Sorption and microbial degradation of naphthalene in soil-water suspensions under denitrification conditions

Abstract

The microbial degradation of naphthalene under denitrification conditions in soil-water suspensions was dependent on solute partitioning between soil and water. Soil-associated naphthalene was in equilibrium with aqueous-phase solute, with the rate of naphthalene degradation being mixed order with respect to aqueous concentration. The rate of degradation was modeled by coupling Michaelis-Menten kinetics for aqueous-phase solute with an intraaggregate radial diffusion model for naphthalene sorption and desorption with soil. It was shown by modeling and confirmed by experiment, for the soil suspension particle sizes employed in these tests, that the naphthalene sorption-desorption process was reversible and rapid compared to the rate of microbial degradation. The maximum rate of microbial degradation was proportional to the soil-to-water ratio and independent of nitrate concentration for initial nitrate concentrations greater than several hundred micrograms per gram of soil. Nitrate reduction was described by utilizing the total mass removal of naphthalene and a stoichiometric conversion factor. A coupled solute desorption-degradation model is presented for microbial degradation of hydrophobic organic compounds that are desorbed from porous soil aggregates, assuming sorbed solute is inaccessible to microorganisms and that the rate of solute release from the solid is rapid compared to the rate of retarded intraaggregate diffusion.

Influence of hydrodynamic conditions on naphthalene dissolution and subsequent biodegradation

“…There are some reports on the direct uptake of hydrophobic substances from surfaces by microorganisms (Guerin and Boyd, 1992;Guerin and Jones, 1988;Hermannson and Marshall, 1985), but generally the desorption or dissolution of PAH to the aqueous phase is considered a prerequisite for biodegradation. The latter view is expressed in most studies and supports the idea that microorganisms can only convert these compounds in the dissolved state (Mihelcic and Luthy, 1991;Scow and Alexander, 1992;Wodzinski and Bertolini, 1972;Wodzinski and Coyle, 1974). Because mass transfer from sorption sites or crystalline surfaces to an aqueous phase with microorganisms is necessary for biodegradation, the physical state of the pollutant in the soil plays an important role (Mihelcic et al, 1993;Rulkens and Bruning, 1995;Wu and Gschwend, 1986).…”

Biodegradation kinetics of naphthalene in nonaqueous phase liquid-water mixed batch systems: Comparison of model predictions and experimental results

“…Various recent investigations have reported on the biodegradation of 2-and 3-ring PAH compounds sorbed on soils (Bauer and Capone, 1988;Mihelcic and Luthy, 1991;Mueller et al, 1991;Park et al, 1990) or present as NAPL components (Efroymson and Alexander, 1994;OrtegaCalvo and Alexander, 1994;Ghoshal et al, 1996;Woodzinski and Larocca, 1977). Laboratory studies employing supersaturated aqueous solutions of PAH compounds have shown that the rates of dissolution control the rates of biodegradation of these compounds (Stucki and Alexander, 1987;Volkering et al, 1993;Woodzinski and Bertolini, 1972;Woodzinski and Coyle, 1974).…”

Oxygen limitations and aging as explanations for the field persistence of naphthalene in coal tar‐contaminated surface sediments

“…Because dioxygenase enzyme complexes (which require molecular oxygen as a cosubstrate) are essential for the known biochemical mechanisms of naphthalene metabolism [25], one obvious explanation for naphthalene's persistence at the site is simply lack of O 2 . However, anaerobic metabolism of naphthalene under nitrate-reducing conditions has also been reported [26][27][28].…”

“…Because naphthalene metabolism under denitrifying conditions had been previously reported [26][27][28], an additional attempt using slurried sediments was implemented. The fate of naphthalene in uninoculated, autoclaved, and viable denitrifying treatments is shown in Figure 3.…”