Dataset: GN01 Sea Ice NO3 NH4 H2O
Deployment: HLY1502

Nitrate (NO3), ammonium (NH4), and oxygen & deuterium isotopic composition from sea ice collected on the US GEOTRACES Arctic cruise, HLY1502

Principal Investigator:

Meredith Hastings (Brown University)

Co-Principal Investigator:

Julie Granger (University of Connecticut, UConn)

BCO-DMO Data Manager:

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

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)

Current State:

Final no updates expected

Deployment Synonyms:

GN01, U.S. GEOTRACES Arctic, 32H120150809

Data URL:

https://www.bco-dmo.org/dataset-deployment/753425/data

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Description

This dataset contains nitrate and ammonium concentrations, as well as the complete isotopic composition of nitrate (d15N, d18O, D17O) and ammonium (d15N) and the oxygen & deuterium isotopic composition (d18O, dD) from sea ice collected during the U.S. GEOTRACES ARCTIC research cruise in 2015.

Methods & Sampling

Dataset acquisition description

Sea ice was collected using a trace metal clean Kovacs T-handle corer to collect 1 m long cores at 6 sea ice stations along the Canada Basin transect. Snow was collected into precleaned HDPE bottles, while seawater was pumped from beneath the sampled sea ice hole into a carboy and filtered into pre-cleaned bottles aboard the Healy. All samples were stored frozen until analyses or further sample prep could take place. Ice cores were bagged and stored at -20 degrees celsius onboard until cores could be cut and sub-sectioned in a cold room at University of Washington in Seattle prior to shipment back to Brown University.

Concentration analysis of samples was completed using an automated colorimetric system (WestCo SmartChem 200); the pooled standard deviation of control standards run within each sample set run was 0.3 micromoles per Liter (6.2 ppb nitrate); detection limit was 0.09 micromoles per Liter. Based upon nitrate concentration, 20 nmol of N were injected into vials containing denitrifying bacteria to convert nitrate to nitrous oxide for isotopic analysis on a ThermoFisher Delta V isotope ratio mass spectrometer. Analysis for d15N and d18O of nitrate are described in Sigman et al. (Analytical Chemistry; 2001), Casciotti et al. (Analytical Chemistry; 2002), McIlvin and Casciotti (Analytical Chemistry; 2011). Kaiser et al. (Analytical Chemistry; 2007) describes similar methodology for the determination of D17O of nitrate. D17O analyses require 50 nmol of N for complete analysis.

Data Processing Description

Dataset Processing Description

NOTES: Volume or concentration limitations prevented analysis of entire dataset for d15N, d18O and D17O. Subset of samples were measured for ammonium. Of those, only 1 sample had enough volume for isotopic analysis of d15N-NH4. Similarly a subset of samples were selected for water isotope analysis.

As described in Kaiser et al. (2007), isotopic data is corrected and standardized to international reference materials IAEA-N3, USGS34, and USGS35, which are run 3-9 times with each sample run. For d15N, samples are corrected for isobaric interferences and a blank associated with the bacteria. For d18O, samples are corrected for isobaric interferences, blank, and exchange between sample nitrate and background water that takes place during denitrification to nitrous oxide. The pooled standard deviation for the reference materials are (n=88): 0.2 per mil for d15N and 0.7 per mil for d18O of IAEA-N3; 0.3 per mil for d15N and 0.7 per mil for d18O of USGS34; and 0.7 per mil for d18O of USGS35 (sample d15N is not corrected for d15N of USGS35, this is used as an internal quality check and pooled standard deviation across all runs in 0.2 per mil). 10 samples were run in duplicate or triplicate and the paired pooled standard deviation (n=10) is 0.2 per mil for d15N and 0.4 per mil for d18O. Pooled standard deviation for USGS34 and USGS35 run for D17O is 0.6 and 0.9 per mil each (n=14 and 15, respectively), and replicate samples were 0.9 per mil (n=4).

Due to low sample volume and concentrations, only 3 samples were analyzed for d15N-NH4 using hypobromite oxidation to nitrite coupled with the denitrifier method (Felix et al., 2013; Zhang et al., 2007; Sigman et al., 2001). Briefly, ammonium is oxidized to nitrite with hypobromite, and nitrite is quantitatively converted to nitrous oxide with denitrifying bacteria. For the three samples with sufficient analyte, oxidations were conducted in triplicate. Samples were calibrated using ammonium reference materials USGS25 and IAEA-N2. Precision for d15N-NH4 of reference materials was ≤ 2.7 per mil and based on the standard deviation of reference replicates. The d15N-NH4 is then computed from the weighted difference from d15N-NO3.

Oxygen and hydrogen isotope ratios of water (d18O-H2O vs. VSMOW, dD-H2O vs. VSMOW) were measured using wavelength-scanned cavity-down ring spectroscopy on a Picarro L1102-I liquid analyzer calibrated to international reference standards USGS46, USGS49 and VSMOW. Raw data are corrected for memory and drift effects followed by normalization using a standard calibration (Vaughn and Claymoore, INSTAAR, University of Colorado). Precision for d18O and dD was better than ±0.1 and ±0.4 per mil, respectively, based upon repeated measures of an internal standard (BW-1).

BCO-DMO Processing:
- modified parameter names (replaced spaces with underscores);
- separated Dates_of_collection field into Date_Start and Date_End (yyyy-mm-dd).

More information about this dataset deployment

Funding

Award Number	Funding Source
OCE-1433989	NSF Division of Ocean Sciences
OCE-1435002	NSF Division of Ocean Sciences

Instruments

Discrete Analyzer

Supplied Name: WestCo SmartChem 200 discrete chemistry analyzer

Supplied Description:

Instrument Type

Generic Name: Discrete Analyzer

Generic Description:

Discrete analyzers utilize discrete reaction wells to mix and develop the colorimetric reaction, allowing for a wide variety of assays to be performed from one sample. These instruments are ideal for drinking water, wastewater, soil testing, environmental and university or research applications where multiple assays and high throughput are required.

Isotope-ratio Mass Spectrometer

Supplied Name: ThermoFisher Delta V isotope ratio mass spectrometer

Supplied Description:

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).

Picarro L1102-i Isotopic Water Liquid Analyzer

Supplied Name: Picarro L1102-I Liquid Analyzer

Supplied Description:

Instrument Type

Generic Name: Picarro L1102-i Isotopic Water Liquid Analyzer

Generic Description:

A portable analyzer designed for laboratories or field based isotope analysis. It uses Cavity Ring-Down Spectroscopy (CRDS) to measure the spectral signature of the molecule of interest. The instrument includes a closed-loop temperature and pressure control. The L1102-i can be used for analysis of liquid water only. It has a typical precision of 0.1 per mil for d18O and 0.5 per mil for dD.

Parameters

Supplied Name	Supplied description	Supplied Units	Standard Name
GEOTRC_SAMPNO	Geotraces Arctic Sample ID	unitless	sample
Dates_of_collection	Cruise collection dates in 2015, mm/dd/yy	unitless	date
Date_Start	Date at start of collection period. Format: yyyy-mm-dd	unitless	date_begin
Date_End	Date at end of collection period. Format: yyyy-mm-dd	unitless	date_end
Latitude	Latitude of collection; positive is North	decimal degrees	lat
Longitude	Longitude of collection; negative is West	decimal degrees	lon
Ice_Station	Collection station number	unitless	station
Sample_Type	Description of sample type (e.g. snow, sea ice, icehole, ice pond)	unitless	sample_type
Starting_Depth_cm	Depth at top of sea ice core section	centimeters (cm)	depth
Ending_Depth_cm	Depth at bottom of sea ice core section	centimeters (cm)	depth
Median_Depth_cm	Mid depth of core sections (or same as depth for non sea ice cores)	centimeters (cm)	depth
NITRATE_D_CONC _ICORE	Nitrate concentration	micromoles per Liter (umol/L)	NO3
NITRATE_15_14_D_DELTA_ICORE	delta 15N of nitrate	permil vs. atmospheric N2	dN15_NO3
NITRATE_18_16_D_DELTA_ICORE	delta 18O of nitrate	permil vs. VSMOW	d18O_NO3
NITRATE_17_16_D_DELTA_ICORE	capital delta 17O (D17O = d170-0.5*d18O) of nitrate	permil vs. VSMOW	D17O_NO3
AMMONIUM_D_CONC_ICORE	Ammonium concentration	micromoles per Liter (umol/L)	NH4
AMMONIUM_15_14_D_DELTA_ICORE	delta 15N of ammonium	permil vs N2	d15N
WATER_18_16_D_DELTA_ICORE	delta 18O of water	permil vs VSMOW	d18O
WATER_D_H_D_DELTA_ICORE	delta Deuterium of water	permil vs VSMOW	d2H

Database

Contribute Data

Dataset: GN01 Sea Ice NO3 NH4 H2O
Deployment: HLY1502

Dataset acquisition description

Dataset Processing Description

Database

Contribute Data

Dataset: GN01 Sea Ice NO3 NH4 H2ODeployment: HLY1502

Dataset acquisition description

Dataset Processing Description

Dataset: GN01 Sea Ice NO3 NH4 H2O
Deployment: HLY1502