Dataset: GP16 d15N NO3
Deployment: TN303

Nitrate isotope data from the US GEOTRACES EPZT cruise.

Principal Investigator:

Karen L. Casciotti (Stanford University)

Co-Principal Investigator:

Mark A. Altabet (University of Massachusetts Dartmouth SMAST, UMASSD-SMAST)

BCO-DMO Data Manager:

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

Project:

GEOTRACES Peru-Tahiti Nitrogen Isotope Measurements (EPZT Nitrogen Isotopes)

U.S. GEOTRACES East Pacific Zonal Transect (GP16) (U.S. GEOTRACES EPZT)

Current State:

Final no updates expected

Version:

24 June 2016

Deployment Synonyms:

GP16, GEOTRACES EPZT, GEOTRACES East Pacific Zonal Transect (EPZT), GT13, 325020131025

Version Date:

2016-06-24

Data URL:

https://www.bco-dmo.org/dataset-deployment/650103/data

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Description

Nitrate isotope data from the US GEOTRACES EPZT cruise.

Methods & Sampling

Dataset acquisition description

Sampling: Full depth and super station samples were collected from the ship's rosette. Samples were filtered through 0.8/0.45 um acropak5 00 filter cartridges into triple-rinsed 60 mL HDPE bottles. Demi station samples were collected from the GETORACES 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 using the denitrifier method (Sigman et al., 2001; Casciotti, et al., 2001, with technical updates described by McIlvin and Casciotti, 2011). In the Casciotti Lab, Nitrate isotope reference materials USGS32 and USGS34 were used to calibrate d15N. Each sample was analyzed 2-6 times. Mean and standard deviations are reported for each sample. Samples were analyzed either on a DeltaPLUS XP or DeltaV PLUS isotope ratio mass spectrometer (IRMS), both with custom-built inlets 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-. Samples containing nitrate concentrations lower than 0.3 uM were not analyzed. Samples containing measurable NO2- concentrations were treated with sulfuric acid prior to analysis (Granger and Sigman, 2009).

Data Processing Description

Dataset Processing Description

Data 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 values to the atmospheric N2 reference scale (McIlvin and Casciotti, 2011).

BCO-DMO Processing:
- modified parameter names to conform with BCO-DMO naming conventions;
- replaced blanks (no data) with 'nd';
- replaced -999 with 'nd';
- joined to EPZT master file (details below).

Additional GEOTRACES Processing by BCO-DMO:
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.

More information about this dataset deployment

Funding

Award Number	Funding Source
OCE-1233339	NSF Division of Ocean Sciences

Instruments

GO-FLO Teflon Trace Metal Bottle

Supplied Name: Go-Flo

Supplied Description:

Instrument Type

Generic Name: GO-FLO Teflon Trace Metal Bottle

Acronym: GO-FLO Teflon TM

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

Generic Description:

GO-FLO Teflon-lined Trace Metal free sampling bottles are used for collecting water samples for trace metal, nutrient and pigment analysis. The GO-FLO sampling bottle is designed specifically 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 Name: IRMS

Supplied Description:

Samples were analyzed either on a DeltaPLUS XP or DeltaV PLUS isotope ratio mass spectrometer (IRMS).

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).

Parameters

Supplied Name	Supplied description	Supplied Units	Standard Name
cruise_id	Cruise identification	unitless	cruise_id
STNNBR	Station number; values added from the EPZT master file.	unitless	station
GEOTRC_EVENTNO	GEOTRACES event number; values added from the EPZT master file.	unitless	event
CASTNO	Cast number; values added from the EPZT master file.	unitless	cast
ISO_DATETIME_UTC_START_EVENT	Date and time, formatted to the ISO 8601 standard, at the start of the sampling event, according to the event log. In the format YYYY-MM-DDTHH:MM:SS[.xx]Z	unitless	ISO_DateTime_UTC
EVENT_LAT	Latitude at the start of the event (according to the event log); north is positive; values added from the EPZT master file.	decimal degrees	lat
EVENT_LON	Longitude at the start of the event (according to the event log); east is positive; values added from the EPZT master file.	decimal degrees	lon
GEOTRC_INSTR	Sampling instrument; values added from the EPZT master file.	unitless	instrument
GEOTRC_SAMPNO	Unique GEOTRACES sample number	unitless	sample
DEPTH_PI	Sampling depth, provided by the PI.	meters	depth
NO3_15_D_DELTA_BOTTLE	Average nitrate delta 15N, reported in units of permil vs. atmospheric N2.	permil	dN15_NO3
NO3_15_D_DELTA_BOTTLE_STDEV	Standard deviation of nitrate delta 15N analysis, reported in units of permil vs. atmospheric N2.	permil	std_dev
num_of_analyses	The number of replicates analyzed for a given sample.	dimensionless	num_reps
NO3_15_D_DELTA_BOTTLE_FLAG	NO3_15_D_DELTA_BOTTLE quality flag. 1 indicates that the sample was treated with sulfamic acid ; 2 indicates that the nitrate concentration of the sample was too low for delta 15N analysis ; 3 indicates that no sample was collected.	dimensionless	flag
SAMPNO	Sequential sample number within the cast (usually corresponds to bottle number); values added from the EPZT master file.	unitless	bottle
BTLNBR	Bottle number; typically 1-24; values added from the EPZT master file.	unitless	bottle
BTLNBR_FLAG_W	Bottle number quality flag; follows WOCE conventions. 2 = good; 3 = questionable; 4 = bad; 9 = missing data; values added from the EPZT master file.	unitless	flag
BTL_ISO_DATETIME_UTC	Date and time, formatted to the ISO 8601 standard, at the time of bottle firing; values added from the EPZT master file.	YYYY-MM-DDTHH:MM:SS[.xx]Z	ISO_DateTime_UTC
BTL_LAT	Latitude of bottle firing; north is positive; values added from the EPZT master file.	decimal degrees	lat
BTL_LON	Lonitude of bottle firing; east is positive; values added from the EPZT master file.	decimal degrees	lon
ODF_CTDPRS	The ODF software acquisition measurement of pressure; values added from the EPZT master file.	decibars	press
SMDEPTH	Saunders-Mantyla depth (integrated; uses dynamic height); values added from the EPZT master file.	meters	depth
FMDEPTH	Fofonoff-Millard depth (non-integrated; also used by SBE); values added from the EPZT master file.	meters	depth
BTMDEPTH	Bottom depth; values added from the EPZT master file.	meters	depth_bottom
CTDPRS	CTD pressure; values added from the EPZT master file.	decibars	press
CTDDEPTH	CTD bottle firing depth; values added from the EPZT master file.	meters	depth

Database

Contribute Data

Dataset: GP16 d15N NO3
Deployment: TN303

Dataset acquisition description

Dataset Processing Description

Database

Contribute Data

Dataset: GP16 d15N NO3Deployment: TN303

Dataset acquisition description

Dataset Processing Description

Dataset: GP16 d15N NO3
Deployment: TN303