Proton and Aluminum Binding Properties of Organic Acids in Surface Waters of the Northeastern U.S.

TitleProton and Aluminum Binding Properties of Organic Acids in Surface Waters of the Northeastern U.S.
Publication TypeJournal Article
Year of Publication2015
AuthorsFakhraei, H, Driscoll, CT
JournalEnvironmental Science & Technology
Volume49
Issue5
Pagination2939 - 2947
Date Published2015/03/03/
ISBN Number0013-936X
Abstract

A variety of mathematical estimators have been used to quantify the degree of protonation of naturally occurring organic acids. These estimators range from monoprotic, diprotic, and triprotic analog models to the discrete and continuous (Gaussian) distributions of a single proton binding-dissociation. Natural water samples from two long-term monitoring programs in the northeastern U.S. were used to quantify proton- and aluminum-binding properties of naturally occurring organic matter. Water chemistry observations were clustered into 0.05 pH intervals (over 3.75?7.35 pH range) and fit to a triprotic analog model. The model optimization indicates that about 5% of dissolved organic carbon participates in ion binding, and organic acids are composed of both strong and weak acids (i.e., pKa1 = 2.54, pKa2 = 6.19, and pKa3 = 7.52 for Adirondack samples). Binding between organic acids and aluminum can substantially influence the acid behavior of dissolved organic matter and the availability of the toxic form of aluminum (i.e., inorganic monomeric aluminum).

URLhttp://dx.doi.org/10.1021/es504024u
Short TitleEnviron. Sci. Technol.