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 Selim, H. M. Articles by Ma, L. Search for Related Content PubMed Articles by Selim, H. M. Articles by Ma, L. Agricola Articles by Selim, H. M. Articles by Ma, L.

Transport of Reactive Solutes in Soils: A Modified Two-Region Approach

Contribution from the Agronomy Dep., Sturgis Hall, Louisiana State Univ., Baton Rouge, LA 70803

* Corresponding author.

ABSTRACT

A modified two-region approach that accounts for chemical and physical nonequilibrium of solute behavior in soils was developed. Chemical nonequilibrium was described by a second-order two-site model, while physical nonequilibrium was represented by a two-region (mobile-immobile) approach. Model validity was based on predictions of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino-s-triazine] miscible displacement experiments in a Sharkey clay soil (very fine, montmorillonitic, nonacid, thermic Vertic Haplaquept) for different aggregate sizes, flow velocities, column lengths, and flow interruption. Independently measured model parameters from kinetic batch experiments were used in model validation. Two model formulations were evaluated. Model I was based on the classical two-region approach where the soil matrix was divided into two fractions. In Model II, we assumed that the rate of reaction within each soil region was a function of the total number of vacant sites in the soil. Thus, the partitioning coefficient f of the two-region concept, which is difficult to measure, need not be specified and the amounts retained by each soil region is solely a function of reaction rate coefficients. Model I with f = F (F = ^m/, mobile/total water contents) provided the worst atrazine predictions. Moreover, based on Model I predictions with f = 1 and f = 0, the significance of physical nonequilibrium was dependent on experimental constraints such as aggregate size and flow velocity. Based on root mean squares, however, the best overall predictions were obtained using Model II. We concluded that Model II, which requires fewer parameters, is superior to Model I in its prediction capability for transport results.

Published as manuscript no. 94-09-8334 of the Louisiana Agric. Exp. Stn.

Received for publication November 15, 1995.

This article has been cited by other articles:

				G. Communar and R. Keren Rate-Limited Boron Transport in Soils: The Effect of Soil Texture and Solution pH Soil Sci. Soc. Am. J., April 19, 2006; 70(3): 882 - 892. [Abstract] [Full Text] [PDF]

				H.M. Selim, L. Ma, and H. Zhu Predicting Solute Transport in Soils: Second-Order Two-Site Models Soil Sci. Soc. Am. J., July 1, 1999; 63(4): 768 - 777. [Abstract] [Full Text]