Untreated and treated limestone from Balagem, Belgium and Massengis, France were exposed to the atmosphere in microcatchment systems and the runoff water from a precisely defined area of each stone was collected weekly. Detailed quantitative analyses were carried out on these samples using ion-chromatography, atomic absorption spectroscopy, flame emission spectroscopy, and potentiometric techniques. Correlations between all the ion concentrations, between ion concentrations and rain characteristics (pH, volume), and between quantity of material loss and rain characteristics were considered. The results of these studies showed how the decay rates of these materials are related to the types of stone, their treatments, and atmospheric conditions. -- AATA