OPTICAL TESTS ON THE SLOW RELEASE OF GAS BUBBLES

摘要

An artifical soil saturated in a liquid with the same refractive index was used to directly observe the formation and movement of gas bubbles in a coarse-grained soil. Gas was injected into the sample at a slow flow rate in order to simulate the release of gas bubbles from fermentation of a carbon substrate for the reductive dehalogenation of a chlorinated hydrocabons. The results showed bubble movement to be buoyancyinduced and characterised by clustering that triggered further upward migration. Slight changes in particle size from a coarse to a medium sand size soil halted bubble movement and led to an accumulation of bubbles beneath the finer soil layer, which would in practice decrease permeability and limit further distribution of the electron donor.