Understanding the nature of the water in the ocean and within the rocks and sediments that create the oceans' floors is fundamental to all aspects of oceanography and Earth's evolution. Interstitial water chemistry can be used to study processes related to the deposition, decomposition, and preservation of organic matter; deposition of minerals; alteration of rock; growth of microbial communities deep in the crust; and many other scientific studies.
ODP analyzed water extracted from cores and either seawater or borehole water collected by downhole instruments. A variety of analytical instruments and methods were used to determine as many as 35 different water chemistry constituents. Nearly 13,000 IW samples were taken during 89 of the 110 ODP cruises. Among the measurements routinely collected were pH, alkalinity, salinity, and chemical elements such as chlorinity (Cl + Br), calcium, magnesium, sodium, and sulfate. Newer technology and instrumentation increased the number of chemical constituents that could be measured in the Chemistry Laboratory on the JOIDES Resolution.
Whole-round samples (5–30 cm in length) were usually taken from sediment cores with a sample density of 1 sample every 10 m in the uppermost 50–100 m of the hole (first 6–10 cores), and 1 sample every 30 m below that (one sample every third core). The sample length was usually shorter at the top of the hole where sediments were less consolidated (more pore water). The deeper core sediments were often more consolidated, so more material was needed to extract enough water to analyze. The whole-round sample was cut from the section shortly after the core arrived on deck. The sample was taken to the laboratory, removed from the core liner, and cleaned by scraping the exterior surface with a spatula to remove potential contamination. It was squeezed for as long as 2 hr in a stainless steel or titanium press to extract pore water. The water could be filtered or unfiltered, stored in glass or plastic vials, acidified or subject to other treatment depending on the requirements of the Shipboard Scientific Party.
The extracted water sample was analyzed by several different techniques and instruments to complete the normal suite of elements and any additional analyses requested by the Shipboard Scientists. Table T11 lists the different instruments and analytical techniques used to measure IW samples during ODP. Note that some of the analytical results may not be associated with the correct instrument or method. Verification of IW data and samples were not completed because of time constraints.
IAPSO standard seawater was the primary standard used to calibrate the instrumentation in the Chemistry Laboratory. These standards were likely run at least once during the leg. Documentation of the standardization procedures and results from the analyses of the standards were not archived.
Specific information about procedures for each measurement can be found in Technical Note 15 (Gieskes et al., 1991). The Initial Reports volumes usually have an extensive discussion of the methods used to collect IW data.
Early in ODP, IW data were collected on log sheets, which were sent to ODP/TAMU at the end of each cruise. The data were entered into the S1032 database, and the log sheets were microfilmed for archival storage. Data entry routines were implemented so that data entry could be done on the ship and the practice of collecting data on log sheets ended. IW analyses were stored in the S1032 database until the Janus database became operational during Leg 171.
The data model for IW data can be found in "Janus IW Chemistry Data Model" in "Appendix E." Included are the relational diagram and list of the tables that contain data pertinent to IW analyses, column names, and definition of each column attribute. ODP Information Services Database Group was responsible for the migration of pre-Leg 171 data to Janus.
IW analyses can be retrieved from Janus Web using a predefined query. The IW query Web page allows the user to extract data using the following variables to restrict the amount of data retrieved: leg, site, hole, core, section, depth ranges, or latitude and longitude ranges. The IW query also gives the user the option of retrieving the method that was used to determine the analytical results. In some instances, two different methods were used to measure one or more constituents in a set of samples. The Web query reports both values and methods in the same record. In the archive ASCII file, additional analyses are reported in a separate record.
Table T12 contains the data fields retrieved from the Janus database using the Janus Web predefined query. The first column contains the data item, the second column indicates the Janus table or tables in which the data were stored, and the third column is the Janus column name or the calculations used to produce the value. "Description of Data Items from IW Query with Analysis Method Option" in "Appendix E" contains additional information about the fields retrieved using the Janus Web IW query and the data format for the archived ASCII files.
The IW data in Janus represent an extensive collection of chemical constituents that characterize waters in Earth's crust. More than 155,000 different analyses were done on the extracted water from sediments. There are few known instances where there was any major problem with data collection. Anything written or typed could be a source of errors. Analytical results were written on log sheets. These data were then typed into the S1032 database. Data entry programs were implemented to add the data to the database, but these programs still required manual entry. Writing down or typing incorrect information occasionally happened, and some mistakes were not identified. Often, the Scientific Party found errors and corrected them for the data included in the Initial Reports volume, but data sent back to ODP/TAMU were not corrected.
Another error found during the migration of IW data was that samples were missing from the database. In those instances, a sample was entered into the database so that the data could be migrated. The verification of those samples and the verification of the entire IW data set were not completed because of time constraints. Most data collected after the Janus database was operational on Leg 171 were verified as part of the Janus data management and verification procedures (see "Janus Data Management and Verification"). Some verification was done on the pre-Leg 171 data; however, if there is a discrepancy between the database and data in the Initial Reports volumes, the published data should be considered more reliable.
Janus does not contain any calibration data for any of the IW analytical methods. Procedures for storing calibration information were not implemented during ODP.