DISSOLUTION OF FELDSPARS IN THE PRESENCE OF NATURAL, ORGANIC SOLUTES

The dissolution rates of feldspars in the presence of naturally occurring organic solutes were compared at pH 5.1. Natural silt or ground feldspar minerals were suspended in water, streamwater, soil water, water extracts of peat and mor and a citrate solution for approximately 100 d. The increase of major cations and silicic acid in the aqueous phase was determined by periodic sampling and rates of dissolution were calculated when concentration increased linearly with time. The dissolution rate for the major cations was 2.7±0.9 (n= 3) times greater for stream‐water and 2.4±0.4 (n= 5) times greater for mor and peat extract than for distilled water. For citrate, the rate was greater by 1.7±0.3 (n=3) times. By inoculating the suspensions with microorganisms weathering rates decreased to the value for distilled water. This suggests that the microorganisms consumed some ‘active’ fraction of the organic solutes. Copyright © 1990, Wiley Blackwell. All rights reserved