Time and PH-dependent detoxification of aluminum in mixing zones between acid and non-acid rivers

Summary

Liming detoxifies Al in a time-dependant process following the increase in pH. Transformation of Ali into non-reactive or colloidal forms of Al reduces toxicity. To investigate the effects of pH on the detoxification rates, Atlantic salmon (Salmo salar) parr were exposed in four identical channel-tank set-ups differing only in mixing ratio (30:70, 16:84 or 6:94) between acid (pH 5.5, total Ali 90 µg Al/L) and non-acid water (pH 6.3, total Ali 3 µg Al/L). Two channels had identical mixing ratio (30:70) , but differed with respect to pH (6.0 or >6.4) due to addition of lime. Fish were exposed for 140 h in water aged from 1 minute up to 4 hours after mixing. Ali decreased within minutes after mixing at pH 6.4. The detoxification process required hours a t pH 6.0. Al accumulation onto fish gills and homeostasis was related to Ali. The data suggests that that the detoxification process, and therefore the water body affected by ongoing polymerization, was strongly influenced by pH, where a pH target for l iming set at pH 6.4 detoxifies water faster than a pH target set at pH 6.0.