NITROUS-OXIDE EMISSIONS FROM ESTUARINE INTERTIDAL SEDIMENTS

From September 1990 through December 1991 nitrous oxide flux measureme nts were made at 9 intertidal mud flat sites in the Scheldt Estuary. N itrous oxide release rates were highly variable both between sites and over time at any one site. Annual nitrous oxide fluxes vary from abou t 10 mmol N m(-2) at the tidal fresh-water end-member site to almost z ero at the most saline stations. Along the estuarine gradient, annual nitrous oxide fluxes are significantly correlated with sedimentary org anic carbon and nitrogen concentrations, ammonium fluxes and annual ni trogen turn-over rates, that are estimated using mass-balance consider ations. Nitrous oxide fluxes seem to respond linearly to an increasing nitrogen load, with one out of each 17 000 atoms nitrogen entering es tuaries being emitted as nitrous oxide.