HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Senesi, N. Articles by Acquafredda, P. Search for Related Content PubMed Articles by Senesi, N. Articles by Acquafredda, P. Agricola Articles by Senesi, N. Articles by Acquafredda, P.

Fractal Dimension of Humic Acids in Aqueous Suspension as a Function of pH and Time

Istituto di Chimica Agraria, Univ. of Bari, Via Amendola 165/A, 70126-Bari, Italy

P. Dellino and P. Acquafredda

Dipartimento Geomineralogico, Univ. of Bari, Via Orabona 4, 70125-Bari, Italy

*Corresponding author (nsenesi{at}mail2.clio.it).

ABSTRACT

The fractal dimensions of soil and peat humic acids equilibrated for various lengths of time in aqueous suspension at different pH values were determined by measuring their turbidity as a function of wavelength, with collaboration by scanning electron microscopy (SEM). Particle-size distributions of the humic acid systems were also determined. The analysis of the power-law dependence of the turbidity on the wavelength revealed that soil and peat humic acids may exhibit either a nonfractal or a mass fractal nature. Peat humic acid could also be described as a surface fractal. The passage from one regime to another depended on the pH and equilibration time. With an increase of either factor, the mass fractal dimension of humic acids decreased from about 2.8 to values close to 1.0. This trend, supported by SEM observations, suggested that humic particles in suspension evolve from compact, almost space-filled structures with smooth surfaces, to less compact, fragmented and elongated structures with increasingly rough and irregular surfaces as the pH or time increases. Values of the mass fractal dimension close to 2.5 would reflect diffusion-limited aggregation (DLA), whereas values close to 2.1 would suggest a reaction-limited cluster-cluster (RLA) aggregation model for humic acid. The fractal dimension thus represents a numerical parameter able to describe quantitatively the morphological features assumed by humic particles in suspension and to provide information on the underlying aggregation processes.

Received for publication February 1, 1995.

This article has been cited by other articles:

				L. Martin-Neto, D. G. Traghetta, C. M.P. Vaz, S. Crestana, and G. Sposito On the Interaction Mechanisms of Atrazine and Hydroxyatrazine with Humic Substances J. Environ. Qual., March 1, 2001; 30(2): 520 - 525. [Abstract] [Full Text] [PDF]