EFFECT OF MICROBIAL AND OTHER NATURALLY-OCCURRING POLYMERS ON MINERAL DISSOLUTION

Several naturally occurring polymers were tested for their effect on mineral dissolution. Polymers composed primarily of neutral sugars had no effect on dissolution, even at concentrations 1000 times greater than average dissolved organic carbon concentration in groundwater. In contrast, alginate, a polysaccharide composed of two uronic acids, inhibited dissolution by 80% at the highest concentration A high-molecular-weight (26 kD) polyaspartate also inhibited dissolution, though a lower molecular weight (6 kD) polyaspartate had no effect. Solutions of fresh microbial extracellular polysaccharides (EPS) extracted from subsurface microbes increased the dissolution rate of feldspars, probably by forming complexes with framework ions in solution. However, EPS inhibited dissolution in experiments with both high- and low-molecular-weight microbial metabolites by irreversibly binding to mineral surfaces.