Analyses for the dissolved halides I-, Br-, and F- were carried out by means of colorimetric methods described in the Ocean Drilling Program (ODP) Technical Note 15 (Gieskes et al., 1991). Accuracies are ~5% for iodide and bromide.
Fluoride determinations utilized the method by Greenhalgh and Riley (1961). A modification of their original method allows the use of 500-µL samples instead of 15-cm3 samples. The scaled-down method used only 500 µL of sample diluted with 1 cm3 of deionized water. Because diluting the sample with deionized water was necessary to ensure sufficient liquid for analysis, samples had higher pH conditions than the optimal range 4.45-4.85 for fluoride determinations (Greenhalgh and Riley, 1961). To readjust the pH values of the samples so that they were within this range, 27 µL of 6 M acetic acid was added. Finally, 800 µL of the mixed lanthanum-alizarin reagent was then added. After all the reagents were added to the sample, the fluoride concentration was determined 30 min later on a spectrophotometer at 622 nm.
The fluoride standards were created in the following manner. A stock solution of NaF was made by dissolving sodium fluoride in deionized water and a small volume of 0.1 M sodium hydroxide. Synthetic seawater was then prepared (558 mM sodium chloride and 3 mM sodium bicarbonate). Appropriate volumes of the stock solution were diluted to 100 mL with the synthetic seawater to create standards of 20, 40, and 60 µM NaF. A blank was also used that was composed only of synthetic seawater. These standards were run using the same method listed above, and sample concentrations were determined from the standard curve. Changes in the concentrations of magnesium and calcium can, in principle, affect the data. However, overall changes will not be affected by this.The accuracy of the fluoride method is ±5 µM.
Dissolved phosphate was analyzed by means of the colorimetric technique described in Gieskes et al. (1991). Accuracies are low because only small quantities of fluids were available for analysis (±2 µM).
Concentrations of Ba2+ and Mn2+ were determined using the ICP-MS at the University of Oldenburg. All data obtained are presented in Tables T1 and T2 of this report. Wherever appropriate, graphic representations are used.