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The chemical laboratory aboard the JOIDES Resolution is a modern, state of-the-art shipboard facility providing an impressive capability for both organic and inorganic geochemical analyses. A primary responsibility of shipboard organic geochemists is to provide data on petroleum hydrocarbons for safety and environmental concerns. In addition, instrumentation is available for determination of source, amount, and maturity of organic matter; carbonate content; and total carbon, nitrogen and sulfur. Inorganic geochemists have a wide array of analytical instruments at their disposal for determination of a large range of interstitial water constituents that typically includes pH, alkalinity, chloride, calcium, magnesium, sulfate, potassium, strontium, sodium, manganese, phosphate, silica, and ammonium and others as desired. Two marine lab specialists provide dedicated, 24-hour technical support to the chemistry laboratory on most cruises.
The Delsi-Nermag Rock-Eval II (Fig. 3) uses a whole-rock pyrolysis technique to identify the type and maturity of organic matter and to detect petroleum potential of the sediments by determining volatile hydrocarbons, hydrocarbons released by thermal cracking of kerogen, and carbon dioxide released by thermal degradation of organic matter. Total organic carbon and Tmax (degrees C), which is a parameter that can access the maturity of organic matter, are also determined.
A Carlo-Erba NA 1500 CNS Analyzer is used to determine total carbon, nitrogen, and sulfur (Fig. 5). With sufficient warning, the CNS analyzer can be plumbed to determine C and N only at the beginning of a cruise.
Shipboard interstitial water analyses are typical performed on waters extracted from 5- to 10-cm3 whole-round sections. For details on methods used for interstitial water analyses on board the JOIDES Resolution, consult Gieskes et al (1991; ODP Technical Note 15).The routine shipboard sampling program for interstitial waters calls for one whole-round sample to be taken every core for the first six cores, and then one sample every third core thereafter. Waters are extracted from the sediment using titanium squeezers (Fig. 3) and applying pressure up to 40,000 lb (about 4150 psi) with an hydraulic press (Fig. 6).
Immediately after extraction and filtration, aliquots are analyzed for salinity by a hand-held Goldberg optical refractometer and for pH and alkalinity by Gran titration with a Brinkman pH electrode and a Metrohm autotitrator (Fig. 7). Other constituents typically analyzed by titration include chloride, calcium, and magnesium. A variety of nutrients and other pore-water constituents (e.g., ammonium, silica, phosphate, bromide, and manganese) can be determined via colorimetric methods using a Milton Roy Spectronic 301 spectrophotometer. Numerous cation and anions can be analyzed by ion chromatography using a recently acquired Dionex DX-120 (Fig. 8), typically sulfate, calcium, and magnesium, but also including potassium and sodium.
A variety of other elements can be determined inductively coupled plasma emission spectrometry on a Jobin-Yvon JY2000 ICP-ES (Fig. 9). A typical suite of elements determined for interstitial waters include Sr, Li, Fe, Mn, and Ba. Technical Note 29 describes recommended preparation, analysis, and data reduction techniques and instructions for interstitial water, sediment, and hard rock chemical analyses by ICP.
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