Aline Grard

The Sturtian 'snowball' glaciation: fire and ice

Abstract The Sturtian ‘snowball’ glaciation (730 Ma) is contemporary with the dislocation of the Rodinia supercontinent. This dislocation is heralded and accompanied by intense magmatic events, including the onset of large basaltic provinces between 825 and 755 Ma. Among these magmatic events, the most important one is the onset of a Laurentian magmatic province at 780 Ma around a latitude of 30°N. The presence of these fresh basaltic provinces increases the weatherability of the continental surfaces, resulting in an enhanced consumption of atmospheric CO 2 through weathering, inducing a global long-term climatic cooling. Based on recent weathering laws for basaltic lithology and on climatic model results, we show that the weathering of a 6×10 6 km 2 basaltic province located within the equatorial region (where weathering of the province and consumption of CO 2 are boosted by optimal climatic conditions) is sufficient to trigger a snowball glaciation, assuming a pre-perturbation PCO 2 value of 280 ppmv. We show that the Laurentian magmatic province might be the main culprit for the initiation of the Sturtian ‘snowball’ glaciation, since the Laurentian magmatic province had drifted within the equatorial region by the time of the glaciation.

Modelling atmospheric CO2 changes at geological time scales

By trapping infrared radiation, atmospheric CO2 contributes significantly to the greenhouse warming of the planetary surface. Hence, it is thought to have played a key role in the evolution of the Earths climate over geological time. The history of atmospheric CO2 is available only for the last few hundred thousand years from the analysis of the air trapped in cores of ice. Therefore, data regarding Pre-Pleistocene atmospheric CO2 must be derived from proxies. These provide indirect estimates of atmospheric CO2 and are much less reliable than ice-core data. The main proxies used to reconstruct atmospheric CO2 are: the 13C isotopic fractionation of marine organisms, the paleo-pH recorded in the boron isotopic composition of ancient carbonates, the stomatal density of fossil leaves and the 13C isotopic composition of paleosols.

PEGASE, an integrated river/basin model dedicated to surface water quality assessment: application to cocaine

Abstract The scientists of the Aquapôle of the University of Liège have been involved in environmental modeling for more than 20 years. Among other, its current R&D unit focuses on the compartment of surface water, and – for modeling processes – is specialized on the water quality. One of its environmental models, called PEGASE (Planification Et Gestion de l’ASsainissement des Eaux), French acronym for “Planning and management of water purification” is devoted to the modeling of the environmental state of surface water, at different scales from small watersheds (10 km2) and basins up to entire transnational Districts (more than 100.000 km2). The software is used operationally by several administrations (Agencies and Ministries) mainly through Europe (France and Benelux, Germany …), and several calculations have also been performed at international District levels for international commissions (Scheldt, Meuse, Moselle …). Recently, the PEGASE model has been adapted to describe the cocaine’s behavior (using a stable metabolite of the cocaine in the environment: the benzoylecgonine) in waste water, waste water treatment plants (WWTP) and surface water. The cocaine is newly described in the model as an additional micropollutant (Pegase already treats numerous heavy metals), thanks to the implementation of new state variable equations and their specific parameterizations. At a first stage, only the urban sources (releases associated to the consumption by inhabitants) were considered as the industrial releases and the soil loads are assumed to be negligible. Simulations of benzoylecgonine have been done in the Walloon and Flemish regions, where many measurements from the COWAT project were available. These first results are showing a good agreement between calculated and measured values. This ability of the model to simulate the fate of the cocaine derivatives in surface waters should be continued and extended to other metabolites.

Modelling Catchment Scale Agricultural Pollution in North Tunisia Using the PEGASE Model

Diffuse pollution in agricultural watershed may contribute to unsustainable use of water resources and implies new challenges in water management.

Lessons Learned from a Partnership Between the University of Liège and Water Agencies for the Management of Surface Water Quality

An innovative partnership has been established between a university team (R&D unit of Aquapole, University of Liege) and public stakeholders managing surface water quality (Water Agencies and Administrations) in order to develop a mathematical model included in a software suite that meets the expectations of operators. This development strategy based on the needs of partners is a guarantee of success, directly benefiting from the quality improvement of aquatic environments. The partners have complementary missions consisting in the monitoring of aquatic environment and in scientific research. The research was carried out in the European context where public water policy has to be supported by robust knowledge to establish the relationships between the state of environment and the associated pressures. In this context, the PegOpera software suite is a tool supporting the management of surface water quality, from local scale to transnational level, up to the River Basin District scale. The main purpose of this operational tool is its ability to explicitly describe the pressure/impact relationships and to help Administrations in their planning missions through prospective simulation of measures (River Basin Management Plans in the scope of the Water Framework Directive 2000/60/EC).