Monitoring and modelling the role of phytoremediation to mitigate non-point source cadmium pollution and groundwater contamination at field scale

The study presented in this paper was carried out within the framework of the EU-Life+ EcoRemed project with the main aim of evaluating the effectiveness of a phytoremediation technique (the EcoRemed protocol) developed for field-scale reclamation of contaminated agricultural sites. The methods discussed here should be viewed as a proof-of-concept and their potential is shown at the Trentola test site subjected to low cadmium contamination, a potentially toxic element (PTE), presenting hazards for human health and the environment. Advanced monitoring equipment and modelling tools are employed to estimate water flow and solute transport in the soil-vegetation-atmosphere system, with specific emphasis to assess potential contaminant movement towards the groundwater. The strength of the phytoextraction process is evaluated by comparing two basic scenarios: i) a bare soil only condition (BS scenario); and ii) a distributed phytoextraction activity in the field obtained by planting poplar trees (Populus nigra spp) (PP scenario). Water and contaminant balance are modelled at plant scale by using the HYDRUS-1D code based on the Richards equation and the advective-dispersive equation, respectively. Sensitivity analyses enabled specific features of the phytoextraction process to be identified and showed the importance of setting up cost-effective monitoring devices to capture the main features of the problem under study. Moreover, especially with the aim of transferring the knowledge gained to public bodies and stakeholders, we suggest that the plant-scale monitoring and modelling activities be conveniently complemented with a modelling exercise applied to the entire field area, using the three-dimensional HydroGeoSphere (HGS) modelling tool.