Dataset: GT10 - Nanomolar Nutrients - Profiles

Name: PO4, NO3, NO2 concentrations along the US GEOTRACES North Atlantic Transect from the R/V Knorr KN199-04 cruise in the subtropical N. Atlantic during 2010 (U.S. GEOTRACES NAT project)
Published: 2013-03-14
License: https://creativecommons.org/licenses/by/4.0/
Keywords: oceans

Cite This Dataset

Project:

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

Principal Investigator:

Gregory Cutter (Old Dominion University, ODU)

Contact:

Gregory Cutter (Old Dominion University, ODU)

BCO-DMO Data Manager:

Stephen R. Gegg (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version Date:

2013-03-14

Validated:

Yes

Current State:

Final no updates expected

Data URL:

https://www.bco-dmo.org/dataset/3521/data

PO4, NO3, NO2 concentrations along the US GEOTRACES North Atlantic Transect from the R/V Knorr KN199-04 cruise in the subtropical N. Atlantic during 2010 (U.S. GEOTRACES NAT project)

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Description

Nutrients - Nanomolar concentrations of PO4, NO3, NO2 - depth profiles for most stations.

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

Filtered (0.4 µm) water samples from the Geotraces surface tow-fish and water from the upper 200 m water column (GEOTRACES Carousel/GoFlo system) 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

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.

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).

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.

BCO-DMO Processing Notes
- Generated from original spreadsheet file "GEOTRACES Knorr199-4 and -5 nanomolar nutrients.xls", sheet: "St. 1-12 depth profile" contributed by Greg Cutter
- Parameter names modified to conform to BCO-DMO convention
- cruise_id added
- Cast, Type, Event, date and time added from cast and event logs
- longitude values converted to negative (West)
- "nd" (no data flag) inserted into blank cells
- Changed event number of sample 6000 from 'nd' to '2215'. (correct event number confirmed by GT10 event log).
- Corrected event number of sample 5622 from 2157 to 2171 (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-0926423
NSF Division of Ocean Sciences	OCE-0926092

Deployments

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

Instruments

GeoFish Towed near-Surface Sampler

(more info)

Short Name: GeoFish

Community Standard Description

Generic Description

The GeoFish towed sampler is a custom designed near surface (<2m) sampling system for the collection of trace metal clean seawater. It consists of a PVC encapsulated lead weighted torpedo and separate PVC depressor vane supporting the intake utilizing all PFA Teflon tubing connected to a deck mounted, air-driven, PFA Teflon dual-diaphragm pump which provides trace-metal clean seawater at up to 3.7L/min. The GeoFish is towed at up to 13kts off to the side of the vessel outside of the ship's wake to avoid possible contamination from the ship's hull. It was developed by Geoffrey Smith and Ken Bruland (University of California, Santa Cruz).

PI supplied instrument name: GeoFish

Dataset-specific description

GO-FLO Bottle

(more info)

Short Name: GO-FLO

Community Standard Description

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.

PI supplied instrument name: GO-FLO Bottle

Dataset-specific description

Niskin bottle

(more info)

Short Name: Niskin bottle

Community Standard Description

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.

PI supplied instrument name: Niskin bottle

Dataset-specific description

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
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.	text	station
Cast	Cast ID number; provided by PI in original data submission.	text	cast
Type	Cast Type. GT-C = GeoTraces Trace Metal Rosette; GeoF = GeoTraces towed 'GeoFish'.	text	unknown
date	Date (GMT)	YYYYMMDD	date
time	Time (GMT)	HHMMSS	time
lat	Station latitude (South is negative)	decimal degrees	lat
lon	Station longitude (West is negative)	decimal degrees	lon
depth	Depth; provided by PI in original data submission.	meters	depth
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.	integer	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
cast_GEOTRC	Cast identifier, numbered consecutively within a station. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	integer	cast
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).	integer	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
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
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
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', this parameter name has been changed to conform to BCO-DMO's GEOTRACES naming conventions.	integer	event

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Dataset: GT10 - Nanomolar Nutrients - Profiles