Délivrable 12 (A) : Interprétation des données disponibles pour les eaux souterraines hors zones de PAP et présentation de l’outil INFO- FONDS partiel.

Pollusol

Controlling factors and occurrence of inorganic and organic compounds in groundwater of urban and industrial areas

A relatively extensive survey of groundwater contaminants is performed in urban and industrial contexts, at the regional scale (Walloon Region of Belgium), outside spots of contamination related to contaminated sites. More specifically, the most detected inorganic trace elements and organic contaminants are identified and their levels of occurrence are described statistically. Mechanisms that can explain their occurrence in groundwater are discussed. From a more pragmatic point of view, the data set has been also used to derive upper limits of pollutant background concentrations to be used in decision-making related to the management of contaminated groundwater in urban and industrial environments. The results presented are based on 243 samples from 8 sectors located in different geological contexts and different urban and industrial contexts. Each groundwater sample was analyzed for 19 inorganic trace elements, 61 organic micro-pollutants and 10 major and minor elements. Five physico-chemical parameters were measured in the field, at the time of sampling to determine the environmental conditions prevailing in groundwater. For comparison, existing groundwater analyses in natural context, available for the entire Walloon Region, were compiled from several databases. Cumulative distribution function plots allow comparing the distributions of inorganic trace elements in urban and industrial sectors to those obtained at the scale of the entire Walloon region. Cumulative distribution function plots are also used to compare the distribution of the inorganic trace elements in the different lithologies, in urban and industrial contexts. The composition of groundwater is altered in urban and industrial sectors with increased concentrations for most inorganic trace elements and organic contaminants. Anthropogenic influence is not limited to inputs of pollutants but also to alterations of subsurface environmental conditions, in particular redox conditions, resulting in the mobilization of pollutants. The influence of lithology is also marked in the data set

Diffuse urban and industrial groundwater pollution with metallic trace elements A comparison between affected and unaffected areas

For metalic trace elements, spatially distributed background concentrations will be defined as a function of geological and hydrogeological context and considering the impact of diffuse pollution.Pollusol

Caractérisation hydrochimique complémentaire visant à établir les sources de contamination de la nappe alluviale de la Meuse entre Engis et Herstal (masse d’eau souterraine RWM073) - Délivrable 2 - Description des résultats obtenus suite à la campagne d’échantillonnage et à l’analyse des échantillons.

Caractérisation hydrochimique complémentaire visant à établir les sources de contamination de la nappe alluviale de la Meuse entre Engis et Herstal (masse d’eau souterraine RWM073

Caractérisation hydrochimique complémentaire visant à établir les sources de contamination de la nappe alluviale de la Meuse entre Engis et Herstal (masse d’eau souterraine RWM073) - Délivrable 1 - Méthodologie pour l’exécution des travaux et plan d’échantillonnage.

Caractérisation hydrochimique complémentaire visant à établir les sources de contamination de la nappe alluviale de la Meuse entre Engis et Herstal (masse d’eau souterraine RWM073

Délivrable 20 (A) : Stratégie d’échantillonnage et interprétation des données récoltées pour les eaux souterraines dans les zones de PAP - Outil INFO-FONDS eau

Pollusol

Délivrable 14 (B) : rapport final parties eaux souterraines. Volet 2.1 : Détermination des concentrations de fond dans les nappes au droit des zones à caractère industriel affectées par des pollutions atmosphériques de proximité, cartographie et compilation des données existantes à propos des concentrations de fond dans les nappes sur le restant du territoire. Volet 3.3 : Développement de solutions de gestion à caractère soutenable et durable pour la maîtrise des risques du transfert vertical et des flux de dispersion à l’origine de sites industriels ou de zones particulières de pollution du sol existant dans les zones de PAP.

Pollusol

Hydrogeochemical mechanisms driving the occurrence of elevated fluoride contents in crystalline aquifers in Benin, Western Africa

Elevated concentrations of fluoride in drinking water is the source of severe healthy problems such as dental or skeletal fluorosis. High concentrations of fluoride are often observed in fractured and altered crystalline aquifers around the world. However, the hydrogeochemical mechanisms leading to such elevated fluoride concentrations are usually not fully understood. In particular, it is important to make the link between these elevated concentrations and the geological context in order to make efficient recommendations on appropriate locations of further groundwater abstraction wells. This is the case in Benin, Western Africa, where groundwater from crystalline bed-rock aquifers is the main source for drinking-water supply. In this context, this research aims to identify the hydrogeochemical processes governing groundwater mineralization and the origin of the high fluoride concentrations. The investigations are based on groundwater samples collected in the central part of the country (Department of Collines), characterized by hard Precambrian aquifers. The hydrogeological system consists of a thin altered bedrock layer (shallow aquifer) and a deeper fractured crystalline bedrock (deep aquifer). The most significant groundwater quality problems in the area relate to the high fluoride (more than 7 mg / l) and nitrate (over 400 mg / l) concentrations in groundwater. The collected hydrogeochemical dataset was explored using geochemical approaches and multivariate statistics. The results reveal that the water mineralization derives from hydrolysis of silicate minerals, but it is also influenced by anthropogenic effects, particularly in the shallow reservoir. However, fluoride has a natural origin, essentially related to weathering of silicate minerals, mainly from biotite. Ion exchanges between groundwater and the rock matrix also contributes to increase fluoride concentrations in groundwater. Earlier saturation of water with calcite and the precipitation of this mineral due to bicarbonate excess reduce calcium activity are favorable of the release of fluoride by rocks. Further investigations are going on to make the link between crystalline rock types, associated primary minerals and fluoride concentrations in order to identify the geological contexts which are more prone to such problems