Temporal and spatial variability in stream waters of Wales, the Welsh borders and part of the West Midlands, UK - 2. Alumino-silicate mineral stability, carbonate and gypsum solubility

Stream water chemical composition, which in many systems represents the int egration of weathering throughout the catchment, has been used to predict t he stability and degree of saturation with respect to a range of minerals, based on the assumption of a pure closed system, and in the case of alumino -silicates, the hydrolysis reaction of a primary mineral phase. The distrib utions of predicted mineral stability and saturation have been mapped for W ales, the Welsh borders and part of the West Midlands. The incorporation of monitoring data from a site-specific study (Plynlimon, mid-Wales) has been used to interpret the significance of factors such as seasonality and hydr ological regime on mineral stability and solubility. The derived maps can b e used to identify: (i) regions in which streams are most susceptible to fr eshwater acidification and (ii) local variations in bedrock geochemistry, s uch as calcite mineralisation, which cannot be identified by conventional f ield mapping. (C) 1999 NERC. Published by Elsevier Science Ltd. Ail rights reserved.