Dataset: GT10 - Nanomolar Nutrients - Surface
Deployment: KN199-04

Nanomolar concentrations of PO4, NO3, NO2 (surface)

Principal Investigator:

Gregory A. Cutter (Old Dominion University, ODU)

Contact:

Gregory A. Cutter (Old Dominion University, ODU)

BCO-DMO Data Manager:

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

Project:

U.S. GEOTRACES North Atlantic Transect (GA03) (U.S. GEOTRACES NAT)

Current State:

Final no updates expected

Version:

03 May 2011

Deployment Synonyms:

GA03, GT10, USGT-NAT-2010, KN199-4, GNAT, U.S. GEOTRACES NAZT Leg 1, knorr199-4/5, Section Cruise (GA03), 316N20101015

Version Date:

2013-02-27

Data URL:

https://www.bco-dmo.org/dataset-deployment/454532/data

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Description

Nanomolar concentrations of PO4, NO3, NO2 - Surface Transects.

Methods & Sampling

Dataset 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

Data Processing Description

Dataset 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)

BCO-DMO Processing Notes:
- Generated from original spreadsheet file "GEOTRACES Knorr199-4 and -5 nanomolar nutrients.xls", sheet: "surface" contributed by Greg Cutter
- Parameter names modified to conform to BCO-DMO convention
- cruise_id added
- date/time reformatted to date as YYYYMMDD
- date/time reformatted to time as HHMM
- longitude values converted to negative (West)
- "nd" (no data flag) inserted into blank cell
- added ISO_DateTime_UTC based on the original date and time fields

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 deployment

Funding

Award Number	Funding Source
OCE-0926092	NSF Division of Ocean Sciences
OCE-0926423	NSF Division of Ocean Sciences

Instruments

GeoFish Towed near-Surface Sampler

Supplied Name: GeoFish

Supplied Description:

Instrument Type

Generic Name: GeoFish Towed near-Surface Sampler

Acronym: GeoFish

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/31/

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).

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) in the format YYYYMMDD	unitless	date
time	time (GMT)	HHMM	time
lat	Station latitude (South is negative)	decimal degrees	lat
lon	Station longitude (West is negative)	decimal degrees	lon
GeoFish_id	Identifying number of a GeoFish tow, numbered consecutively within a cruise. PI-supplied values were identical to those in the intermediate US GEOTRACES master file. Originally submitted as 'Fish_ID', this parameter name has been changed to conform to BCO-DMO's GEOTRACES naming conventions.	integer	sample
GeoTraces_ID	Unique identifiers for ALL vertical profile samples (and surface fish samples when we arrive on station, or depart).	integer	dataset_id
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
Remarks	Remarks	text	activity_and_comments
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
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. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	dimensionless	sample
ISO_DateTime_UTC	Date/Time (UTC) formatted to ISO8601. T indicates start of time string; Z indicates UTC. Calculated from the original date and time fields.	YYYY-mm-ddTHH:MM:SS.ssZ	ISO_DateTime_UTC

Database

Contribute Data

Dataset: GT10 - Nanomolar Nutrients - Surface
Deployment: KN199-04

Dataset acquisition description

Dataset Processing Description

Database

Contribute Data

Dataset: GT10 - Nanomolar Nutrients - SurfaceDeployment: KN199-04

Dataset acquisition description

Dataset Processing Description

Dataset: GT10 - Nanomolar Nutrients - Surface
Deployment: KN199-04