Tracking the Fate of Plagioclase Weathering Products

TitleTracking the Fate of Plagioclase Weathering Products
Publication TypeBook Chapter
Year of Publication2020
AuthorsBailey, SW
Book TitleBiogeochemical Cycles
Pagination151 - 162
PublisherAmerican Geophysical Union (AGU)
ISBN Number978-1-119-41333-2
KeywordsAcid deposition, Aluminum, and models, Biogeochemical cycles, Calcium, Catchment, forest disturbance, processes, Silicon, sodium, Soils, Surface water quality, weathering

Catchment mass balance demonstrates the role of hydrologic, pedogenic, and human influences on cycling of Ca, Al, Na, and Si, derived from plagioclase dissolution. As Na is little taken up by vegetation, does not accumulate in secondary soil pools, and is primarily in plagioclase, net Na output is a measure of plagioclase dissolution. Net Na flux is proportional to streamflow, illustrating hydrologic control of weathering. Rates of Ca, Al, and Si release from mineral dissolution are more difficult to evaluate as they are variably taken up by vegetation or stored in secondary soil pools. However, plagioclase stoichiometry provides a benchmark by which the net storage or release of these elements may be gauged. Net export of Ca relative to Na shows that Ca export was enhanced in the 1960s, peaking in the 1970s, taken as an indication of acid deposition effects on the soil exchange pool, which were further exacerbated by harvesting treatments. Net export of Si and Al relative to Na suggest dynamic biotic Si pools and provide a measure of the podzolization soil development process. Net catchment export ratios provide a tool for comparing biogeochemical processes across catchments and a basis for investigating processes controlling pool accumulation.