Effects of sorbate speciation on sorption of selected sulfonamides in three loamy soils

Journal of Agricultural and Food Chemistry
By: , and 



Sorption of sulfamethazine (SMN) and sulfathiazole (STZ) was investigated in three soils, a North Carolina loamy sand, an Iowa sandy loam, and a Missouri loam, under various pH conditions. A significant increase in the sorption coefficient (KD) was observed in all three soils, as the sulfonamides converted from an anionic form at higher pH to a neutral/cationic form at lower pH. Above pH 7.5, sulfonamides exist primarily in anionic form and have higher aqueous solubility and no cationic character, thereby consequently leading to lower sorption to soils. The effect of speciation on sorption is not the same for all sulfonamides; it is a function of the pH of the soil and the pKa of the sulfonamides. The results indicate that, for the soils under investigation, SMN has comparatively lower KD values than STZ. The pH-dependent sorption of sulfonamides was observed to be consistent in all three soils investigated. The KD values for each speciated formcationic, neutral, and anionicwere calculated using an empirical model in which the species-specific sorption coefficients (KD0, KD1, and KD2) were weighted with their respective fractions present at any given pH.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Effects of sorbate speciation on sorption of selected sulfonamides in three loamy soils
Series title Journal of Agricultural and Food Chemistry
DOI 10.1021/jf060612o
Volume 55
Issue 4
Year Published 2007
Language English
Publisher American Chemical Society
Contributing office(s) Toxic Substances Hydrology Program
Description 7 p.
First page 1370
Last page 1376
Country United States
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