SS2.02 Biogeochemical Process at the Sediment-Water Interfaces
Date: Tuesday, June 11, 2002
Time: 4:30:00 PM
Location: Carson B
LavermanAM, Department of Geochemistry, Utrecht, Netherlands,
Wieringa, E, , MPI for Marine Microbiology, Bremen, Germany,
Meile, C, , Department of Geochemistry, Utrecht, Netherlands,
Van Cappellen, P, , Department of Geochemistry, Utrecht, Netherlands,
Denitrification plays a key role in nitrogen cycling in estuarine sediments. The vertical variation in denitrification rates was determined at different sites in the Scheldt estuary (Belgium, The Netherlands) using two different methods. Microsensors were used to record N2O profiles in the presence of the N2O reductase inhibitor acetylene. This method allows in situ rate measurements and high spatial resolution with negligible disturbance of the sediment. Additionally, intact sediment plugs of 1 cm, from 4 different depths were incubated in flow-through reactors to determine denitrification rates. This method has a lower resolution than the microprofiling, but kinetic parameters like Ks and Rm can be calculated. Highest denitrification rates, on average 300 uM N/h by microprofing and 400 uM N/h by plug flow-through reactor, were found in fresh water sediment. In the brackish sediment rates were lower being on average 100 uN/h determined by plug flow-through reactor incubation. The combination of the two methods, allowing fine-scaled resolution or determining kinetic parameters, seems promising in predicting denitrifying reaction rates in response to environmental variables (e.g. salinity, temperature) in sediments.