Context

The assessment of environmental and human exposure to the various contaminants present in the environment is essential to identify their determinants and limit their impacts. Agroecosystems, particularly in the peri-urban context, are our main subject of study. This context allows us to sweep away a gradient of conditions ranging from a purely agricultural environment to an urban one. We characterize the contamination of different environmental compartments - soil, air, water, plants and soil organisms - by a diversity of contaminants of interest to agroecosystems (e.g. pesticides and pharmaceutical products, PAH, metals, atmospheric contaminants -NH3, O3, VOC, N reactive, AOS, etc. and biotic contaminants as fungal plant pathogens, toxins, etc …), either because they are agricultural inputs (e.g. pesticides; fertilizers; contaminants related with the recycling of organic biomasses), or because they impact agricultural production.

We seek to consider the agricultural practices and their evolution, particularly in an agro-ecological transition framework, or environmental conditions evolution related to climate change. This may lead us to requestion our tools to be able to evaluate all practices (presence of crop residues on soil surface, catch crops, intra-field heterogeneity due to mixture of crop species, etc.) or test their validity under various soil and climate conditions. On the other hand, we seek, as far as possible, to develop tools integrating a diversity of ecosystems at the landscape scale (e.g. various types of crop, hedges/woods in atmospheric dispersion models) and describing all relevant processes in the different compartments.

Dealing with the effects, until now we have mainly studied the effects of these contaminants on soil organisms (plants, wildlife, microorganisms), from the subindividual to the community scale, and also on soil, water and air qualities and plant health. These studies have combined (i) the understanding of processes and underlying mechanisms, (e.g. contaminant transfer between compartments, (bio) availability, ecotoxicity, optimization of the use of genetic resistance to disease of arable crop), (ii) their integration (in terms of scales, multiple exposures, exposure/impact links) and (iii) scenario evaluation (environmental risks and performance) via experimental (laboratory, in situ) and modeling (in silico, mechanistic) approaches.

In the short term, we would like to extend our work to the study of human exposure to pesticides via the atmosphere, a topic of great concern to society and public authorities, as well as the contamination of agricultural products by emerging contaminants (e.g. harvested on soils amended with recycled organic biomasses).

Several knowledges, methodological and analytical gaps remain. The knowledge gaps include the long-term fate of contaminants (formation and fate of non-extractable residues, evolution of virulence of biotic particles), the interactions with soil organic matter at fine scales, the fate of (bio)transformation/(bio)degradation products, the consideration of soil with cropping practice heterogeneity in a changing climate and transition for agroecology, the determinism of (bio)-availability of contaminants or taking into account of the huge number of potential contaminants and their potential interactions (mixtures, co-formulant effects on the active ingredient's behavior for pesticides). As for the effects on organisms of interest (soil organisms, plants), strong challenges concern the consequences of multi- stress, whether they are of climatic origin or linked to multi-exposure (mixture of pollutants, exposure routes), long- term effects and their impacts on ecological functions (i.e. soil structure, nutrients recycling, organic pollutant degradation) and consequences on ecosystem services (i.e. organic waste recycling, climate and landslide risk regulation).

Scientific questions and objectives

In this context, the general scientific questions are the following:

-  How to predict spatio-temporal environmental, plant and human exposure to (bio)contaminants in a multi-exposure context (in terms of exposure routes and/or vectors) in relation to agricultural activities, either because they impact the quality of the environment or are impacted by environmental contamination?

-  To what extent are the identified levers of action efficient to limit these exposures and effects on the ecosystems?

Based on the expertise of the lab in terms of knowledge on determinants of contaminant dynamics in the agroecosystem in connection with agricultural practices and developed tools, we propose in future years, to structure our work around two main operational objectives:

1)  The first objective focuses on pesticides, one of our strong identifiers. The objective is to assess spatio-temporal contaminations of the environment (pesticide residues in environmental compartments) in order to study the exposition of ecosystems as well as the human exposure via the atmosphere with targeted populations being bystanders, local residents, and even the general population. The operational output will be the definition of spatio-temporal exposure maps obtained with modeling tools developed or used in the lab such as environmental fate models, atmospheric dispersion models, modeling platform such as V-Soil and Open Fluid (Project Muse, PhD planned), TyPol tool with the recently integrated ecotoxicity and toxicity parameters will be used to identify relevant compounds to study (REPAIR, PHYLODISPO projects) or to predict environmental behavior of new compounds in complement to suspect screening approaches (INSPECT project). The objectives are:

• to consolidate our knowledge on pesticide dissipation pathways up to the landscape scale;
• to improve the modeling tools by taking into account the various sources of diffuse contamination, describing as far as possible the links between agroecosystem management and pesticide dynamics in the environment and the impact of spatial configuration of plots or other landscape elements on their dissipation (linked with “Diversity” ST4);
• to improve our knowledge and associated models regarding the processes determining the environmental fate of pesticides and pesticide bioavailability by considering the medium-long term, the emergence of degradation products or the effect of formulation on active ingredient behavior.

• to better assess the long-term effects of pesticides on certain soil organisms (carabids, oligochaetes).
• to extend the scope of the current tools developed for arable crops to other contexts of pesticides practices (e.g. in viticulture)

2)  The second objective aims at assessing the environmental conditions and the management measures identified to favour or limit exposures and/or effects of contaminants. Besides pesticides, many other contaminants are studied at ECOSYS (gaseous N compounds, biotic particles - pathogens and their virulence, contaminants related with recycled biomasses such as pharmaceuticals, persistent organic contaminants, metals) which may be present in various compartments (soil, air, water, plants and soil organisms). Depending on the contaminant and related practices, various management measures can be proposed to attenuate the impacts of contaminants. For example, soil injection, hedge implantation, tillage/no tillage will have an impact on the gaseous emissions. The choice of cultivar and species mixture increase biodiversity and may limit the dispersion of biotic particles and pesticide use (“Diversity” structuring theme). The use of less impacting substitute compounds may be proposed (less impacting pharmaceutical, pesticide…). These management levers may have an impact on different steps of the exposure or effect, however, they may increase other impacts (e.g. GHG emission, nitrate leaching…). So, global impacts of the management practices need to be assessed. Looking for an integrated risk assessment and to enrich the environmental component in a multi-criteria assessment, we will base our analysis on tools already used in the lab such as 1) soil/vegetation/atmosphere pollutant exchange models and air dispersion/deposit models (ranging from the organ to the plot scale), soil transfer models (Pastis-Mulch,…), crop models, tools to the landscape or regional scale (Nitroscape, Chimere, …), modeling platforms (V-soil, …), metamodels (NH3 emission) or Typol (PhD on biodegradation of pharmaceutical, …). We will seek to improve them in order to ensure an adequate description of the factors involved during the implementation of the management practices and to address impacts that may be multiple in relation to multi-contamination and 2) biological models (earthworms, enchytraeids, carabids and micro-organisms) used to depict the mechanisms of toxic effects and to develop biological tools to assess ecotoxic effects. The implemented researches on these biological models aim to link the exposure of organisms to contaminants, to the toxic effects, considering the variability of specie sensitivity, and the influence of environmental parameters in realistic conditions of exposure, in order to predict impact of contaminants on the ecosystems. Short-term perspectives will focus on:

• identify together the levers of action to evaluate, the exposure routes to explore in order to make our approaches converge as well as possible (discussion will be organized in the first months).
• disentangle confounding effects with recycled organic biomasses (in relation with “Biomasses” structuring theme)
• a better integration of the plant / contaminants response and interactions. Processes under study are gaseous, particulate and fungal airborne deposits on the aerial parts, contamination of harvested products with emerging contaminants, description of contaminants behavior within crop models, etc... These contaminants may lead to stresses together with nowadays and future environmental conditions impacting plant health. The impact of these different stresses (alone or combined) have an impact on the plant's functioning, and in particular on its carbon and nitrogen metabolism and on its disease vulnerability (OPERATE and H2020 DECIPHER projects).

The preferred scales will be the plot and cropping system, with finer scale studies when necessary. The achievement of these objectives relies on the work developed in each of the 3 teams (following sections) and interactions will help in identifying common case studies to be considered as well as improvements required in terms of methodologies or developed tools. In terms of methodologies, being able to deal with the diversity of exposure-effect scenarios (contaminants x practices x climate) raises the question of sufficient knowledge on environmental factors (surface properties, meteorological variables) and agricultural practices (detailed information on inputs but also tillage and crop successions, cultivar choices) which is not always the case but remains essential for assessing the effects of confounding factors. A strengthening of our collaboration with agronomists may help us in that way. A reflection will also be required on the identification of reference situations to interpret observations, as the choice of these situations is far from trivial. In terms of methodology, beside the improvement of models as already mentioned, non-target screening approaches would make possible to go further in the evaluation of multiple contaminations, particularly for organic contaminants and their transformation products (in relation to some practices, cf. e.g. "Biomasses" theme), expanding our analytical capabilities for measurements in real multi-matrix conditions (air, plants, organisms) and multi-residues (including a priori screening) would also be of interest for establishing a balance of contaminants between all compartments.

Insertion within ECOSYS

The three teams of the unit are involved in this multidisciplinary theme: physical transfers in soils and atmosphere, ecotoxicology, surface physico-chemistry, environmental chemistry, ecophysiology, plant pathology. The connections are strong with the other structuring themes, which, either provide the forcing variables and the studied systems (climate, land uses, inputs, crop model), or receive the outputs of this structuring theme (e.g. models for landscape approaches).

The variety of implemented approaches and the range of studied objects, require a diversity of skills and the development of dedicated experimental systems, continuous monitoring on long-term observation or modeling devices. This creates a strong need for human resources to cover this diversity of skills as well as in budgetary terms to cover the numerous chemical, physical and biological analyzes based on an analytical park to be maintained and renewed. Many current projects and funding sources supply these activities: European projects -H2020 Pesticides to come, LIFE, ANR, INRAE, ADEME, thematic APR, ANAEE, private.... (e.g. AGRIMULTIPOL, AMP’AIR BAGAGES, COPP’R, DABARES, DICOV, DIGESTATE, EVAPRO, MIPP, … Appendix 4). The dispersion of activities is a major risk, which we will endeavor to limit by sharing our approaches (in modeling and experimentation) and by promoting their genericity and level of integration. In addition, we are developing collaborations within a diversity of structures such as LabEx BASC, FIRE, national institutes and technical institutes as well as at the international level ; for example dealing with atmospheric contaminants, with LSCE, IRCELYON, LA Toulouse, CESBIO, LCE Marseilles, IPS2, ESE, Ineris, Citepa, Meteo-France, UNIFA, APCA, AASQA- AirParif, PACA, …-, CEH, Alterra,...); for organic contaminants, with Metis, IMPMC, ICMMO, INRAE-LISAH, LBE, AgroEcologie, Agronomie, AGIR, EMMAH, ISPA- IRSTEA -Lyon, Antony, Montpellier...-, CIRAD -Recycling and Risks Unit-, Veolia, Chrono-Environnement, Univ. Claude Bernard Lyon, Univ. Paris Est Créteil (LEESU), ISA CNRS Lyon, Univ. Lyon (LEM), SLU Sweden, Alterra The Netherlands, Universities of Missouri and Toronto, ..; for biotic contaminants with BIOGER, ESPCI, MIT, …  and for metals with Veolia, CIRAD, INRAE-LSE, Agroecologie, ISPA, …- University of Zagreb,... To achieve the objectives defined within the framework of this structuring theme, in addition to strengthening these collaborations – e.g. with the Agronomy unit in Grignon in terms of agricultural practices to be considered-, we need to initiate new collaborations towards laboratories studying the fate and transformations of contaminants in living organisms, including plants (DTU, …) and human health partners (via “phytopharmacovigilance”, environmental health specialists such as the CHU de Bordeaux, toxicologists, epidemiologists...), or aquatic ecotoxicoly. As for operational issues, our research is oriented towards transferring the outputs of these activities to public decision-making (ERA - ANSES for example, ministries, APCA or at more local scales - territories, catchments, ONEMA/AFB, Ministry, CITEPA …), but it remains a challenge.