Sample concentrations were determined on a weight basis. Data for dissolved Y, Cd, La, Pb, Mn, Fe, Co, Ni, Cu, Zn and Ga are presented in concentrations units of pmol/kg (Y, Cd, La, Pb, Ga) or nmol/kg (Mn, Fe, Ni, Cu, Zn).
UV oxidization of the samples prior to extraction was necessary for dissolved Co and Cu. Samples were analyzed with and without prior treatment by UV oxidation. Only the UV-treated sample data should be used for dissolved Co and Cu. For the other trace elements, all the data was averaged.
On the GEOTRACES 2011 cruise (Stations 10, 12 and 20), some sporadic contamination of Cu, Zn and Ni was observed. The contamination problem for Cu was the worst and it occurred at roughly a constant ratio of Cu:Ni:Zn. Samples with obvious Cu contamination were eliminated from the Corrected UV data sets. Samples that were obviously significantly contaminated for Cu also showed significant Zn and Ni contamination and were eliminated from the corrected Zn and Ni average data sets.
Data for the SAFe and GEOTRACES Reference Samples are included with each data set submitted along with blanks and detection limits.
Related references:
Cutter, G.A. and K.W. Bruland. Rapid and non-contaminating sampling system for trace elements in global ocean surveys. Limnology and Oceanography: Methods, 10: 425-436 (2012).
Biller, D.V. and K.W. Bruland. Analysis of Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in seawater using the Nobias-chelate PA1 resin and magnetic sector inductively coupled plasma mass spectrometry. Marine Chemistry, 130/131: 12-20 (2012).
Additional GEOTRACES Processing: After the data were submitted to the International Data Management Office, BODC, the office noticed that important identifying information was missing in many datasets. With the agreement of BODC and the US GEOTRACES lead PIs, BCO-DMO added standard US GEOTRACES information, such as the US GEOTRACES event number, to each submitted dataset lacking this information. To accomplish this, BCO-DMO compiled a 'master' dataset composed of the following parameters: station_GEOTRC, cast_GEOTRC (bottle and pump data only), event_GEOTRC, sample_GEOTRC, sample_bottle_GEOTRC (bottle data only), bottle_GEOTRC (bottle data only), depth_GEOTRC_CTD (bottle data only), depth_GEOTRC_CTD_rounded (bottle data only), BTL_ISO_DateTime_UTC (bottle data only), and GeoFish_id (GeoFish data only). This added information will facilitate subsequent analysis and inter comparison of the datasets.
Bottle parameters in the master file were taken from the GT-C_Bottle_GT10, GT-C_Bottle_GT11, ODF_Bottle_GT10, and ODF_Bottle_GT11 datasets. Non-bottle parameters, including those from GeoFish tows, Aerosol sampling, and McLane Pumps, were taken from the Event_Log_GT10 and Event_Log_GT11 datasets. McLane pump cast numbers missing in event logs were taken from the Particulate Th-234 dataset submitted by Ken Buesseler.
A standardized BCO-DMO method (called “join”) was then used to merge the missing parameters to each US GEOTRACES dataset, most often by matching on sample_GEOTRC or on some unique combination of other parameters.
If the master parameters were included in the original data file and the values did not differ from the master file, the original data columns were retained and the name of the parameters were changed from the PI-submitted names to the standardized master names. If there were differences between the PI-supplied parameter values and those in the master file, both columns were retained. If the original data submission included all of the master parameters, no additional columns were added, but parameter names were modified to match the naming conventions of the master file.
See the dataset parameters documentation for a description of which parameters were supplied by the PI and which were added via the join method.
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