A Whole-Core Squeezer for Interfacial Pore-Water Sampling

The "whole-core squeezer" is a simple pore-water sampler designed for millimeter depth resolution near the sediment-water interface. Various tests have been done to determine how accurately true gradients are reproduced by whole-core squeezing. Tracer studies show that any mixing associated with squeezing does not smear the profiles by more than a few millimeters. Benthic fluxes of SiO2calculated from interfacial concentration gradients resolved with the whole-core squeezer in San Clemente Basin are in good agreement with "bell-jar" values measured with the benthic chambers of a bottom lander. Oxygen profiles determined with the whole-core squeezer are very similar to values determined with an oxygen microelectrode. These comparisons confirm that interfacial gradients and (by calculation from models) fluxes of O2, NO3 -, SiO2, and other particle-unreactive ions and molecules can be determined with the instrument. On the other hand, the composition of squeezed pore waters is very susceptible to rapid alteration by solid-solution reactions. Therefore the method is not suitable for determining pore-water profiles of trace metals and other particle-reactive chemicals.