Dataset: GT11 - Nanomolar Nutrients - Profiles

Name: Profiles of nanomolar Phosphate, Nitrate, and Nitrite concentrations from R/V Knorr cruise KN204-01 in the Subtropical North Atlantic Ocean in 2011 (U.S. GEOTRACES NAT project)
Published: 2013-03-14
Keywords: oceans

Cite This Dataset

Spatial Extent: N:39.41 E:-24.3 S:17.2399 W:-69.48

Project:

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

Program:

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

Principal Investigator:

Gregory Cutter (Old Dominion University, ODU)

Contact:

Gregory Cutter (Old Dominion University, ODU)

BCO-DMO Data Manager:

Theresa McKee (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

04 January 2013

Version Date:

2013-03-14

Validated:

Yes

Current State:

Final no updates expected

Data URL:

https://www.bco-dmo.org/dataset/3839/data

Profiles of nanomolar Phosphate, Nitrate, and Nitrite concentrations from R/V Knorr cruise KN204-01 in the Subtropical North Atlantic Ocean in 2011 (U.S. GEOTRACES NAT project)

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Description

Depth profiles of nanomolar concentrations of dissolved (<0.4 micromole) ortho-/reactive phosphate, nitrate, and nitrites for Stations 1, 2, 3, 5, 6, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, and 24.

Please note that some US GEOTRACES data may not be final, pending intercalibration results and further analysis. If you are interested in following changes to US GEOTRACES NAT data, there is an RSS feed available via the BCO-DMO US GEOTRACES project page (scroll down and expand the "Datasets" section).

Acquisition Description

Water samples were collected using the GEOTRACES Carousel/GoFlo system.

Filtered (0.4 µm) water samples from the upper 200 m water column were analyzed on an Astoria Pacific 300 series gas-segmented continuous flow nutrient auto-analyzer modified with 200 cm liquid waveguide capillary cells (LWCC; World Precision Instruments). Nitrate was reduced to nitrite using a Cd-column, then determined spectrophotometrically following formation of a highly colored dye, but slightly modified for use with a liquid core waveguide (see references below). Nitrite is measured separately without the Cd column and then subtracted from the combined nitrate+nitrite sample. The molybdenum blue method modified for use with liquid core wave guide was used for phosphate (references below).

Recovery for phosphate measurements for LWCC relative to the MAGIC method is 100 ± 15 % for concentrations below 100 nmol/L. The relative standard deviation for nine measurements of 5 nmol/L phosphate was 1.6 %. The relative standard deviation for nine measurements of 60 nM phosphate was 0.9 %. LWCC detection limit (3 x σ of blank) for phosphate was 0.5 nmol/L, 1.5 nmol/L for nitrate and 0.6 nmol/L for nitrite.

Upper working limit for LWCC:
Phosphate 100 nmol/L
Nitrate 200 nmol/L
Nitrite 200 nmol/L

Processing Description

Data Processing:
Nitrate = (Nitrate+nitrite) – nitrite

Samples were measured in triplicate (flag =6)

Samples out of linear calibration range for LWCC (flag = 10)

Related files and references:
Karl, D. M. and G. Tien (1992). "MAGIC: A sensitive and precise method for measuring dissolved phosphorus in aquatic environments." Limnology and Oceanography 37(1): 105-116.

Li, Q. P. and D. A. Hansell (2008). "Intercomparison and coupling of magnesium-induced co-precipitation and long-path liquid-waveguide capillary cell techniques for trace analysis of phosphate in seawater." Analytica Chimica Acta 611(1): 68-72.

Li, Q. P., D. A. Hansell, et al. (2008). "Underway monitoring of nanomolar nitrate plus nitrite and phosphate in oligotrophic seawater." Limnology and Oceanography: Methods 6: 319-326.

Murphy, J. and J. P. Riley (1962). "A modified single solution method for the determination of phosphate in natural waters." Analytica Chimica Acta 27: 31-36.

Patey, M. D., M. J. A. Rijkenberg, et al. (2008). "Determination of nitrate and phosphate in seawater at nanomolar concentrations." TrAC Trends in Analytical Chemistry 27(2): 169-182.

Zhang, J.-Z. (2000). "Shipboard automated determination of trace concentrations of nitrite and nitrate in oligotrophic water by gas-segmented continuous flow analysis with a liquid waveguide capillary flow cell." Deep Sea Research Part I: Oceanographic Research Papers 47(6): 1157-1171.

BCO-DMO Processing Note: Changed sample number of '6292' to '6192' per GT11 event log and correspondence with dataset contact person (14 March 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.

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-0926092

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
KN204-01	GT11 KN204-01A KN204-01B USGT-NAT-2011 USGNAZT GNAT 316N20111106 KN204-1 GA03	2011-11-06	R/V Knorr	Edward A. Boyle (Chief Scientist) Gregory Cutter (Co-Chief Scientist)	data info

Instruments

GO-FLO Bottle

Supplied Description:

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.

Nutrient Autoanalyzer

Supplied Description:

Instrument Type

Generic Name: Nutrient Autoanalyzer

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB04/

Generic Description:

Nutrient Autoanalyzer is a generic term used when specific type, make and model were not specified. In general, a Nutrient Autoanalyzer is an automated flow-thru system for doing nutrient analysis (nitrate, ammonium, orthophosphate, and silicate) on seawater samples.

Parameters

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
date	date (GMT)	YYYYMMDD	date
lat	Station latitude (South is negative)	decimal degrees	lat
lon	Station longitude (West is negative)	decimal degrees	lon
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
PO4	PO4: phosphate (reactive - or ortho-phosphate)	nmol/L	PO4
PO4_Flag	PO4 Data Flag: Samples were measured in triplicate (flag=6); Samples out of linear calibration range for LWCC (flag=10)	integer	flag
NO3	NO3: Nitrate = (Nitrate+nitrite) - nitrite	nmol/L	NO3
NO3_Flag	NO3 Data Flag: Samples were measured in triplicate (flag=6); Samples out of linear calibration range for LWCC (flag=10)	integer	flag
NO2	NO2: Nitrite	nmol/L	NO2
NO2_Flag	NO2 Data Flag: Samples were measured in triplicate (flag=6); Samples out of linear calibration range for LWCC (flag=10)	integer	flag
cruise_part	Part of cruise. For KN204-01: A = 11/6/2011 to 11/18/2011 (Woods Hole to Bermuda) B = 11/19/2011 to 12/11/2011 (Bermuda to Praia, Cabo Verde)	dimensionless	cruise_part
depth	depth of sample; provided by PI in original data submission.	meters	depth
station	station number; provided by PI in original data submission.	dimensionless	station
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. Some GeoFish stations are denoted as X_to_Y indicating the tow occurred between stations X and Y. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	dimensionless	station
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. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	dimensionless	event
cast_GEOTRC	Cast identifier, numbered consecutively within a station. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	dimensionless	cast
depth_GEOTRC_CTD	Observation/sample depth in meters, calculated from CTD pressure. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	meters	depth
sample_bottle_GEOTRC	Unique identification numbers given to samples taken from bottles; ranges from 1 to 24; often used synonymously with bottle number. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	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. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	dimensionless	bottle
BTL_ISO_DateTime_UTC	Date and time (UTC) variable recorded at the bottle sampling time 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-ddTHH:MM:SS.ssZ	ISO_DateTime_UTC

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Dataset: GT11 - Nanomolar Nutrients - Profiles