<div><p>A subsample of 0.8 - 51 um-sized suspended particles collected using McLane in situ pumps was provided by P. Lam. Details of the sampling methodology are described in Ohnemus & Lam (2015). For a small number of samples, a low volume of seawater drawn through the filter resulted in unreliable data (see Data Processing).</p>
<p>The "labile" phase of the suspended particles was determined by leaching with a pH 8 solution of 0.1M oxalic acid and 0.05M EDTA for 2 hours at 90 C. Method is described in Revels et al (2015). Concentrations of Al, P, V, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ba, Ce, La and Pb in the labile phase were determined by analysis of the leachate on a Thermo Scientific Element XR ICP-MS. Samples were run alongside blanks and standards prepared in the same matrix, with all samples, blanks and standards spiked with In as an internal standard. Repeat analyses of blanks and standards were carried out throughout analysis sequences as a further check on instrumental drift and reproducibility of data.</p>
<p>Aliquots of the leachate containing a known quantity of Fe were then spiked with an Fe-57-Fe-58 double-spike and purified by anion exchange chromatography and Fe concentration and d56Fe were measured by Thermo Neptune multi-collector ICP-MS. The method is fully described in Revels et al (2015).</p>
<p><strong>References:</strong><br />
D.C. Ohnemus and P.J. Lam (2015) Cycling of lithogenic marine particles in the US GEOTRACES North Atlantic transect. Deep-Sea Research II 116, 283-302. doi:<a href="https://dx.doi.org/10.1016/j.dsr2.2014.11.019" target="_blank">10.1016/j.dsr2.2014.11.019</a><br />
B.N. Revels, D.C. Ohnemus, P.J. Lam, T.M. Conway, S.G. John (2015) The isotopic signature and distribution of particulate iron in the North Atlantic Ocean. Deep-Sea Research II 116, 321-331. doi:<a href="https://dx.doi.org/10.1016/j.dsr2.2014.12.004" target="_blank">10.1016/j.dsr2.2014.12.004</a></p></div>
Particulate iron (pFe) isotope concentrations from the GEOTRACES EPZT cruise
<div><p>Particulate iron (pFe) isotope concentrations from the GEOTRACES EPZT cruise</p></div>
GP16 Particulate Iron Isotopes
<div><p><strong>Data Processing:</strong><br />
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".</p>
<p>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)).</p>
<p>Data have been giving the following quality flags:<br />
2 – good data<br />
3 – suspect data<br />
4 – bad data<br />
5 – no data</p>
<p><strong>BCO-DMO Processing:</strong><br />
- modified parameter names to conform with BCO-DMO and GEOTRACES naming conventions;<br />
- replaced "<DL" with "BDL" (below detection limit);<br />
- replaced missing data with "nd" (no data).</p>
<p><strong>Additional GEOTRACES Processing:</strong><br />
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:</p>
<p>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.</p>
<p>This added information will facilitate subsequent analysis and inter comparison of the datasets.</p>
<p>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.</p>
<p>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.</p>
<p>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.</p>
<p>See the dataset parameters documentation for a description of which parameters were supplied by the PI and which were added via the join method.</p></div>
669178
GP16 Particulate Iron Isotopes
2016-12-08T11:48:44-05:00
2016-12-08T11:48:44-05:00
2023-07-07T16:10:26-04:00
urn:bcodmo:dataset:669178
Particulate iron (pFe) isotope concentrations from the GEOTRACES EPZT cruise (R/V Thomas G. Thompson TN303) in the Eastern Tropical Pacific from October to December 2013
false
John, S. G. (2016) Particulate iron (pFe) isotope concentrations from the GEOTRACES EPZT cruise (R/V Thomas G. Thompson TN303) in the Eastern Tropical Pacific from October to December 2013. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 09 December 2016) Version Date 2016-12-09 [if applicable, indicate subset used]. http://lod.bco-dmo.org/id/dataset/669178 [access date]
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09 December 2016
false
2016-12-09
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