Determination of mineral surface area in relation to the calculation of weathering rates

Abstract

The release of base cations by the weathering of soil minerals provides the primary buffer against the detrimental impact of acid deposition on the soil. The rate of release of base cations will be governed by mineral composition and the exposed surface area of mineral grains. In theory it is possible to calculate the surface area of a mixture of grains on the basis of particle size and geometry. An alternative is the use of correlations. It has been suggested (Sverdrup et al. 1990, Nordic Council of Ministers 98) that mineral surface area can be related to soil particle size distribution via a simple empirical equation. This contribution compares the surface areas of soils as calculated by geometric equations and Sverdrup's equation with actual BET measurements. The equations tested do not appear to be applicable to the soils used in the current work. Modified versions of the equation suggested by Sverdrup, applied to subsets of our data, based on sites and soil types, yield better results for the soils used in the current work. Statistically significant improved fits are obtained when soil mineralogy as well as soil texture is taken into account.