Strontium isotopes as tracers of ecosystem processes: theory and methods

• Published in: Geoderma 1998-02, Vol.82 (1), p.197-225
• Main Authors: Capo, Rosemary C., Stewart, Brian W., Chadwick, Oliver A.
• Format: Article
• Language: English
• Subjects: atmosphere; biogeochemistry; eolian; isotopes; soil; Strontium; weathering
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/S0016-7061(97)00102-X

The strontium (Sr) isotope method can be a powerful tool in studies of chemical weathering and soil genesis, cation provenance and mobility, and the chronostratigraphic correlation of marine sediments. It is a sensitive geochemical tracer, applicable to large-scale ecosystem studies as well as to centimeter-scaled examination of cation mobility within a soil profile. The 87Sr/ 86Sr ratios of natural materials reflect the sources of strontium available during their formation. Isotopically distinct inputs from precipitation, dryfall, soil parent material, and surface or groundwater allow determination of the relative proportions of those materials entering or leaving an ecosystem. The isotopic compositions of labile (soil exchange complex and soil solution) strontium and Sr in vegetation reflect the sources of cations available to plants. Strontium isotopes can be used to track the biogeochemical cycling of nutrient cations such as calcium. The extent of cation contributions from in situ weathering and external additions to soil from dust and rain can also be resolved with this method. In this paper, we review the geochemistry and isotopic systematics of strontium, and discuss the use of this method as a tracer of earth surface processes.