Abstract: This review discusses recent trends in chemical speciation of aluminum in natural waters. Several difficulties which arise from the complexity of aluminum species present in natural samples as well as its participation in dynamic equilibrium are highlights. Taking this into account various approaches for speciation of Al described in the literature are critically evaluated. The strategy of fractionation procedures based on the rate of reaction, sorption efficiency, chromatographic behavior of the aluminum compounds or size of the molecules are described in the paper. Besides conventional procedures involving various measuring and separation techniques, a special emphasis is focused on mechanised flow injection methodologies. This was found to be very important in order to ensure precise control of the reaction time. which is essential in aluminum species equilibrium system. The analytical performance of several separation procedures based on flow injection approaches as well as the detection methods are discussed and compared.

Abstract: 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 AI(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 AI(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. Copyright (C) 1997 Elsevier Science Ltd 39 References