My Account: Log In | Join | Renew
Search
Author
Title
Vol.
Issue
Year
1st Page

Abstract

 

This article in JEQ

  1. Vol. 20 No. 4, p. 839-845
     
    Received: Mar 16, 1990
    Published: Oct, 1991


    * Corresponding author(s):
 View
 Download
 Alerts
 Permissions
 Share

doi:10.2134/jeq1991.00472425002000040022x

Acid-Base Chemistry of Dissolved Organic Matter in Aqueous Leaf Extracts: Application to Organic Acids in Throughfall

  1. Aaron D. Brown * and
  2. Garrison Sposito
  1. Dep. of Soil and Environ. Sciences, Univ. of California, Riverside, CA 92521-0424;
    Dep. of Soil Science, Univ. of California, Berkeley, CA 94720.

Abstract

Abstract

Elemental composition data were obtained for bulk precipitation and throughfall samples and for aqueous extracts of the leaves 6of three woody plant species common in t6he subalpine Sierra Nevada range, California: chinquapin (Chrysolepis sempervirens Hjelmqvist), western white pine (Pinus monticola Dougl.), and willow (Salix orestera Schneider). The acid-base equilibria of the extracts were characterized by potentiometric titration and proton formation functions were computed. The latter then were modeled assuming four classes of quasiparticle acidic functional groups, yielding negative logarithms of conditional protonation constants in the range 4.8 to 5.0, 6.1 to 6.6, 7.4 to 7.7, and 9.1 to 9.4. The relative concentration of a given acidic functional group class varied markedly among the three woody species, but the conditional protonation constants were very similar. The model parameters, along with dissolved organic C concentration and pH values, were used to estimate net anion deficits in throughfall samples collected from the same sites as the leaf samples. On average, the calculated charge concentration of free organic anions in the western white pine extract matched the throughfall anion deficit, whereas the deficits in the chinquapin and willow throughfall samples were not accounted for by free anion concentrations. Metal complexation and in situ, species-dependent leaf surface processes may account for these latter differences. In general, the anion deficit and, therefore, organic acids were an important component of rainfall and throughfall charge balance.

Contribution from the Dep. of Soil and Environ. Sci., Univ. of California, Riverside.

  Please view the pdf by using the Full Text (PDF) link under 'View' to the left.

Copyright © .