ICPMS: All data were normalized to an In-115 internal standard and quantified using an external standard curve. After accounting for sample dilutions due to acid digestion steps, quantities of each element per filter (pmol/filter) were calculated for each analytical run. The contribution of the "bomb blank" (measured as the element concentration in an empty digestion vial treated like a sample) was then subtracted. We then subtracted the contribution of the "process blank" (measured as the elements contained in an acid-washed filter through which 0.2-micrometer filtered water was passed during the cruise). Separate process blanks were calculated for the labile (acetic acid/hydroxylamine), refractory (HCl/HNO3/HF following acetic acid/hydroxylamine), and total (HCl/HNO3/HF) digestions. The average process blanks for each digestion scheme and each element is given in the "process blanks" pdf document below.

Following blank corrections, element concentrations (per volume of water filtered) were calculated by dividing the pmol/filter measurements by the volume of water passed through each filter (measured volumetrically on the ship following each filtration).

Nearly all of the samples were well above the instrumental detection limits for all elements. The factor limiting our ability to detect particulate elements in the water is the signal associated with the process blank (i.e., the filter substrate itself). We therefore calculated the detection limits for the whole method as 3 times the standard deviation of the process blanks for the relevant digestion procedure (labile, refractory, or total). The elemental content of the process blank (pmol/filter) was converted into a concentration using the average volume filtered for either GO-Flo samples (6.5 L) or surface fish samples (2.8 L). The detection limits are reported.

Three data flags are used:
1: good
2: questionable
3: rejected
4: below detection limit of method

SXRF Between 9 and 20 cells were analyzed from the shallowest bottle and deep chlorophyll maximum at the subset of stations. The elemental content of each cell has been corrected for elements contained in the carbon substrate. Trace element concentrations are presented as mmol/mol P. Geometric mean concentrations (+/- standard error of the mean) are presented, along with the number of cells analyzed.

References:

Berger, C. J. M., S. M. Lippiatt, M. G. Lawrence, and K. W. Bruland. 2008. Application of a chemical leach technique for estimating labile particulate aluminum, iron, and manganese in the Columbia River plume and coastal waters off Oregon and Washington. Journal of Geophysical Research-Oceans 113.
Cutter, G. and others 2010. Sampling and sample-handling protocols for GEOTRACES cruises.
Twining, B. S., S. B. Baines, J. B. Bozard, S. Vogt, E. A. Walker, and D. M. Nelson. 2011. Metal quotas of plankton in the equatorial Pacific Ocean. Deep-Sea Research II 58: 325-341.

Related documents:

GEOTRACES_NAZT_Twining_metadata_CRM_detection_limit.pdf
GEOTRACES_NAZT_Twining_metadata_CRM_precision.pdf
GEOTRACES_NAZT_Twining_metadata_CRM_process_blanks.pdf
GEOTRACES_NAZT_Twining_metadata_CRMs.pdf

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.

Version information:

August 2013 -- spreadsheet was resubmitted, replacing previous versions entirely. Reference materials (linked PDF files) were all updated. Awaiting review by contributor. Co and Zn were updated using corrected spreadsheet provided by Twining on Jan. 18 2013.

December 9, 2013: A completely new version of the data was submitted - a version that corresponds with the others in the project.

Feb. 18, 2014 -- Another revised data file was submitted, 2/18/2014. This one has the plankton data put back in. It was removed for the Intermediate Data Product assembly.

March 10, 2014: depth_PI was removed from displayed data.

Particulate_Trace_Elements_joined_v5.csv