Influence of biofilms on transport of fluids in subsurface granitic environments — some mineralogical and petrographical observations of materials from column experiments

Abstract

Landfill and radioactive waste disposal risk assessments focus on contaminant transport and are principally concerned with understanding the movement of gas, water and solutes through engineered barriers and natural groundwater systems. However, microbiological activity can impact on transport processes changing the chemical and physical characteristics of the subsurface environment. Such effects are generally caused by biofilms attached to rock surfaces. This paper will present some mineralogical and petrographical observations of materials extracted at the completion of an experimental column study which examined the influences of biofilm growth on groundwater flow through crushed diorite from the Äspö Hard Rock

Microbiological influences on fracture surfaces of intact mudstone and the implications for geological disposal of radioactive waste

“…Finally, these filaments from the biotic experiment were observed to have locally etched the mineral substrate, and again this was not seen in the starting material. Similar biofilaments have been observed in other flow-through column experiments examining biofilm impacts on fluid transport through crushed diorite but under unpressurized conditions (Hama et al, 2001;Tuck et al, 2006;Coombs et al, 2008). Therefore, it can be concluded that although the starting material had been affected by the activity of microbial contamination, this was completely different from the microbial effects seen in the biotic column experiment.…”

“…Finally, these filaments from the biotic experiment were observed to have locally etched the mineral substrate, and again this was not seen in the starting material. Similar biofilaments have been observed in other flow-through column experiments examining biofilm impacts on fluid transport through crushed diorite but under unpressurised conditions (Hama et al, 2001;Tuck et al, 2006;Coombs et al, 2008).…”

“…As these sudden changes in pressure were only observed in the biotic column experiment, it was probably due to the formation of the observed biofilm. Previous unpressurised flow-through experiments with crushed diorite have also showed that biofilms influenced fluid flow (Hama et al, 2001;Tuck et al, 2006;Coombs et al, 2008).…”

“…Consequently, the significance of microbial activity on the transport properties of potential host rocks for geological repositories is now being investigated (e.g. Pedersen 1999;Ferris et al, 1999;Hama et al, 2001;Vaughan et al, 2001;Brydie et al, 2005;Anderson et al, 2006;Tuck et al, 2006;Coombs et al, 2008). Most of this work has focussed on granitic environments that are potential hosts for nuclear waste repositories.…”

Microbial biomineralization of iron seepage water: Implication for the iron ores formation in intertidal zone of Zhoushan Archipelago, East China Sea

“…It is known that ancient wood layers could produce enough organic acids during their buried process, which can accelerate the weathering process of the nearby granite bedrock with the chemical or biological reaction (Hama et al, 2001;Coombs et al, 2008). Based on the investigation in the field, a thick peat layer was buried under the ancient wood layer and its measured pH value is about 3.0.…”