<div><p><strong>Sampling:</strong><br />
Full depth and super station samples were collected from the ship's rosette. Samples were filtered through 0.8/0.45 um acropak500 filter cartridges into triple-rinsed 60 mL HDPE bottles. Demi station samples were collected from the GEOTRACES Go-Flo rosette. Samples were filtered through 0.2 um acropak capsule filters into triple-rinsed 60 mL HDPE bottles. Each sample was collected in triplicate. Samples were frozen at -20 C immediately and stored frozen until analysis.</p>
<p><strong>Analysis:</strong><br />
Samples were analyzed for nitrate d15N and d18O using the denitrifier method (Sigman et al., 2001; Casciotti, et al., 2001, with technical updates described by McIlvin and Casciotti, 2011). Nitrate isotope reference materials USGS32, USGS34, and USGS35 were used to calibrate d18O and USGS32 and USGS34 to calibrate d15N. Each sample was analyzed 2-6 times. Mean and standard deviations are reported for each sample. All samples were analyzed on a DeltaPLUS XP isotope ratio mass spectrometer, with custom-built inlet described in McIlvin and Casciotti, 2011.</p>
<p>Where possible (concentrations exceeded 2 uM), samples and standards were analyzed in 20 nanomole aliquots. When NO3- concentrations were below 2 uM, samples were injected in maximum volume (10 mL) and calibrated using interpolations between standard curves of 5 and 20 nano moles NO3-. Some samples contained nitrate concentrations lower than the typical analytical window (300 nM NO3-), but were analyzed nonetheless. Samples analyzed with concentrations below 0.3 uM are were flagged as "low concentration". These samples contained a subset with major ion peak areas (m/z 44) less than 1 volt-second, which are flagged at "low area". Two of these samples are flagged as having elevated d18O-NO3 values relative to their d15N-NO3 values. The flagged samples should be treated with caution.</p>
<p>This version (16 March 2013) has not been thoroughly intercalibrated with data from the Sigman Lab. Currently, there exists no detachable d15N offset between the datasets. However, Casciotti d18O data are approximately 0.6 permil higher than Sigman d18O data.</p></div>
delta 15N of nitrate from GT10 and GT11 cruises.
<div><p>Dataset includes delta 15N of nitrate (NO3) measurements from the GT10 and GT11 (KN199-04 and KN204-01) U.S. GEOTRACES North Atlantic Transect cruises.</p></div>
GT10-11 - delta 15N-NO3
<div><p><strong>Processing:</strong><br />
Raw data were calibrated to USGS standards analyzed 6x with each batch of samples. The measured values of these reference materials were used to calibrated the measured d15N and d18O values to the atmospheric N2 and VSMOW reference scales (McIlvin and Casciotti, 2011).</p>
<p><strong>References:</strong><br />
McIlvin, M., and K. L. Casciotti. 2011. Technical updates to the bacterial method for nitrate isotopic analyses. Analytical Chemistry 83: 1850-1856.</p>
<p><strong>BCO-DMO Processing Notes:</strong><br />
- Modified parameter names to conform with BCO-DMO naming conventions.<br />
- Separated original date field into month, day, and year.<br />
- Replaced asterisks in the flag columns with the text "low_area" or "low_concentration". "no_flag" added for unflagged data.<br />
- Replaced blanks with 'nd' to indicate 'no data'.<br />
- Corrected event numbers of KN199-04 station 6 cast 1, station 7 cast 6, and station 9 cast 3 to be consistent with those in the event log and bottle files, per approval by PI. (29-April-2013)</p>
<p><strong>Additional GEOTRACES Processing:</strong><br />
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.</p>
<p>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.</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>
3913
GT10-11 - delta 15N-NO3
2013-04-15T16:11:39-04:00
2013-04-15T16:11:39-04:00
2023-07-07T16:10:26-04:00
urn:bcodmo:dataset:3913
delta 15N of nitrate from R/V Knorr cruise KN199-04 & KN204-01 in the Subtropical northern Atlantic Ocean from 2010-2011 (U.S. GEOTRACES NAT project)
Dataset includes delta 15N of nitrate (NO3) measurements from the GT10 and GT11 (KN199-04 and KN204-01) U.S. GEOTRACES North Atlantic Transect cruises.
false
Casciotti, K., Sigman, D. (2020) delta 15N of nitrate from R/V Knorr cruise KN199-04 & KN204-01 in the Subtropical northern Atlantic Ocean from 2010-2011 (U.S. GEOTRACES NAT project). Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2013-04-29 [if applicable, indicate subset used]. doi:10.26008/1912/bco-dmo.3913.1 [access date]
true
1
10.26008/1912/bco-dmo.3913.1
false
2013-04-29
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