Oxidation effect on the analysis of iron in the interstitial water of recent anoxic sediments

RECENT studies on the changes in composition of interstitial water during its separation from sediments 1–3 prompted us to evaluate the effect of squeezing on the concentration of ferrous iron within the interstitial water. Sediment samples were taken in northern Chesapeake Bay (38°56′ N and 76°25′ W) with a Benthos gravity corer. Layers of sediment were immediately extruded from the plastic coring tube and loaded into nylon squeezer barrels. The interstitial water was squeezed from the sediment through a 0.22 µm Millipore filter by the pressure of nitrogen acting against a rubber diaphragm 4 . The water drained directly into a calibrated test tube containing a solution of o -phenanthroline, buffered at p H 3.6, and the iron content was determined colorimetrically 5 .