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D340A Discrete Dissolved Oxygen Sampling Document

Originator's Protocol for Data Acquisition and Analysis

Water samples were collected immediately following recovery of the CTD using a silicon tube attached to the Niskin bottle spigot. The silicon tube was lowered into the bottom of a volume calibrated glass bottle and water from the Niskin bottle was allowed to overflow from the bottle until it had been flushed with approximately three times the volume required to fill it.

Samples were fixed by adding 1 ml of manganese chloride followed by 1 ml of alkaline iodide with care being taken not to introduce any air bubbles to the solutions. An hour after collection samples were shaken and subsequent analysis occured within four hours of this.

1 ml 5M sulphuric acid was added to the sample, which was then stirred with a small magnetic stirrer on a Radiometer autotitrator (ABU91) until the precipitate was dissolved. The titration was performed using pre-standardised sodium thiosulphate with the end-point being determined spectrophotometrically.

References Cited

Sherwin T. A. et al. , 2009. Cruise D340A Reykjavic to Dunstaffnage via Rockall and the Wyville Thomson Ridge. Internal Report No 264. Scottish Association for Marine Science.

Available - Cruise D430A Internal Report

BODC Data Processing Procedures

The dissolved oxygen data were supplied to BODC in Microsoft Excel format and values were extracted from these and saved in ASCII format prior to being loaded into BODC's ocean database under the ORACLE Relational Database Management System. Replicate sample data were averaged, where appropriate, prior to loading to the database. Data that were considered unrealistic were flagged suspect..

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