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Anion Transport through Columns of Highly Weathered Acid Soil: Adsorption and Retardation
Author(s) -
Bellini Giampaola,
Sumner Malcolm E.,
Radcliffe David E.,
Qafoku Nikolla P.
Publication year - 1996
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1996.03615995006000010021x
Subject(s) - subsoil , chemistry , retardation factor , soil water , topsoil , dispersion (optics) , cation exchange capacity , adsorption , soil science , geology , chromatography , physics , column chromatography , organic chemistry , optics
Subsoils of highly weathered, acid soils usually contain appreciable quantities of anion‐exchange capacity (AEC), which retards the passage of anions through the profile. This AEC varies in magnitude with ambient soil solution parameters such as pH and ionic strength. In order to be able to predict NO ‐ 3 movement in such soils, estimates of the effect of subsoil charge characteristics on retardation are required. The effect of subsoil liming and ionic strength on the movement of NO ‐ 3 in repacked Kanhapludult soil columns was studied for this purpose. Columns comprising topsoil (untreated) over subsoil limed to different levels to give a range of AEC were used. The soil was first leached with a solution of 10 mmol c Ca(NO 3 ) 2 L ‐1 followed by a 10 mmol c CaCl 2 L ‐1 solution. Convection‐dispersion equation (CDE) parameters for Cl ‐ were determined using CXTFIT. Liming reduced the retardation coefficient ( R ) from 2.39 in the unamended subsoil to 1.12 in the treatment that received 2.08 g Ca(OH) 2 kg ‐1 . Both subsoil pH ( r 2 = 0.96) and AEC ( r 2 = 0.98) were correlated with R for Cl ‐ . To test the effect of electrolyte concentration on retardation, columns of untreated subsoil were leached with solutions of Ca(NO 3 ) 2 and CaCl 2 at four input concentrations: 5, 10, 20, and 30 mmol c L ‐1 . Retardation coefficients for Cl ‐ at these concentrations were 2.81, 2.25, 1.76, and 1.51, respectively. Anion retardation needs to be taken into account in modeling NO ‐ 3 movement through acid subsoils.