Bog ground aquifer system as a natural analogue for future redox conditions in flooded underground mines

To characterize the future redox milieu caused by natural degradation of wood in flooded mines, the aquifer of a highland bog ground was studied as a natural analogue site. Going from the surface to a depth of one meter in the bog water, the redox potential measured with a platinum electrode changes from 593 mV to -95 mV. From the depth-water analyses of bog gas extracted from the ground, an Eh value of -119 +/- 5 mV could be calculated. Methane and hydrogen sulfide were found in the gas, characterizing the strongly reducing condition in the bog ground. From that, the conclusion for the future mine situation can be drawn that uranium(VI) and arsenic(V) will be reduced and precipitated as U(OH)₄ and As₂S₃. In that way, decontamination of the mine water takes place as a consequence of a natural attenuation process.