The North Atlantic Ocean as a source of atmospheric N2O

The nitrogen cycle: perturbations due to man and their impact on atmospheric N 2 O and O 3

Features of the global cycle of fixed nitrogen are reviewed with an emphasis on perturbations due to man. It is argued that agricultural practices and combustion may lead to an increase in the concentration of atmospheric N 2 O with consequent effects on 0 3 . The level of 0 3 may drop by about 20 % over the next 100 years if world population and the demand for food should continue to grow at anything like rates which prevailed in the recent past. Uncertainties in the model are highlighted and note is taken of areas where there is need for additional data.

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.