Metadata Report for BODC Series Reference Number 920533
Metadata Summary
Problem Reports
Data Access Policy
Narrative Documents
Project Information
Data Activity or Cruise Information
Fixed Station Information
BODC Quality Flags
Metadata Summary
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Time Co-ordinates(UT) |
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Parameters |
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Problem Reports
No Problem Report Found in the Database
Data Quality Report
There are no data quality issues to report.
Data Access Policy
Public domain data
These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.
The recommended acknowledgment is
"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."
Narrative Documents
Ruthern Instruments Marine pH Monitor
A pH monitor designed for use in estuarine and coastal waters. The sensor is based on a capillary liquid junction and pH is measuremed on the free ion concentration scale. The instrument measures pH of a pumped water supply, either continuously or in batch mode.
This system was built in collaboration with the UK Environment Agency and the Plymouth Marine Laboratory. Two versions were developed: one for permanent bulkhead mounting in small coastal vessels and a portable version for up-stream use in small boats.
Specifications
| Accuracy | better than ± 0.01 pH units |
| Salinity range | 1 to 40 ppt |
| Temperature precision | 0.02°C |
Further details can be found here.
BODC Data Processing
The data arrived at BODC in spreadsheet file format representing continuous pH measurements of the ship's non-toxic seawater supply collected during SOLAS D326 cruise. These were reformatted to the BODC internal QXF (NetCDF) format using BODC transfer function 410. The following table shows how the pH variables were mapped to the appropriate BODC parameter codes:
| Originator's Variable | Units | Description | BODC Parameter Code | Units |
|---|---|---|---|---|
| Latitude | degrees | Latitude (north) | ALATGP01 | degrees |
| Longitude | degrees | Longitude (east) | ALONGP01 | degrees |
| pH total scale | pH units | pH of a water body measured by a pH electrode | PHXXPR01 | pH units |
Data were banked according to BODC standard procedures. No averaging or other modifications were applied to the data received.
Originator's Data Processing
A potentiometric pH system was installed on the non-toxic seawater supply and was run continuously during the cruise where measurements were set to a rate of 1 minute intervals.
The potentiometric method for the determination of pH in seawater consists of the measurement of the electromotive force of a cell composed of a silver/silver chloride electrode and a glass pH electrode. To avoid errors with electrode drift, calibration of the system was undertaken every 8 to 12 hours with Tris buffer made up in artificial seawater according to Millero (1986). Tris buffer was run as a sample after each batch of new buffer was made in order to check the accuracy of the measurements. Difference observed between theoretical pH and measured pH was 0.01 to 0.03 pH units. The buffer was brought approximately to the seawater temperature (within 5°C) in order to maximise the accuracy. The overall precision of the method is 0.01 pH unit. The pH scale used in the pH calculation of the system is the free hydrogen ion concentration scale, pHF, which uses the concentration of free protons to define the hydrogen ion activity (Bates, 1975)
References
Bates, R.G., 1975. pH scales for seawater. In: The nature of seawater. Physical and Chemical Sciences Research Reports, 315-338. Millero F.J., 1986 The pH of estuarine waters. Limnology and Oceanography, 31(4), 839-847.
Continuous pH monitor, Ruthern Instruments
The pH monitor from Ruthern Instruments employs a potentiometric method for the determination of pH in seawater. The system consists of a highly reproducible free-diffusion liquid junction. A capillary liquid junction is formed between the reference reservoir (containing the silver/silver chloride electrode) and the pH cell (containing the pH electrode and the sample to be analysed). The bridge solution (2.5 M KCl in deonised water) allows the ionic contact between the hydrogen and reference electrode and is introduced below the sample via a solenoid pump.
Project Information
UK SOLAS, Chasing Saharan Dust Storms
This project was led by Dr Eric Achterberg of The School of Ocean and Earth Science (University of Southampton), National Oceanography Centre (NOC), Southampton, UK in collaboration with University of Leeds, University of East Anglia, Essex University, University of Liverpool, University of Birmingham and University of Strathclyde.
The goal of this project was to improve understanding of the atmospheric transport, cycling and deposition of dust and nutrients into the North Atlantic, which was achieved by activities conducted on two research cruises (PO332 and D326) in the tropical North Atlantic. Fieldwork was designed in particular to assess:
- the dust input to the North Atlantic
- the dissolution of nutrients including iron from the dust into seawater
- the impact of dust deposition events on the biology and nutrient chemistry of surface waters
More detailed information on this project may be found in the official cruise reports for the DUST cruises, PO332 andD326.
Weblink: http:/www.nerc.ac.uk/solas/
Data Activity or Cruise Information
Cruise
| Cruise Name | D326 |
| Departure Date | 2008-01-05 |
| Arrival Date | 2008-02-05 |
| Principal Scientist(s) | Eric P Achterberg (University of Southampton School of Ocean and Earth Science) |
| Ship | RRS Discovery |
Complete Cruise Metadata Report is available here
Fixed Station Information
No Fixed Station Information held for the Series
BODC Quality Control Flags
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
| Flag | Description |
|---|---|
| Blank | Unqualified |
| < | Below detection limit |
| > | In excess of quoted value |
| A | Taxonomic flag for affinis (aff.) |
| B | Beginning of CTD Down/Up Cast |
| C | Taxonomic flag for confer (cf.) |
| D | Thermometric depth |
| E | End of CTD Down/Up Cast |
| G | Non-taxonomic biological characteristic uncertainty |
| H | Extrapolated value |
| I | Taxonomic flag for single species (sp.) |
| K | Improbable value - unknown quality control source |
| L | Improbable value - originator's quality control |
| M | Improbable value - BODC quality control |
| N | Null value |
| O | Improbable value - user quality control |
| P | Trace/calm |
| Q | Indeterminate |
| R | Replacement value |
| S | Estimated value |
| T | Interpolated value |
| U | Uncalibrated |
| W | Control value |
| X | Excessive difference |
