Aluminum binding to humic substances determined by high performance cation exchange chromatography

• Published in: Geochimica et cosmochimica acta 1997, Vol.61 (1), p.1-9
• Main Authors: Sutheimer, Susan H., Cabaniss, Stephen E.
• Format: Article
• Language: English
• ISSN: 0016-7037; 1872-9533
• DOI: 10.1016/S0016-7037(96)00297-9

Aluminum binding to humic substances is studied using high performance cation exchange chromatography (HP-CEC) in both laboratory and field samples. HP-CEC provides independent quantification of both free and complexed Al(III), eliminating many of the uncertainties associated with previous measurements of aluminum speciation. We formulate and calibrate a simple aluminum complexation model, using solutions with variable total Al(III) (0.2–11 μM) and pH (4.0–8.2) and constant organic composition (12.4 mg/l Suwannee River fulvic acid, FA). The model is verified with HP-CEC data from a group of acid lakes and from literature data. The results indicate that Al(III) complexation by natural organic matter in several environments is similar to complexation by FA, and that Al dimers are potentially important species even at low environmental concentrations of Al. Furthermore, organic complexation of Al is not limited to acidic waters but appears to be important even at the alkaline pH values typical of marine systems.