The inorganic geochemistry program during Leg 180 was designed to identify the various geochemical reactions taking place throughout key lithologic sections. The bulk of the shipboard inorganic geochemistry focused on the analysis of squeezed IW to identify major changes in the composition of the sediments and the water/rock interactions therein.

Shipboard IW analyses were performed on waters extracted from 5- to 15-cm-long whole-round sections that were cut immediately after core retrieval on deck. Specific details of the sampling resolution are described in the individual site chapters. After extrusion from the core liner, the outer few millimeters of each whole round were carefully removed with a clean spatula to minimize potential contamination. Interstitial waters were collected using a titanium squeezer, modified after the standard ODP stainless steel squeezer of Manheim and Sayles (1974), to provide contamination-free IW samples. Scraped excess material was saved and archived for any future potential research needs. After loading the squeezer, pore water was extruded through Whatman No. 1 filters fitted on a titanium screen by applying pressures up to 40,000 lb (~4150 psi) with a hydraulic press.

The IW samples were double filtered. IW was collected through 0.45-µm Gelman polysulfone disposable filters into scrupulously cleaned (acid washed with 10% volume/volume [v/v] HCl or HNO₃) 50-mL plastic syringes. The IW was subsequently refiltered through 0.45-µm Gelman polysulfone disposable filters as needed. Trace element splits for postcruise shore-based research were subsequently processed under "clean conditions" in a Class 100 laminar flow hood, filtered through acid-washed 0.22-µm Gelman polysulfone disposable filters, and acidified with 100 µL of double quartz distilled 8.7 N HNO₃ per 25 mL of IW. Samples for postcruise isotopic analyses were heat sealed in glass vials. Samples for shipboard work were stored in plastic vials before analysis.

In the deeper portions of the core, where IW sampling became more difficult because of lithification of the sediments, larger whole-round samples were selected from what appeared to be the softer portions of the core. These samples were placed inside several plastic bags and crushed with a hammer. The crushed sample was then squeezed in the normal manner described above. This procedure was previously used during Leg 166 and found to yield a much greater volume of pore water than obtainable by simply squeezing the original whole-round material (Leg 166, Shipboard Scientific Party, 1997).

The IW samples were routinely analyzed for salinity as total dissolved solids in grams per kilogram with a Goldberg optical handheld Reichart refractometer. The alkalinity was measured by Gran titration with a Brinkmann pH electrode and a Metrohm autotitrator. The pH was measured on the National Bureau of Standards (NBS) scale as part of the alkalinity titration. It should be noted that pH measurements obtained in this fashion are not always reliable given that the algorithm employed for pH measurement before the start of the alkalinity titration is adversely affected by degassing.

Dissolved chloride was determined by titration and by ion chromatography (IC; see paragraph below). Dissolved SiO₂ and NH₄⁺ were determined by spectrophotometric methods with a Milton Roy Spectronic 301 spectrophotometer (Gieskes et al., 1991). The standard deviations of the analyses described above are as follows: alkalinity = <1.5%; chloride = <0.5%; and SiO₂ and NH₄⁺ = ~3%.

Sodium, potassium, magnesium, calcium, chloride, and sulfate were analyzed by IC using a Dionex DX-100 automated system equipped with an autosampler. Typical 1- standard deviations were as follows: potassium = <6%; magnesium and calcium = <3%; sulfate = <4%; and sodium = <5%. Chloride measurements by IC, which are often systematically higher by ~3%-5% than those obtained by titration, were more accurate with the new IC installed at the beginning of Leg 180. Titrations were routinely performed to compare results obtained by the two techniques except in IW from Site 1108. Dissolved Cl^- measurements made by AgNO₃ titration are still better constrained than those by IC and are deemed more reliable. Excursions were observed to occur in Cl^- data from IC on a run-by-run basis, with notable divergence of the titration and IC data observed in the first 150 mbsf of Site 1109 (see Fig. F70A, in the "Site 1109" chapter).

Lithium and strontium concentrations were quantified using flame atomic emission spectrometry (AES) and atomic absorption spectrometry (AAS) on a Varian SpectrAA-20. Tenfold dilutions of the IW were used for lithium and five- to twentyfold dilutions were employed for strontium analyses. Air-acetylene (Li) and nitrous oxide-acetylene (Sr) flames were utilized for these analyses. Standards for all flame AAS/AES techniques were matrix matched as closely as possible to samples (Li and Sr). Matrix matching is particularly important for Li determinations, because large variations in salinity and matrix composition of the IW result in interferences that lead to erroneously high Li concentrations (E. De Carlo and P. Kramer, unpubl. data). A more detailed description of analytical methods and standards used can be found in ODP Technical Note 15 (Gieskes et al., 1991). The 1- standard deviations were <2% for lithium and ~3%-4% for strontium.