Porewater convection induced by peeper emplacement in saline sediment

Grigg, Nicola J., Ian T. Webster, Phillip W. Ford

Limnol. Oceanogr., 44(2), 1999, 425-430 | DOI: 10.4319/lo.1999.44.2.0425

ABSTRACT: "Peepers" (dialysis samplers) rely on exchange across a dialysis membrane between fluid-filled cells and the surrounding sediment in order to sample the pore water at various depths. In the current study, we show that under some realistic circumstances, where there is a large density difference between the pore water and the cell fluid in permeable sediments, the resulting convective motion in the pore water distorts concentration distributions near the peeper. Peepers withdrawn prematurely in these conditions will contain seriously misrepresentative samples. We present numerical model and laboratory experiment results that show that the equilibration dynamics are complex and that the time required for equilibration may be far in excess of the duration predicted by a simple molecular diffusion model.

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