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MINERAL WEATHERING RATES FROM SMALL-PLOT EXPERIMENTS, WMP SITE, BEAR BROOKS, MAINE
Citation:
Drever, J. AND N. Swoboda-Colberg. MINERAL WEATHERING RATES FROM SMALL-PLOT EXPERIMENTS, WMP SITE, BEAR BROOKS, MAINE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/A-93/246 (NTIS PB94107992), 1993.
Description:
The pH-dependence of silicate mineral weathering rates was measured in small-plot experiments at the Bear Brooks Watershed Manipulation Project site in Maine, U.S.A. ix 2 m2 plots were acidified with solutions of HCL in deionized water at pH values of 2, 2.5, and 3. Acid application was at the rate of 3 cm/week for approximately 26 weeks per year for 2 years. oil solutions were collected by tension lysimeters at 25 and SO cm depths. he composition of the soil solutions, together with the grain-size distribution and mineralogy of the soil, were used to calculate mineral weathering rates. he dissolution rate of the 75-150 um size fraction of soil from the site was also measured in flowthrough reactors at the same pH as the soil solutions. n the field plots the release of silica (a measure of weathering rate) was proportional to [H+]0.7. In the lab experiments, the dependence of base cation release rates on pH varied from cation to cation, reflecting the different behavior of different minerals. issolution rates observed in the field, normalized on the basis of geometrical mineral surface area, were smaller than laboratory rates by a factor of about 200. aboratory dissolution experiments can be used to predict the pH-dependence of mineral weathering in the field, but not absolute rates.
