Analytical models for the simulation of contaminants’ fate and transport in the unsaturated zone are used in many engineering applications concerning groundwater resource management and risk assessment. As a consequence, several scientific studies dealing with the development and application of analytical solutions have been carried out. Six models have been selected and compared based on common characteristics to identify pros and cons as well as to highlight any difference in the final output. The analyzed models have been clustered into three groups according to the assumptions on contaminant source and physico-chemical mechanisms occurring during the transport. Comparative simulations were carried out with five target contaminants (Benzene, Benzo(a)pyrene, Vinyl Chloride, Trichloroethylene and Aldrin) with different decay’s coefficient, three types of soil (sand, loam and clay) and three different thicknesses of the contaminant source. The calculated concentration at a given depth in the soil for the same contamination scenario varied greatly among the models. A significant variability of the concentrations was shown due to the variation of contaminant and soil characteristics. As a general finding, the more advanced is the model, the lower the predicted concentrations; thus, models that are too simplified could lead to outcomes of some orders of magnitude greater than the advanced one.

Soil contamination is an issue of paramount importance to assess human health (HHRA) as well as ecological (ERA) risk assessment. To analyze risk scenarios related to contaminated soils, the identification of sources, either of primary or secondary type, as well as the assessment of propagation and fate processes is needed. Although many studies refer to the transport of pollutants in fully saturated porous media, little efforts have been made concerning the case of partially saturated soils so far. The matter is of interest as the contamination in the fully saturated region may take place as a result of the percolation in the vadose zone. Governing equations ruling fate and transport processes in partially saturated soils are here solved numerically by means of a finite element method approach. Richards equations are adopted to describe flow dynamics through the hydraulic conductivity coefficient Ks, while contaminant fate is mainly described by the sorption coefficient Kp. As for the boundary conditions, we consider a local and continuous spill of contaminant at the upper ground of variable thickness. Precipitations are given as step functions whose intensity is derived by considering pluviometric data at the station of Gròmola, Campania Region, Italy. Benzene and tetrachloroethylene (PCE) are taken into account. A comparative analysis is carried out for permeability Ks and distribution Kd coefficients in the range [10−6, 10−4] m/s and [10−5, 10−3] m3/kg. Results are then compared and discussed.