Time and pH-Dependent detoxification of aluminum in mixing zones between acid and non-acid rivers

Liming detoxifies aluminum in a time-dependent process following the increa se in pH. Transformation of Ali into non-reactive or colloidal forms of Al reduces toxicity. To investigate the effects of pH on the detoxification ra te, Atlantic salmon (Salmo salar) parr were exposed in four identical chann el-tank setups differing only in mixing ratio (30:70, 16:84 or 6:94) betwee n acid (pH 5.6, total Ali 90 mug Al .L-1) and non-acid water (pH 6.3, total Ali 3 mug Al .L-1). Two channels had identical mixing ratio (30:70), but d iffered with respect to pH (6.0 or >6.4) due to addition of lime. Fish were exposed for 140 hrs. in waters aged from 1 minute and up to 4 hours after mixing. Ali decreased within minutes after mixing at pH 6.4. The detoxifica tion process required hours at pH 6.0. Al accumulation onto fish gills and fish homeostasis was related to Ali. The data suggest that the detoxificati on process, and therefore the water body affected by ongoing polymerization , was strongly influenced by pH, where a pH target for liming set at pH 6.4 detoxified water faster than a pH target of pH 6.0.