Abstract

Chemical weathering reactions  are important for the physical, chemical, and biological development of the critical zone. We present findings from aqueous phase chemical analyses of surface and soil pore waters during a 15 month study in a small semi-arid mountain catchment of the Santa Catalina Mountain Critical Zone Observatory. Stream water geochemical solutes are sourced to two distinct locations – fractured bedrock baseflow stores and soil quickflow stores. Solid phase observations of albite, anorthite, and K-feldspar transformation to Ca-montmorillonite and kaolinite are supported by stream water saturation states calculated via a PHREEQC geochemical model. While differences in mineral assemblages, soil depths, and horizonation suggest greater weathering in schist versus granite lithologies and in  hillslope divergent versus convergent zones, soil pore water solute ratio analysis does not readily distinguish these differences. However, preliminary investigation of aqueous rare earth elements suggests detectable lithologic and landscape positional  differences warranting focus for future research efforts.

Citation

Jardine A. (2011): Aqueous phase tracers of chemical weathering in a semi-arid critical zone. MS Thesis in Hydrology and Water Resources. University of Arizona, Tucson, Arizona, 94 pp..

This Paper/Book acknowledges NSF CZO grant support.