BEHAVIOR OF NITROGEN-SUBSTITUTED NAPHTHALENES IN FLOODED SOIL .2.. EFFECT OF BIOAVAILABILITY ON BIODEGRADATION KINETICS

Mineralization of 1-aminonaphthalene, 2-aminonaphthalene and 1-amino-2-methyl-naphthalene under aerobic conditions in hooded soil was found to proceed with a biphasic pattern, an initial fast phase followed by a slower second one. Also the sorption isotherms of these substrates were found to be hyperbolic and were best described by the Langmuir model. When initial mineralization rates were expressed in terms of initial aqueous-phase concentrations, they gave rise to simple hyperbolic kinetics that obeyed Michaelis-Menten model for enzyme-catalysed reactions. These initial mineralization rates were found to be directly proportional to the substrate aqueous concentration reaching their maxima at about 100 mu g g(-1) (aminonaphthalene/soil slurry). Whereas the second phase mineralization rates were found to be first order with respect to the adsorbed fraction of the substrate and showed no sign of saturation, thus indicating that biodegradation is controlled by the rate of desorption.