Large tank experiment on nitrate fate and transport: The role of permeability distribution

A long-term elution experiment to study the saturated transport of pre-accumulated fertilizers by-products, was conducted within a large tank (4 × 8 × 1.4 m) equipped with 26 standard piezometers. Sandy sediments (35 m3), used to fill the tank, were excavated from an unconfined alluvial aquifer near Ferrara (Northern Italy); the field site was connected to a pit lake located in a former agricultural field. To evaluate spatial heterogeneity, the tank's filling material was characterized via slug tests and grain-size distribution analysis. The investigated sediments were characterized by a large spectrum of textures and a heterogeneous hydraulic conductivity (k) field. Initial tank pore water composition exhibited high concentration of nitrate (NO3-) sulfate (SO42-) calcium (Ca2+), and magnesium (Mg2+), due to fertilizer leaching from the top soil in the field site. The initial spatial distribution of NO3- and SO42- was heterogeneous and not related to the finer grain-size content (