Occurrence of nitric and nitrous oxides in a coastal marine sediment.

The distribution of denitrification activity in a coastal marine sediment was determined by the acetylene inhibition technique and compared to concentration profiles of NO3-, NO2-, NO, and N2O. The bulk of the denitrification activity was associated with the accumulation of NO3- in the oxidized surface zone of the sediment, but a secondary denitrification zone was occasionally found in the deeper layers where oxidized patches had been introduced by the burrowing activity of the macrofauna. Maxima of NO and N2O were not associated with the peak activity of denitrification in the surface zone but were located at the lower edge of the activity profile. Significant accumulation of NO was found at the redox transition zone towards the deeper, sulfide-rich layers.