『Abstract
Concentrations of weathering products in streams often show relatively
little variation compared to changes in discharge, both at event
and annual scales. In this study, several hypothesized mechanisms
for this “chemostatic behavior” were evaluated, and the potential
for those mechanisms to influence relations between climate, weathering
fluxes, and CO2 consumption via mineral weathering
was assessed. Data from Loch Vale, an alpine catchment in the
Colorado Rocky Mountains, indicates that cation exchange and seasonal
precipitation and dissolution of amorphous or poorly crystalline
aluminosilicates are important processes that help regulate solute
concentrations in the stream; however, those processes have no
direct effect on CO2 consumption in catchments.
Hydrograph separation analyses indicate that almost one-half of
annual fluxes of Na and SiO2 in the stream;
thus, flushing of old water by new water (snowmelt) is an important
component of chemostatic behavior. Hydrologic flushing of subsurface
materials further induces chemostatic behavior by reducing mineral
saturation indices and increasing reactive mineral surface area,
which stimulate mineral weathering rates. CO2
consumption by carbonic acid mediated mineral weathering was quantified
using mass-balance calculations; results indicated that silicate
mineral weathering was responsible for approximately two-thirds
of annual CO2 consumption, and carbonate
weathering was responsible for the remaining one-third. CO2 consumption was strongly dependent on annual
precipitation and temperature; these relations were captured in
a simple statistical model that accounted for 71% of the annual
variation in CO2 consumption via mineral
weathering in Loch Vale.
Keywords: Mineral; Weathering; Carbon; CO2;
Sequestration』
1. Introduction
1.1. Description of study site
2. Methods
2.1. Sample collection and analyses
2.2. Solute flux calculations
2.3. Geochemical modeling
2.4. Experimental methods
3. Results
3.1. Concentration-discharge relations and weathering fluxes
3.2. Cation exchange
3.3. Flushing of subsurface waters
3.4. Seasonal precipitation/dissolution of amorphos aluminosilicates
3.5. Chemical affinity
3.6. Variations in reactive mineral surface area
3.7. Laboratory experiments
4. Discussion
4.1. Implications for consumption of CO2
by chemical weathering
5.Summary and conclusions
Acknowledgements
References