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 diaphragm⁴. The water drained directly into a calibrated test tube containing a solution of o-phenanthroline, buffered at pH 3.6, and the iron content was determined colorimetrically⁵. © 1974 Nature Publishing Group.