A marine sediment concept defining how particles accumulate, are reworked, and change after burial on the seafloor. It governs depositional processes, physical properties, and post-depositional reactions measured through cores and laboratory analyses. It does not uniquely identify sources or processes without supporting stratigraphic, mineralogical, and geochemical evidence. It materially affects habitat, slope stability, and climate records by controlling the properties and composition of seabed deposits. The concept is generally stable, though analytical resolution and property measurement methods improve over time.

Principle

Mechanical compression reduces pore volume and expels interstitial fluid through filters or porous plates; the procedure separates liquid and solid phases but can alter particulate content, dissolved concentrations, and redox-sensitive species if not controlled.

Demonstration

Placing a subcore into a mechanical squeezer lined with filter paper, applying calibrated pressure until pore fluids are expressed into a collection vial, and analyzing the collected water for sulfate, nutrients, and dissolved metals.

Misapplication

Applying excessive pressure, using inappropriate filter media, or allowing heating during squeezing can release colloids, mobilize adsorbed species, or change oxidation states, producing pore water that does not reflect in situ chemistry.

Consequence

Squeezed pore water can provide relatively large-volume samples for multiple analyses and yield bulk interstitial concentrations, but results must be interpreted in light of possible mechanical and compositional alterations.

Reversal

Low‑disturbance sampling like rhizon extraction or in situ microsensor profiling that aim to preserve fine-scale redox gradients and avoid particulate mobilization inherent to squeezing.

Boundary

Suitable for cohesive, fine-grained sediments where pressure will express fluids; less appropriate for very coarse or highly permeable sediments and for analytes extremely sensitive to pressure- or oxygen-induced transformations.

Semantic Tension

Sometimes equated with centrifuged pore water or rhizon extracts; squeezed pore water often yields larger volumes and different particulate loads, so it is not strictly interchangeable with gentler extraction methods.

Synthesis

Squeezed pore water is the mechanically expressed interstitial fluid collected by compressing sediment cores, useful for obtaining ample sample volumes but requiring careful method control and interpretation due to potential alteration of chemistry.