Microbial degradation of polycyclic aromatic hydrocarbons under denitrification conditions in soil-water suspensions: Final report

Abstract

The microbial degradation of polycyclic aromatic hydrocarbons (PAH) under different redox conditions was examined for soil-water suspensions, with particular emphasis on microbial degradation under denitrification conditions. Batch microbial degradation tests of naphthol, naphthalene, and acenaphthene with 1 gram of soil per 50-ml aqueous phase were conducted under aerobic and anaerobic conditions. A conceptual model was proposed to describe the aqueous-phase concentration of PAH solute under denitrification conditions for soil-water systems maintained under gentle suspension. The approach combined an intra-aggregate radial diffusion model to represent solute sorption and desorption with soil, with either Monod or first-order kinetics to describe the microbial degradation of solute from the bulk-aqueous phase. The microbial degradation of naphthalene in soil-water suspensions under denitrification conditions was modeled by the coupled desorption-degradation approach in order to evaluate unexplored situations in which soil particle size may affect the rate of microbial degradation. A preliminary assessment of the effect of solute hydrophobicity on microbial degradation was modeled for volumetric mean particle radii in the range of 0.01 to 0.1 cm. The coupled desorption-degradation model and first-order aerobic degradation kinetic information from the literature used to predict the aqueous- and sorbed-phase concentrations for the solutes naphthalene, anthracene, and benzo(a)pyrene. 43 refs.,more » 53 figs., 10 tabs.« less