N2/Ar and denitrification in tama estuary sediments

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Abstract
N2, Ar, O2, and CH4 in sedimentary pore waters of the Tama Estuary, Tokyo, were determined. The distributions of N2 and Ar reflected seasonal changes in these gases in the overlying water. N2/Ar ratios were always higher than in water in equilibrium with the atmosphere, providing direct evidence for denitrification in the sediment. N2 production from nitrate by bacteria in the sediment was simultaneously determined using a 15N tracer technique. The distribution of the excess N2 so produced was calculated using a one‐dimensional diffusion model and compared with observations. Rapid loss of N2 from sediment to overlying water is suggested.