Metadata Report for BODC Series Reference Number 2108244

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

Metrohm 702 SM Titrino Potentiometric Titrator

The Metrohm 702 SM Titrino is a potentiometric titrator used for monotonic, set endpoint and manual determination of solution concentrations. The titrator can be used in applications such as aqueous and non-aqueous, redox, precipitation and complexometric titrations. The operation modes include Monotonic Equivalence-point Titration (MET), Set Endpoint Titration (SET), Measurement (MEAS) and pH Calibration (CAL), all of which link various commands and methods to a titration procedure. The methods are stored ready for use which can also be loaded, modified and overwritten by the user.

The instrument consists of an exchange unit with a small two line display and a remote control. The instrument can be connected to either a magnetic stirrer, rod stirrer or Ti stand. The remote control gives access to all functions but once programmed the instrument can be operated for routine applications by using the keys on the front panel. The instrument is also completely remote controllable from a computer and can be connected to a balance and printer.

Specifications

Further details can be found in the manufacturer's user manual.

Niskin Bottle

The Niskin bottle is a device used by oceanographers to collect subsurface seawater samples. It is a plastic bottle with caps and rubber seals at each end and is deployed with the caps held open, allowing free-flushing of the bottle as it moves through the water column.

Standard Niskin

The standard version of the bottle includes a plastic-coated metal spring or elastic cord running through the interior of the bottle that joins the two caps, and the caps are held open against the spring by plastic lanyards. When the bottle reaches the desired depth the lanyards are released by a pressure-actuated switch, command signal or messenger weight and the caps are forced shut and sealed, trapping the seawater sample.

Lever Action Niskin

The Lever Action Niskin Bottle differs from the standard version, in that the caps are held open during deployment by externally mounted stainless steel springs rather than an internal spring or cord. Lever Action Niskins are recommended for applications where a completely clear sample chamber is critical or for use in deep cold water.

Clean Sampling

A modified version of the standard Niskin bottle has been developed for clean sampling. This is teflon-coated and uses a latex cord to close the caps rather than a metal spring. The clean version of the Levered Action Niskin bottle is also teflon-coated and uses epoxy covered springs in place of the stainless steel springs. These bottles are specifically designed to minimise metal contamination when sampling trace metals.

Deployment

Bottles may be deployed singly clamped to a wire or in groups of up to 48 on a rosette. Standard bottles and Lever Action bottles have a capacity between 1.7 and 30 L. Reversing thermometers may be attached to a spring-loaded disk that rotates through 180° on bottle closure.

Oxygen concentrations from Niskin bottle samples collected during UKOA cruise JC073

Originator's Protocol for Data Acquisition and Analysis

Oxygen concentration measurements from Niskin bottle samples were made at the start and end of UKOA cruise JC073 to compare to the CTD oxygen measurements. The dissolved oxygen concentrations were determined using automated Winkler titration with a polarographic electrode sensor using standard methods described in Hansen (1999).

Samples were collected by siphoning water from the Niskin bottles to 250 mL borosilicate glass bottles with ground glass stoppers. While filling the sample bottles at least twice the volume of the bottle was run to waste to ensure all air bubbles were displaced. 1 cm³ of manganous sulphate was then added to each sample bottle followed by 1 cm³ of alkaline iodide solution after which the stoppers of the sample bottles were immediately replaced to ensure no air bubbles were included in the sample. All samples were shaken for the manganous hydroxide to precipitate and then settle, after which the bottles were shaken again.

Standardisation of the sodium thiosulphate was completed by titrating sodium thiosulphate against an accurate volume of potassium iodate solution which was an accurately known concentration. 5 mL of potassium iodate standard solution was added to the reaction vessel using a glass pipette. 1 mL alkaline iodide solution and 1 mL of 5 M sulphuric acid was then added, before adding a stirring magnet, and auto-titrating with sodium thiosulphate solution. This was repeated 3 times to reduce variation on the titre volume, until consistent by 0.005 mL or less.

To titrate the samples, the stoppers were removed from the sample bottles and 1 cm³ of 5 M sulphuric acid was pipetted into each sample. A magnetic stirrer was then placed in the sample bottles and auto-titration completed using the sodium thiosulphate solution with an accurately molarity determined above.

References Cited

Hansen H.P., 1999. Determination of oxygen. In: Grasshoff K, Kremling K, Ehrhardt M (eds) Methods of Seawater Analysis. Verlag Chemie pp. 75-89

Instrumentation

Metrohm 702 SM Titrino Potentiometric Titrator

BODC Data Processing Procedures

Data were taken from Table 5.2 on page 30 of the cruise report where the table contains the oxygen contractions as well as the following metadata: date, CTD cast number and depth.

The data were reformatted and assigned BODC parameter codes which had different units to the data and so a conversion of * 31.252 was applied to the oxygen concentrations. The data contained triplicate samples at each depth which were averaged during reformatting and the standard deviation calculated. Data were loaded in BODC's samples database under Oracle Relational Database Management System using established BODC data banking procedures. Sample metadata were checked against information held in the database where no discrepancies were found.

The oxygen concentration and the calculated standard deviation were mapped to BODC parameter codes as follows:

Data Quality Report

The originator excluded one of the triplicate samples at 130 m of cast 11 from the CTD calibration due to the precipitate not dissolving completely after acid addition. As the originator excluded this value, the value was also excluded when calculating the average and standard deviation for this depth during BODC processing. There are no further QC comments from the originator and as the remaining values are very similar to the oxygen concentrations collected by the CTD any flagging of data is not required.

Project Information

UKOARP Theme B: Ocean acidification impacts on sea surface biology, biogeochemistry and climate

The overall aim of this theme is to obtain a quantitative understanding of the impact of ocean acidification (OA) on the surface ocean biology and ecosystem and on the role of the surface ocean within the overall Earth System.

The aims of the theme are:

• To ascertain the impact of OA on planktonic organisms (in terms of physiological impacts, morphology, population abundances and community composition).
• To quantify the impacts of OA on biogeochemical processes affecting the ocean carbon cycle (both directly and indirectly, such as via availability of bio-limiting nutrients).
• To quantify the impacts of OA on the air-sea flux of climate active gases (DMS and N₂O in particular).

The main consortium activities will consist of in-situ measurements on three dedicated cruises, as well as on-deck bioassay experiments probing the response of the in-situ community to elevated CO₂. Most of the planned work will be carried out on the three cruises to locations with strong gradients in seawater carbon chemistry and pH; the Arctic Ocean, around the British Isles and the Southern Ocean.

Weblink: http://www.oceanacidification.org.uk/research_programme/surface_ocean.aspx

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for JC073_CTD_CTD11

Please note:the supplied parameters may not have been sampled from all the bottle firings described in the table above. Cross-match the Sample Reference Number above against the SAMPRFNM value in the data file to identify the relevant metadata.

Related Data Activity activities are detailed in Appendix 1

Cruise

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:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Appendix 1: JC073_CTD_CTD11

Related series for this Data Activity are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.