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) produc tion in river sediments at fifty sites in north-east England during on e season in order to investigate the relationship between rates and en vironmental factors likely to influence these processes. The sites wer e 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. Denitrifica tion rate ranged from less than 0.005-260 nmol N g(-1) DW h(-1), tendi ng to increase in a downstream direction. N2O production ranged from n egative values (net consumption) to 13 nmol N2O-N g(-1) DW h(-1) and a ccounted for 0-115% of the N gases produced. 3. Denitrification rate a nd N2O concentration in the sediment were correlated positively with n itrate concentration in the water column, water content of the sedimen t and percentage of fine (< 100 mu m) particles in the sediment. 4. Th e 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 fo und for N2O production.