Quantifying microbially-mediated basaltic glass dissolution in situ by X-ray absorption spectroscopy (XAS)

While microbial activity might have potentially dramatic impact towards silicate reactivity and CO2 sequestration in basalts, the magnitude of this impact remains unknown. Using HP/HT autoclave available on the FAME beamline, we have recently demonstrated in hour-scale in situ measurements, an increase in Fe release from basaltic glass grains induced by Pyrobaculum species, an Fe-reducing archaeal strain that we have recently identified in basaltic geothermal aquifers in Iceland. This proposal is a follow-up study aiming to determine how Fe availability for microbial reduction is regulated by cellular metabolism (Fe chelation), and how this in turn influences the dissolution kinetics of basaltic glass. By monitoring the release and speciation of Fe in situ we expect to get unprecedented mechanistic understanding of microbial contribution to alteration of Fe-rich silicates, and pave the way for quantifying the impact of deep biota on silicate reactivity in basaltic settings.