Dataset: GP16 Particulate Iron Isotopes

Data Processing:
All concentration data has been corrected for "dipped filter" blanks – filters that were deployed on each cast but did not have any seawater pumped through them. For each element, concentrations from all dipped filter blanks were averaged. The median dipped filter blank has been subtracted from this data. The given uncertainties in concentration data were calculated by propagating uncertainties from instrument precision and the standard deviation of dipped filter blanks. Detection limits are defined as three times the standard deviation of the dipped filter blanks. Concentrations below detection limit are identified as "BDL".

Iron isotope measurements have been corrected for the leach reagent blank and uncertainties were calculated by an isotope mass balance equation involving the instrument precision and the mean and standard deviation of the reagent blank (equation 2 in Revels et al (2015)).

Data have been giving the following quality flags:
2 – good data
3 – suspect data
4 – bad data
5 – no data

BCO-DMO Processing:
- modified parameter names to conform with BCO-DMO and GEOTRACES naming conventions;
- replaced "<DL" with "BDL" (below detection limit);
- replaced missing data with "nd" (no data).

Additional GEOTRACES Processing:
As was done for the GEOTRACES-NAT data, 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:

cruise_id, EXPOCODE,SECT_ID, STNNBR, CASTNO, GEOTRC_EVENTNO, GEOTRC_SAMPNO, GEOTRC_INSTR, SAMPNO, GF_NO, BTLNBR, BTLNBR_FLAG_W, DATE_START_EVENT, TIME_START_EVENT, ISO_DATETIME_UTC_START_EVENT, EVENT_LAT, EVENT_LON, DEPTH_MIN, DEPTH_MAX,  BTL_DATE, BTL_TIME, BTL_ISO_DATETIME_UTC, BTL_LAT, BTL_LON, ODF_CTDPRS, SMDEPTH, FMDEPTH, BTMDEPTH, CTDPRS, CTDDEPTH.

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 and ODF_Bottle datasets. Non-bottle parameters, including those from GeoFish tows, Aerosol sampling, and McLane Pumps, were taken from the TN303 Event Log (version 30 Oct 2014). Where applicable, pump information was taken from the PUMP_Nuts_Sals dataset.

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.