| Resumo: |
Nitrification and repartition of nitrifying bacteria were investigated in the autoepuration zone of the Scheldt estuary. Measurements of vertical profiles of nitrate and nitrite concentrations in the interstitial water of sediments show that nitrification in sediments is very low, implying that most of the nitrate and nitrate production occurs in the water of the river itself. Nitrifying bacteria, probably of terrestrial origin, are present throughout the water along a longitudinal profile of the estuary, with a regular decrease in numbers downstream. However, nitrification occurs only in a zone of favourable oxidation-reduction conditions, which coincides with the thermodynamic stability fields of nitrate and nitrite with respect to ammonium.
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