Abstract
The variation of water quality arising from the hydrolysis of aluminum in the acidified river was evaluated by field investigations and multivariate analyses. Field investigations were conducted in Matsu River, a typical example of an acidified river in Japan, which receives inflow of acid mine drainage from the abandoned Nishiazuma sulfur mine. The results of the investigation of the acidified river basin indicated that the loading of aluminum ions decreased at the upper to middle reaches of the river because aluminum was precipitated onto the riverbed. Additionally, an increase in pH was inhibited by consumption of the alkali component through hydrolysis of aluminum ions. Multivariate analysis of the metal ion concentrations and water level in the middle reaches of the river was conducted using the data from intensive field investigations. Two processes including dilution by inflows of rainfall and snowmelt, and hydrolysis of Al, influenced the variation in the water quality of the river. Therefore, the pH behavior could be attributed not only to dilution but also to the hydrolysis of aluminum acting as a pH buffer in an acidified river containing excess aluminum.
