Modeling Short-Term Soil−Water Distribution of Aromatic Amines

Abstract

The applicability of a distributed parameter model for describing the distribution of aniline and α-naphthylamine between soil and aqueous phases at short contact times was assessed. Mass action equations considered in the distributed parameter model were (a) acid dissociation of the protonated organic amine (BH+); (b) sorption of the neutral species (B) to soil organic carbon through the partition coefficient Koc; and (c) ion exchange of the protonated organic amine and inorganic divalent cations (Ca2+ + Mg2+ = D2+). The last reaction was expressed mathematically as separated association reactions for each cation to unoccupied cation exchange sites, with constants KBH and KD. A Gaussian distribution on log KBH values with mode μ and standard deviation σ was employed. The overall model was expressed as a system of two nonlinear equations with two unknown values (BH+ and D2+). The model was evaluated with aniline and α-naphthylamine isotherms measured on three Indiana soils ranging in pH (4.5−7.0) and adde...