Numerical modeling of the pollutant spread and a web application for environmental monitoring to support mine reclamation activities

Heavy metal pollution is a serious and urgent issue of integrated watershed management in Sardinia and worldwide. To determine the effective management strategies for pollution control, it is essential to quantify the input and output fluxes of metal by analyzing the environmental system in all its main components. Numerical physically-based models can simulate the behavior of a system, such as a river’s watershed, starting from the knowledges of the physical processes that occur in the studied area. In this work, the Rio San Giorgio basin was studied, due to the mining activities in the Iglesias Mine District, that caused severe pollution in the area. This area is in fact characterized by several mining areas, wastes and tailings, abandoned after centuries of intense mining activity, that mainly exploited minerals of Zn and Pb. SWAT hydrological model (Arnold et al., 1998) and SWAT Heavy Metal (HM) module (Meng et al., 2018) were used to simulate the fate and the transport of the Zn and Pb in the different mediums of the watershed system. Moreover, future simulations were run using Regional Climate Models of the Euro-CORDEX experiment (Giorgi et al., 2009) as climate forcing for the watershed models. This toolset allowed to simulate transport of Zn and Pb in the surface waters of Rio San Giorgio for a historical and a future period, with evaluation of some waste management scenarios. The general decrease of mean rainfall and the increase of extreme precipitation events projected by the RCMs for the future is well reflected in the results of the SWAT and SWAT-HM modellization. In fact, the mean loads of Zn and Pb in the river tend to a decrease, but extreme loads are projected for the future in occurrence of intense precipitations predicted by the RCMs models. A web-application (CESApp) Decision Support System (DSS) was also developed to share the results of the modeling, such as models’ inputs, outputs and the different scenarios of the metals spread with researchers and stakeholders.