Shipboard interstitial water analyses were performed on 5- to 15-cm-long whole-round sections that were cut immediately after the core arrived on deck. In most cases, one whole-round section was taken from the lower third of each core. To avoid the destruction of critical intervals, whole-round sections were not removed from cores adjacent to such intervals as determined by shipboard biostratigraphy. Details of the sampling resolution are described in the individual site chapters of this volume. After extrusion from the core liner, the surface of each whole-round section was scraped with a spatula to remove potential contamination. Interstitial waters were collected using a titanium squeezer, modified after the standard ODP stainless steel squeezer of Manheim and Sayles (1974). Pressure up to 205 MPa (30,000 psi) was applied using a hydraulic press. Pore waters were passed through prewashed Whatman number 1 filters fitted above a titanium screen and subsequently extruded into a plastic syringe attached to the bottom of the squeezer assembly. All interstitial water samples were double-filtered through 0.45-µm polycarbonate filters. Samples for shipboard analysis were stored in plastic vials pending analysis. Aliquots for future shore-based analyses were placed in glass ampules or plastic tubes and heat-sealed.
Interstitial water samples were routinely analyzed for salinity as total dissolved solids with a Goldberg optical handheld refractometer. The pH and alkalinity were determined by Gran titration with a Brinkmann pH electrode and a Metrohm autotitrator. Dissolved chloride was determined by titration with AgCl. Sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), and sulfate (SO42-) were analyzed by ion chromatography using a Dionex DX-120. Silica (Si(OH)4), phosphate (HPO42-), and ammonium (NH4+) concentrations were determined by spectrophotometric methods using a Milton Roy Spectronic 301 spectrophotometer (Gieskes et al., 1991). Iron (Fe2+), manganese (Mn2+), boron (H3BO3), lithium (Li+), strontium (Sr2+), and barium (Ba2+) concentrations were determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) following the general procedure outlined by Murray et al. (2000). In preparation for analysis by ICP-AES, aliquots of interstitial waters were acidified with nitric acid (HNO3) and diluted tenfold with deionized (DI) water (0.5 mL of sample and 4.5 mL of DI water). Analytical blanks were prepared identically by analyzing DI water, which was acidified to matrix match the samples. At all sites, sodium was determined using charge balance calculations, where Scationcharge = Sanion charge. The chemical data for interstitial waters are reported in molar units. The reproducibility of results, determined via multiple determinations of International Association for the Physical Sciences of the Ocean standard seawater (alkalinity, Cl-, Ca2+, Mg2+, K+, and SO42-), spiked surface seawater (ICP-AES determinations), or through the use of a calibration curve (NH4+, HPO42-, and Si(OH)4), is available in Table T6.