rainfall-induced peaks in pesticide concentrations can occur rapidly. Low frequency sampling may therefore largely underestimate maximum pesticide concentrations and fluxes. Detailed storm-based sampling of pesticide concentrations in runoff water to better predict pesticide sources, transport pathways and toxicity within the headwater catchments is lacking. High frequency monitoring (2min) of seven pesticides (Dimetomorph, Fluopicolide, Glyphosate, Iprovalicarb, Tebuconazole, Tetraconazole and Triadimenol) and one degradation product (AMPA) were assessed for 20 runoff events from 2009 to 2012 at the outlet of a vineyard catchment in the Layon catchment in France. The maximum pesticide concentrations were 387μgL-1. Samples from all of the runoff events exceeded the legal limit of 0.1μgL-1 for at least one pesticide (European directive 2013/39/EC). High resolution sampling used to detect the peak pesticide levels revealed that Toxic Units (TU) for algae, invertebrates and fish often exceeded the European Uniform principles (25%). The point and average (time or discharge-weighted) concentrations indicated up to a 30- or 4-fold underestimation of the TU obtained when measuring the maximum concentrations, respectively. This highlights the important role of sampling methods for assessing peak exposure. High resolution sampling combined with concentration-discharge hysteresis analyses revealed that clockwise responses were predominant (52%), indicating that Hortonian runoff is the prevailing surface runoff trigger mechanism in the study catchment. The hysteresis patterns for suspended solids and pesticides were highly dynamic and storm- and chemical-dependent. Intense rainfall events induced stronger C-Q hysteresis (magnitude). This study provides new insights into the complexity of pesticide dynamics in runoff water and highlights the ability of hysteresis analysis to improve understanding of pesticide supply and transport.

Copper in soil fractions and runoff in a vineyard catchment: Insights from copper stable isotopes

Understanding the fate of copper (Cu) fungicides in vineyard soils and catchments is a prerequisite to limit the off-site impact of Cu. Using Cu stable isotopes, Cu retention in soils and runoff transport was investigated in relation to the use of Cu fungicides and the hydrological conditions in a vineyard catchment (Rouffach, Haut-Rhin, France; mean slope: 15%). The δ(65)Cu values of the bulk vineyard soil varied moderately through the depth of the soil profiles (-0.12 to 0.24‰±0.08‰). The values were in the range of those of the fungicides (-0.21 to 0.11‰) and included the geogenic δ(65)Cu value of the untreated soil (0.08‰). However, δ(65)Cu values significantly differed between particle-size soil fractions (-0.37±0.10‰ in fine clays and 0.23±0.07‰ in silt). Together with the soil mineralogy, the results suggested Cu isotope fractionation primarily associated with the clay and fine clay fractions that include both SOM and mineral phases. The vegetation did not affect the Cu isotope patterns in the vineyard soils. Cu export by runoff from the catchment accounted for 1% of the applied Cu mass from 11th May to 20(th) July 2011, covering most of the Cu use period. 84% of the exported Cu mass was Cu bound to suspended particulate matter (SPM). The runoff displayed δ(65)Cu values from 0.52 to 1.35‰ in the dissolved phase (<0.45μm) compared to -0.34 to -0.02‰ in the SPM phase, indicating that clay and fine clay fractions were the main vectors of SPM-bound Cu in runoff. Overall, this study shows that Cu stable isotopes may allow identifying the Cu distribution in the soil fractions and their contribution to Cu export in runoff from Cu-contaminated catchments.

Sensitivity of effective rainfall amount to land use description using GIS tool. Case of a small mediterranean catchment

Abstract Distributed modelling in hydrology assess catchment subdivision to take into account physic characteristics. In this paper, we test the effect of land use aggregation scheme on catchment hydrological response. Evolution of intra-subcatchment land use is studied using statistic and entropy methods. The SCS-CN method is used to calculate effective rainfall which is here assimilated to hydrological response. Our purpose is to determine the existence of a critical threshold-area appropriate for the application of hydrological modelling. Land use aggregation effects on effective rainfall is assessed on small mediterranean catchment. The results show that land use aggregation and land use classification type have significant effects on hydrological modelling and in particular on effective rainfall modelling.