Si Precipitation During Weathering in Different Icelandic Andosols

Basaltic weathering from volcanic islands plays a critical role in the climate feedback loop. Geochemical and climate models require information on the rate of secondary mineral formation. We provide direct evidence for precipitation of amorphous Si in organic rich and acidic Histic Andosols compared to preferential allophane formation in organic poor and less acidic Haplic Andosols. Similar results have been obtained from the pioneering work by Opfergelt et al1 using Si isotope composition. Additionally, enhanced allophane precipitation in Haplic Andosols, independent of long-term soil property changes, highlight the potential role of land use and management on secondary mineral formation.