This study clarified the origin of Al in spring water and stream water by analyzing the size distribution of Al of ground water, spring water, stream water, and soil extracts obtained by batch and column experiments using samples from a suburban secondary forest on granite bedrock in Aichi Prefecture. The high concentration of dissolved Al (Al 0.45 ; fraction through 0.45-mm filter) in water samples obtained from this study site was divided into completely dissolved and small colloidal forms (<0.20 mm; Al 0.20 ) and large colloidal forms (0.20-0.45 mm). More than 50% of dissolved Al (Al 0.45 ) in spring water existed in large colloidal form. By comparing the size distribution and concentration of various elements including Al in the samples from soil batch and column experiments, we suggest that the high concentration of Al in spring water is caused by the release of Al from surface soils when ground water emerges as spring water.

This study examined the distribution of waterextractable Al in soils from forest sites near Nagoya in Aichi Prefecture. The mean concentrations of waterextractable Al in surface soils varied markedly among sites, with the values at site FGB (126 mg/kg) higher than those at sites FG (11.8 mg/kg) and FCB (33.8 mg/kg). Comparisons of the acid buffer capacity of vegetation at the sites revealed that forest cover has a higher capacity for neutralization than the denuded state. We found that the effects of acidic accumulation in the surface soils of suburban forests might depend on vegetation history, and that forest soils that once had no vegetation cover accumulated labile Al due to acidification. The phenomenon was particularly distinct on granite bedrock.