pH and Carbonate Saturation. An instru- 

 ment to measure in situ pH and carbonate 

 saturation is being used in the Pacific legs of 

 GEOSECS. The apparatus consists of two 

 high pressure pH electrodes and a reference 

 electrode attached to a pressure housing 

 which contains the necessary electronics. An 

 in situ pump periodically flushes a carbonate 

 cell with surrounding seawater while the pH 

 of the slurry is monitored continuously. The 

 pH shift due to seawater-carbonate reaction is 

 used to calculate the degree of saturation of 

 the seawater with respect to the carbonate 

 material. 



Data Handling, Processing & Display 



Data from the underwater sensor package 

 are transmitted by frequency shift keying 

 along the coaxial lowering cable. On board 

 ship the raw data are recorded on analogue 

 magnetic tape and directed to a Nova 1200 

 mini-computer for preprocessing. Selected 

 portions of the data, normally about one in 

 every sixteen data points, are transmitted to 

 an IBM 1800 computer which maintains proc- 

 essed data files and controls four storage 

 scopes which can be used to plot the data or 

 any function thereof. 



Profiles of salinity, temperature, oxygen and 

 light scattering versus depth are displayed on 

 two scopes, while density versus depth and 

 potential temperature-salinity correlations are 

 shown on a third scope. The fourth scope is 

 used for temporary displays of detailed blow- 

 ups of significant parts of the water column 

 and for review of those laboratory systems 

 that are interfaced with the computer. 



As they are accumulated, discrete sample 

 data are fed to the 1800, either directly or by 

 punched cards, and station master files are 

 stored which are available for review by the 

 scientists within 24 hours of the start of the 

 station. In addition, master files from past 

 stations may be recalled at any time for com- 

 parison with the current data. 



Large- Volume Water Sampling 



Large-volume water samples are required 

 for many of the radioactive elements meas- 

 ured during the project. Analysis of C'^ re- 

 quires 200 liters; Sr"" and Cs'", 100 liters; 

 Ra^^**, 100 liters; Ra--\ 800 liters; and particu- 

 late matter, 250-400 liters of sea water. In 

 some cases the same sample may be used for 



two or more measurements. A surface pump- 

 ing system is used to obtain large-volume sam- 

 ples down to 250 m depths. The requirement 

 of 18 large-volume samples per station neces- 

 sitates both multiple casts and the use of 

 multiple sampling devices [270-liter Gerard- 

 Ewing samplers) on a single wire. 



Shoreside Analysis 



C"' and H'— The GEOSECS project will 

 generate about 1,200 C'^ samples and about 

 2,500 H-' samples. Of the C'^ samples, about 

 900 most likely will be collected below 200 

 meters, and the greatest possible precision and 

 accuracy is desired for these. In the C'^ scale, 

 a precision of better than four parts per mill, 

 experimental errors included, was stipulated 

 by the GEOSECS Advisory Committee and is 

 being met by the researchers. 



Analytical facilities were built at the Uni- 

 versity of Miami and at the University of 

 Washington. No other existing radiocarbon 

 laboratories in the U.S. can presently process 

 a significant number of samples meeting these 

 criteria. 



Trace Elements — The Trace Elements Panel 

 of GEOSECS has identified four trace ele- 

 ments — iron, zinc, barium and strontium — for 

 principal study during 1972-73. All have an 

 ocean-wide variance significantly in excess of 

 the sampling and measurement error, and all 

 are involved in processes of particulate trans- 

 port in the oceans but probably with different 

 fractions of the suspended matter. The possi- 

 bility exists that iron is injected into midwater 

 regions of the Pacific Ocean from the rift val- 

 leys of midocean ridges. Other elements will 

 be determined at selected stations. Particulate 

 matter samples and data being obtained as 

 part of the GEOSECS program include: Con- 

 centration data throughout the water column; 

 C, N and P in samples through the thermo- 

 cline; distribution of elements such as Fe, 

 Ba, Zn, Sr, Si and Al in suspended matter 

 throughout the water column (by chemical 

 electron scanning and x-ray probe tech- 

 niques); and concentration, size fractionation, 

 mineralogical and chemical composition data 

 on detailed near-bottom profiles in the nephe- 

 loid layer. 



Major Elements — Difference chromatogra- 

 phy is used to study the proportional varia- 

 tions of the major ions in sea water. The 

 sensitivity of the method is sufficient that 



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