KINETICS OF FES-MEDIATED DENITRIFICATION IN SEDIMENTS FROM THE CAMARGUE (RHONE DELTA, SOUTHERN FRANCE)

Denitrification rates were measured in sediments after the addition of different concentrations of FeS. A decrease of the denitrification ra te was observed when high concentrations of ferrous iron (> 10 mM) wer e present. In the experiments with no significant concentrations of fr ee Fe2+, the relationship between NO3- reduction and FeS concentration followed Michaelis and Menten kinetics. The maximum rate was 0.273 mm ol l(-1) d(-1), 6 times as much as the basal rate 0.046 mmol l(-1) d(- 1), which was attributed to organic matter; the K-s was 1.45 mM FeS. T he stoichiometry of the overall reaction involving NO3- reduction and the concomitant S2- oxidation was also investigated. Measured Delta S/ Delta N ratios ranged between 0.55 and 0.64, with Sigma H2S+SO42- chan ging less than 10%. These values agree with the theoretically expected value of 0.56.