SS2.02 Biogeochemical Process at the Sediment-Water Interfaces
Date: Tuesday, June 11, 2002
Time: 10:30:00 AM
Location: Carson B
 
PalludCE, Utrecht University, Utrecht, Netherlands, c.pallud@geo.uu.nl
Laverman, A, M, Utrecht University, Utrecht, Netherlands, anniet@geo.uu.nl
Van Cappellen, P, , Utrecht University, Utrecht, Netherlands, pvc@geo.uu.nl
 
NITRATE AND SULFATE REDUCTION RATES MEASURED WITH PLUG FLOW-THROUGH REACTORS IN SALTMARSH SEDIMENTS
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Microbial activity plays a dominant role in biogeochemical cycling in sediments. Here we investigate the kinetics of two important respiration pathways in saltmarsh sediments (Eastern Scheldt, The Netherlands) using plug flow-through reactors, which contain intact sediment slices obtained from a hand-pushed corer. Experiments are performed to measure the variability with depth below the sediment surface, as well as the influence of substrate concentration and availability of organic carbon on nitrate and sulfate reduction rates. In parallel, potential rates are measured in slurry incubations, while nitrate and sulfate-reducers are enumerated with the MPN (Most Probable Number) method. Densities of nitrate and sulfate-reducers are 102-106 and 106-108 g-1. Nitrate reduction occurs instantaneously, while sulfate reduction only starts after a relatively long lag time (a week). Nitrate-reduction rate is high (about 130 microM.h-1) and homogeneous in the uppermost 4 cm. Sulfate reduction is only measurable when labile dissolved organic carbon is added to the reactors. The low sulfate reduction activity contrasts with the high MPN counts and the observed pore water sulfate depletion at the site.