Is. Ahn et al., MICROSCALE-BASED MODELING OF POLYNUCLEAR AROMATIC HYDROCARBON TRANSPORT AND BIODEGRADATION IN SOIL, Biotechnology and bioengineering, 51(1), 1996, pp. 1-14
A mathematical model to describe polynuclear aromatic hydrocarbon (PAH
) desorption, transport, and biodegradation in saturated soil was cons
tructed by describing kinetics at a microscopic level and incorporatin
g this description into macroscale transport equations. This approach
is novel in that the macroscale predictions are made independently fro
m a knowledge of microscale kinetics and macroscopic fluid dynamics an
d no adjustable parameters are used to fit the macroscopic response. i
t was assumed that soil organic matter, the principal site of PAH sorp
tion, was composed of a continuum of compartments with a gamma distrib
ution of desorption rate coefficients. The mass transport of substrate
s and microorganisms in a mesopore was described by diffusion and that
in a macropore by one-dimensional advection and dispersion. Naphthale
ne was considered as a test PAH compound for initial model simulations
. Three mechanisms of naphthalene biodegradation were considered: grow
th-associated degradation as a carbon and energy source for microbial
growth; degradation for maintenance energy; and growth-independent deg
radation. The Haldane modification of the Monod equation was used to d
escribe microbial growth rates and to account for possible growth inhi
bition by naphthalene. Multisubstrate interactions were considered and
described with a noninteractive model for specific growth rates. The
sensitivity of selected model parameters was analyzed under conditions
when naphthalene was the sole growth-rate-limiting substrate. The tim
e necessary to achieve a specific degree of naphthalene biodegradation
was found to be proportional to the initial concentration of naphthal
ene in soil organic matter. The biodegradation rate of naphthalene inc
reased when the sorption equilibrium constant of naphthalene was reduc
ed. The presence of an alternative carbon source inhibited naphthalene
biodegradation in spite of the calculated increase in biomass. (C) 19
96 John Wiley & Sons, Inc.