ALUMINUM CHEMISTRY AND POTENTIAL TOXICITY IN ACIDIC SURFACE WATERS.

Although past investigations have often ignored non-hydroxide complexes of Al, it appears that organic and F complexes are the predominant forms of Al in dilute (low ionic strength) acidic surface waters. The concentration of inorganic forms of Al increases exponentially with decreases in solution pH. This response is similar to the theoretical pH dependent solubility of Al mineral phases. The concentration of organic forms of Al, however, is strongly correlated with variations in organic carbon concentration of surface waters rather than pH. Elevated levels of Al in dilute acidic waters are of interest because: Al is an important pH buffer; Al may influence the cycling of important elements like P and organic carbon; and Al is potentially toxic to aquatic organisms.