Unit Organic Carbon Research Articles

Sorption of methabenzthiazuron (tribunil) on soil particle‐size separates, based on their organic carbon content

The adsorption of methabenzthiazuron (3‐(2‐benzothiazolyl)‐1,3 dimethyl urea) was studied on four soil particle‐size separates (ranging from 2 to 0.05 mm in diameter) of an alfisol and a vertisol. The Freundlich constants (K) of these fractions were inversely related to their organic carbon content. The Freundlich constants per unit organic carbon (Koc ) were remarkably similar. Thus, when Aoc, the adsorption per unit organic carbon was used, the adsorption isotherms of the individual fractions, coalesced to a single isotherm of the type Aoc = K‘ocC1/n, with K‘oc= 1106±200 and n=1.4. Thus, it may be possible to estimate the sorption capacity of the different particle‐size fractions, from a knowledge of their organic carbon content and the Freundlich constant in a single or limited number of fractions.