Shore-based Total Alkalinity Analyses

The TALK concentration in 139 samples was determined on shore at the laboratory of C. Goyet of WHOI. Samples were collected in 250-mL, standard borosilicate glass, screw-cap bottles and poisoned with 50 µ L of saturated solution of HgCl2. The samples were stored at room temperature and sent to WHOI for TALK analysis. TALK was determined by potentiometric titration; the method used was derived from one first described by Dyrssen (1965) and later modified by Bradshaw et al. (1981). The automated titration was performed in a closed cell maintained at constant temperature (25 ± 0.1oC). To be similar to seawater, the ionic strength of the hydrochloric acid solution (0.1 N) was adjusted with NaCl. The ratio of the acid normality over the cell volume was calibrated before and after the sample analysis. The calibration consisted of preparing solutions of known TALK concentration and measuring them as described by Brewer et al. (1986). The precision of the measurements was estimated to be better than 0.1%.

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