DETERMINATION OF MINERAL SURFACE-AREA IN RELATION TO THE CALCULATION OF WEATHERING RATES

The release of base cations by the weathering of soil minerals provide s 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 g rains on the basis of particle size and geometry. An alternative is th e use of correlations. It has been suggested (Sverdrup et al. 1990, No rdic council of Ministers 98) that mineral surface area can be related to soil particle size distribution via a simple empirical equation. T his contribution compares the surface areas of soils as calculated by geometric equations and Sverdrup's equation with actual BET measuremen ts. The equations tested do not appear to be applicable to the soils u sed in the current work. Modified versions of the equation suggested b y Sverdrup, applied to subsets of our data, based on sites and soil ty pes, yield better results for the soils used in the current work. Stat istically significant improved fits are obtained when soil mineralogy as well as soil texture is taken into account. (C) 1998 Elsevier Scien ce B.V.