Dataset: GT10-11 - delta 15N-NO3

Name: 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)
Published: 2013-04-29
Keywords: oceans

Cite This Dataset

DOI:10.26008/1912/bco-dmo.3913.1

Spatial Extent: N:39.7014 E:-9.6601 S:17.3497 W:-69.8644

Temporal Extent: 2010-10-16 - 2011-12-10

Project:

U.S. GEOTRACES North Atlantic Transect (GA03) (U.S. GEOTRACES NAT)

Program:

U.S. GEOTRACES (U.S. GEOTRACES)

Principal Investigator:

Karen L. Casciotti (Stanford University)

Co-Principal Investigator:

Daniel M. Sigman (Princeton University)

BCO-DMO Data Manager:

Shannon Rauch (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

Version Date:

2013-04-29

Restricted:

Validated:

Yes

Current State:

Final no updates expected

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)

Abstract:

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.

Expand/Collapse All

Archival Copy

Version Date	Archive	Persistent Identifier	Date Assigned
2013-04-29	Marine Biological Laboratory/Woods Hole Oceanographic Institution Library (MBLWHOI DLA)	10.26008/1912/bco-dmo.3913.1	2020-03-31

Description

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.

Methods & Sampling

Sampling:
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.

Analysis:
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.

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.

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.

Data Processing Description

Processing:
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).

References:
McIlvin, M., and K. L. Casciotti. 2011. Technical updates to the bacterial method for nitrate isotopic analyses. Analytical Chemistry 83: 1850-1856.

BCO-DMO Processing Notes:
- Modified parameter names to conform with BCO-DMO naming conventions.
- Separated original date field into month, day, and year.
- Replaced asterisks in the flag columns with the text "low_area" or "low_concentration". "no_flag" added for unflagged data.
- Replaced blanks with 'nd' to indicate 'no data'.
- 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)

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.

Data Files

File
delta_15N-NO3_joined.csv (Comma Separated Values (.csv), 62.95 KB) MD5:fa412758d10c672f1f731eab60eddd48 Primary data file for dataset ID 3913

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-1138360

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
KN199-04	GA03 GT10 USGT-NAT-2010 KN199-4 GNAT U.S. GEOTRACES NAZT Leg 1 knorr199-4/5 Section Cruise (GA03) 316N20101015	2010-10-15	R/V Knorr	William J. Jenkins (Chief Scientist) Edward A. Boyle (Co-Chief Scientist) Gregory A. Cutter (Co-Chief Scientist)	data info
KN204-01	GA03 GT11 KN204-01A KN204-01B USGT-NAT-2011 USGNAZT GNAT 316N20111106 KN204-1	2011-11-06	R/V Knorr	Edward A. Boyle (Chief Scientist) Gregory A. Cutter (Co-Chief Scientist)	data info

Instruments

GO-FLO Bottle

Supplied Description:

Demi station samples were collected from the GEOTRACES GO-FLO rosette. The U.S. GEOTRACES sampling system consisted of 24 Teflon-coated GO-FLO bottles.

Instrument Type

Generic Name: GO-FLO Bottle

Acronym: GO-FLO

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/30/

Generic Description:

GO-FLO bottle cast used to collect water samples for pigment, nutrient, plankton, etc. The GO-FLO sampling bottle is specially designed to avoid sample contamination at the surface, internal spring contamination, loss of sample on deck (internal seals), and exchange of water from different depths.

Isotope-ratio Mass Spectrometer

Supplied Description:

All samples were analyzed on a DeltaPLUS XP isotope ratio mass spectrometer, with custom-built inlet described in McIlvin and Casciotti, 2011.

Instrument Type

Generic Name: Isotope-ratio Mass Spectrometer

Acronym: IR Mass Spec; IRMS

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB16/

Generic Description:

The Isotope-ratio Mass Spectrometer is a particular type of mass spectrometer used to measure the relative abundance of isotopes in a given sample (e.g. VG Prism II Isotope Ratio Mass-Spectrometer).

Niskin bottle

Supplied Description:

Instrument Type

Generic Name: Niskin bottle

Community Identifier: http://vocab.nerc.ac.uk/collection/L22/current/TOOL0412/

Generic Description:

A Niskin bottle (a next generation water sampler based on the Nansen bottle) is a cylindrical, non-metallic water collection device with stoppers at both ends. The bottles can be attached individually on a hydrowire or deployed in 12, 24, or 36 bottle Rosette systems mounted on a frame and combined with a CTD. Niskin bottles are used to collect discrete water samples for a range of measurements including pigments, nutrients, plankton, etc.

Parameters

Date and time formats are described in python strftime() syntax.

Supplied Name	Supplied description	Supplied Units	Standard Name
cruise_id	Official cruise identifier e.g. KN199-04 = R/V Knorr cruise number 199-04.	text	cruise_id
station_GEOTRC	GEOTRACES station number; ranges from 1 through 12 for KN199-04 and 1 through 24 for KN204-01. Stations 7 and 9 were skipped on KN204-01. PI-supplied values were identical to those in the intermediate US GEOTRACES master file. Originally submitted as 'Station', this parameter name has been changed to conform to BCO-DMO's GEOTRACES naming conventions.	dimensionless	station
depth_GEOTRC_CTD	Observation/sample depth in meters, calculated from CTD pressure. PI-supplied values were identical to those in the intermediate US GEOTRACES master file. Originally submitted as 'CTD Depth', this parameter name has been changed to conform to BCO-DMO's GEOTRACES naming conventions.	meters	depth
press	Pressure (dbars) from CTD.	decibars	press
event_GEOTRC	Unique identifying number for US GEOTRACES sampling events; ranges from 2001 to 2225 for KN199-04 events and from 3001 to 3282 for KN204-01 events. PI-supplied values were identical to those in the intermediate US GEOTRACES master file. Originally submitted as 'Event number', this parameter name has been changed to conform to BCO-DMO's GEOTRACES naming conventions.	dimensionless	event
cast_GEOTRC	Cast identifier, numbered consecutively within a station. PI-supplied values were identical to those in the intermediate US GEOTRACES master file. Originally submitted as 'Cast', this parameter name has been changed to conform to BCO-DMO's GEOTRACES naming conventions.	dimensionless	cast
sample_GEOTRC	Unique identifying number for US GEOTRACES samples; ranges from 5033 to 6078 for KN199-04 and from 6112 to 8148 for KN204-01. PI-supplied values were identical to those in the intermediate US GEOTRACES master file. Originally submitted as 'GEOTRACES ID', this parameter name has been changed to conform to BCO-DMO's GEOTRACES naming conventions.	dimensionless	sample
sample_bottle_GEOTRC	Unique identification numbers given to samples taken from bottles; rangies from 1 to 24; often used synonymously with bottle number. PI-supplied values were identical to those in the intermediate US GEOTRACES master file. Originally submitted as 'Sample #', this parameter name has been changed to conform to BCO-DMO's GEOTRACES naming conventions.	dimensionless	bot_Nis
bottle_GEOTRC	Alphanumeric characters identifying bottle type (e.g., NIS representing Niskin and GF representing GOFLO) and position on a CTD rosette. PI-supplied values were identical to those in the intermediate US GEOTRACES master file. Originally submitted as 'Bottle number', this parameter name has been changed to conform to BCO-DMO's GEOTRACES naming conventions.	dimensionless	bottle
month_gmt	2-digit month of year (GMT). in the format mm (01 to 12)	unitless	month_gmt
day_gmt	2-digit day of month (GMT). in the format dd (01 to 31)	unitless	day_gmt
year	4-digit year. in the format YYYY	unitless	year
time_gmt	Time (GMT) in hours and minutes when the event occurred; 24-hour clock. in the format HHMM	unitless	time_gmt
lat	Latitude in decimal degrees. North = Positive.	decimal degrees	lat
lon	Longitude in decimal degrees. West = Negative.	decimal degrees	lon
d15N_NO3	Nitrate delta 15N, reported in units of permil vs. atmospheric N2.	per mil	dN15_NO3
d15N_NO3_sd	Standard deviation of d15N_NO3.	per mil	std_dev
n	n; number of observations/measurements.	dimensionless	numb_obs
flag_low_area	Samples that contained major ion peak areas (m/z 44) less than 1 volt-second are flagged at "low area". The flagged samples should be treated with caution.	dimensionless	q_flag
flag_low_conc	Samples analyzed with concentrations below 0.3 uM are were flagged as "low concentration". The flagged samples should be treated with caution.	dimensionless	q_flag
ISO_DateTime_UTC	Date/Time (UTC) of the cast formatted to the ISO8601 standard. T indicates start of time string; Z indicates UTC. in the format YYYY-mm-ddTHH:MM:SS.ssZ	unitless	ISO_DateTime_UTC
BTL_ISO_DateTime_UTC	Date and time (UTC) that the bottle was fired, in ISO compliant format. Values were added from the intermediate US GEOTRACES master file (see Processing Description). This standard is based on ISO 8601:2004(E) and takes on the following form: 2009-08-30T14:05:00[.xx]Z (UTC time)	yyyy-MM-dd'T'HH:mm:ss.SS'Z'	ISO_DateTime_UTC