Risks assessment of water pollution by pesticides at local scale (Pesteaux Project): study of polluting pressure

Pollution of water resources (surface waters and ground waters) by pesticide uses is one of the key point of the European policy with the imptementation of the Water Frame Work Directive (2000/60/EC) and the thematic Strategy on the Sustainable use of pesticides. According to this Legislation, the Member States must initiale measures to limit environmental and toxicologieal effects caused by pesticide uses. The Agricultural Research Centre of Wallonia (CRA-W) emphasized the need of a toot for spatial risk analysis and develops it within the framework of PESTEAUX project. The originality of the approach proposed by the CRA-W is to generate maps to identify the risk of pollution at locale scale (agricultural parcel). The risk will be assessed according to the study of different factors, grouped under 3 data's tayers: polluting pressure, vulnerability of the physical environment (soil) and meteorological data. This approach is directly based on the risk's definition which takes into account the polluting pressure, linked te the human activities, and the vulnerabitity of the soil, defined by factors of physical environment which characterize the water flow in the parcel. Moreover, meteorological data influence the intensity and likelihoad flow of water, and indirectly pesticide by leaching or runoff. The PESTEAUX's approach to study the pollution is based on the model "source-vector-target". The source is the polluting pressure, in other words, the pesticides which could reach the targets. The main vector is the water which vehicles the pesticide on and trough the soil until the target which are the surface waters or ground waters. ln this paper we introduce the factors contributing to the polluting pressure. These factors are linking to the human activities and more precisely, to the pesticide uses. The factors considered have an influence on pesticide's transport by water (in its solid state or in dissolved state by leaching, run-off, or erosion) but also on a set of process controlling pesticide behavior in the environment such as degradation, sorption, ...

Evaluation de la sensibilité des sols au transfert de pesticides vers les eaux souterraines en Région wallonne (Belgique)

peer reviewedCette étude présente l'utilisation du métamodèle MetaPEARL (Tiktak et al., 2006) pour évaluer la sensibilité des sols au transfert des pesticides vers les eaux souterraines en Wallonie. MetaPEARL prédit la concentration de pesticide lixivié au bas du profil pédologique en fonction de données facilement disponibles sur les sols, le climat, et les propriétés des pesticides. MetaPEARL a été appliqué pour quatre pesticides génériques A, B, C et D (FOCUS, 2000). Les résultats obtenus montrent une sensibilité plus importante des sols de Wallonie aux transferts des pesticides de type A et B, permettant ainsi de distinguer des régions relativement contrastées d’un point de vue de la sensibilité de leurs sols au transfert des pesticides vers les eaux souterraines. Ce contraste régional est corrélé d’une part à la variabilité régionale des teneurs en matière organique des sols, et d’autre part au gradient pluviométrique nord-sud observé en Wallonie. On constate également que la concentration en pesticide lixivié est plus importante en automne qu’au printemps

Valorization of the Digitalized Soil information for the modelling of pesticide lixiviation into groundwater

In Wallonia (southern Belgium), 81% of human drinking water is captured from groundwater tables. In spite of actions implemented under the European directives and thematic strategies, the required standard (0.1 µg L-1 by pesticide and 0.5 µg L-1 for all pesticides) for human drinking water is most often exceeded at some catchments. Tools such as mechanistic models are appropriate since they allow an a priori estimation of pesticide concentrations leached at the bottom of soil profile, which could reach the groundwater tables. However, simulations often lead to a degree of uncertainty due to the approximations noted in the models, or due to the reliability of available data. The main objective of this thesis was to improve the usefulness of the Digital Soil Map of Wallonia (DSMW) and the associated soil analysis database named “Aardewerk” in the framework of the evaluation of the groundwater table contamination by pesticides, in order to reduce approximations associated with the GeoPEARL model and its meta-model MetaPEARL in the area of Condroz. In order to cover the broad spectrum of pesticides used in agriculture in Wallonia, nine theoretical pesticides have been defined. The first research question is to measure the sensitivity of GeoPEARL to two soil data parameterization schemes at the regional scale, depending on whether we first aggregate soil data at a regional scale before application of the model (AC approach); or we first apply the model to soil profiles and aggregate simulated leached concentrations afterwards (CA approach). The results show a significant difference between the two approaches, compared on the basis of a spatial threshold (80th percentile) calculated by soil type. Moreover, this difference varies depending on pesticide type, and is more important when the simulated concentrations are very low. It is also clear from this analysis that only pesticides located in certain ranges of DT50 (30 and 67 days) and Kom (58 and 252 dm3 kg-1) give concentrations more often above water potability standard of 0.1 µg L-1. The second research question is to calibrate MetaPEARL metamodel (simplified model) based on GeoPEARL simulated concentrations, from which it was derived by considering only the most sensitive parameters of GeoPEARL. The objective by developing a metamodel is to provide a simple tool, usable for a first evaluation of pesticides leaching in order to identify the most risk-prone areas, but also readily transposable for a global decision support system. In contrast to the approach of MetaPEARL calibration used until now, taking into account soil morphology through soil horizons (layers) types explains about 80% of the spatial variability of pesticide concentrations obtained from the complete original GeoPEARL model. The third research question is to take into account the spatial variability of input variables within the same soil typological unit using stochastic simulations to assess the uncertainty associated with deterministic simulations (taking into account average values by soil type for the input variables at the regional scale) obtained from MetaPEARL. The random spread of soil characteristics variability leads to a very significant spreading of simulated pesticide concentrations. Moreover, we obtain values of 80th spatial probabilistic percentile higher than those obtained from the deterministic approach. Consequently, for a risk mapping designed to aid decision-making tools, the probabilistic approach should be used since it allows, by taking into account the spatial variability of the model input parameters, to obtain more realistic concentrations of leached pesticides

Caractérisation pédogénétique et évaluation des sols en vue d’une gestion environnementale et d’un aménagement durable du terroir de Ticuantepe (Nicaragua)

Ce travail porte sur l'étude du terroir de Ticuantepe, situé au sud-est de Managua, dans la région Pacifique du Nicaragua. Il a été question de le caractériser d'un point de vue pédogénétique et agropédologique, et de dégager les potentialités de ses sols, en vue d'une gestion environnementale et d'un aménagement durable. Dans une première étape, divers documents concernant le contexte environnemental ont été récoltés, exploités et confrontés. Ce qui a aboutit à la délimitation d’une zone d’étude représentative du terroir, et à l'identification au sein de celle-ci de trois secteurs, correspondant à quatre unités géomorphopédologiques. Le terrain a été abordé via quatre toposéquences, parcourues depuis le volcan Masaya (à l'est) jusqu’aux contreforts des sierras (à l'ouest), pour la réalisation de sondages à la tarière pédologique. Sur base des observations réalisées, six profils (fosses) pédologiques ont été creusés, décrits, et échantillonnés pour les analyses au laboratoire. De cette étude, il ressort que les sols de Ticuantepe sont jeunes et développés sur cendres volcaniques et scories. Ils sont riches en verres mais ont des propriétés allophaniques peu marquées. Le secteur montrant les meilleures potentialités agropédologiques est le Nord. A l’opposé, celui présentant les plus faibles est le Sud. Quant au secteur centre, il se rattache à la fois au Sud et au Nord, respectivement dans ses parties est et ouest. Ce gradient de potentialité sud-nord et est-ouest, suit l'aplanissement du relief et l'éloignement par rapport au volcan Masaya.This study has been carried out in Ticuantepe, south est of Managua, Pacific region of Nicaragua. The pedogenetical and agropedological factors of soil agricultural potentialities have been studied within a sustainable development perspective. In a preliminary stage, the analysis of existing map informations have lead to the delimitation of a representative study zone and to the identification of three sectors and four geomorphopedological units within this zone. Four toposequences, in east-west directions, from Masaya Volcano to the Sierras spurs, were studied on the ground. This survey consisted in soil observations (augerings and pit profiles) as well as land use and crop types identification. Soil samples were collected for laboratory analysis. A conclusion of this study is the relatively young character of the soils, which developed from volcanic ashes or scoria. They are rich in glass but present few evidences of allophonic properties. The soils from north sector show the highest agricultural properties. To the opposite, the south sector appears to be the least suitable for agricultural management. The Central sector is a transitional area between South and North. A fertility gradient was identified as a result of the landscape shape and the distance from the Masaya Volcano.En la región del Pacífico de Nicaragua; al sud de Managua, se ha iniciado estudios, correspondientes al territorio de Ticuantepe ; caracterizando el territorio desde el punto de vista pedogenético, para llegar a mostrar las potencialidades agropedológicas, dentro un objetivo de la gestión del medio ambiente y de ordenamiento estable. Antes de iniciar el trabajo de campo, muchos documentos referidos al contexto del medio ambiente de la zona de estudio han sido recopilados, comparados y analizados. Es así que nos ha llevado a la delimitación de una zona de estudio representativa del territorio del sud de Managua, y a la identificación en esta zona de tres sectores principales, correspondientes a cuatro unidades geomorfológicas. Estos tres sectores son : 1) el sector sud, con un relieve muy escarpado, reagrupando las unidades 1 y 2 ;2) el sector central, menos escarpado y más ondulado, correspondiendo a las unidades 3 ; y 3) el sector norte, plano y que corresponde a la unidad 4. El terreno ha sido seguidamente abordado en cuatro secuencias, recortando la zona de estudio dentro la dirección este-oeste, después del volcán Masaya hasta los contrafuertes de las sierras. Se han realizado sondajes pedológicos a lo largo de las cuatro secuencias. En base a las observaciones durante la campaña de sondajes ; seis perfiles pedológicos han sido abiertos, descritos de manera exhaustiva, y muestreados para ser analizados en laboratorio. La integración de fases de campo y de laboratorio a permitido caracterizar los suelos y evaluar sus potencialidades agropedológicas. La investigación, nos mostró que los suelos de Ticuantepe son jovenes y desarrollados sobre cenizas volcánicas y escorias. Son ricos en cristales y muestran propiedades alofánicas poco marcadas. El sector que presenta las mejores potencialidades agropedológicas se encuentra al norte. De manera contraria, al sector sud que presenta las condiciones de potencialidad agropedológica más pobres. En cuanto al sector central, se encuentra entre las dos, la parte este muestra las potencialidades similares a las del sector sud, mientras que la parte oeste está ligada al sector norte. Este gradiente de potencialidades sud-nord y este-oeste, es seguido por el aplanamiento del relieve y el alejamiento con respecto al volcán Masaya

Analyse des résultats du contrôle APL 2013 et évolution depuis 2008 à l’échelle des masses d’eau souterraine de Wallonie

Programme de gestion durable de l’azote en agriculture wallonn