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Atmospheric carbon dioxide drawdown from the chemical weathering of rocks peaks across a range of moderate erosion rates, according to a new study.
The findings provide new insights into the constraints of weathering-mediated carbon dioxide drawdown and help resolve conflicting data on the impact of erosion on the carbon cycle.
The chemical weathering mediates the concentration of carbon dioxide in the atmosphere and, thereby, the planet’s climate.
CO₂ from chemical weathering
Chemical weathering can act as both a source and a sink for atmospheric CO₂.
Here's the breakdown:
CO₂ Consumption: The most common scenario is that chemical weathering acts as a sink for CO₂.
Rainwater reacts with atmospheric CO₂ to become slightly acidic.
This acidic water then interacts with rocks, breaking them down.
Certain minerals, like those found in limestone (carbonate rocks), react with this weak carbonic acid and dissolve, releasing bicarbonate ions (HCO₃⁻) into the water and consuming CO₂ in the process.
This bicarbonate is eventually transported by rivers to the oceans, where some of it can precipitate out as carbonate minerals, locking away the CO₂ for millions of years.
CO₂ Production: However, under specific conditions, chemical weathering can also release CO₂.
When strong acids, like sulfuric acid formed from atmospheric sulfur dioxide (SO₂), are involved in weathering, they can break down minerals that don't necessarily consume CO₂ in the process.
For instance, the weathering of some silicate rocks can release CO₂ along with other dissolved ions.
Overall, chemical weathering plays a crucial role in regulating atmospheric CO₂ levels, although the balance can be tipped in either direction depending on the specific minerals being weathered and the type of acids involved.
This natural process acts as a thermostat for Earth's climate over long timescales.
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