REPLY TO COMMENT BY ROBERT A. BERNER ON 'EFFECT ECT OF ORGANIC LIGANDS AND HETEROTROPHIC BACTERIA ON WOLLASTONITE DISSOLUTION KINETICS',AMERICAN JOURNAL OF SCIENCE,V. 309, P. 731-772

摘要

R. A. Berner is right saying that the last statement of our paper should have been clarified to apply only to non-aluminous basic silicates. Indeed, by "basic, Ca-Mg bearing silicates" we mean pyroxenes, olivines and pyroxenoids. We also agree that Fe release from olivine and pyroxenes is influenced by the presence of organic acids and chelators as also demonstrated by works on Fe and trace element mobilization from basalt (Hausrath and others, 2009). We further agree with R. A. Berner that the use of wollastonite as an example for the weathering of most basic igneous rocks is misleading for a number of reasons. First, wollastonite forms much thicker Si-rich, Ca-depleted layers, compared to other Ca, Mg-bearings silicates; this altered layer may control overall reactivity of the mineral (Schott and others, 2009). Secondly, alumosilciate minerals, which dominate many weathering systems are likely to be more affected by thepresence of soil biota because organic ligands may decrease the aqueous activity of Al~3+ thus: i) increasing the chemical affinity of the dissolving phase and ii) increasing the solubility of secondary phases so more dissolved constituents remain in solution and move to the ocean (Oelkers and Schott, 1998).