Effects of carbon dioxide on mineral weathering rates at earth surface conditions

The weathering of silicate minerals is an important long-term control on the global carbon budget. While the rate of mineral weathering is influenced by the atmospheric variations in atmospheric carbon dioxide, the only measurements of those effects have occurred during dissolution experiments at temperatures much higher than earth surface conditions. Thus, any climate models that include such a relationship may not be able to fully couple variations in atmospheric carbon dioxide with the lithospheric sinks.Our study presents a relationship for the dependence of plagioclase dissolution rates on PCO2 based on field data from a site in the southeastern Sierra Nevada drainages. A series of canyons that have similar drainages show wide variability in water chemistry that is attributed to variations in PCO2 from geothermal sources. This setting allowed us to isolate the effect of PCO2 on weathering rates in conditions relevant to climate models. The results show that mineral dissolution rates are proportional to PCO20.45 when the observed variations are attributed solely to variations in PCO2. This relationship is likely to be more applicable to climate models than prior laboratory derived data.