Denitrification Rates in a Marine Sediment as Measured by the Acetylene Inhibition Technique

A method has been developed for measurement of denitrification activity in sediments by application of the acetylene inhibition technique. Acetylene-saturated water was injected, at close intervals, into sediment cores which were then incubated for a few hours at the in situ temperature. Frozen segments of the cores were assayed for accumulation of N(2)O by a combined gas extraction and detection system. The segments were thawed under a stream of helium from which N(2)O (and other gases) was collected in a liquid N(2) trap, and the quantity of N(2)O was measured by gas chromatography. The maximum rate of denitrification in a coastal marine sediment was 35 nmol of N per cm of sediment per day at 2.5 degrees C, and the rate of denitrification for the total sediment was 0.99 nmol of N per m per day.