Metadata Report for BODC Series Reference Number 2003287

• 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.

Atlantic Meridional Transect cruise DY084 (AMT27) Micro-molar Nutrients from CTD Bottles

Originator's Protocol for Data Acquisition and Analysis

A total of 79 vertical CTD profiles were carried out along the cruise track, and of these 71 were analysed for nutrients for the Atlantic Meridional Transect (AMT) Project. Water samples were collected from a 24 x 20 litre bottle stainless steel framed CTD / Rosette system (Seabird). Typically, every unique depth was sampled from each CTD cast and these were sub-sampled into clean (acid-washed) 60ml HDPE (Nalgene) sample bottles, which were rinsed x3 with sample seawater prior to filling.

Micro-molar nutrient analysis was carried out using a 4 channel Bran and Luebbe AAIII segmented flow, colourimetric, auto-analyser. Established, proven analytical protocols were used: nitrate (Brewer and Riley, 1965), nitrite (Grasshoff,K., 1976), phosphate and silicate (Kirkwood, D.S., 1989).

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

Further information can be found in the DY084 Cruise report.

BODC Data Processing Procedures

Data were received in Excel format and were archived under BODC's accession number PML190012. The data were provided with metadata including CTD number, Niskin bottle number and depth. The metadata provided were matched to the records already held in the BODC database using CTD number and Niskin Bottle number in the majority of cases. Only nutrient samples collected for the AMT project are included in this dataset, those collected for SONIC have been ommitted. The data were loaded into the BODC database using established BODC data banking procedures. A parameter mapping table is provided below:

Data Quality Report

Some samples supplied were below the limit of detection for the parameter. In these cases, the data were supplied with a < flag and the detection limit. This information was loaded to the BODC database. The detection limits are 0.01 µM (Nitrite); 0.02 µM (Nitrate+Nitrite) and 0.02 µM (Phosphate).

Project Information

PML National Capability

The Plymouth Marine Laboratory National Capability focuses on long term science concerned with basin/decadal variability of the Ocean.

Data Activity or Cruise Information

Data Activity

No Document Information Held for the Series

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: DY084_CTD_CTD059

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

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