Nitrification in sediment cores measured with acetylene inhibition

A new and accurate method for measuring nitrification in intact sediment cores is presented. Sediment-water fluxes of NH4+ were measured for 4–8 h in individual cores before and after inhibition of nitrification with acetylene. The difference in the fluxes corresponded to the rate of nitrification. Oxygen depletion of the water during incubation was avoided by oxygen enrichment of the overlying gas phase. Results from a sandy sediment in a Danish estuary give rates of 0.60±0.07 mmol N m−2 d−1.