Biotic and Abiotic Weathering of Aquifer Rock

摘要

In the work performed in the period from 8/16/95, experiments were performed (1)to compare the weathering of orthoclase by bacteria in a glucose-yeast extract-mineral salts medium (GYM) with that in a sucrose-mineral salts medium (SM), and (2) to determine if bacteria that can weather orthoclase produce an extracellular enzyme that hydrolyzes polysilicate. A difference in Si and Al solubilization was noted in GYM and SM medium. Once the medium pH of the culture medium has been lowered by the bacteria below 4.5, the molar Si/Al ratio in GYM medium approached 1 whereas that in SM medium was around 3 or higher. No clear evidence for an extracellular enzyme capable of hydrolyzing a synthetic polysilicate mixture was found, but intact cells were shown to bind polysilicate to their surface. The cell surface location of the polysilicate was supported by EDX data but no change in appearance of the cell surface after polysilicate binding was noted on SEM examination. Ortho-silicate binding under the same condition was not observed.