Chemical Reference Materials Setting the Standards for Ocean Science (2002) / Chapter Skim
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Pages 17-28
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From page 17... ...
17 2 Improving Chemical Oceanographic Data Consistently comparable data collected on a global scale and over time are essential for the global monitoring programs and process studies described in the previous chapter. Individual investigators involved in mechanistic studies will also benefit from consistent and comparable analytical results.
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18 CHEMICAL REFERENCE MATERIALS surement method. This choice is based on several considerations.
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IMPROVING CHEMICAL OCEANOGRAPHIC DATA 19 A Initial Data Time drift correction sample sample SRM SRM Method 1 Method 2 B
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20 CHEMICAL REFERENCE MATERIALS over time or whether the measurement method itself caused this shift. Method 1 indicates the concentration has remained constant with time, whereas Method 2 suggests it has changed.
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IMPROVING CHEMICAL OCEANOGRAPHIC DATA 21 age the development of improved analytical methods. In the specific case of oceanographic studies, where accurate analyses of major elements in many commonly encountered matrices are not yet routine, it is therefore premature to standardize measurement methods for most analytes.
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22 CHEMICAL REFERENCE MATERIALS tions may require measurement of a different component. The best way to resolve this type of problem is for authors to report in detail their collection methods so that later investigators will know what component was being measured and can draw their own conclusions.
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IMPROVING CHEMICAL OCEANOGRAPHIC DATA 23 Box 2.1 Case Study: Salinity (S) Early chemists found that the relative composition of the major components of seawater were constant (Marcet, 1819)
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24 CHEMICAL REFERENCE MATERIALS Box 2.2 Case Study: Dissolved Organic Carbon (DOC) The measurement of DOC in seawater has long been a challenge to oceanographers and marine scientists (Hansell and Carlson, 2002)
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IMPROVING CHEMICAL OCEANOGRAPHIC DATA 25 5 FIGURE 2.2 Example of the use of reference materials on the agreement between analysts. Analysts 1-34 represent data from all analyses of the Pacific Ocean surface sample from the Seattle Workshop (Hedges et al., 1993)
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26 CHEMICAL REFERENCE MATERIALS Box 2.3 Case Study: Dissolved Inorganic Carbon (DIC) High quality measurements of ocean CO2 have been an integral part of the JGOFS and World Ocean Circulation Experiment (WOCE)
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IMPROVING CHEMICAL OCEANOGRAPHIC DATA 27 -5 0 5 10 15 20 25 1970 1975 1980 1985 1990 1995 2000 Year of Cruise Offset in CT µmol kg –1 GEOSECS INDIGO TTO TAS SAVE WOCE PACIFIC WOCE INDIAN FIGURE 2.3 Estimated data offsets for total DIC measurements on various cruises (Gruber et al., 1996; Gruber, 1998; Sabine et al., 1999; Lamb et al., 2002)
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28 CHEMICAL REFERENCE MATERIALS Box 2.4 Case Study: Pigments Pigment intercalibration exercises have been performed in support of NSF's JGOFS program (Latasa et al., 1996) and for NASA's Sea-viewing Wide Field-ofview Sensor (SeaWiFS)
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