Velbel,M.A. and Price,J.R.(2007): Solute geochemical mass-balances and mineral weathering rates in small watersheds: Methodology, recent advances, and future directions. Applied Geochemistry, 22, 1682-1700.

『小集水域における溶質組成のマスバランスと鉱物風化速度:方法論、最近の進歩、そして将来への方向性』


Abstract
 Solute-based geochemical mass balance methods are commonly used in small-watershed studies to estimate rates of a variety of geochemical processes at the Earth's surface, including primary-mineral weathering and soil formation, and the quantitative contribution of these elemental transfer processes to cation budgets, nutrient cycling, and landscape susceptibility to acid deposition. Weathering rates of individual minerals in watwershed mass-balance studies are determined by soving a system of simultaneous linear geochemical mass-balance equations with constant (stoichiometric) coefficienta. These equations relate the measured net fluxes to the )known) stoichiometries and (unknown) rates of weathering reactions for multiple minerals in the weathering profiles. Solving the system of equations requires petrologic, mineralogic, hydrologic, notanical, and aqueous geochemical data. The number of mineral-weathering rates that can be determined is limited by the number of elements for which solute mass-balance equations can be written. In addition to calculating mineral weathering rates, elemental transfer into or out of the biomass may also be calculated. Elemental uptake by aggrading forest vegetation can act as an intrawatershed sink for at least some mineral-derived cations, producing mineral weathering rates higher than would be estimated from solute fluxes alone; similarly, element releases from decaying forest biomass can result in higher solute fluxes than are produced by weathering alone. The mathematics of, significant contributions from, role of biomass in, and recent advances in, watershed geochemical mass-balance methods are discussed using examples from the Appalachian headwaters watersheds of the Coweeta Hydrologic Laboratory in the southern Blue Ridge Physiographic Province of North Carolina, USA.』

1. Introduction
2. Study area
3. Methods and background
 3.1. Mathematics of watershed geochemical mass balance
 3.2. Histric background and significant contributions to watershed geochemical mass-balance techniques
 3.3. Overcoming more unknowns tha equations
  3.3.1. Assumptions to reduce the number of unknowns
  3.3.2. Increasing the number of equations
 3.4. Calcium problem
4. Discussion
 4.1. Use of assumed rather than actual mineral stoichiometries
 4.2. Weathering products determined using thermodynamics
 4.3. Exclusion of a biomass term
 4.4. Future directions in watershed mass-balance calculations
5. Summary and conclusions
Acknowledgements
References


戻る