PNNL

Abstract

Sorption of 9H-carbazole was investigated from aqueous and co-solvent solutions on soils with different physical and chemical properties. Sorption was nonlinear, but well correlated to the organic carbon (OC) content of the soils. The variability of the Freundlich adsorption constant (Kt), normalized to OC (Kfoc) is small between A horizons of two Mollisols and two Ultisols but increases to about 0.8 log units between C horizons of the Mollisols and Ultisols. This variability combined with the absence of linear partitioning leads to poor predictability by C reference partitioning based on octanol/water or water solubility parameters in the highly weathered soils. Differences in structure and type of the associated OC may be a factor affecting predictability. The presence of methanol and acetone induces a log-linear decrease in carbazole sorption with mole fraction cosolvent. For a given solvent (i.e., MeOH, acetone) the log-linear behavior is independent of sorbent properties and exhibits a common slope, thus attesting to the importance of the solvent interaction. In contrast, pyridine as a cosolvent is actively sorbed by some soils creating a more oleophilic surface and a tendency to increase carbazole partitioning to the soil surface.