Olkiluoto deep subsurface groundwater activations

Crystalline bedrock has been chosen for deep geologic long-term storage of used nuclear fuel in Finland. The construction of the geological final disposal facility, bedrock disturbances and hydraulic gradients cause changes that affect the microbial steady-state. For studying the induced metabolism of deep microbial communities in changing environmental conditions, the activating effect of different electron donors and acceptors were measured with redox sensing fluorescent dyes. Fluids originating from two different fracture zones of the Finnish disposal site in Olkiluoto, were studied. These fracture fluids were very dissimilar both chemically and in terms of bacterial and archaeal diversity. However, the microbial communities of both fracture fluids were activated, especially with acetate.