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Biodegradation process is the result of substrates mixing. Because of limited of supply of electron acceptors, biodegradation mainly happens at the fringe of the plume and transverse dispersion plays a very important role. A novel non-invasive imaging technique was developed to investigate the mixing process of dissolved oxygen and plume in a two dimensional porous media at laboratory and a mathematical model was used to simulate the processes. A small aquifer (160 mm length, 130 mm width and 3 mm thickness) is made up of quartz plates and quartz sand (60-100 micrometers) in order to let UV light pass through. Potassium acetate was used as a substrate and was continuously injected into the aquifer to form a plume. Pyrenebutyric acid (PBA), a fluorescent dye which can be quenched by dissolved oxygen, was used as an indicator of dissolved oxygen. Under the UV (350 nm) light, PBA can be excited and emits fluorescence (376 nm and 395 nm). The intensity of the fluorescence depends on the concentration of oxygen. The imaging pictures of oxygen distribution in porous media were recorded by a CCD camera. Lab experiments show that at the core of the plume, oxygen was exhausted by instantaneous reaction and oxygen was only supplied by transverse mixing. To readily degradable substrates, main biodegradation only happened at the fringe of the plume and the rate of biodegradation was controlled by transverse dispersion. Reaction kinetics was established and an analytical solution for instantaneous reaction was used to simulate the experimental results.

* w. huang@ sheffield. ac. uk 1. GPRG, Dept. of Civil & Structural …