Metadata Report for BODC Series Reference Number 2108281

• 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

GEOTRACES - data access conditions

Access to this data is currently restricted and it is not available via BODC's normal delivery mechanisms.

GEOTRACES data are published via the GEOTRACES IDP, available at:

• IDP 2014
• IDP 2017

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.

Dissolved seawater Ba stable isotopes ( 138/134Ba) and Ba concentration (nM) collected on the GEOTRACES JC086 cruise in the South Atlantic Ocean

Responsible investigator

Professor Gideon M. Henderson
email: gideon.henderson@earth.ox.ac.uk
Department of Earth Sciences
University of Oxford
South Parks Road
Oxford, OX1 3AN
United Kingdom

Data contributor

Alan Hsieh
Email: yuteh@earth.ox.ac.uk
Department of Earth Sciences
University of Oxford
South Parks Road
Oxford, OX1 3AN
United Kingdom

Laboratory of analysis

University of Oxford, Department of Earth Sciences

Originator's Protocol for Data Acquisition and Analysis

In order to understand seawater Ba stable isotope fractionation, twelve filtered seawater samples, collected from the UK-GEOTRACES cruise GA10W (JC068) in the South Atlantic, were measured for Ba stable isotopes and Ba concentrations by Alan Hsieh, using the thermal ionization mass spectrometer (TIMS) at the University of Oxford.

Seawater samples were collected from the Niskin bottle rosette, immediately filtered with 0.45-micrometer Acropak cartridge filters, stored in pre-cleaned polypropylene bottles, and acidified to a pH of 1-2 with distilled HCl.

The method of seawater Ba purification is modified from the method described in Foster et al. (2006). 50mL of seawater (~ 250ng Ba) was weighed, and spiked with a 137Ba-135Ba double spike prepared in Oxford for correcting the mass dependent fractionation during the chemical procedure and instrument analysis. The double spike was calibrated against the NIST3104a standard for both the Ba isotopic composition and Ba concentration. A 3 mL 0.9M Na2CO3 solution (Ba cleaned) was added into the samples to co-precipitate Ba with the CaCO3 precipitates. The precipitates were centrifuged, cleaned and separated from the remaining seawater before being dissolved in 2 mL 3M HCl for the column separation. The AG50-X8 (200-400 mesh, 2 mL) columns were used to purify Ba from Ca, Mg, Sr, and REEs.

The high precision Ba isotopic analyses were preformed on a thermo ionization mass spectrometer (TIMS), Triton, at the University of Oxford. The sample loading method is adapted from Carlson et al. (2007). The purified Ba samples and standards were dissolved in 2 uL of distilled 2M HCl, and loaded onto a single rhenium (Re) filament. A current of 0.68 A was continuously applied during the loading. Once the sample had dried on the filament, 2 uL of activator (a mixture of 50 mg Ta2O5 powder and 3mL 5% H3PO4) was loaded on top of the sample. During the analysis, Ba-138, 137, 136, 135, 134, Ce-140 and La-139 ion beams were simultaneously monitored in 7 Faraday cups. Ce-140 and La-139 were used for the interference correction. Each sample was measured for 54 blocks in total, and each block had 10 cycles of 8 seconds integration time per cycle. The instrument baseline was monitored between each block.

The Ba-isotope data are reported in the d-notation (o/oo) relative to the Ba standard NIST3104a:

138/134Ba = (138/134Basample / 138/134BaNIST - 1) x 1000

The long-term reproducibility of the Ba isotopic analysis is around 0.01o/oo (2 standard deviations, 2 S.D.) based on repeated measurements of NIST3104a and seawater standards. However, incomplete separation of matrix elements from samples leads to somewhat larger uncertainty, between 0.01 and 0.05‰ (2-standard error, 2 S.E.) in some samples. Seawater Ba concentration is measured using the Ba isotope dilution technique. The 137Ba-135Ba double spike concentration is calibrated against the NIST3104a standard (certified Ba concentration: 10.014±0.036 mg/g 2 S.D.)

The overall procedure blank is between 0.7 and 1.2 ng of Ba, which was < 0.5% of the total Ba in seawater samples (250 ng).

References Cited

Carlson, R.W., Boyet, M., Horan, M., 2007. Chondrite barium, neodymium, and samarium isotopic heterogeneity and early earth differentiation. Science 316, 1175-1178. doi:10.1126/science.1140189

Foster, D.A., Staubwasser, M., Henderson, G.M., 2004. 226Ra and Ba concentrations in the Ross Sea measured with multicollector ICP mass spectrometry. Mar. Chem. 87, 59-71. doi:10.1016/j.marchem.2004.02.003

BODC Data Processing Procedures

Data were received by BODC in a Microsoft Excel format and the values were extracted for loading into BODC's ocean database under the ORACLE Relational Database Management System.

The mapping between the originator's channels and the BODC parameter codes are detailed in the table below.

Data Quality Report

None

Project Information

GEOTRACES

Introduction

GEOTRACES is an international programme sponsored by SCOR which aims to improve our understanding of biogeochemical cycles and large-scale distribution of trace elements and their isotopes (TEIs) in the marine environment. The global field programme started in 2009 and will run for at least a decade. Before the official launch of GEOTRACES, fieldwork was carried out as part of the International Polar Year (IPY)(2007-2009) where 14 cruises were connected to GEOTRACES.

GEOTRACES is expected to become the largest programme to focus on the chemistry of the oceans and will improve our understanding of past, present and future distributions of TEIs and their relationships to important global processes.

This initiative was prompted by the increasing recognition that TEIs are playing a crucial role as regulators and recorders of important biogeochemical and physical processes that control the structure and productivity of marine ecosystems, the dispersion of contaminants in the marine environment, the level of greenhouse gases in the atmosphere, and global climate.

Scientific Objectives

GEOTRACES mission is: To identify processes and quantify fluxes that control the distribution of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions.

Three overriding goals support the GEOTRACES mission

• Determine ocean distributions of selected TEIs at all major ocean basins
• Evaluate the sources, sinks, and internal cycling of these TEIs and thereby characterize more completely their global biogeochemical cycles
• Provide a baseline distribution in the Polar Regions as reference for assessing past and future changes.

These goals will be pursued through complementary research strategies, including observations, experiments and modelling.

Fieldwork

The central component of GEOTRACES fieldwork will be a series of cruises spanning all Ocean basins see map below.

Three types of cruise are required to meet the goals set out by GEOTRACES. These are

• Section cruises - These will measure all the key parameters (see below) over the full depth of the water column. The sections were discussed and approved by the International GEOTRACES Scientific Steering Committee at the basin workshops.
• Process Studies - These will investigate a particular process relevant to the cycling of trace metal and isotopes. They must follow the "Criteria for Establishing GEOTRACES Process Studies" and be approved by the International GEOTRACES Scientific Steering Committee.
• Cruises collecting GEOTRACES compliant data - These will collect some trace element or isotope data. They must follow the GEOTRACES Intercalibration and Data Management protocols

IPY-GEOTRACES

The IPY-GEOTRACES programme comprised of 14 research cruises on ships from 7 nations; Australia, Canada, France, Germany, New Zealand, Japan and Russia. The cruises will not be classified in the same way as the full GEOTRACES programme since the intercalibration protocols and data management protocols had not been established before the start of the IPY. But IPY-GEOTRACES data will still be quality controlled by GDAC and in the majority of cases verified versus Intercalibration standards or protocols.

Key parameters

The key parameters as set out by the GEOTRACES science plan are as follows: Fe, Al, Zn, Mn, Cd, Cu; 15N, 13C; 230Th, 231Pa; Pb isotopes, Nd isotopes; stored sample, particles, aerosols.

Weblink:

http://www.bodc.ac.uk/geotraces/
http://www.geotraces.org/

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for JC068_CTD_CTD051_SS

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: JC068_CTD_CTD051_SS

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.