D379 discrete dissolved oxygen sampling document
Originator's protocol for data acquisition and analysis
The following information contains extracts from the D379 cruise report.
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 5 M sulphuric acid was added to the sample, which was then stirred with a small magnetic stirrer on a Radiometer autotitrator until the precipitate was dissolved. The titration was performed using pre-standardised sodium thiosulphate with the end-point being determined spectrophotometrically.
Triplicate oxygen samples were collected from up to 3 selected depths on 16 CTD casts deployed throughout the D379 cruise. 118 samples in total were collected and analysed.
BODC data processing procedures
The dissolved oxygen data were supplied to BODC in Microsoft Excel format and values were extracted from these and loaded into BODC's Oracle relational database. Replicate sample data were averaged, where present. Standard deviatons were calculated by the Originator. Data that were considered unrealistic were flagged suspect. Metadata collected from the various data files were favoured by BODC over the metadata recorded in the cruise report logs present in the D379 cruise report.
Content of data series
| Originator's Parameter | Unit | Description | BODC Parameter code | BODC Unit | Comments |
|---|---|---|---|---|---|
| Dissolved oxygen | µM | Concentration of oxygen per unit volume of the water column by Winkler titration | DOXYWITX | µmol l -1 | No unit conversion necessary |
Data quality report
No problems reported and no significant issues encountered during BODC data banking procedures.
References cited
Griffiths C. R. et al. , (2012). RRS Discovery Cruise D379, 31 Jul 2012 - 17 Aug 2012. Southampton to Reykjavic - the Extended Ellett Line. Scottish Association for Marine Science, 184pp. (Scottish Marine Institute, Oban.)
Available - Cruise D379 Internal Report
