References of "Bah, Boubacar Billo"
     in
Bookmark and Share    
Full Text
See detailValorisation de l’information pédologique numérisée pour la modélisation de la percolation des pesticides vers les eaux souterraines
Bah, Boubacar Billo ULg

Doctoral thesis (2014)

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 ... [more ▼]

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. [less ▲]

Detailed reference viewed: 13 (3 ULg)
Full Text
See detailOn the use of Belgian Soil Map to predict risk of nitrate and pesticide lixiviation
Bah, Boubacar Billo ULg; Vandenberghe, Christophe ULg; Deneufbourg, Mathieu ULg et al

Poster (2014, February 26)

Pollution by nitrate and pesticides has impacts on drinking water reserves and aquatic systems. Nowadays, this problem is the key point of the European Policy with the implementation of the Water ... [more ▼]

Pollution by nitrate and pesticides has impacts on drinking water reserves and aquatic systems. Nowadays, this problem is the key point of the European Policy with the implementation of the Water Framework Directive (Directive 2000/60/EC). According to these legislations, Member States are supposed to take measures to limit environmental and toxicological effects caused by nitrate and pesticides use. This paper presents three different approaches allowing assessment of diffuse (non-point sources) pollution risks of water resources by nitrate and pesticides. The first approach consists on the interpretation of the geomorphopedological information (geologic substratum type, presence of karst phenomena, soil texture, natural drainage, profile development, type and percent of stoniness, soil thickness, …) provided by the Digital Soil Map of Wallonia. Soil physical characteristics are assessed in terms of soil water percolation/infiltration, runoff, pollutants retention, mineralization, and erosion. Second approach consists on the use of spatially distributed mechanistic models. Nitrate lixiviation from agricultural land to groundwater has been simulated from the SWAT model. Pesticide lixiviation from soil to groundwater has been predicted from the one-dimensional, dynamic, multi-layered model named PEARL (Pesticide Emission Assessment at Regional and Local scales). Model input parameters are mainly extracted from the existing soil physical and physico-chemical, crop and pesticides properties databases. Relevant soil parameters not directly available in existing databases, such as bulk density, hydraulic conductivity, potential evapotranspiration… have been derived from pedotransfers functions. Third approach consists on in situ lixiviation studies by the way of lysimeters. Concentrations measured at the bottom (2 m deep) of lysimeters represent a straight “index of risk” for groundwater and, on the other hand, allow the validation of simulation models used to predict nitrate and pesticides lixiviation risk under different scenarios. The Digital Soil Map of Wallonia, one of the core data source, allows the spatialisation of the predicted lixiviation risk at regional level, providing to the local authorities and the decision makers a tool for the identification of the areas at risk of pollution, where specific monitoring actions and prevention measures for the protection of waters can be implemented. [less ▲]

Detailed reference viewed: 33 (6 ULg)
Full Text
See detailSurface water diffuse pollution by PPP: focus on runoff & erosion
Bah, Boubacar Billo ULg; Vandendael, Laurent; Oger, Robert ULg et al

Conference (2012, April 04)

Detailed reference viewed: 79 (11 ULg)
Full Text
Peer Reviewed
See detailMise au point d'un Système d'Information Géographique (SIG), à l'échelle de la parcelle, pour l'évaluation du risque de pollution des eaux de surface et souterraines par l'usage des pesticides.
Bah, Boubacar Billo ULg; Limbourg, Quentin; Vandendael, Laurent et al

in Conférence sur les Techniques d’Application de Produits de Protection des Plantes. 15 et 16 mars 2012, Lyon, France (2012, March 15)

L’étude aborde la mise au point d’un outil SIG décisionnel, basé sur une approche « expert » par logique floue, pour l’évaluation du risque de pollution des eaux de surface et souterraines par les ... [more ▼]

L’étude aborde la mise au point d’un outil SIG décisionnel, basé sur une approche « expert » par logique floue, pour l’évaluation du risque de pollution des eaux de surface et souterraines par les pesticides. Une enquête de terrain combinée aux propriétés physico-chimiques des pesticides, a permis d’identifier la pression polluante agricole liée aux propriétés des pesticides et aux activités anthropiques. La sensibilité des sols au transfert des pesticides vers les eaux de surface et souterraines a été évaluée sur base, d’une part d’une approche par modélisation mécaniste, et d’autre part à partir de l’exploitation de l’information qualitative de la carte des sols, jugée pertinente et non explicitement valorisée par le modèle mécaniste. L’évaluation du risque global a ensuite été réalisée à partir de la construction d’un système expert basée sur la logique floue, qui intègre les évaluations spécifiques aux propriétés des pesticides, aux pratiques culturales et à la sensibilité des sols au transfert des pesticides vers les eaux, en tant que milieu transit-vecteur. L’approche par « logique floue » est un outil robuste qui permet notamment d’agréger de façon uniforme des informations de sources variées, mais aussi d’intégrer l’incertitude (imprécision) associée à certaines données, telles que celles liées aux caractéristiques physico-chimiques des pesticides ou des sols. [less ▲]

Detailed reference viewed: 153 (1 ULg)
Full Text
Peer Reviewed
See detailValorisation de la Carte Numérique des Sols de Wallonie et d’une base de données disponible en analyse de sols, dans le cadre de l’évaluation du risque de pollution des eaux souterraines par les pesticides
Bah, Boubacar Billo ULg; Vanclooster, Marnik; Oger, Robert ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(S2), 709-726

This study shows how the Digital Soil Map of Wallonia and the associated soil database Aardewerk can be combined with the MetaPEARL model to assess the sensitivity of agricultural soils to pesticide ... [more ▼]

This study shows how the Digital Soil Map of Wallonia and the associated soil database Aardewerk can be combined with the MetaPEARL model to assess the sensitivity of agricultural soils to pesticide transfer into underground water tables in Wallonia (Southern Belgium). MetaPEARL is based on an analytical expression which describes the concentration of leached pesticides at the soil profile bottom depending on available data on soil characteristics, climate and pesticide properties. The results show an important soil sensitivity to pesticide transfer with a coefficient of retention on organic matter (Kom) very weak (about 10 dm3.kg-1) or with a relatively high half-life time (DT50 about 60 days). In this case, the pesticide is weakly retained by soil organic matter or slowly degraded and then stays available in the soil and can be quickly leached during rainfalls. In other respects, the pesticide sensitivity to leaching is strongly correlated with soil texture and its organic matter content. It is also observed that the concentration of leached pesticide is strongly depending of the rainfall surplus (water flux into the soil or hydrous balance). A sensitivity analysis has shown that the model is very sensitive to soil thickness, to organic matter content, to the bulk density of the mineral fraction by textural classes and of the organic matter. Therefore, these pedological variables have to be assessed with the highest precision to avoid adding further uncertainty to the predictions obtained. On the basis of the most sensitive soil variables, the analysis of “spatial” uncertainty related to the results delivered by MetaPEARL, due to the consideration of an unique representative value by soil type and by region (deterministic approach), shows that this approach tends to under-estimate the concentration of pesticide leached in the soil. And that compared to the use of a stochastic simulation (probabilistic approach) which takes into account the soil characteristic variability within a given soil type. This stochastic approach allows also the calculation of a more relevant threshold of risk probability (percentile) which can be compared to an imposed standard in view to enhance a sustainable management of natural resources. [less ▲]

Detailed reference viewed: 116 (7 ULg)
See detailExploitation of the Soil map in Belgium
Bah, Boubacar Billo ULg; Legrain, Xavier ULg; Colinet, Gilles ULg

Conference (2011, October 14)

Detailed reference viewed: 14 (6 ULg)
See detailPESTEAUX: Implementing MetaPEARL for the Walloon Region in Belgium
Bah, Boubacar Billo ULg; Vanclooster, Marnik; Oger, Robert ULg

Scientific conference (2011, March 29)

Detailed reference viewed: 12 (2 ULg)
Full Text
Peer Reviewed
See detailÉvaluation de la sensibilité des sols au transfert des pesticides vers les eaux souterraines en Wallonie (Belgique) avec le métamodèle MetaPEARL
Bah, Boubacar Billo ULg; Mattern, Samuel; Vanclooster, Marnik et al

in Milieux Poreux et Transferts Hydriques (2010), 56

Cette étude présente l'utilisation du métamodèle MetaPEARL pour évaluer la sensibilité des sols au transfert des pesticides vers les eaux souterraines en Wallonie. MetaPEARL prédit la concentration de ... [more ▼]

Cette étude présente l'utilisation du métamodèle MetaPEARL 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. [less ▲]

Detailed reference viewed: 19 (0 ULg)
Peer Reviewed
See detailEvaluation de la sensibilité des sols au transfert de pesticides vers les eaux souterraines en Région wallonne (Belgique)
Bah, Boubacar Billo ULg; Mattern, Samuel; Vanclooster, Marnik et al

in Actes des 35èmes Journées du Groupe Francophone Humidimétrie et TraNsferts en milieux poreux (GFHN), Louvain-la-Neuve, Belgique, 23-25 novembre 2010 (2010, November)

Cette 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 ... [more ▼]

Cette 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. [less ▲]

Detailed reference viewed: 35 (2 ULg)
See detailDevelopment of a version of GeoPEARL for the Walloon region of Belgium
Bah, Boubacar Billo ULg; Vanclooster, Marnik; Oger, Robert ULg

Scientific conference (2009, November)

Detailed reference viewed: 19 (0 ULg)