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- Title
A critical evaluation of the use of the PROFILE model in calculatingmineral weathering rates
- Authors
Wilson, M. J.; Langan, S. J.; Hodson, M. E.
- Abstract
The PROFILE model is used extensively in the European Critical Loadsprogramme as an aid to international negotiations on SO 2 emission abatement. PROFILE calculates the rates of cation release by mineral weathering and it then uses these data to calculate soil solution and runoff chemistry. No independent assessment of the underlying assumptions and data in the model has been published and this paper reports such an assessment. The rate equations, which are the keyto the PROFILE model require rate coefficients and constants. These have been derived from the literature but more work is required to produce a consistent set of constants. Manipulation of these rates to take into account the exposed reactive surface area of the minerals isfraught with problems. Calculation of exposed mineral surface area from soil textural data results in under-estimates and the requirementto determine the surface area fraction of the different minerals in the soil to be known is extremely difficult if not impossible. Further uncertainty is introduced by adjustment of the rates to take into account temperature differences and by the use of a default mineralogywhich is compositionally unrealistic. Despite its flaws PROFILE usually predicts similar weathering rates to other methods of calculation. It is argued that the unrealistic constraints imposed by the use ofthe surface area equation may be responsible for limiting calculatedweathering rate to a fixed range which coincides with characteristically determined values for weathering rates.
- Subjects
MATHEMATICAL models; ACID precipitation (Meteorology)
- Publication
Water, Air & Soil Pollution, 1997, Vol 98, Issue 1-2, p79
- ISSN
0049-6979
- Publication type
Article