There have been recent reports of high nitrite concentrations occurrin
g in both terrestrial and aquatic ecosystems. In the present study, mo
delling procedures were applied to results from soil incubation studie
s in order to quantify the relative contribution of nitrification and
denitrification to nitrite accumulation. In order to quantify the simu
ltaneous rates of nitrite formation from these processes, N-15 pool di
lution calculations were employed. These rates were employed as rate-d
etermining steps in an empirical model describing the kinetics of the
how of N between ammonium, nitrite and nitrate compartments in order t
o simulate nitrite accumulation. Employing nitrification as the sole p
rocess generating nitrite results showed excellent agreement between o
bserved and predicted nitrite accumulation. The rate of ammonium oxida
tion was only required to be slightly in excess of nitrite oxidation i
n order to generate nitrite accumulation. The available evidence sugge
sts this imbalance in rates was due to nitrite oxidizers (Nitrobacter)
being inhibited by free ammonia to a greater extent than ammonium oxi
dizers (Nitrosomonas). (C) 1997 Elsevier Science Ltd.