Data Processing:
Data are flagged as 1 (good) or 2 (questionable). Data points flagged as questionable are considered to be potential outliers. This may be because the difference between replicate analyses is much larger than the presumed analytical error, (the separation between two replicates was > 4x the 2s error) or because the data appear oceanographically inconsistent (e.g. values which are very different from samples taken above and below), even though there is no obvious analytical reason to dismiss them.
References
Conway, T. M., and John, S. G. (2014). The biogeochemical cycling of zinc and zinc isotopes in the North Atlantic Ocean. Global Biogeochemical Cycles. 28 (10). 1111-1128. doi:10.1002/2014GB004862.
Conway, T. M., and John. S. G. (2014). Quantification of dissolved iron sources to the North Atlantic Ocean. Nature. 511. 212-215. doi:10.1038/nature13482.
Conway, T. M., and John, S. G. (2015). Biogeochemical cycling of cadmium isotopes along a high-resolution section through the North Atlantic Ocean. Geochimica et Cosmochimica Acta. 148 (1). 269-283. doi: 10.1016/j.gca.2014.09.032.
Conway, T.M., Rosenberg, A.D., Adkins, J.F., and S.G. John. (2013). A new method for precise determination of iron, zinc and cadmium stable isotope ratios in seawater by double-spike mass spectrometry. Analytica Chimica Acta, 793: 44-52.
John, S. (2012). Optimizing sample and spike concentrations for isotopic analysis by double-spike ICP-MS. Journal of Analytical Atomic Spectrometry, 27: 2123-2131.
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 names 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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