『Abstract
Geochemical research on natural weathering has often been directed
towards explanations of the chemical composition of surface water
and ground water resulting from subsurface water-rock interactions.
These interactions are often defined as the incongruent dissolution
of primary silicates, such as feldspar, producing secondary weathering
products, such as clay minerals and oxyhydroxides, and solute
fluxes (Meunier and Velde, 1979). The chemical composition of
the clay-mineral product is often ignored. However, in earlier
investigations, the saprolitic weathering profile at the South
Fork Brokenback Run (SFBR) watershed, Shenandoah National Park,
Virginia, was characterized extensively in terms of its mineralogical
and chemical composition (Piccoli, 1987; Pochatila et al., 2006;
Jones et al., 2007) and its basic hydrology. O'Brien et al.(1997)
attempted to determine the contribution of primary mineral weathering
to observed stream chemistry at SFBR. Mass-balance model results,
however, could provide only a rough estimate of the weathering
reactions because idealized mineral compositions were utilized
in the calculations. Making use of detailed information on the
mineral occurrence in the regolith, the objective of the present
study was to evaluate the effects of compositional variation on
mineral-solute mass-balance modelling and to generate plausible
quantitative weathering reactions that support both the chemical
evolution of the surface water and ground water in the catchment,
as well as the mineralogical evolution of the weathering profile.』
Methods
Site description
Water samples
Mass-balance modelling
Discussion
Conclusions
References