Hydrogeological characterization of a closed MSW landfill using multivariate statistical analysis and groundwater numerical modelling

This work deals with a groundwater pollution event from a Municipal Solid Waste (MSW) landfill, at present closed and subjected to the post-operative managing since 2003. The study area is located in the alluvial plain of southern Lombardy region (North Italy), and the landfill is placed on a Holocene alluvial terrace produced by subsequent depositions and erosions phases of the Lambro River (Fig 1). In 2014, intense rainfalls (up to 1400 mm/year compared to 600 mm/year on average) greatly contributed to increase the leachate level up to overflow the land surface around the landfill. The consequent percolation through the soil induced a deterioration of the groundwater quality. The work aimed to a) define the conceptual model both of the aquifer system and the pollution; b) identify the consequences of the leachate infiltration on groundwater c) understand if a complete natural attenuation (NA) was achieved. To this end, a hydrogeological and a hydrochemical characterization was obtained using a standard approach coupled to hierarchical cluster analysis (HCA) and numerical groundwater flow modeling