Evaluation of suspended sediments dynamics in a catchment contaminated with PCBs (Samme River – Belgium)

GISSe

Mapping hotspots of environmental burdens in the framework of cumulative risk assessment in wallonia

Differential exposure to multiple environmental burdens and benefits across populations with varying vulnerability can contribute heavily to health inequalities. Developing environment and health information systems has therefore become a major focus for public health. In this framework, the Scientific Institute of Public Service (ISSeP) works on building an integrated approach of environmental exposure assessment in the Walloon region, Belgium. This study develops an indexbased approach to assess the multiple environmental burdens at regional level and detailed local resolution that can be used in a spatial web tool. Indicators are based on environmental measure of pollutants in ambient air and soil, and on stressors for citizens related to noise and radon. Two methods were combined to identify both zones where pollutions and stressors are cumulating, even below threshold values, and zones where the exceedance of threshold values is frequent. First, a ratio value is calculated for each spatial unit (i.e. statistical sector) by dividing the indicator value by the corresponding threshold values quoted by the WHO or Walloon legal limit values. Other pollution sources (roads, industries, landfills, mine heaps, ...) are estimated by specific GIS processing based on Euclidean distance analysis which vary in relation to pollution effect to population. Secondly, environmental indicators are mapped as proportions of spatial units where the level of potential detrimental environmental factors exceeds the limit values. The spatial tool makes then possible the flexible and weighted combination of the normalized indicators, by computing online the resulting composite indicator. The approach developed in the present study will be compared to other case studies and their aggregation methods by focusing on results and the possible implications on planning interventions by the decision makers

Suspended sediment and contaminant transport monitoring in navigable and unnavigable waterways (Wallonia, Belgium)

GISSe

Fate of TiO2 Nanoparticles in Carbonate and Silicate Aquifers

The increasing use of engirneered nanoparticles leads to their relaese in the environment, i.e. in aquifers. However, their transport through aquifers remains unclear up until now. Nanoparticle stability in solutions depends on its surface charge which varies with pH conditions but also on the ionic strength of the solution. Consequently, nano-sized TiO2 (nTiO2) are expected to behave differently in silicate and carbonate aquifers as groundwater chemistry is influenced by the host rock mineralogy. To assess the vulnerability of these types of aquifers to engineered nanoparticles, the stability of nTiO2 is evaluated in four different types of water pumped from carbonate and silicate aquifers and in Milli-Q water. A suspension of nTiO2 (30 g/l, pH 1.3 with HNO3) was diluted in each type of water (2 replicates) to reach a concentration of 30 ppm and sonicated at 330W during 3 minutes. These suspensions were then allowed to settle undisturbed for up to 5 days for a stabilisation experiment with daily measurements of Ti concentrations. Diameters of the particles were measured for samples of the first day of the stabilisation experiment but also on a second bench of samples. These suspensions were prepared by diluting the same nTiO2 suspension in filtered groundwater (0.45 μm). TiO2 concentrations in supernatant Milli-Q solution (pH= 3.9) were stable during the experiment. In contrast, nTiO2 concentrations measured in groundwater (pH=7.6±0.5) dropped from 30 ppm to ca 1 ppm in 1 day. Sedimentation rates were slightly higher for water from carbonate aquifers compared to silicate aquifers during the first day. After two days, this difference was already insignificant. Diameters of particles present in the samples were the largest in natural groundwater, smaller in filtered groundwater and the smallest in Milli-Q water. This experiment proved that groundwater composition favours rapid aggregation, the likely effect of pH-conditions and the presence of natural suspended particles. Further analyses are needed to determine how these aggregates behave in the aquifer matrix

Application of the HFEMC method to an abandoned coalfield in Belgium: From conceptualisation to scenario simulations

The Hybrid Finite Element Mixing Cell (HFEMC) method is a flexible modelling technique particularly suited to mining context (Brouyère et al., 2009). The principle of this method is to subdivide the modelled zone into several subdomains and to select a specific equation, ranging from the simple linear reservoir equation to the groundwater flow in porous media equation, to model groundwater flow in each subdomain. The model can be run in transient conditions, which makes it a useful tool for managing mine closure post-issues such as groundwater rebound and water inrushes. An application of the HFEMC method to an abandoned underground coal mine near the city of Liège (Belgium) is presented. The case study zone has been discretized taking advantage of the flexibility of the method. Then, the model has been calibrated in both steady-state and transient flow regimes based on hydraulic head and water discharge rate observations. Finally, the calibrated model has been used to run several scenarios in order to assess the impacts of possible future phenomena on the hydraulic heads and the water discharge rates. Among others, the simulation of a strong rainfall event shows a quick and strong increase in hydraulic heads in some exploited zones coupled with a strong increase in associated water discharge rates. This could lead to stability problems in the hill slopes near the exploited zones. This kind of predictions can greatly help managing and predicting mine water problems in this particularly complex mining system

Quantitative and qualitative evaluation of sediment and contaminant transport in the Samme river catchment (Brabant region - Belgium)

In Wallonia (Belgium), the maintenance of waterways is currently exclusively managed in a curative way. When local sediment accumulations are detected in waterways, bathymetric surveys are conducted in order to quantify the volume of sediment to be removed and chemical analyses of samples allow the characterization of sediment quality. Collected data only allow a short-term management of the matter generated by dredging operations. Medium- or long-term planning of dredging operations is currently not possible, due to a lack of knowledge on sediment fluxes and associated pollutant transport. In particular, issues related to the interactions and mixing of recent and older sediments, or to the input of sediment from unnavigable waterways into larger navigable waterways, are poorly understood. Operational tools allowing the assessment of the effectiveness of preventive measures to be implemented in order to improve the management of sediment in Walloon waterways also have to be developed. This research project aims at contributing to the development of such tools and focuses on the Samme river watershed (Senne catchment – loamy Brabant Region), deemed to be representative of Walloon issues. The Samme river is categorized as an unnavigable waterway. It runs along the old Charleroi-Brussels canal and flows into the new Charleroi-Brussels canal at the foot of the Ronquières inclined plane. The sediments of the bed of the Samme river are characterized by a high concentration of micropollutants (mainly PCB) and contribute to the contamination of a greater volume of sediments in the new Charleroi-Brussels canal, significantly increasing the cost of periodic dredging operations in the canal. The methodology developed is based on (I) an extended monitoring of sediment and pollutant fluxes at the outlet of the catchment and (II) an assessment of within-catchment sediment and pollutant transport. The origin of the Samme riverbed sediments contamination by PCB is poorly understood. Chemical analyses of the sediments of the bed were carried out along the linear course of the Samme river and its main tributary in order to identify the source of pollution. However, numerous connections between the old canal and the Samme river contribute to the transfer of stream sediments and pollutants between both systems and complicate the identification of the source of PCB. At the outlet of the catchment, different methods of river sediment sampling (automatic samplers, turbidity sensors, Time Integrated Samplers) are currently being implemented in order to (I) monitor the amount of suspended matter carried by the Samme river into the Charleroi-Brussels canal, (II) evaluate the associated fluxes of pollutants and (III) evaluate the possibility of setting up a system of retention of the sediments in the Samme catchment.GISSe

Document guide pour l'utilisation d'une cavité existante (mine / carrière) comme réservoir d'une installation hydroélectrique à accumulation par pompage

Underground mines/quarries or open pits are manmade earthworks resulting from previous extraction of natural resources. They were mostly abandoned after resources depletion but underground or surface excavations remain. Pumped Storage Hydroelectricity (PSH) is one of the only efficient solutions for large scale energy storage. During peaks of energy production, water is pumped from a lower reservoir to an upper reservoir. On the other hand when demand peaks, energy is generated when water is transferred to the lower reservoir. The objective of this work is to study the recovering of abandoned excavation volumes as lower reservoirs for pumped storage hydroelectricity. Underground Pumped Storage Hydroelectricity (UPSH) is a particular case where at least one of the reservoir lies below the surface. Compare to classical PSH plants, using an existing cavity as a reservoir raises three main additional problems: 1) What are the water movements and thus discharge availability at the pump/turbine location depending on the reservoir (complex) geometry? 2) What are the exchanges between the reservoir (usually not watertight) and the surrounding medium? 3) How can the reservoir sides resist to cyclic loading imposed by the plant operation? In the following, some simplified criteria and issues are provided to carry out feasibility assessments of such rehabilitation projects, from the existing reservoir point of view. These criteria do no replace a detailed and complete study but draws the attention on problems specific to PSH using existing cavities as reservoir. They do not concern problems existing for every PSH project, such as location of electricity transport lines, availability of water

Stockage électrique par pompage turbinage souterrain en Wallonie (Belgique) - Potential et challenges

peer reviewedPumped Storage Hydroelectricity (PSH) is a well-known and efficient technology to store various amounts of electricity. In most parts of Europe, appropriate sites for new classical PSH plants are getting scarce. An alternative consists in using underground volumes as lower reservoirs to build so-called Underground Pumping Storage Hydroelectricity (UPSH) plants. The paper presents the main results of a research project currently investigating the potential and feasibility of such innovative plants in the context of Wallonia, where numerous abandoned mines and quarries are located all over the territory. After a description of the main types of reservoir configurations existing in the considered region and the evaluation of their expected energy storage potential, the tools and methodology developed in the scope of the project are presented. Their application to the case of an underground slates quarry and an open pit chalk mine helps in identifying the remaining challenge

Smartwater - WP5 - Sites de stockage hydraulique : Inventaire, Analyses géomécanique, hydrogéologique et hydraulique

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