Metadata Report for BODC Series Reference Number 2097496

• 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

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.

GO-FLO Bottle

A water sampling bottle featuring close-open-close operation. The bottle opens automatically at approximately 10 metres and flushes until closed. Sampling with these bottles avoids contamination at the surface, internal spring contamination, loss of sample on deck and exchange of water from different depths.

There are several sizes available, from 1.7 to 100 litres and are made of PVC with a depth rating of up to 500 m. These bottles can be attached to a rosette or placed on a cable at selected positions.

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).

References

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.

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.

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.

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

BODC Sample Metadata Report for CH51_CTD_1854

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

Fixed Station Information

North Sea Project Survey Mooring Site C and CTD Site DM

Site C was one of six fixed stations where moorings were deployed during the North Sea Project Survey. This location is also one of 123 North Sea Project CTD Sites.

The site was characterised by moderate tidal currents, up to a maximum of 1.1 m/s. In summer months, the site was situated in a frontal region between stratified water to the north and vertically well mixed water to the south.

The rigs deployed here lie within a box bounded by co-ordinates 54.32N 0.393E at the southwest corner and 54.34N 0.422E at the northeast corner. Magnetic variation at this site was 4.9° west.

Site C deployment history is summarised below:

ADCP = Acoustic Doppler Current Profiler
CM = Current Meter (Aanderaa or S4)
THCH = Thermistor Chain

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:

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: CH51_CTD_1854

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.

Appendix 2: NSP Survey C and CTD Site DM

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.