HR: 0830h
AN: B21B-0702    [PDF]
TI: Alginic Acid Accelerates Calcite Dissolution
AU: * Perry, T D
EM: tperry@deas.harvard.edu
AU: Duckworth, O W
EM: duckwort@fas.harvard.edu
AU: McNamara, C J
EM: mcnamara@deas.harvard.edu
AU: Martin, S T
EM: smartin@deas.harvard.edu
AU: Mitchell, R
EM: mitchell@deas.harvard.edu
AB: Accelerated carbonate weathering through biological activity affects both geochemical cycling and the local pH and alkalinity of terrestrial and marine waters. Microbes affect carbonate dissolution through metabolic activity, production of acidic or chelating exudates, and cation binding by cell walls. Dissolution occurs within microbial biofilms - communities of microorganisms attached to stone in an exopolymer matrix. We investigated the effect of alginic acid, a common biological polymer produced by bacteria and algae, on calcite dissolution using a paired atomic force microscopy/flow-through reactor apparatus. The alginic acid caused up to an order of magnitude increase in dissolution rate at 3 $<$ pH $<$ 12. Additionally, the polymer preferentially binds to the obtuse pit steps and increases step velocity. We propose that the polymer is actively chelating surficial cations reducing the activation energy and increasing dissolution rate. The role of biologically produced polymers in mineral weathering is important in the protection of cultural heritage materials and understanding of marine and terrestrial systems.
DE: 0330 Geochemical cycles
DE: 4825 Geochemistry
DE: 4840 Microbiology
DE: 4885 Weathering
SC: Biogeosciences [B]
MN: 2003 Fall Meeting