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Process-based modeling of silicate mineral weathering responses to increasing atmospheric CO2 and climate change
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
2009 (English)In: Global Biogeochemical Cycles, ISSN 0886-6236, Vol. 23, GB4013- p.Article in journal (Refereed) Published
Abstract [en]

A mathematical model describes silicate mineral weathering processes in modern soils located in the boreal coniferous region of northern Europe. The process model results demonstrate a stabilizing biological feedback mechanism between atmospheric CO2 levels and silicate weathering rates as is generally postulated for atmospheric evolution. The process model feedback response agrees within a factor of 2 of that calculated by a weathering feedback function of the type generally employed in global geochemical carbon cycle models of the Earth's Phanerozoic CO2 history. Sensitivity analysis of parameter values in the process model provides insight into the key mechanisms that influence the strength of the biological feedback to weathering. First, the process model accounts for the alkalinity released by weathering, whereby its acceleration stabilizes pH at values that are higher than expected. Although the process model yields faster weathering with increasing temperature, because of activation energy effects on mineral dissolution kinetics at warmer temperature, the mineral dissolution rate laws utilized in the process model also result in lower dissolution rates at higher pH values. Hence, as dissolution rates increase under warmer conditions, more alkalinity is released by the weathering reaction, helping maintain higher pH values thus stabilizing the weathering rate. Second, the process model yields a relatively low sensitivity of soil pH to increasing plant productivity. This is due to more rapid decomposition of dissolved organic carbon (DOC) under warmer conditions. Because DOC fluxes strongly influence the soil water proton balance and pH, this increased decomposition rate dampens the feedback between productivity and weathering. The process model is most sensitive to parameters reflecting soil structure; depth, porosity, and water content. This suggests that the role of biota to influence these characteristics of the weathering profile is as important, if not more important, than the role of biota to influence mineral dissolution rates through changes in soil water chemistry. This process-modeling approach to quantify the biological weathering feedback to atmospheric CO2 demonstrates the potential for a far more mechanistic description of weathering feedback in simulations of the global geochemical carbon cycle.

Place, publisher, year, edition, pages
2009. Vol. 23, GB4013- p.
Keyword [en]
National Category
Environmental Sciences
URN: urn:nbn:se:kth:diva-32315DOI: 10.1029/2008GB003243ISI: 000271131000001ScopusID: 2-s2.0-77950602594OAI: diva2:410082
QC 20110412Available from: 2011-04-12 Created: 2011-04-12 Last updated: 2012-03-19Bibliographically approved

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