Influence of fluvial sediment abrasion on carbonate, silicate, and sulfide weathering
Abstract
Chemical weathering of rocks plays a key role in the global carbon cycle and regulation of Earth's climate over geologic timescales. Weathering is typically assumed to occur predominately on hillslopes and in sedimentary deposits where order ky-My residence times of solids can compensate for slow kinetics. Large volumes of sediment pass through rivers during source to sink transport, and, in active landscapes, bedrock landsliding may allow much of this sediment to bypass weathering on hillslopes before entering river channels. Rivers may act as hotspots for weathering, as sediment abrasion increases surface area, allowing faster reaction rates; however, the influence of fluvial transport on chemical weathering has yet to be quantified. Here, we test the hypothesis that sediment abrasion increases chemical weathering using a series of hydraulically-scaled annular flume experiments. We performed 14 experiments varying lithology (shale, basalt, and granite) and grain size to explore the influence of mineralogy, surface area, and abrasion on chemical weathering. Experiments lasted ~50 days, producing ~1000 km of transport, and we assessed weathering by evaluating changes in the dissolved load through time. We separated solutes into contributions from carbonate weathering, silicate weathering, and sulfide oxidation. Preliminary results show that sediment abrasion in shale experiments led to a ~3.5-fold increase in carbonate cation production and a ~2-fold increase in sulfate production relative to replicate experiments in static tanks without transport. In the basalt experiments, sediment abrasion led to a ~1.5-fold increase in silicate cation production relative to static tanks, and granite experiments showed no detectable influence of sediment abrasion. These results provide proof-of-concept evidence for mineralogy-dependent enhancement of weathering due to sediment abrasion and are allowing ongoing work to compare weathering fluxes between in-river and hillslope processes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP42A..01S
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 1030 Geochemical cycles;
- GEOCHEMISTRY;
- 1815 Erosion;
- HYDROLOGY;
- 1862 Sediment transport;
- HYDROLOGY