Metadata Report for BODC Series Reference Number 1987441

• 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

SPX Bran+Luebbe Autoanalyser 3

The instrument uses continuous flow analysis (CFA) with a continuous stream of material divided by air bubbles into discrete segments in which chemical reactions occur. The continuous stream of liquid samples and reagents are combined and transported in tubing and mixing coils. The tubing passes the samples from one apparatus to the other with each apparatus performing different functions, such as distillation, dialysis, extraction, ion exchange, heating, incubation, and subsequent recording of a signal.

An essential principle of the system is the introduction of air bubbles. The air bubbles segment each sample into discrete packets and act as a barrier between packets to prevent cross contamination as they travel down the length of the tubing. The air bubbles also assist mixing by creating turbulent flow (bolus flow), and provide operators with a quick and easy check of the flow characteristics of the liquid.

Samples and standards are treated in an exactly identical manner as they travel the length of the tubing, eliminating the necessity of a steady state signal, however, since the presence of bubbles create an almost square wave profile, bringing the system to steady state does not significantly decrease throughput and is desirable in that steady state signals (chemical equilibrium) are more accurate and reproducible.

The autoanalyzer can consist of different modules including a sampler, pump, mixing coils, optional sample treatments (dialysis, distillation, heating, etc), a detector, and data generator. Most continuous flow analyzers depend on color reactions using a flow through colorimeter, however other methods have been developed that use ISE, flame photometry, ICAP, fluorometry, and so forth.

More details can be found in the manufacturer's introduction to autoanalysers andinstrument description.

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.

Inorganic nutrient concentrations from CTD bottle samples on RidgeMix cruise JR15007

Originator's Protocol for Data Acquisition and Analysis

Seawater samples were taken from 20 L Niskin bottles on a rosette sampler throughout the RidgeMix cruise JR15007. The samples were collected in acid washed 60 mL HDPE (Nalgene) sample bottles which were rinsed three times with sample water prior to filling. Samples were either analysed directly from the CTD or stored in a refrigerator and analysed within four hours of sampling. Nutrient analysis was carried out using a four channel - nitrate (Brewer and Riley, 1965), nitrite (Grasshoff K., 1976), phosphate and silicate (Kirkwood D.S., 1989) - Bran & Luebbe AAIII segmented flow colorimetric autoanalyser.

Nitrate was reduced to nitrate a copper/cadmium column, in an ammonium chloride solution (pH = 8.5). The nitrite ions reacted with an acidic sulphanilimide solution to form a diazochloride. This was then reacted with the N-1-naphthylethylenediamine dihydrochloride (NEDD), to form a reddish purple azo dye. The concentration of nitrate was obtained by subtracting the nitrite concentration from the combined combination obtained here from nitrate plus nitrite.

Phosphate determination was based on the production of the phosphor-molybdinum-blue complex by reaction with molybdate and ascorbic acid, and the catalyst of potassium antimony tartrate.

Silicate determination involved the reaction of inorganic silicate with the ammonium molybdate to form mainly silicomolybdic acid. This was reduced by the ascorbic acid to form a silico-molybdenum blue complex. The oxalic acid ensured that there was no competitive reaction from phosphates.

References Cited

Brewer P.G. and Riley J.P., 1965.The automatic determination of nitrate in seawater. Deep Sea Research, 12: 765-772.

Grasshoff K., 1976. Methods of sea-water analysis, Verlag Chemie, Weiheim: pp.317.

Kirkwood D.S., 1989. Simultaneous determination of selected nutrients in sea-water, ICES CM 1989/C:29 JR15-007/Cruise Report 52.

Instrumentation Description

4 channel Bran & Luebbe AAIII segmented flow colorimetric autoanalyser

BODC Data Processing Procedures

Data were submitted by email to BODC as an Excel spreadsheet containing nitrite, silicate, phosphate and nitrate concentrations along with the following metadata: cruise, station, CTD number, latitude, longitude, depth and Niskin. A pdf document detailing the sampling protocol and analytical methods was submitted alongside the data. The data and metadata were archived following standard BODC procedure.

The data were reformatted and assigned BODC parameter codes which were in equivalent units to the data and so no unit conversions were necessary. During reformatting, five negative values were found - three in the nitrite channel and two in the phosphate channel. These values were discussed with the originator who corrected all negative values to 0 µM. Data were then loaded in BODC's samples database under Oracle Relational Database Management System using established data banking procedures.

The originator's parameters were mapped to BODC parameter codes as follows:

Data Quality Report

The originator did not provide any quality control comments and during BODC processing it was not deemed that any values required flagging.

Project Information

A nutrient and carbon pump over mid-ocean ridges (RidgeMix)

RidgeMix is a five year (August 2014 to February 2019) research programme which received funding from the Natural Environment Research Council (NERC). The aim of the programme was to address the problem of how deep nutrients are transported into the surface waters in mid-latitudes, by testing a new view: tides passing over the mid-Atlantic ridge generate enhanced turbulence and mixing, which in turn provides a nutrient supply to the upper thermocline waters. These nutrients are then transported horizontally along density surfaces over the western side of the basin, probably being swept along the Gulf Stream and eventually passing into the winter mixed surface layer. When this surface layer shallows and warms in spring, the nutrients are then available to the phytoplankton.

Fieldwork involved collecting measurements of the turbulence and nutrient concentrations over and adjacent to the Mid-Atlantic Ridge, using a novel long-term moored array of instruments along the ridge, deployed over a five-week research cruise. Sampling was done sufficiently quickly to resolve tidal changes in currents and mixing over the ridge. A second component of the fieldwork will use computer models of circulation in the Atlantic to explore the wider implications of the fieldwork observations, to determine whether or not mixing over the mid-Atlantic ridge really does provide enough nutrients to explain the phytoplankton production in the mid-latitude North Atlantic.

RidgeMix was a collaborative project involving five organisations, of which three were UK based and two were US based. The project was led by the Professor Jonathan Sharples, University of Liverpool, Earth, Ocean and Ecological Sciences. Collaborators were:

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for JR15007_CTD_CTD_008

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: JR15007_CTD_CTD_008

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.