Use of EMSL Scanning Microscopy Capabilities to Study Soil Mineral Weathering
EMSL Project ID
2544
Abstract
Our research concerns the effect of rooted plants on chemical weathering of minerals, focusing on the associated export or loss of base cations in drainage and runoff (chemical denudation). Our work on experimental ecosystems suggests that conifer rhizospheres have developed mechanisms to insulate mineral nutrient uptake from bulk soil water, thereby increasing nutrient dequestration efficiency and reducing chemical denudation. Microbes almost certainly play an important role in these processes (Banfield et al. 1999; Olsson and Wallander 1998), particularly in the podzolization process (Van Breemen et al. 2000) where ectomycorrhizal fungi appear to bore holes in minerals (Van Breemen et al. 1997). Such studies clearly establish intimate spatial associations of microbes and mineral surfaces, and some recent studies demonstrate how these associations facilitate nutrient uptake (e.g., Lower et al. 2001). We hypothesize that the flip side of these spatially intimate associations is limitation of nutirent mass transfer (loss) to the bulk soil solution. We would like to use the high resolution SEM and the new FEI ESEM to support our investigation of this question in the context of our experimental ecosystems. Research Plan: More specifically, our ideas are: 1. In the conifer ecosystem, look for evidence of attached fungal hyphae, bacteria, and mineral-grain surface features attributable to their weathering action. We are particularly interested in how water potential affects the spatial relationship of microbes on surfaces determined by SEM. We think we need to be in a partial pressure of water. 2. Compare mineral-grain surface features of substrate which has weathered for 20 years under (conifer) rhizospheric v. (control) abiotic conditions. Attempt by mass balance to attribute volumetric mineral loss by rhizospheric pitting, etching, etc., determined by SEM to known denuation fluxes and ecosystem pool changes. Dry or in water vapor background would probably be fine. 3. Perform weathering experiments with microbes on a mineral cleavage plane, in which we synoptically monitor an index solution chemistry parameter and microscopic surface feature evolution (determined by SEM either dry or in water vapor background). References: Banfield, JF., W.W. Barker, S.A. Welch, and A. Taunton, 1999: Biological impact on mineral dissolution: Application of the lichen model to understanding mineral weathering in the Rhizosphere. Proc. Natl. Acad. Sci., USA Vol. 96, pp. 3404-3411. Lower, S.K., M.F. Hochella Jr., and T.J. Beveridge, 2001. Bacterial recognition of mineral surfaces: Nanoscale interactions between Shewanella and a-FeOOH. Science 292: 1360-1363. Olsson, P.a., and H. Wallander, 1998. Interaction between Ectomycorrhizal fungi and the bacterial community in soils amended with various primary minerals. FEMS Microbiology Ecology 27: 195-205. van Breemen, N., A. G. Jongmans, U. Lundstrom, P.A.W. van Hees, R.D. Finaly, M. Srnivasan, T. Unestam, R. Giesler, P.-A. Melkerud, and M. Olsson, 1997. Rock-eating fungi. Nature vol. 389. 1997. pp. 682-683. van Breemen, N., U.S. Lunstrom, and A.G. Jongmans, 2000. Do plants drive podzolization via rock-eating mycorrhizal fungi? Geoderma 94: 163:171.
Project Details
Project type
Exploratory Research
Start Date
2002-06-26
End Date
2002-07-26
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
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