Dataset: GT10-11 - Cu Speciation

All samples for total dissolved copper on this cruise were well above our detection limit of 100pM determined from the standard deviation of procedural blanks using our ICP-MS methods.

Data points below the detection limit of the cathodic stripping voltammetry technique (~ 0.15 nM) were not used in the titration. However, all titrations had a significant number of points to fit a non-linear regression curve. However, in instances where the fit did not converged, or converged at a non-realistic value (e.g. negative numbers) the data were flagged.

The standard error for [Cu2+] is asymmetric because it is not determined the same way - hence the different values in columns M and N.

The Cu2+ error propagation was derived from the standard deviations of K and [L] when used in equation 11 from Moffett and Dupont 2007 to calculate [Cu2+].

Moffett and Dupont, 2007. Cu complexation by organic ligands in the sub-arctic NW Pacific and Bering Sea. Deep-Sea Research I 54:586-595.

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.