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Metadata Report for BODC Series Reference Number 2097195

Metadata Summary

Data Description

Data Category Water sample data
Instrument Type
Niskin bottle  discrete water samplers
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Dr Reg Uncles
Originating Organization Plymouth Marine Laboratory
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) North Sea Project 1987-1992

Data Identifiers

Originator's Identifier CH51_CTD_TMXX_4:1821
BODC Series Reference 2097195

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1989-05-03 16:23
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -

Spatial Co-ordinates

Latitude 55.49951 N ( 55° 30.0' N )
Longitude 6.50332 E ( 6° 30.2' E )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 1.8 m
Maximum Sensor or Sampling Depth 37.5 m
Minimum Sensor or Sampling Height 5.2 m
Maximum Sensor or Sampling Height 40.9 m
Sea Floor Depth 42.7 m
Sea Floor Depth Source PEVENT
Sensor or Sampling Distribution Unspecified -
Sensor or Sampling Depth Datum Unspecified -
Sea Floor Depth Datum Unspecified -


BODC CODERankUnitsTitle
ADEPZZ011MetresDepth (spatial coordinate) relative to water surface in the water body
ALXXLGD21Nanomoles per litreConcentration of aluminium {Al CAS 7429-90-5} per unit volume of the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration and lumogallion fluorescence
BOTTFLAG1Not applicableSampling process quality flag (BODC C22)
SAMPRFNM1DimensionlessSample reference number

Definition of BOTTFLAG

0The sampling event occurred without any incident being reported to BODC.
1The filter in an in-situ sampling pump physically ruptured during sample resulting in an unquantifiable loss of sampled material.
2Analytical evidence (e.g. surface water salinity measured on a sample collected at depth) indicates that the water sample has been contaminated by water from depths other than the depths of sampling.
3The feedback indicator on the deck unit reported that the bottle closure command had failed. General Oceanics deck units used on NERC vessels in the 80s and 90s were renowned for reporting misfires when the bottle had been closed. This flag is also suitable for when a trigger command is mistakenly sent to a bottle that has previously been fired.
4During the sampling deployment the bottle was fired in an order other than incrementing rosette position. Indicative of the potential for errors in the assignment of bottle firing depth, especially with General Oceanics rosettes.
5Water was reported to be escaping from the bottle as the rosette was being recovered.
6The bottle seals were observed to be incorrectly seated and the bottle was only part full of water on recovery.
7Either the bottle was found to contain no sample on recovery or there was no bottle fitted to the rosette position fired (but SBE35 record may exist).
8There is reason to doubt the accuracy of the sampling depth associated with the sample.
9The bottle air vent had not been closed prior to deployment giving rise to a risk of sample contamination through leakage.

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

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

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.


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.

Dissolved Trace Metals (Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn, Al, Hg) and arsenic species as part of the North Sea Project

Document History

Converted from CDROM documentation

Sampling strategy and methodology

Samples for trace metal analysis were collected, using clean techniques, in 10 litre Teflon-lined Go-Flo bottles, modified to reduce the contamination potential for trace metals, fitted to the CTD rosette sampler. Initial sample handling for trace metals was carried out on board using the facilities of the RVS clean chemistry container (Morley et al., 1988).

Each sea water sample was pressure-filtered (ca. 0.7 bar) in-line through a 0.4 µm Nuclepore membrane filter. The filtrate (samples for dissolved metal analysis) were acidified to ca. pH 2 by the addition of sub-boiled nitric acid (1 ml per litre of sea water) in order to stabilise the total-dissolved concentrations of metals. For a substantial proportion of the samples large volume filtration systems were used to obtain sufficient suspended particulate material for trace metal analysis.

The filters were stored and processed for particulate trace metals. Consequently, the particulate and dissolved trace metal data form an integrated data set from a single set of samples using compatible analytical procedures which greatly enhances their value.

Analysis of Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn

This was undertaken using the specialised clean facilities in the Department of Oceanography, University of Southampton. Dissolved metals were extracted and preconcentrated following the dithiocarbamate complexation-freon extraction method of Danielsson et al. (1978), as modified by Statham (1985) and Tappin (1988), and were determined by graphite furnace atomic absorption spectrophotometry (GFAAS). Within batch analytical precision of the method is generally less than 10% (coefficient of variation) for each metal. More details of the method are given in Tappin et al. (1992).

Quality control (i.e. accuracy and between batch analytical precision) of the data was assessed by regularly analysing aliquots of the CASS-1 coastal sea water reference sample for dissolved trace metals and a bulk filtered acidified sea water sample which was used for batch-to-batch quality control. Results of these analyses were satisfactory, with very few exceptions, and ensure that the data are of high quality.

Additionally, the data set was examined to identify any values which appeared to have been affected by contamination on the basis of supporting data. Only an insignificant fraction of the total data were shown to have been contaminated and rejected.

Analysis of aluminium

An aliquot of the water sample was separately vacuum filtered through a 0.4 µm Nucleopore membrane and analysed for aluminium using the method of Hydes and Liss (1972). The complete analytical procedure was undertaken at sea, usually in the general laboratory.

It should be noted that whilst most samples were collected using the ultra-clean trace metal bottles described above, a few were collected using standard 10 litre Go-Flo bottles. As a general rule if there is aluminium data for a sample but no other trace metals then it should be assumed that a standard bottle was used to collect the sample.

Analysis of arsenic

A separate aliquot of water was filtered, in the clean laboratory, through a 0.45 µm Millipore filter for arsenic analysis. The samples were stored at 4°C to reduce biological activity and keep losses of monomethyl arsenic (MMA) and dimethyl arsenic (DMA) to a minimum. Nevertheless, some losses were inevitable as the samples had to be stored on board ship for the cruise duration (up to 2 weeks) and subjected to a 2-3 week analytical procedure. These losses have been quantified for samples from the Tamar Estuary in Kitts (1991).

The technique used for inorganic arsenic was to add 6M Analar HCl and 2 per cent Spectrosol NaBH4 solution to the water sample to generate arsines. These were purged from the apparatus by a stream of nitrogen for analysis by flame atomic absorption spectroscopy.

MMA and DMA were analysed using a similar technique using a lower acid concentration (1M) to favour the formation of organic arsines. The lower concentrations required the incorporation of an arsine trapping procedure. The nitrogen purgative, dried by NaOH traps, was passed through a glass U tube packed with glass beads cooled to -196°C by liquid nitrogen. The trap was allowed to gradually warm to room temperature giving up the trapped arsines as a series of pulses, thus achieving separation of the arsenic species. Each species was analysed by flame atomic absorption spectroscopy.

A full description and discussion of the analytical techniques is given in Kitts, 1991.

Analysis of mercury

Reactive mercury, i.e. mercury which can be determined without prior oxidation, was determined by the reduction of the mercury in the acidified sample to elemental form by the addition of tin (II) chloride. This was then removed from solution by purging with oxygen-free nitrogen and the mercury vapour trapped as an amalgam on gold chips. Once purging was complete, the gold chips were inductively heated to vaporize the mercury as a pulse which was quantified by atomic absorption spectroscopy.

Total mercury was measured by the above method on samples which had been oxidised by addition of hydrochloric acid, potassium bromide and potassium bromate. Samples were left to oxidise for at least an hour before the bromine was reduced by the addition of excess hydroxylammonium chloride solution.

Total mercury was determined on both unfiltered sea water and on sea water which had been filtered through an ashed (450°C for 24 hours) GFF filter paper. Reactive mercury was determined on filtered samples only. Full details of the methodology are given in Harper et al (1989).


Danielsson, L.-G., B. Magnusson and S. Westerlund (1978) An improved metal extraction procedure for the determination of trace metals in sea water by atomic absorption spectrometry with electrothermal atomization. Analytica Chimica Acta 98, 47-57.

Harper, D.J., C.F. Fileman, P.V. May and J.E. Portmann (1989). Methods of analysis for trace metals in marine and other samples. Aquatic environment protection: analytical methods number 3. MAFF Directorate of Fisheries Research, 38pp.

Hydes, D.J. and P.S. Liss (1976). A fluorometric method for the determination of low concentrations of dissolved aluminium in natural waters. The Analyst 101, 922-931.

Kitts, H. (1991). Estuaries as sources of methylated arsenic to the North Sea. Ph.D. thesis, Polytechnic South West.

Morley, N.H., P.J. Statham and C. Fay (1988) Design and use of a clean shipboard handling system for sea water samples. In: Advances in Underwater Technology, Ocean Science and Offshore Engineering, Volume 16 (Oceanology '88), Graham and Trotman, London, 283-290.

Statham, P.J. (1985) The determination of dissolved manganese and cadmium in sea water at low nmol/l concentrations by chelation and extraction followed by electrothermal atomic absorption spectrophotometry. Analytica Chimica Acta 169, 149-159.

Tappin, A.D. (1988) Trace metals in shelf seas of the British Isles, Ph.D. Thesis, University of Southampton, 279pp.

Tappin A.D., D.J. Hydes, P.J. Statham and J.D. Burton (1992) Concentrations, distributions and seasonal variability of dissolved Cd, Co, Cu, Mn, Ni, Pb and Zn in the English Channel. Continental Shelf Research (vol 12, in press).

Project Information

North Sea Project

The North Sea Project (NSP) was the first Marine Sciences Community Research project of the Natural Environment Research Council (NERC). It evolved from a NERC review of shelf sea research, which identified the need for a concerted multidisciplinary study of circulation, transport and production.

The ultimate aim of the NERC North Sea Project was the development of a suite of prognostic water quality models to aid management of the North Sea. To progress towards water quality models, three intermediate objectives were pursued in parallel:

  • Production of a 3-D transport model for any conservative passive constituent, incorporating improved representations of the necessary physics - hydrodynamics and dispersion;
  • Identifying and quantifying non-conservative processes - sources and sinks determining the cycling and fate of individual constituents;
  • Defining a complete seasonal cycle as a database for all the observational studies needed to formulate, drive and test models.

Proudman Oceanographic Laboratory hosted the project, which involved over 200 scientists and support staff from NERC and other Government funded laboratories, as well as seven universities and polytechnics.

The project ran from 1987 to 1992, with marine field data collection between April 1988 and October 1989. One shakedown (CH28) and fifteen survey cruises (Table 1), each lasting 12 days and following the same track, were repeated monthly. The track selected covered the summer-stratified waters of the north and the homogeneous waters in the Southern Bight in about equal lengths together with their separating frontal band from Flamborough head to Dogger Bank, the Friesian Islands and the German Bight. Mooring stations were maintained at six sites for the duration of the project.

Table 1: Details of NSP Survey Cruises on RRS Challenger
Cruise No. Date
CH28 29/04/88 - 15/05/88
CH33 04/08/88 - 16/08/88
CH35 03/09/88 - 15/09/88
CH37 02/10/88 - 14/10/88
CH39 01/11/88 - 13/11/88
CH41 01/12/88 - 13/12/88
CH43 30/12/88 - 12/01/89
CH45 28/01/89 - 10/02/89
CH47 27/02/89 - 12/03/89
CH49 29/03/89 - 10/04/89
CH51 27/04/89 - 09/05/89
CH53 26/05/89 - 07/06/89
CH55 24/06/89 - 07/07/89
CH57 24/07/89 - 06/08/89
CH59 23/08/89 - 04/09/89
CH61 21/09/89 - 03/10/89

Alternating with the survey cruises were process study cruises (Table 2), which investigated some particular aspect of the science of the North Sea. These included fronts (nearshore, circulation and mixing), sandwaves and sandbanks, plumes (Humber, Wash, Thames and Rhine), resuspension, air-sea exchange, primary productivity and blooms/chemistry.

Table 2: Details of NSP Process cruises on RRS Challenger
Cruise No. Date Process
CH34 18/08/88 - 01/09/88 Fronts - nearshore
CH36 16/09/88 - 30/09/88 Fronts - mixing
CH56 08/07/89 - 22/07/89 Fronts - circulation
CH58 07/08/89 - 21/08/89 Fronts - mixing
CH38 24/10/88 - 31/10/88 Sandwaves
CH40 15/11/88 - 29/11/88 Sandbanks
CH42 15/12/88 - 29/12/88 Plumes/Sandbanks
CH46 12/02/89 - 26/02/89 Plumes/Sandwaves
CH44 13/01/89 - 27/01/89 Resuspension
CH52 11/05/89 - 24/05/89 Resuspension
CH60 06/09/89 - 19/09/89 Resuspension
CH48 13/03/89 - 27/03/89 Air/sea exchanges
CH62 05/10/89 - 19/10/89 Air/sea exchanges
CH50 12/04/89 - 25/04/89 Blooms/chemistry
CH54 09/06/89 - 22/06/89 Production

In addition to the main data collection period, a series of cruises took place between October 1989 and October 1990 that followed up work done on previous cruises (Table 3). Process studies relating to blooms, plumes (Humber, Wash and Rhine), sandwaves and the flux of contaminants through the Dover Strait were carried out as well as two `survey' cruises.

Table 3: Details of NSP `Follow up' cruises on RRS Challenger
Cruise No. Date Process
CH62A 23/10/89 - 03/11/89 Blooms
CH64 03/04/90 - 03/05/90 Blooms
CH65 06/05/90 - 17/05/90 Humber plume
CH66A 20/05/90 - 31/05/90 Survey
CH66B 03/06/90 - 18/06/90 Contaminants through Dover Strait
CH69 26/07/90 - 07/08/90 Resuspension/Plumes
CH72A 20/09/90 - 02/10/90 Survey
CH72B 04/10/90 - 06/10/90 Sandwaves/STABLE
CH72C 06/10/90 - 19/10/90 Rhine plume

The data collected during the observational phase of the North Sea Project comprised one of the most detailed sets of observations ever undertaken in any shallow shelf sea at that time.

Data Activity or Cruise Information

Data Activity

Start Date (yyyy-mm-dd) 1989-05-03
End Date (yyyy-mm-dd) 1989-05-03
Organization Undertaking ActivityPlymouth Marine Laboratory
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierCH51_CTD_1821
Platform Categorylowered unmanned submersible

BODC Sample Metadata Report for CH51_CTD_1821

Sample reference number Nominal collection volume(l) Bottle rosette position Bottle firing sequence number Minimum pressure sampled (dbar) Maximum pressure sampled (dbar) Depth of sampling point (m) Bottle type Sample quality flag Bottle reference Comments
286928   10.00       40.70   41.00   37.50 Niskin bottle No problem reported    
286931   10.00       21.50   21.80   18.60 Niskin bottle No problem reported    
286945   10.00        4.40    5.10    1.80 Niskin bottle No problem reported    

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 Name CH51
Departure Date 1989-04-27
Arrival Date 1989-05-09
Principal Scientist(s)Alan W Morris (Plymouth Marine Laboratory)
Ship RRS Challenger

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Station NameNSP CTD Site CI
CategoryOffshore location
Latitude55° 30.18' N
Longitude6° 30.10' E
Water depth below MSL

North Sea Project CTD Site CI

Site CI was one of 123 North Sea Project CTD fixed stations.

Casts were performed by 14 cruises between 10/08/1988 and 29/09/1990, the measurements collected lie within a box bounded by co-ordinates 55.49597°N, 6.49857°E at the southwest corner and 55.50986°N, 6.50481°E at the northeast corner.

Related Fixed Station activities are detailed in Appendix 2

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

SeaDataNet Quality Control Flags

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

Flag Description
0 no quality control
1 good value
2 probably good value
3 probably bad value
4 bad value
5 changed value
6 value below detection
7 value in excess
8 interpolated value
9 missing value
A value phenomenon uncertain
B nominal value
Q value below limit of quantification

Appendix 1: CH51_CTD_1821

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.

Series IdentifierData CategoryStart date/timeStart positionCruise
2082424Water sample data1989-05-03 16:23:4255.49951 N, 6.50332 ERRS Challenger CH51
1244918Water sample data1989-05-03 16:24:0055.49951 N, 6.50332 ERRS Challenger CH51
1705925Water sample data1989-05-03 16:24:0055.49951 N, 6.50332 ERRS Challenger CH51
1861129Water sample data1989-05-03 16:24:0055.49951 N, 6.50332 ERRS Challenger CH51

Appendix 2: NSP CTD Site CI

Related series for this Fixed Station 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.

Series IdentifierData CategoryStart date/timeStart positionCruise
769563CTD or STD cast1988-08-10 18:27:0055.49617 N, 6.503 ERRS Challenger CH33
783661CTD or STD cast1988-09-09 12:30:0055.50233 N, 6.50117 ERRS Challenger CH35
821885CTD or STD cast1988-11-07 05:42:0055.496 N, 6.5035 ERRS Challenger CH39
786879CTD or STD cast1989-01-09 21:57:0055.49883 N, 6.4985 ERRS Challenger CH43
791648CTD or STD cast1989-02-03 16:10:0055.4975 N, 6.50483 ERRS Challenger CH45
792916CTD or STD cast1989-03-05 16:52:0055.50167 N, 6.5005 ERRS Challenger CH47
1857677Water sample data1989-03-05 16:55:0055.50165 N, 6.50052 ERRS Challenger CH47
795293CTD or STD cast1989-05-03 16:17:0055.4995 N, 6.50333 ERRS Challenger CH51
2082424Water sample data1989-05-03 16:23:4255.49951 N, 6.50332 ERRS Challenger CH51
1861129Water sample data1989-05-03 16:24:0055.49951 N, 6.50332 ERRS Challenger CH51
796641CTD or STD cast1989-06-01 09:22:0055.49917 N, 6.50017 ERRS Challenger CH53
1863658Water sample data1989-06-01 09:27:0055.49921 N, 6.50013 ERRS Challenger CH53
797957CTD or STD cast1989-06-30 06:28:0055.50983 N, 6.50083 ERRS Challenger CH55
1656868Water sample data1989-06-30 06:32:0055.50986 N, 6.50077 ERRS Challenger CH55
1866146Water sample data1989-06-30 06:32:0055.50986 N, 6.50077 ERRS Challenger CH55
799337CTD or STD cast1989-07-30 11:48:0055.5005 N, 6.50117 ERRS Challenger CH57
1246187Water sample data1989-07-30 11:52:0055.50049 N, 6.50113 ERRS Challenger CH57
1709649Water sample data1989-07-30 11:52:0055.50049 N, 6.50113 ERRS Challenger CH57
1864987Water sample data1989-07-30 11:52:0055.50049 N, 6.50113 ERRS Challenger CH57
801835CTD or STD cast1989-08-29 11:16:0055.5 N, 6.50017 ERRS Challenger CH59
1856533Water sample data1989-08-29 11:17:0055.5 N, 6.50024 ERRS Challenger CH59
800487CTD or STD cast1989-09-27 19:55:0055.50133 N, 6.501 ERRS Challenger CH61
2087729Water sample data1989-09-27 19:59:3155.50134 N, 6.50102 ERRS Challenger CH61
1855265Water sample data1989-09-27 20:00:0055.50134 N, 6.50102 ERRS Challenger CH61
803196CTD or STD cast1990-05-27 17:52:0055.50017 N, 6.4995 ERRS Challenger CH66A
804998CTD or STD cast1990-09-29 03:54:0055.49917 N, 6.50233 ERRS Challenger CH72A