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

Abstract

1. A survey was made of denitrification and nitrous oxide (N 2 O) 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 N 2 O 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. N 2 O production ranged from negative values (net consumption) to 13 nmol N 2 O‐N g–1 DW h–1 and accounted for 0–115% of the N gases produced. 3. Denitrification rate and N 2 O 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 N 2 O production.