Dataset: GN01 CFC and SF6
Deployment: HLY1502

Concentrations of CFC-11, CFC-12, CFC-113 and SF6 in seawater

Principal Investigator:

David T. Ho (University of Hawaii, UH)

William M. Smethie Jr. (Lamont-Doherty Earth Observatory, LDEO)

Technician:

Eugene Gorman (Lamont-Doherty Earth Observatory, LDEO)

Benjamin Hickman (University of Hawaii, UH)

Data Manager:

Hoyle Lee (Lamont-Doherty Earth Observatory, LDEO)

BCO-DMO Data Manager:

Nancy Copley (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Project:

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

US GEOTRACES Arctic Section - Water mass composition, circulation and mean residence times derived from measurements of natural and manmade tracers (GT-Arctic Tracer Circulation)

Deployment Synonyms:

GN01, U.S. GEOTRACES Arctic, 32H120150809

Version Date:

2016-10-24

Data URL:

https://www.bco-dmo.org/dataset-deployment/643172/data

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Description

Concentrations of CFC-11, CFC-12, CFC-113 and SF6 in seawater from the Artic section of the US-GEOTRACES project.

CFC-11 CCl3F trichlorofluoromethane pmol/kg (10^-12 moles/kg)
CFC-12 CCl2F2 dichlorodifluoromethane pmol/kg
CFC-113 C2Cl3F3 1,1,2-trichlorotrifluloroethane pmol/kg
SF6 sulfur hexafluoride fmol/kg (10^-15 moles/kg)

Methods & Sampling

Dataset acquisition description

Water samples for CFC and SF6 measurements were collected using either a 12-place 30-liter bottle rosette or a 36-place 10-liter bottle rosette. The CFC/SF6 sample was the first sample drawn from the rosette bottle. The samples were collected in a 500 cc glass stoppered bottle through a PVC tube connected to the rosette bottle drain valve. Bubbles were cleared from the tube with water flowing and the tube was inserted to the bottom of the 500 cc glass bottle. The glass bottle was placed in a wide mouth plastic jar that extended above the opening of the glass bottle by 4 cm. The overflow water collected in the jar, filling and overflowing the jar and covering the glass bottle opening. The flow continued for 3 overflow volumes of the glass bottle (1.5 liters) and the glass stopper was then inserted underwater preventing air from being trapped in the sample. The jar was then capped and the sample stored at room temperature until measurement, which was within 8 hours of collection. The measurements were carried out using a dual purge and trap system interfaced to a dual ECD (electron capture detector) HP6890 gas chromatograph. When a water sample is introduced into the system, it is split into two aliquots, a 20 cc aliquot for CFC measurement and a 350 cc aliquot for SF6 measurement. The aliquots are transferred to appropriately sized sparging chambers and stripped with ultra high purity nitrogen, which transports the extracted gases to cold traps (Unibeads-2s for CFCs, Carboxan-1000 for SF6) cooled to -80°C. The traps are then heated to 110°C for CFCs and 165°C for SF6 and flushed into the gas chromatograph where CFCs are separated with a Porasil-B pre-column and a Carbograph 1AC main column and SF6 is separated with a pre-column and main column of Molecular Sieve 5A. The gases are detected by the ECDs. The ECDs are calibrated by running gas standards with known concentrations of CFCs and SF6. Duplicate samples are collected and measured to provide a combined precision for sampling and measurement. The average differences from these duplicate measurements was the larger of 0.005 pmol/kg or 0.5% for CFC-11, 0.008 pmol/kg or 1.1% for CFC-12, 0.005 pmol/kg for CFC-113 and 0.02 fmol/kg or 1.5% for SF6.

Data Processing Description

Dataset Processing Description

The gas chromatograph produces a peak for each compound being measured. Each chromatogram is digitally acquired on a PC and the peak areas integrated with software developed specifically for this purpose. Calibration curves relating peak area to concentration are generated using the gas standard data and this information is used to convert peak areas for the samples to concentrations. Blanks and reference standards are run about every 2 hours to provide data to correct for detector drift and blanks. After completion of the cruise, plots of the CFCs and SF6 against each other and against hydrographic variables are prepared to determine trends in the data and identify questionable data. Questionable data are checked for possible data processing errors, sampling problems, equipment problems, etc. Mistakes are corrected and samples judged to be bad measurements are flagged as such. The WOCE flagging convention is used. The gas standard used was prepared by Dr. John Bullister of NOAA/PMEL specifically for the CLIVAR Repeat Hydrography program; CFC concentrations are reported on the SIO98 calibration scale and SF6 concentrations on the SIO2005 calibration scale.

BCO-DMO Processing Notes:
2016-04-22: initially served data
2016-10-24: changed parameter names from F11, F12, F113 to CFC-11, CFC-12, CFC113
2017-05-24: dataset made publicly available

More information about this dataset deployment

Funding

Award Number	Funding Source
OCE-1436125	NSF Division of Ocean Sciences
OCE-1436666	NSF Division of Ocean Sciences

Instruments

Automated Purge and Trap System

Supplied Name:

Supplied Description:

Instrument Type

Generic Name: Automated Purge and Trap System

Generic Description:

This equipment removes dissolved gases from the water samples, traps the extracted compounds on a cold trap and then heats the trap and injects the trapped gases into the gas chromatograph. It is automated and controlled by a laptop computer.

Gas Chromatograph

Supplied Name:

Supplied Description:

Dual ECD (electron capture detector) HP6890 gas chromatograph

Instrument Type

Generic Name: Gas Chromatograph

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB02/

Generic Description:

Instrument separating gases, volatile substances, or substances dissolved in a volatile solvent by transporting an inert gas through a column packed with a sorbent to a detector for assay. (from SeaDataNet, BODC)

Niskin bottle

Supplied Name:

Supplied Description:

Two rosettes were used, one with 30-l bottles and one with 10-l 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

Supplied Name	Supplied description	Supplied Units	Standard Name
cruise_id	Cruise identification	unitless	cruise_id
station	Station Number	unitless	station
cast	Cast number	unitless	cast
GEOTRC_EVENTNO	GEOTRACES Event Number. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	unitless	event
sample	GEOTRACES sample number	unitless	sample
BTLNBR	Bottle number. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	unitless	bottle
mon	Month	1-12	month
day	UTC day	1-31	day
year	Year	yyyy	year
lat	Latitude of bottle firing; north is positive. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	decimal degrees	lat
lon	Lonitude of bottle firing; east is positive. Values were added from the intermediate US GEOTRACES master file (see Processing Description).	decimal degrees	lon
depth_w	Water depth	meters	depth_w
PRES_R	Pressure	decibars	press
TEMP	Temperature	degrees Celsius	temp
CTDSAL	Salinity from the CTD	PSU	sal_ctd
SALT	Salinity from bottle	PSU	sal_bottle
CTDO2	Oxygen concentration from CTD	ml/l	O2
OXYCTD_umol_kg	Oxygen concentration from CTD	umol/kg	O2
O2_ml_l	Oxygen concentration from bottle	ml/l	O2_ml_L
BTLOXY_umol_kg	Oxygen concentration from bottle	umol/kg	O2
SIO3_CONC	SiO3 silicate concentration	umol/kg	Silicate
NO3_CONC	NO3 nitrate concentration	umol/kg	NO3
NO2_CONC	NO2 nitrite concentration	umol/kg	NO2
PO4_CONC	PO4 phosphate concentration	umol/kg	PO4
F11_CONC	CCl3F trichlorofluoromethane	pmol/kg (10-12 moles/kg)	no_bcodmo_term
FLAG_F11	WOCE quality flag: 2 = good; 3 = questionable; 4 = bad; 9 = missing dat	unitless	q_flag
F12_CONC	CCl₂F₂ dichlorodifluoromethane	pmol/kg	no_bcodmo_term
FLAG_F12	WOCE quality flag: 2 = good; 3 = questionable; 4 = bad; 9 = missing dat	unitless	q_flag
F113_CONC	C₂Cl₃F₃ 1,1,2-trichlorotrifluloroethane	pmol/kg	no_bcodmo_term
FLAG_F113	WOCE quality flag: 2 = good; 3 = questionable; 4 = bad; 9 = missing dat	unitless	q_flag
SF6_CONC	SF6 sulfur hexafluoride	fmol/kg (10-15 moles/kg)	SF6
FLAG_SF6	WOCE quality flag: 2 = good; 3 = questionable; 4 = bad; 9 = missing dat	unitless	q_flag

Database

Contribute Data

Dataset: GN01 CFC and SF6
Deployment: HLY1502

Dataset acquisition description

Dataset Processing Description

Database

Contribute Data

Dataset: GN01 CFC and SF6Deployment: HLY1502

Dataset acquisition description

Dataset Processing Description

Dataset: GN01 CFC and SF6
Deployment: HLY1502