Modeling short-term soil-water distribution of aromatic amines
- Purdue Univ., West Lafayette, IN (United States)
The applicability of a distributed parameter model for describing the distribution of aniline and {alpha}-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{sup +}); (b) sorption of the neutral species (B) to soil organic carbon through the partition coefficient K{sub oc}; and (c) ion exchange of the protonated organic amine and inorganic divalent cations (Ca{sup 2+} + Mg{sup 2+} = D{sup 2+}). The last reaction was expressed mathematically as separated association reactions for each cation to unoccupied cation exchange sites, with constants K{sub BH} and K{sub D}. A Gaussian distribution on log K{sub BH} values with mode {mu} and standard deviation {sigma} was employed. The overall model was expressed as a system of two nonlinear equations with two unknown values (BH{sup +} and D{sup 2+}). The model was evaluated with aniline and {alpha}-naphthylamine isotherms measured on three Indiana soils ranging in pH (4.5--7.0) and added calcium concentration after a 24 h contact period. The parameters K{sub oc}, {mu}, and {sigma} for each amine were obtained by minimizing the sum of squared residuals between predicted and measured aqueous-phase organic amine concentrations for all soil, pH, and CaCl{sub 2} conditions, simultaneously. Calculated isotherms were compared against those calculated with the general form of the speciation model in which a singular value of K{sub BH} was employed.
- OSTI ID:
- 655452
- Journal Information:
- Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 18 Vol. 32; ISSN ESTHAG; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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