Metadata Report for BODC Series Reference Number 1131556

• 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 Quality Report - see processing documentation

Data quality information is included in the general documentation for this series. Please read.

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.

World Precision Instruments Liquid Waveguide Capillary Cell

Liquid Waveguide Capillary Cell (LWCC) is a flow cell for absorbance measurements in the ultraviolet, visible and near infra-red ranges. Pathlengths range from 50-500cm, with increasing measurement sensitivity from 50 to 500-fold. The flow cells are fiber coupled and have a very small sample volume ranging from 125µL (50cm pathlength) to 1,250µL (500cm pathlength).

The sample solution is introduced into the LWCC at the liquid input. Light is coupled into the LWCC from a light source via a fiber optic cable. After passing through the LWCC, light is collected with an optical fiber and guided to a detector. The concentration of the sample is determined by measuring its absorbance in the LWCC, similar to a standard UV/VIS spectrometer.

Specifications

Maximum Pressure 100 PSI

Wetted Material PEEK, Fused Silica, PTFE

Liquid Input Standard 10-32 Coned Port Fitting

* Referenced using coupled 500µm fibers

** Measured using ASTM E685-93

*** A one-meter waveguide of 550µm internal diameter requires approximately 1.5 psi for water flow of 1.0 mL/min.

Further details can be found in the manufacturer's specification sheet.

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.

AMT13 Nutrient (micro- and nano-molar) measurements from CTD bottle and surface underway samples

Originator's Protocol for Data Acquisition and Analysis

Water samples were taken from the Sea-Bird CTD rosette system on most casts and from the non-toxic supply tap at 15:00 on days where concentrations were lower than the detection limit of the micro-molar analyses. The water samples were sub-sampled into acid-clean 60 ml HDPE (nalgene) sample bottles. Analysis for nutrients was completed within 3 hours of sampling in all cases. Clean handling techniques were employed to avoid contamination of the samples.

The main nutrient analyser was a 5-channel Bran and Luebbe AAIII segmented flow autoanalyser. The samples were analysed for nitrate (Brewer and Riley, 1965), for nitrite (Grasshoff, 1976), phosphate and silicate (Kirkwood, 1989), and ammonium (Mantoura and Woodward, 1983).

Nanomolar ammonium concentrations were obtained with a fluorescent analysis technique following ammonia gas diffusion out of the samples, passing across a hydrophobic Teflon membrane due to differential pH chemistry (adapted from Jones, 1991).

Nanomolar nitrate+nitrite, nitrate and phosphate concentrations were obtained on some samples using a 3-channel nanomolar analyser. This method combines sensitive segmented flow colorimetric analytical techniques with a Liquid Waveguide Capillary Cell (LWCC). The phosphate waveguide did not produce consistently reliable results.

References Cited

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

Grasshoff K., 1976. Methods of seawater analysis. Verlag Chemie, Weiheim: 317 pp.

Jones R.D., 1991. An improved fluorescence method for the determination of nanomolar concentrations of ammonium in natural waters. Limnology and Oceanography, 36, 814-819.

Kirkwood D.S., 1989. Simultaneous determination of selected nutrients in seawater. ICES CM1989/C:29, 12pp.

Mantoura R.F.C. and Woodward E.M.S., 1983. Optimisation of the indophenol blue method for the automated determination of ammonia in estuarine waters. Estuarine, Coastal and Shelf Science, 17, 219-224.

BODC Data Processing Procedures

Data were submitted to BODC in Microsoft Excel spreadsheet format and saved to the BODC archive with accession number PML040070. Sample metadata were checked against information held in the database.

There were few discrepancies between information from the Sea-bird log files (used by BODC as a main reference for CTD rosette bottle metadata information) and the data originator's records regarding the depth of the bottle firing. A number of these discrepancies could be resolved by identifying CTD rosette bottles that had misfired. This information was provided by the data originator and the bottles were flagged in the database. It was decided that unless obviously incorrect the data should be loaded into the database by matching the originators' Niskin rosette position number to the depth recorded by the Sea-bird instrument (see section "Problem Report" for details of affected stations and depths).

Data from the nanomolar ammonium and LWCC systems were submitted in units of nmol/l. Nano-molar data were divided by 1000 to convert the units to µmol/l for storage in the database.Users should be aware that these LWCC measurements are valid to the fourth decimal place. The data were assigned parameter codes defined in BODC parameter dictionary. Data loaded into BODC's database using established BODC data banking procedures.

A parameter mapping table is provided below;

Data Quality Report

The dataset has been checked by the data originator - any suspect data values were removed from the data set before submission to BODC.

Measurement precision information from data originators:

The detection limits for measurements from the AAIII Bran and Luebbe autoanalyser have are 0.02 µmol l^-1, except the colorimetric ammonium which has a detection limit of 0.08 µmol l^-1. Samples in the database with a flag of "<" had concentrations below the specified detection limits.

At low concentrations, the values obtained by the LWCC are likely to be more accurate than those from the AAIII analyser.

Problem Report

Because of a few remaining uncertainties in matching sample measurements with SeaBird bottle firing depths, users should exert caution when using data from the following CTD cast and depth:

CTD 24, 66.1 and 101 m: bottle 21 and 22 firing depth inverted in data originator as compared to Sea-bird (and database). The data were loaded by BODC by matching bottle sample depths and the rosette position numbers in the database are therefore currently different from that provided by the originator.

CTD 36, nano-molar nutrients supplied with depth typos for rosette position numbers 22 and 24 (provided 0.5 m for both where should be 500 m and 1000 m respectively as for the micro-nutrient data). The data were loaded by BODC by matching bottle rosette position numbers and the sample depths in the database are therefore currently different from that provided by the originator.

CTD 42, bottles from 50 m to 200 m (7,8, 9,10,11,12,13,14,18,19,21,22): mismatch in firing depth between Sea-bird and originator apparently due to bottles that did not fire. The data were loaded at BODC by matching bottle rosette position numbers and the sample depths in the database are therefore currently different from that originally provided by the originator.

CTD 53, 180.5 and 225.4 m: bottles 21 and 22 depth firing depth inverted in data originator as compared to Sea-bird (and database). The data were loaded at BODC by matching bottle rosette position numbers and the sample depths in the database are therefore currently different from that provided by the originator.

CTD 61, 1000 m: bottles 22 and 24 were both fired at ~1000 m according to SeaBird bottle firing information but attributed to 500 m and 1000 m by data originator. Nutrient concentrations clearly indicated that the samples originated from different depths so these data were loaded into the database according to the depths given by the originator.

CTD 67, 1000 m: bottles 22 and 24 were both fired at ~1000 m according to SeaBird bottle firing information but attributed to 500 m and 1000 m by data originator. Nutrient concentrations clearly indicated that the samples originated from different depths so these data were loaded into the database according to the depths given by the originator.

The table below provides a comparison between the depths in the source files and in BODC's database:

Project Information

The Atlantic Meridional Transect - Phase 2 (2002-2006)

Who was involved in the project?

The Atlantic Meridional Transect Phase 2 was designed by and implemented by a number of UK research centres and universities. The programme was hosted by Plymouth Marine Laboratory in collaboration with the National Oceanography Centre, Southampton. The universities involved were:

• University of Liverpool
• University of Newcastle
• University of Plymouth
• University of Southampton
• University of East Anglia

What was the project about?

AMT began in 1995, with scientific aims to assess mesoscale to basin scale phytoplankton processes, the functional interpretation of bio-optical signatures and the seasonal, regional and latitudinal variations in mesozooplankton dynamics. In 2002, when the programme restarted, the scientific aims were broadened to address a suite of cross-disciplinary questions concerning ocean plankton ecology and biogeochemistry and the links to atmospheric processes.

The objectives included the determination of:

• how the structure, functional properties and trophic status of the major planktonic ecosystems vary in space and time
• how physical processes control the rates of nutrient supply to the planktonic ecosystem
• how atmosphere-ocean exchange and photo-degradation influence the formation and fate of organic matter

The data were collected with the aim of being distributed for use in the development of models to describe the interactions between the global climate system and ocean biogeochemistry.

When was the project active?

The second phase of funding allowed the project to continue for the period 2002 to 2006 and consisted of six research cruises. The first phase of the AMT programme ran from 1995 to 2000.

Brief summary of the project fieldwork/data

The fieldwork on the first three cruises was carried out along transects from the UK to the Falkland Islands in September and from the Falkland Islands to the UK in April. The last three cruises followed a cruise track between the UK and South Africa, only deviating from the traditional transect in the southern hemisphere. During this phase the research cruises sampled further into the centre of the North and South Atlantic Ocean and also along the north-west coast of Africa where upwelled nutrient rich water is known to provide a significant source of climatically important gases.

Who funded the project?

Natural Environment Research Council (NERC)

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for AMT13_CTD_A13_54

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: AMT13_CTD_A13_54

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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