Consensus Values for the GEOTRACES 2008 and SAFe Reference Samples

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SAFe 2004 S, D1 and D2 valuesAl Cd Co Cu Fe Mn Ni Pb Zn
GEOTRACES 2008 GD and GS valuesAl Cd Co Cu Fe Mn Ni Pb Zn
Values Updated May 16 2013

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scientific party SAFe 2004
Scientific Party SAFe 2004

Consensus Values for the SAFe and North Atlantic GEOTRACES Reference Samples have been updated and are reported here as of May 2013.

During the SAFe (Sampling and Analysis of Fe) program and the GEOTRACES Intercalibration North Atlantic and North Pacific cruises, we (Geoffrey Smith and Ken Bruland) collected large volumes of homogenized surface and deep seawater to provide 0.5 L reference samples to researchers investigating the marine chemistry of trace metals in both the U.S. and international trace metal communities. The SAFe S and GEOTRACES GS (BATS), GSP (SAFe station) and GSC (Santa Barbara Channel) surface seawater samples were collected from ~2 meters depth outside of ship's influence using the UCSC designed "GeoFish" towed sampling system. All surface samples were filtered as described below and then homogenized in one or two of the 500 L SAFe tanks. The SAFe D1 and D2 1000 m seawater samples were collected with multiple four-bottle casts using our TeflonTM coated, 30 L, GO-Flo samplers deployed on KevlarTM hydroline (Bruland et al. 1979) while the GEOTRACES GD (BATS) 2000 m deep reference sample was collected with 5 separate casts of the GEOTRACES rosette to rinse and fill a tank. All three deep reference samples were filtered as described below and then homogenized in one of the SAFe tanks.

Our GeoFish/SAFe tank system consists of PFA TeflonTM tubing, an all PFA TeflonTM diaphragm pump, sequential filtration through 0.45 µm then 0.2 µm pore size polycarbonate, track etched (PCTE) pleated filter cartridges and two 500 L fluorinated low density polyethylene tanks connected with all TeflonTM tubing, valves and fittings. All filtrations, acidifications and bottling of the SAFe and GEOTRACES samples were performed inside of Class-100 clean benches in a portable clean van.

picture of the SAFe tanks inside the plastic clean bubble in the Melville´s aft hanger, SAFe Pacific 2004
SAFe tanks, RV Melville, 2004

We successfully collected and continue to provide to an international trace metal community the following reference seawater samples:

surface seawater

650 each S (SAFe Intercalibration North Pacific 2004)

200 each GS (GEOTRACES Intercalibration North Atlantic BATS 2008, no longer available)

280 each GSP (GEOTRACES Intercalibration North Pacific 2009; SAFe site)

600 each GSC (GEOTRACES Intercalibration North Pacific 2009; Santa Barbara Channel during bloom conditions)

deep seawater

630 each D1 (SAFe Intercalibration North Pacific 2004; 1000m)

600 each D2 (SAFe Intercalibration North Pacific 2004; 1000m)

200 each GD (GEOTRACES Intercalibration North Atlantic BATS 2008; 2000m, no longer available)

picture of the scientific party, leg 1 GEOTRACES 2008
Scientific Party leg 1 Geotraces 2008
picture of the scientific party, leg 2 GEOTRACES 2008
Scientific Party leg 2 Geotraces 2008

These samples have been stored in rigorously acid cleaned LDPE bottles for up to over seven years and have proven stable for dissolved Fe and other trace metals. Thus, a range of GEOTRACES reference samples are available with different concentrations and chemistries representative of what one encounters in the real ocean. The SAFe and GEOTRACES reference samples are proving to be valuable for a suite of GEOTRACES key and non-key trace metals.

The GEOTRACES website and Bruland's laboratory website (http://es.ucsc.edu/~kbruland/) provide current "consensus" values for the concentrations of a suite of dissolved trace metals for the SAFe 2004 (S, D1, and D2) and GEOTRACES North Atlantic Intercalibration 2008 (GS and GD) reference samples. We have included results that have been reported to Bruland () as of November 2011. The GEOTRACES North Pacific Intercalibration 2009 reference samples (GSC and GSP), however, are still being treated as "unknown or blind" samples until more data is gathered.

It is our hope that updating the SAFe values along with posting the GEOTRACES GS and GD consensus values will provide an incentive for more scientists to both analyze/reanalyze these reference samples and report their data to Ken Bruland to generate improved consensus values in the future. Once a researcher reports their data, Bruland then shares what other data he has gathered for the metal of interest on the relevant reference samples with that investigator and they try to further investigate any problems that may exist. This stage is a confidential process and is an important component of the intercalibration exercises and part of the international "learning curve" to help raise the level of expertise of the international trace metal community.

To obtain any of these reference samples, contact Geoffrey Smith ( ). There is no cost for the reference samples, but a Fed Ex, UPS or DHL account number must be provided to cover shipping costs. Results of any trace metal concentrations from analyses of all reference samples and the GEOTRACES baseline profiles are being reported to Ken Bruland ( ) for validation to facilitate merging of data sets required for the US and international GEOTRACES programs.

picture of the scientific party GEOTRACES 2009
Scientific Party GEOTRACES 2009
The development of this website and most of the research described here was supported by grants from the National Science Foundation.
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