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Light Non-Aqueous Phase Liquid (LNAPL) flow on the water table is highly mobile and is sensitive to the fluctuation of groundwater. This process is highly complex and involves the migration of three immiscible phases (i.e. water, LNAPL and air) which need the explicit definition of multiple parameters. A coupled experimental and numerical simulation methodology is performed by using Time Domain Reflectrometer (TDR) and multiphase simulation of a controlled environment to mimic the water table fluctuation and its effect on the LNAPL residual saturation. TDR probes are installed in different locations of a 2D tank (i.e. a cuboid box with relatively low off-plane thickness) and the bulk permittivity of the phases are measured through artificially imposed boundary conditions. The bulk permittivity is then translated into saturation of the three different phases. The translated residual saturations along with the previously measured porous media properties (e.g. porosity and saturated permeability) are then inserted into the numerical simulator (i.e. COMSOL Multiphysics®) and the migration of the three phase in porous media is simulated. The numerical exponents and entry pressures needed for the simulation of the multiphase flow are estimated using the temporal experimental values. The exponents of water LNAPL relative permeability were estimated to be around 2 while the exponents gas LNAPL relative permeability were estimated to be closer to 3. The results, simulated with the optimized parameters, are then evaluated with pictures taken from the transparent face of the 2D tank different stages of the experiment. The temporal evolution of different phase saturation has been compared and validated between the experimental results obtained and interpreted by the TDR probe measurements and the simulations. The relative error stays in the 5 % confidence level for most reported points and only in the highly dynamic flow time steps the error reaches around 12% which are discussed in the text and is accepted due to the highly nonlinear nature of the problem., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Groundwater table fluctuation during natural and anthropogenic processes can facilitate the interaction between oxygen (O 2 ) from the unsaturated zone and ferrous iron (Fe 2+ ) from the saturated zone. In light of previous findings that Fe(III)-reducing bacteria can be killed by the reactive oxidants produced from Fe 2+ oxidation under static oxic conditions, we hypothesize that Fe(III)-reducing bacteria will be attenuated during groundwater table fluctuations. To test this hypothesis, this study explored the variations of cell numbers of Shewanella oneidensis strain MR-1 (MR-1), a typical strain of Fe(III)-reducing bacteria, together with dissolved oxygen (DO) and Fe 2+ , at different points during controlled groundwater table fluctuations in a sand column. The results showed that, during the rise of the water table, O 2 in the pore air was entrapped by the deoxygenated groundwater, and Fe 2+ in the groundwater was oxidized by the entrapped O 2 . In this process, 1.40-2.42 orders of magnitude of viable MR-1 cells were killed at different points in the column. Further investigation proposed that the death of MR-1 is caused by the production of intracellular reactive oxidants, such as O 2 • - and OH•, from the oxidation of adsorbed/absorbed Fe 2+ instead of by bulk reactive oxidants, such as OH• and Fe(IV), produced from the oxidation of aqueous Fe 2+ . The findings here provide new insights for Fe biogeochemical cycling in the redox-dynamic zone., (Copyright © 2019 Elsevier B.V. All rights reserved.)