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Denitrification in river sediments: relationship between process rate and properties of water and sediment

1. A survey was made of denitrification and nitrous oxide (N2O) production in river sediments at fifty sites in north-east England during one season in order to investigate the relationship between rates and environmental factors likely to influence these processes. The sites were chosen to represent a wide range of physical and chemical conditions. Denitrification rate and N2O production were measured within 5 h of sampling using the slurry acetylene blockage technique. 
 
 
 
2. Denitrification rate ranged from less than 0.005–260 nmol N g–1 DW h–1, tending to increase in a downstream direction. N2O production ranged from negative values (net consumption) to 13 nmol N2O-N g–1 DW h–1 and accounted for 0–115% of the N gases produced. 
 
 
 
3. Denitrification rate and N2O concentration in the sediment were correlated positively with nitrate concentration in the water column, water content of the sediment and percentage of fine (< 100 μm) particles in the sediment. 
 
 
 
4. The variation in denitrification rate was satisfactorily explained (64% total variance) by a model employing measurements of water nitrate and water content of sediments. No simple or multiple relationship was found for N2O production.