Abstract
The mobility of elements during weathering was quantitatively estimated. The mobility, ranging from zero (immobile) to unity (mobile), is expressed as 1-(R/R0), where R and Ro are the concentration ratio of a given element to a reference element in the weathered rock and in the corresponding unweathered rock, respectively. Ideally the reference element should be strictly immobile under supergene conditions. As Ti meets this requirement, the calculation of the mobility was made by using Ti as the reference element. The mobility of elements as obtained from weathered quartz diorite is in the decreasing order: Ca, Na>K>Si, Mg>Al. Fe is also immobile like Al in the neutral environment. The variation in the mobility of selected elements was discussed in terms of p H. Under acid conditions, Fe was found to become mobile prior to Al. Thus the monitoring of Fe concentration in the ground water may be effective in detecting the beginning of soil degradation caused by acid rain. The relative composition of the ground water affected by acid rain can be predicted based on Eq.(1) and the mobility data.
