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.     

Mitigation of agricultural nonpoint-source pesticide pollution in artificial wetland ecosystems

Contamination caused by pesticides in agriculture is a source of environmental poor water quality in some of the European Union countries. Without treatment or targeted mitigation, this pollution is diffused in the environment. Pesticides and some metabolites are of increasing concern because of their potential impacts on the environment, wildlife and human health. Within the context of the European Union (EU) water framework directive context to promote low pesticide-input farming and best management practices, the EU LIFE project ArtWET assessed the efficiency of ecological bioengineering methods using different artificial wetland (AW) prototypes throughout Europe. We optimized physical and biological processes to mitigate agricultural nonpoint-source pesticide pollution in artificial wetland ecosystems. Mitigation solutions were implemented at full-scale demonstration and experimental sites. We tested various bioremediation methods at seven experimental sites. These sites involved (1) experimental prototypes, such as vegetated ditches, a forest microcosm and 12 wetland mesocosms, and (2) demonstration prototypes: vegetated ditches, three detention ponds enhanced with technology of constructed wetlands, an outdoor bioreactor and a biomassbed. This set up provides a variety of hydrologic conditions, with some systems permanently flooded and others temporarily flooded. It also allowed to study the processes both in field and controlled conditions. In order to compare the efficiency of the wetlands, mass balances at the inlet and outlet of the artificial wetland will be used, taking into account the partition of the studied compound in water, sediments, plants, and suspended solids. The literature background necessary to harmonize the interdisciplinary work is reviewed here and the theoretical framework regarding pesticide removal mechanisms in artificial wetland is discussed. The development and the implementation of innovative approaches concerning various water quality sampling strategies for pesticide load estimates during flood, specific biological endpoints, innovative bioprocess applied to herbicide and copper mitigation to enhance the pesticide retention time within the artificial wetland, fate and transport using a 2D mixed hybrid finite element model are introduced. These future results will be useful to optimize hydraulic functioning, e.g., pesticide resident time, and biogeochemical conditions, e.g., dissipation, inside the artificial wetlands. Hydraulic retention times are generally too low to allow an optimized adsorption on sediment and organic materials accumulated in artificial wetlands. Absorption by plants is not either effective. The control of the hydraulic design and the use of adsorbing materials can be useful to increase the pesticides residence time and the contact between pesticides and biocatalyzers. Pesticide fluxes can be reduced by 50–80% when hydraulic pathways in artificial wetlands are optimized by increasing ten times the retention time, by recirculation of water, and by deceleration of the flow. Thus, using a bioremediation method should lead to an almost complete disappearance of pesticides pollution. To retain and treat the agricultural nonpoint-source po a major stake for a sustainable development.     

Fungicides transport in runoff from vineyard plot and catchment: contribution of non-target areas

Surface runoff and erosion during the course of rainfall events are major processes of pesticides transport from agricultural land to aquatic ecosystem. These processes are generally evaluated either at the plot or the catchment scale. Here, we compared at both scales the transport and partitioning in runoff water of two widely used fungicides, i.e., kresoxim-methyl (KM) and cyazofamid (CY). The objective was to evaluate the relationship between fungicides runoff from the plot and from the vineyard catchment. The results show that seasonal exports for KM and CY at the catchment were larger than those obtained at the plot. This underlines that non-target areas within the catchment largely contribute to the overall load of runoff-associated fungicides. Estimations show that 85 and 62 % of the loads observed for KM and CY at the catchment outlet cannot be explained by the vineyard plots. However, the partitioning of KM and CY between three fractions, i.e., the suspended solids (>0.7 μm) and two dissolved fractions (i.e., between 0.22 and 0.7 µm and <0.22 µm) in runoff water was similar at both scales. KM was predominantly detected below 0.22 μm, whereas CY was mainly detected in the fraction between 0.22 and 0.7 μm. Although KM and CY have similar physicochemical properties and are expected to behave similarly, our results show that their partitioning between two fractions of the dissolved phase differs largely. It is concluded that combined observations of pesticide runoff at both the catchment and the plot scales enable to evaluate the sources areas of pesticide off-site transport.     

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.     

RECOTOX,a French initiative in ecotoxicology-toxicology to monitor,understand and mitigate the ecotoxicological impacts of pollutants in socioagroecosystems

RECOTOX is a cross-cutting initiative promoting an integrated research to respond to the challenges of monitoring, understanding, and mitigating environmental and health impacts of pesticides in agroecosystems. The added value of RECOTOX is to develop a common culture around spatial ecotoxicology including the whole chain of pressure-exposure-impact, while strengthening an integrated network of in natura specifically equipped sites. In particular, it promotes transversal approaches at relevant socioecological system scales, to capitalize knowledge, expertise, and ongoing research in ecotoxicology and, to a lesser extent, environmental toxicology. Thus, it will open existing research infrastructures in environmental sciences to research programs in ecotoxicology of pesticides.     

Multi-elemental compound-specific isotope analysis of pesticides for source identification and monitoring of degradation in soil: a review

Environmental Chemistry Letters - The transfer of pesticides from agricultural soils to food and drinking water is a major health issue. There are actually few robust methods to identify,...