Dataset: GN01 Isotope ratios of N and O in nitrate

Name: Nitrate N and O isotope ratios from CTD niskin depth profiles collected along section HLY1502-GN01 in the Western Arctic Ocean from August to October 2015
Published: 2020-07-09
Keywords: oceans

Cite This Dataset

DOI:10.26008/1912/bco-dmo.733109.2

Spatial Extent: N:89.9876 E:179.1997 S:60.252 W:-179.8086

Temporal Extent: 2015-08-12 - 2015-10-05

Project:

Collaborative Research: GEOTRACES Arctic Ocean section-Constraining Nitrogen Cycling in the western Arctic Ocean. (US GEOTRACES Arctic Nitrogen Flux)

U.S. Arctic GEOTRACES Study (GN01) (U.S. GEOTRACES Arctic)

Program:

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

Principal Investigator:

Julie Granger (University of Connecticut, UConn)

BCO-DMO Data Manager:

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

Version:

Version Date:

2020-07-09

Restricted:

Validated:

Yes

Current State:

Final no updates expected

Nitrate N and O isotope ratios from CTD niskin depth profiles collected along section HLY1502-GN01 in the Western Arctic Ocean from August to October 2015

Abstract:

High precision measurements of Nitrogen (15N/14N) and Oxygen (18O/16O) isotope ratios in depth profiles along the GEOTRACES transect to the western Arctic Ocean (HLY1502-GN01) were made in order to trace nitrogen cycling in different parts of the basin and within different water masses. Nitrate isotope ratio analyses were performed by Richard Dabundo in the Granger Laboratory at the University of Connecticut.

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Archival Copy

Version Date	Archive	Persistent Identifier	Date Assigned
2020-07-09	Marine Biological Laboratory/Woods Hole Oceanographic Institution Library (MBLWHOI DLA)	10.26008/1912/bco-dmo.733109.2	2020-07-27

Description

Isotope ratios of N and O in nitrate from US GEOTRACES-Arctic cruise HLY1502 in 2015.

Methods & Sampling

Seawater samples for nitrate isotope analyses were filtered through a 0.2-um pore-size polyethersulfone membrane into pre-rinsed 60-ml high density polyethylene bottles and were stored frozen until analysis.

The naturally occurring isotope ratios of nitrogen (15N/14N) and oxygen (18O/16O) in nitrate (NO3-) were analyzed by the denitrifier method (Casciotti et al., 2002; Sigman et al., 2001). Briefly, 20 nmol of NO3- were quantitatively reduced to nitrous oxide (N2O) gas by denitrifying bacteria that lack an active terminal N2O reductase (P. chlororaphis f. sp. aureofaciens; ATCC #13985). The product N2O was analyzed by continuous flow isotope ratio mass spectrometry on a Thermo Delta V Advantage isotope ratio mass spectrometer interfaced with a purpose-built, gas chromatography-based device for N2O extraction, concentration, and purification (Casciotti et al., 2002; McIlvin & Casciotti, 2011). Nitrite (NO2-), which interferes with the NO3- isotope analyses, was removed from samples with sulfamic acid (Granger & Sigman, 2009) prior to analysis in the few samples where it was detected. Individual analyses were referenced to injections from a laboratory standard N2O tank and calibrated using the NO3- reference materials IAEA-N3 (4.7‰vs. N2 and 25.6‰vs. VSMOW; Böhlke et al., 2003; Gonfiantiniet al., 1995) and U.S. Geological Survey-34 (+1.8‰vs. N2; -27.9‰vs. VSMOW; Böhlke et al., 2003), with monitoring of reproducibility by analysis of an internal seawater NO3- standard from the deep North Atlantic. NO3- standards in individual runs were diluted in nutrient-free seawater to concentrations equivalent to those of samples to account for potential matrix effects on δ18ONO3 measurements (Weigand et al., 2016). In order to ensure measurement accuracy, samples were analyzed in duplicate within runs, for a minimum of three discrete runs, yielding average standard deviations of 0.2‰ for N and 0.3‰ for O, although with a lower precision averaging 0.4‰ for δ18ONO3 at lower NO3- concentrations (<10 μM).

Data Processing Description

BCO-DMO Processing:
- re-formatted time so values are all 4 digits;
- added date/time columns in ISO8601 format;
- renamed fields.

Data Files

File
Nitrate_Isotopes.csv (Comma Separated Values (.csv), 29.00 KB) MD5:f0c4659da394f07babbfccbd4807ce37 Primary data file for dataset ID 733109

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-1435002

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
HLY1502	GN01 U.S. GEOTRACES Arctic 32H120150809	2015-08-09	USCGC Healy	David C. Kadko (Chief Scientist) William M. Landing (Co-Chief Scientist)	data info

Instruments

Isotope-ratio Mass Spectrometer

Supplied Name: GC-IRMS

Supplied Description:

The product N2O was analyzed by continuous flow isotope ratio mass spectrometry on a Thermo Delta V Advantage isotope ratio mass spectrometer interfaced with a purpose-built, gas chromatography-based device for N2O extraction, concentration, and purification.

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:

Water samples from Niskin bottles were filtered through 0.2 µm pore-size PES membrane filter and stored frozen in acid-washed 60 mL HDPE bottles.

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
Station_ID	Station number	unitless	station
CASTNO	Cast number	unitless	cast
Start_Date_UTC	Sampling start date (UTC); format: YYYYMMDD	unitless	date
Start_Time_UTC	Sampling start time (UTC); format: hh:mm	unitless	time
Start_ISO_DateTime_UTC	Sampling start date/time (UTC) formatted to ISO8601 standard: YYYY-MM-DDThh:mmz	unitless	ISO_DateTime_UTC
End_Date_UTC	Sampling end date (UTC); format: YYYYMMDD	unitless	date
End_Time_UTC	Sampling end time (UTC); format: hh:mm	unitless	time
Start_Latitude	Sampling start latitude	decimal degrees North	lat
Start_Longitude	Sampling start longitude	decimal degrees East	lon
End_Latitude	Sampling end latitude	decimal degrees North	lat
End_Longitude	Sampling end longitude	decimal degrees East	lon
Event_ID	GEOTRACES event number	unitless	event
Sample_ID	GEOTRACES sample number	unitless	sample
Sample_Depth	Sample depth	meters (m)	depth
NITRATE_15_14_D_DELTA_BOTTLE_qwo9pn	Atom ratio of dissolved N isotopes in NITRATE expressed in conventional DELTA notation referenced to Air N2, samples may or may not have been filtered	per mil	no_bcodmo_term
SD1_NITRATE_15_14_D_DELTA_BOTTLE_qwo9pn	One standard deviation of NITRATE_15_14_D_DELTA_BOTTLE_qwo9pn	per mil	no_bcodmo_term
Flag_NITRATE_15_14_D_DELTA_BOTTLE_qwo9pn	Quality flag for NITRATE_15_14_D_DELTA_BOTTLE_qwo9pn	unitless	q_flag
NITRATE_18_16_D_DELTA_BOTTLE_qmffoc	Atom ratio of dissolved O isotopes in NITRATE expressed in conventional DELTA notation referenced to {VSMOW}, samples may or may not have been filtered	per mil	no_bcodmo_term
SD1_NITRATE_18_16_D_DELTA_BOTTLE_qmffoc	One standard deviation of NITRATE_18_16_D_DELTA_BOTTLE_qmffoc	per mil	no_bcodmo_term
Flag_NITRATE_18_16_D_DELTA_BOTTLE_qmffoc	Quality flag for NITRATE_18_16_D_DELTA_BOTTLE_qmffoc	unitless	q_flag

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Dataset: GN01 Isotope ratios of N and O in nitrate