MEPS 182:29-35 (1999)  -  doi:10.3354/meps182029

Distribution of adsorbed ammonium pools in two intertidal sedimentary structures, Marennes-Oléron Bay, France

M. J. C. Laima1,*, M. F. Girard2, F. Vouvé2, G. F. Blanchard2, D. Gouleau2, R. Galois2, P. Richard2

1University of Aarhus, Department of Earth Sciences, Ny Munkegade, Building 520, DK-8000 Aarhus C, Denmark
2CREMA, CNRS-IFREMER, Place du Seminaire, BP 5, F-17137 L'Houmeau, France

ABSTRACT: The 1-step and multiple-step KCl extraction technique was used to evaluate quantitatively the distribution of adsorbed NH4+ in the 0-5 cm strata of 2 intertidal muddy structures from Marennes-Oléron Bay, France. KCl extraction efficiency was higher in the reconstituted sediment slurries and decreased significantly in the presence of porewater ions, leading to underestimations of the size of the pool of adsorbed, easily desorbed NH4+. Various pools of adsorbed NH4+ were displaced from the sediment after reaction with KCl in multiple steps. Pools of tightly bound NH4+ were much larger in runnels as opposed to ridges, and accounted for up to 32% (ridge) and 40% (runnel) of the NH4+ desorbed from the sediment. These pools have important implications for the calculation of the KD value, the dimensionless NH4+ distribution coefficient. Differing relationships between easily desorbed NH4+ or tightly bound NH4+, on the one hand, and the sediment grain size, CaCO3 and N content, on the other, suggest multiple origins for particulate matter in the sediment.

KEY WORDS: Ammonium · Adsorption · Mudflat · Ridge · Runnel

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