Oceanographic analysis

National Environmental Satellite Service, Oceanographic Analysis July 28,... 

Another unglamorous, but vitally important, aspect of oceanographic analysis is the area of calibration and standards. Standard reference materials appropriate for most of the constituents in seawater simply do not exist, and considering the low concentration levels usually involved and the unstable nature of natural seawater samples, the way to approach the problem is by no means obvious. Calibration of laboratory methods... 

Elderfield and Greaves [629] have described a method for the mass spectromet-ric isotope dilution analysis of rare earth elements in seawater. In this method, the rare earth elements are concentrated from seawater by coprecipitation with ferric hydroxide and separated from other elements and into groups for analysis by anion exchange [630-635] using mixed solvents. Results for synthetic mixtures and standards show that the method is accurate and precise to 1% and blanks are low (e.g., 1() 12 moles La and 10 14 moles Eu). The method has been applied to the determination of nine rare earth elements in a variety of oceanographic samples. Results for North Atlantic Ocean water below the mixed layer are (in 10 12 mol/kg) 13.0 La, 16.8 Ce, 12.8 Nd, 2.67 Sm, 0.644 Eu, 3.41 Gd, 4.78 Dy, 407 Er, and 3.55 Yb, with enrichment of rare earth elements in deep ocean water by a factor of 2 for the light rare earth elements, and a factor of 1.3 for the heavy rare earth elements. 

Petroleum pollution monitoring laboratories in the Mediterranean region participated (1984-1986) in two intercalibration exercises (MEDCALI and II) to evaluate the International Oceanographic Commission (IOC) Manual for petroleum hydrocarbon determination in sediment (IOC, Manuals and Guides, No. 11). The main source of error in the analysis was the extraction/ partition step. When the results were corrected for recoveries, relative standard deviations for w-alkancs, UCM (unresolved complex mixture) and total aromatics, which had previously been 60, 56 and 49%, respectively, were reduced to 17, 30 and 6%, respectively. 

We thank M.I. Lucas, M.O. Bergh, R.C. Newell, F.V. Wulff and S.3. Painting for help and discussion in developing the models, and S. Tolosana and D. Gianakouras for help in preparing the manuscript. The work was supported by the South Africa National Committee for Oceanographic Research as part of the Systems Analysis Project of the... 

---