Oxygen concentrations from CTD bottle samples collected during AMT15
Originator's Protocol for Data Acquisition and Analysis
This data originates from analyses on samples collected from 34 CTD casts. Water samples were taken directly from the bottles in the Sea-Bird CTD rosette system using silicon tubing.
Dissolved oxygen concentration was determined by automated Winkler titration with photometric end-point detection (Williamson and Jenkinson, 1982).
References Cited
Williams P.J.leB. and Jenkinson N.W., 1982. A transportable micro processor controlled precise Winkler titration suitable for field station and shipboard use. Limnology and Oceanography, 27, 576-584.
Instrumentation Description
Not applicable for this data set.
BODC Data Processing Procedures
Data were submitted via email in an Excel spreadsheet archived under BODC's accession number PML060015. The data were received in a spreadsheet containing CTD station number, Niskin bottle number, Depth, Oxygen bottle number, fixation temperature, in situ temperature and salinity. Sample metadata (CTD cast, bottle number and depth) were checked against information held in the database. There were a number of discrepancies:
- For a number of samples the bottle numbers did not match the depths of bottle firing from the SeaBird files and in these cases the data were loaded against the depth provided.
- The data provided for cast 1 had sample depths which matched cast 2 not cast 1 and were loaded to cast 2.
- Cast 18 bottle number 10 had depth 120 m provided. The SeaBird files indicate this bottle was fired at 86 m and the value provided was a more accurate fit for the oxygen sensor calibration at 86m bottle firing.
- Cast 25 bottle number 10 had no depth provided. The SeaBird files indicate this bottle was fired at 86 m.
- Cast 48 had data from an unidentified cast included. This was seperated out and compared against the bottle firing and depth pattern for titanium rig casts after cast 48. The data were loaded against cast 51 but flagged as the cast number was not confirmed.
- Cast 71 had data from an unidentified cast included. This was seperated out and compared against the bottle firing and depth pattern for stainless steel rig casts after cast 71. The data were loaded against cast 82 but flagged as the cast number was not confirmed.
- Cast 95 had a bottle number/depth combinations (6/125 m and 1/500m) that could not be matched to the SeaBird bottle firing depths (6/499 m and 1/1m). These data were loaded to the database based on the rosette bottle number and have been flagged as there appears to have been a mix up with the bottles.
The concentration data were provided in micromoles per litre. These units for the concentration data were consistent with the BODC parameter code units and no conversion was applied.
The data were reformatted and loaded in BODC's samples database under Oracle Relational Database Management System. Data were marked up with BODC parameter codes and loaded into the database. Individual samples were matched through rosette sampling bottle and depth.
A parameter mapping table is provided below;
Originator's Parameter | Units | Description | BODC Parameter Code | Units | Comments |
---|---|---|---|---|---|
Oxygen concentration (mean) by titration | µmol l -1 | Concentration of oxygen {O 2 } per unit volume of the water body [dissolved phase] by Winkler titration | DOXYWITX | µmol l -1 | n/a |
Data Quality Report
BODC was not advised of any specific quality issues with the data. The data were checked visually and used for the calibration of the CTD sensor. Where there were questions over the metadata flags have been added.
Problem Report
Not relevant to this data set.