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Mineral Weathering & Carbon Cycle

Mineral weathering in critical zones is a vital process that significantly affects the carbon cycle and climate. Silicate and carbonate minerals react with carbonic acid (formed when CO2 dissolves in water) and sulfuric acid (formed from pyrite oxidation), releasing carbon into rivers as dissolved bicarbonate ions (HCO3-), which are eventually transported to the oceans. Over long timescales (>10 Kyr), this dissolved carbon precipitates as carbonate minerals, a process that can ultimately release CO2 back into the atmosphere. Meanwhile, the flux of HCO3- delivered to the ocean is determined by the transport capacity of rivers. Many rivers become saturated with respect to calcite, resulting in continental carbonate precipitation and the release of CO2 from the water. This is an important CO2 source from rivers on short-term timescales.

These transfers of carbon between reservoirs play a crucial role in regulating atmospheric CO2 levels, profoundly influencing global climate change.

The Long-Term CO2 Emissions in SW Taiwan
In the orogenic regions of southwestern Taiwan, we analyzed river water chemistry using a Newton-Raphson algorithm to determine weathering pathways. Our findings show that carbonate weathering predominates, accounting for 50–80% of the total, with sulfuric acid contributing to 50–67% of this dissolution. We observed a strong correlation between river discharge and sulfuric acid-mediated carbonate weathering. This suggests that during wetter periods, increased water flow introduces minerals like pyrite, which boosts sulfuric acid production and enhances carbonate dissolution.
FOR THE FIRST TIME, we developed a machine learning model to calibrate the relationship between river discharge and CO2 flux associated with mineral weathering. Our model indicates a critical threshold at 4.6 m3/s, marking a shift from CO2 sink to source; accordingly, mineral weathering in southwestern Taiwan acts as a CO2 source over long-term timescales (>10 kyr).

Research Highlight

Hydrology controls sulfuric acid-mediated weathering in an orogenic regime of ​southwestern Taiwan

Science of the Total Environment, doi:10.1016/j.scitotenv.2024.175630
The Short-Term CO2 Emissions in SW Taiwan
In SW Taiwan, increased river discharge not only amplifies carbonate dissolution but also facilitates secondary carbonate precipitation, significantly enhancing CO2 outgassing from carbonate-saturated rivers. By employing triple strontium isotopes (87Sr/86Sr and δ88/86Sr), we precisely quantified the precipitation-derived δ88/86Sr fractionation in rivers. Our findings reveal a median of 48% of Sr and 69% of the originally weathered Ca were incorporated into carbonates. This process is closely linked to elevated bicarbonate (HCO3-) concentrations in waters, driven by intensified carbonate weathering during periods of high discharge. According to our machine learning model, the CO2 outgassing from precipitation in rivers is nearly double the long-term emission flux, highlighting its significant role in the terrestrial carbon cycle of orogenic regions.

Research Highlight

Carbonate precipitation-derived CO2 outgassing offsets the mineral weathering sink in the orogenic regime of southwestern Taiwan: Insights from triple Sr isotopes

Science of the Total Environment, doi:10.1016/j.scitotenv.2024.177370

AI in Geochemistry

The relationship between hydrology and mineral weathering in SW Taiwan underscores the significant role of river discharge in the carbon cycle. These findings highlight the necessity of considering hydrological factors when evaluating the carbon budget and climate implications of mineral weathering in mountainous regions. Capitalizing on the strong correlation between river discharge and the carbon balance driven by mineral weathering, NSI employed machine learning technology to accurately determine CO2 fluxes based on daily river discharge data.
🕑 Update: March 3, 2025