Dissolution and Etching Rate of Hornblende Under Ambient Conditions

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This award in the Environmental Geochemistry and Biogeochemistry Program is made to Dr. Susan L. Brantley, Department of Geosciences, and Dr. Carol G. Pantano, Department of Materials Science and Engineering, both of Pennsylvania State University, for research on weathering of hornblende. The work is jointly supported by the Division of Chemistry and the Division of Earth Sciences. The rate of etch pit development and the rate of dissolution of hornblende under laboratory conditions will be studied and compared to hornblende etching rates observed in soils. The effects of bacteria on hornblende dissolution will also be investigated in order to isolate direct and indirect microbial interactions with the mineral surface. Changes in the surface will be analyzed using x-ray photoelectron spectroscopy and secondary ion mass spectrometry. Not only will the rate of hornblende weathering be determined, but the role of oxygen, acidity, pit formation, and bacterial reactions will be determined. Dissolution of hornblende is the principal source of iron and magnesium to natural waters from soils developed on granite lithologies and is a contributor to reduction of atmospheric carbon dioxide reduction through silicate weathering. Methods from geochemistry, materials and microbiology will be used to achieve an integrated understanding of the nature of hornblende weathering in the field and to develop a model that can be used in laboratory investigations.