We examined the sediment denitrification rate and factors affecting
the denitrification in Barato lake, an eutrophic oxbow lake in lower Ishikari
river basin. Denitrification rate was measured using acetylene inhibition
technique on the sediment samples collected during August 2009 to July 2010.
The sediment denitrification rate ranged from 0.13 to 2.21 μg N g
$^{-1}$
DMh
$^{-1}$
with an average of 0.91 μg N g
$^{-1}$
DM h
$^{-1}$
in Barato lake.
Denitrification rate showed positive correlation with dissolved nitrate
concentration of lake water, indicating that water column nitrate concentration
control the sediment denitrification rate in Barato lake. Nutrient amended
denitrification assay experiments showed that denitrification rate increased
significantly with addition of nitrate regardless of sediment C content, while
no significant variation was observed with addition of labile C (glucose).
Temperature positively affected the rate of denitrification with five-fold
increase in activity on increasing temperature from 5°C to
20°C. Nitrate controlled denitrification followed
Michaelis-Menten kinetics with
$V_{max}$
as 2.65 μg N g
$^{-1}$
DM h
$^{-1}$
and
K
$_m$
as 0.48 mg/l NO
$_3^-$
-N. The value of K
$_m$
was comparable with other studies
but was well below the median dissolved nitrate concentration (2.95 mg/l NO
$_3^-$
-N) indicating that the process of
denitrification was saturated in Barato lake.
