Variation of the stability of complexes of Al(III) with a fulvic acid extracted from a humic cambisol soil in the pH range three to five

• Type: Article in International Scientific Journal
• Date: 1997

Authors

dasilva, jcge (Author) FCUP; machado, aasc (Author) Other; ramos, ma (Author) Other; arce, f (Author) Other; rey, f (Author) Other

Journal

Title: Environmental Toxicology and Chemistry

Vol. 16

Pages: 1845-1850

ISSN: 0730-7268

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 6 Citations

Scopus - 9 Citations

Scientific classification

FOS: Natural sciences > Earth and related Environmental sciences

Other information

Authenticus ID: P-001-AQQ

DOI: 10.1897/1551-5028(1997)016

Abstract (EN): The interaction of the aluminum ion [AI(III)I with the major constituent of soil organic matter, fulvic acids (FA), was investigated in the acid pH range. The complexation of a FA extracted from a humic cambisol soil (at a concentration of 83 mg/L) when titrated with Al(III) were monitored directly by synchronous fluorescence (SyF) spectroscopy at five pH values (3.0, 3.5, 4.0, 4.5, and 5.0), at 25 degrees C and with 0.1 N KNO3. Inverted second derivative SyF data were preprocessed by a self-modeling mixture analysis method to obtain fluorescence enhancement profiles as a function of the increasing AI(III) concentration. Assuming that the concentration of complexes formed between Al(VI) and FA is proportional to the fluorescence intensity, these profiles were adjusted to a 1:1 complexation model and the following conditional stability constants (log K-c) were calculated (standard deviation in parenthesis), pH = 3.0, 4.3 (1); pH = 3.5, 4.3 (1); pH = 4.0, 5.0 (1); pH = 4.5, 5.1 (3); end pH = 5.0, 5.3 (2). These constants show that the stability of the complexes decreases markedly at pH < 4. The environmental implication of this result is that an increase in the extent of the dissociation of the Al(III) + FA complexes is expected at pH < 4, increasing the free Al(III) concentration and probably its ecotoxicity.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 6