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For the determination of groundwater recharge processes in arid environments, vadose zone water fluxes and water storage should be considered. To better understand and quantify vadose zone processes influencing groundwater recharge, a soil column experimental setup has been developed that mimics arid atmospheric conditions and measures water and temperature fluxes in high temporal and spatial resolution. The focus of the experiment was on the determination of water infiltration, redistribution, evaporation and percolation under non-isothermal conditions. TDR rod sensors and a specific TDR ''Taupe'' cable sensor were used for water content measurements and allowed the infiltration fronts to be traced over the whole column length. Applying single irrigations of different amount and intensity showed the applicability of the experimental setup for the measurement of water movement in the unsaturated soil column.

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Aquifers at industrial sites are commonly characterized by a multitude of contaminant source zones. Conceivably, dissolved contaminants originating from an up-gradient residual nonaqueous phase liquid (NAPL) source zone may be transported along the groundwater flow path into another residual NAPL source zone down-gradient. However, if and how contaminants from different zones may affect one another with regard to dissolution and transport has thus far been unknown. To identify and understand such potential interactions, the numerical model BIONAPL3D was applied to simulate the behavior of six dissolved polycyclic aromatic hydrocarbons (PAHs), stemming simultaneously from an up-gradient NAPL source zone, when they encounter a down-gradient NAPL source zone. The down-gradient NAPL source zone was assumed to be a residual benzene phase with a saturation of 10%. When the dissolved PAHs entered the benzene source zone, the aqueous PAH concentrations declined significantly due to their partitioning into the residual benzene phase. As benzene rapidly dissolved intothe aqueous phase,the PAHswere resolubilized with negligible impact due to benzene co-solvency. The degree of resolubilization was much smaller than the initial loss due to partitioning into the benzene phase. Thus, the PAHs formed a new residual NAPL phase that, over time, replaced the original benzene source zone. The new NAPL phase continued to grow even after all of the benzene was dissolved. Our modeling approach is the first theoretical demonstration of a significant interaction of contaminants emanating from multiple source zones. It should be regarded as a starting point to consider source zone interactions at polluted field sites.