Short-term interactions of aniline and benzidine with three soils in both natural and artificial matrices

The fate of aromatic amines in natural systems is important to understand due to the persistence and toxicity of these chemicals. Laboratory experiments were performed to elucidate aniline and benzidine behavior in silty-clay, sandy loam, and sandy soils, and six background matrices (rainwater, 12.5 mM CaCl2, 25 mM CaCl2, and each passed through soil columns). The goals of this study were to test the validity of using CaCl2 as a laboratory simulation for rainwater and to observe how short-term sorption (24 h) of aniline and benzidine changed when these solutions were passed through soil columns. Results indicated that neither CaCl2 solution exactly predicted the sorption of these chemicals in corresponding rainwater solutions, likely due to varying soil properties that influenced the sorption mechanisms. Statistical analyses revealed that the passage of rainwater or CaCl2 solutions through soil columns did not significantly affect the sorption of aniline or benzidine. Cation exchange and solubility plots were created to identify the sorption mechanisms taking place in the short-term batch experiments. These plots indicated that cation exchange played a role in the sorption of both aniline and benzidine under all conditions, while solubility plots showed higher correlations for benzidine, a consequence of its lower aqueous solubility.