Application of a mechanistic desorption-biodegradation model to describe the behavior of polycyclic aromatic hydrocarbons in peat soil aggregates

A procedure was developed to obtain three size fractions (2360 < d(p) < 100 0, 1000 < d(p) < 710, and 710 < d(p) < 425 mum) of stable aggregates from K oopveen peat soil by application of an intense mixing regime prior to sievi ng of the soil material. The organic matter content, aggregation structure and the microstructure of these aggregates were determined and the particle s were artificially contaminated with naphthalene and phenanthrene via a so lvent phase. A nonlinear Freundlich sorption isotherm was determined for th e naphthalene contaminated soil aggregates (n = 0.39; K-F = 1.13 x 10(-2) m (1.17) kg(-0.39)). The applicability of a mathematical model, that describe s sorption equilibrium, intraparticle mass-transfer, and nonlinear bacteria l degradation kinetics, was tested by fitting results of dynamic desorption and biodegradation experiments, generated in this study and earlier work o n the peat soil aggregates. The experimental data were described adequately although strong variations in the values of the fit parameter, the intra-p article porosity (0.30 < <epsilon> < 0.88), were found. This indicates the necessity of further investigations. (C) 2000 Elsevier Science Ltd. All rig hts reserved.