The general objective of the project is to develop an innovative methodology, coupling numerical modelling and monitoring, to investigate the transport of pollutants through the vadose zone and across scales. Numerical modeling will be combined with noninvasive geophysical techniques to infer in situ dynamic water flow and solute transport characteristics.
The project will require a detailed characterization of an experimental site both at field scale (the applicative scale) and at laboratory scale on large undisturbed soil columns. The experimental site will include a strongly layered soil, with at least two-three layers of contrasting physical and pedological characteristics. The soil columns will be not less than 100 cm height and 30 cm diameter, to include at least two-three soil layers of the field profile.
Actually, the scale problem will be the core of the project because of its complexity, arising from the large spatial variability of
physical, chemical and biological properties involved in the pollutant transport through the soil profile. Accordingly, experiments to be carried out both on large soil columns and at field scale will allow to account for the role of heterogeneities at different scales on determining the transport behavior through the vadose zone.
Specific objectives will be to gain understanding and insight into (i) the contaminant transport processes through strongly layered soil profiles, also by accounting for root uptake and preferential flow processes in the root zone (ii) the role of the layers interface between and how this influences the correlation between contaminant travel times and thus the solute transport mechanisms, which is crucial to deduce the travel times distribution along the unsaturated profile; iii) the contaminant transport through preferential paths; iv) the potential of using non-invasive geophysical technologies to rapidly characterize the solute transport behavior of the soil-profiles (even in presence of the bedrock), systems at applicative scales.
After analyzing specific transport mechanism at the laboratory scale, numerical simulation with a specifically developed
physically-based mathematical model will be performed for both the case study systems. The model mechanisms and
parameterization will be tested by a field experiment where contaminants concentration and water content will be monitored along a 50m transect. First, a deterministic representation will be used for the layered profile, to gain insight into the mean behavior. Second, a stochastic heterogeneous description with Monte Carlo analysis will be used to investigate how the processes and mechanisms of interest are influenced by the soil and rock heterogeneity and the possible preferential flow facilitated contaminant transport.