Dataset: Underway O2 Ar
Deployment: RB-08-02

Underway O2 Ar

Principal Investigator:

Roberta C. Hamme (University of Victoria, UVic)

Co-Principal Investigator:

Dr Michael L. Bender (Princeton University)

Dr Nicolas Cassar (Duke University)

Contact:

Burke Hales (Oregon State University, OSU-CEOAS)

BCO-DMO Data Manager:

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

Project:

Southern Ocean Gas Exchange Experiment (SO_GasEx)

Current State:

Preliminary and in progress

Version:

14 October 2013

Deployment Synonyms:

RB0802, RHB_SO-GasEx

Version Date:

2013-10-14

Data URL:

https://www.bco-dmo.org/dataset-deployment/456151/data

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Description

Dataset Description:
Final Underway Oxygen/Argon, Oxygen concentration, and associated productivity calculations

Operation Description:
Continuous analysis of oxygen/argon ratios by equilibrator inlet mass spectrometry (EIMS) and oxygen concentrations by optode on the underway seawater line.

Methods & Sampling

Dataset acquisition description

Overall Sampling Strategy:
Plan was to collect mass spectrometry and optode data continuously from the underway seawater system, except for tracer injection and brief service intervals. Calibration was to be performed vs. discrete samples from the surface on every CTD cast and from the underway system at other times to create a calibration point ever 6-12 hours.

Continuous Sample Collection:
Flow of seawater to the EIMS and optode was controlled by a small ball valve to about 3-5 L/min. Seawater flowed through a coarse filter and into a 1L plastic graduated cylinder. A flow of 100mL/min was withdrawn from the graduated cylinder through a fine sock-shaped filter using a small pump. The rest of the seawater flow exited through holes in the side of the graduated cylinder into a bucket the cylinder was immersed in. This bucket drained from its halfway point to a sink draining directly into the sea. The smaller flow was pumped through a small Liquicel equilibrator cartridge and then through a flow meter and finally discharged to the bucket. The equilibrator cartridge was immersed in the bucket to provide temperature stabilization. A capillary picked off gas from the equilibrator cartrige and sent it through a valco switching valve to the quadrupole mass spectrometer for analysis. The switching valve allowed for direct sampling of lab air by a second capillary of similar length. The optode was immersed at the top of the graduated cylinder near the overflow holes. Seven thermistors measured water and air temperatures.

Data Processing Description

Dataset Processing Description

Analytical method:
Quadrupole mass spectrometer is Michael Bender's second instrument, a Pfeiffer Vacuum Prisma. Ion currents measured at masses 18, 28, 29, 32, 40, 44, 45, 64 as well as pressure within mass spectrometer. Inlet capillary switched from equilibrator to air for 10 minutes of every 2 hours for calibration. Quadrupole housing made from PVC pipe with heater and fan controlled at 50oC. Temperature within housing and of electronics unit continuously monitored. Small pump is a Micropump GA-V21.J8FTC. Flowmeter is a McMillan 101 Flo-Sen. Equilibrator cartridge is Membrana LiquiCel MicroModule G569 with flow-through water but only one air-side inlet/outlet. Optode was borrowed from Mike DeGrandpre's group and is model 4175 with analog converter. Ship's electronic's technician made a cable for it which is read by both an RS232 and by the Omega AtoD converter. Tenma EX354D dual power supply 280W suppling 8-8.5V to run the small pump and 12.3V to power the optode. Omega OMB-DAQ-56 AtoD converter being used to read seven thermistors, small pump flow rate, and optode analog signals. Flowmeter calibration applied is 100.39*signal - 5.64. All tubing in air upstream of equilibrator cartridge was insulated with gasketing material to slow warming of water. Capillary is 0.05mm fused silica tubing, catalog 602038 Grace Davison Discovery Science. Capillary length from valco valve to mass spec about 1.15m, capillary lengths from equilibrator cartridge to valco valve and from air to valco valve about 0.85m and closely matched. Air capillary tucked into cable tie or bungee cord holding mass spec housing together. Valco valve is 6 port Cheminert C5 HPLC stream connector valve with microelectric actuator. Used FS1.3-5 ferrules at beginning of cruise and switched to FS1.4-5 ferrules on March 15.

Calculations:
O2/Ar ion currents during each 10-min air standard sampling were averaged together and then interpolated to each water sample time. O2/Ar sat was calculated as the ratio of the ion current for the equilibrator divided by that for the air standard (minus one, and times 100). Data was then binned on one-minute intervals. O2/Ar saturations were corrected for observed offsets from the discrete samples based on an average offset derived for each equilibrator. Optode O2 values were calibrated against discrete O2 detemined by Winkler titration following Uchida et al. (2008). Note that timestamp is only accurate within ~2 minutes as computer clock drifted badly and had to be continually reset to ship's timeserver. Net community oxygen production is calculated from the O2/Arsat data, T, S, and a weighted gas exchange rate. This value approximates the NOP of the mixed layer over 10 days prior to the measurement of O2/Ar. For gas exchnage, we use the Reuer et al. (2007) wind speed weighting over 60 days prior to the measurement using combined QuikSCAT/NCEP wind speeds and the Ho et al. (2006) gas exchange parameterization. For more details see Hamme, R. C., et al. (2012), Dissolved O2/Ar and other methods reveal rapid changes in productivity during a Lagrangian experiment in the Southern Ocean, J. Geophys. Res., 117, C00F12, doi:10.1029/2011JC007046.

BCO-DMO Processing Notes
Original file: "Hamme2012_underway.csv" contributed by Roberta Hamme
Metadata file: "Metadata_report_UnderwayMassSpec_Final.xls" contributed by Roberta Hamme
- year, month, date combined into a single date field formatted as YYYYMMDD
- hour, minute combined into a single time field formatted as HHMM
- Parameter names edited to conform to BCO-DMO parameter naming conventions

More information about this dataset deployment

Funding

Award Number	Funding Source
328290-2006	National Sciences and Engineering Research Council of Canada
NNX08AF12G	National Aeronautics & Space Administration
PLR-0636744	NSF Antarctic Sciences
unknown SO_GasEx NOAA	National Oceanic and Atmospheric Administration

Instruments

Equilibrator Inlet Mass Spectrometer

Supplied Description:

Continuous analysis of oxygen/argon ratios by equilibrator inlet mass spectrometry (EIMS)

Liquicel equilibrator cartridge - Equilibrator cartridge is Membrana LiquiCel MicroModule G569 with flow-through water but only one air-side inlet/outlet.

Instrument Type

Generic Name: Equilibrator Inlet Mass Spectrometer

Acronym: EIMS

Generic Description:

Cassar N, Barnett BA, Bender ML, Kaiser J, Hamme RC, Tilbrook B., Continuous high-frequency dissolved O2/Ar measurements by equilibrator inlet mass spectrometry. Anal Chem. 2009 Mar 1;81(5):1855-64. doi: 10.1021/ac802300u.

Source: Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA. ncassar@princeton.edu

Abstract
The oxygen (O(2)) concentration in the surface ocean is influenced by biological and physical processes. With concurrent measurements of argon (Ar), which has similar solubility properties as oxygen, we can remove the physical contribution to O(2) supersaturation and determine the biological oxygen supersaturation. Biological O(2) supersaturation in the surface ocean reflects the net metabolic balance between photosynthesis and respiration, i.e., the net community productivity (NCP). We present a new method for continuous shipboard measurements of O(2)/Ar by equilibrator inlet mass spectrometry (EIMS). From these measurements and an appropriate gas exchange parametrization, NCP can be estimated at high spatial and temporal resolution. In the EIMS configuration, seawater from the ship's continuous intake flows through a cartridge enclosing a gas-permeable microporous membrane contactor. Gases in the headspace of the cartridge equilibrate with dissolved gases in the flowing seawater. A fused-silica capillary continuously samples headspace gases, and the O(2)/Ar ratio is measured by mass spectrometry. The ion current measurements on the mass spectrometer reflect the partial pressures of dissolved gases in the water flowing through the equilibrator. Calibration of the O(2)/Ar ion current ratio (32/40) is performed automatically every 2 h by sampling ambient air through a second capillary. A conceptual model demonstrates that the ratio of gases reaching the mass spectrometer is dependent on several parameters, such as the differences in molecular diffusivities and solubilities of the gases. Laboratory experiments and field observations performed by EIMS are discussed. We also present preliminary evidence that other gas measurements, such as N(2)/Ar and pCO(2) measurements, may potentially be performed with EIMS. Finally, we compare the characteristics of the EIMS with the previously described membrane inlet mass spectrometry (MIMS) approach.

PMID: 19193192 [PubMed - indexed for MEDLINE]

Flow Meter

Supplied Name: McMillan 101 Flo-Sen

Supplied Description:

Flowmeter is a McMillan 101 Flo-Sen

Instrument Type

Generic Name: Flow Meter

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/388/

Generic Description:

General term for a sensor that quantifies the rate at which fluids (e.g. water or air) pass through sensor packages, instruments, or sampling devices. A flow meter may be mechanical, optical, electromagnetic, etc.

Mass Spectrometer

Supplied Name: Quadrupole mass spectrometer - A Pfeiffer Vacuum Prisma

Supplied Description:

Quadrupole mass spectrometer is Michael Bender's second instrument, a Pfeiffer Vacuum Prisma.

Instrument Type

Generic Name: Mass Spectrometer

Acronym: Mass Spec

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB16/

Generic Description:

General term for instruments used to measure the mass-to-charge ratio of ions; generally used to find the composition of a sample by generating a mass spectrum representing the masses of sample components.

Optode

Supplied Description:

Optode was borrowed from Mike DeGrandpre's group and is model 4175 with analog converter

Instrument Type

Generic Name: Optode

Generic Description:

An optode or optrode is an optical sensor device that optically measures a specific substance usually with the aid of a chemical transducer.

Pump

Supplied Name: Micropump GA-V21.J8FTC

Supplied Description:

Small pump is a Micropump GA-V21.J8FTC

Instrument Type

Generic Name: Pump

Generic Description:

A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid: direct lift, displacement, and gravity pumps

Pump - Surface Underway Ship Intake

Supplied Name: Pump - surface underway ship intake

Supplied Description:

Plan was to collect mass spectrometry continuously from the underway seawater system, except for tracer injection and brief service intervals.

Instrument Type

Generic Name: Pump - Surface Underway Ship Intake

Acronym: Pump-Ship Intake

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

Generic Description:

The 'Pump-underway ship intake' system indicates that samples are from the ship's clean water intake pump. This is essentially a surface water sample from a source of uncontaminated near-surface (commonly 3 to 7 m) seawater that can be pumped continuously to shipboard laboratories on research vessels. There is typically a temperature sensor near the intake (known as the hull temperature) to provide measurements that are as close as possible to the ambient water temperature. The flow from the supply is typically directed through continuously logged sensors such as a thermosalinograph and a fluorometer. Water samples are often collected from the underway supply that may also be referred to as the non-toxic supply. Ideally the data contributor has specified the depth in the ship's hull at which the pump is mounted.

Thermistor

Supplied Description:

Seven thermistors measured water and air temperatures.

Instrument Type

Generic Name: Thermistor

Generic Description:

A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements.

Thermistors differ from resistance temperature detectors (RTD) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a higher precision within a limited temperature range, typically 90C to 130C.

Parameters

Supplied Name	Supplied description	Supplied Units	Standard Name
date	date (UTC)	YYYYMMDD	date
time	time (UTC)	HHMMSS	time
latitude	latitude; negative denotes South	decimal degrees	lat
longitude	longitude; negative denotes West	decimal degrees	lon
sal	underway salinity from data by David Drapeau measured on a nearby SBE45 but corrected for observed CTD/underway offsets; except used salinity measurement from pCO2 system when Drapeau data was unavailable	PSS-78	sal
O2_conc	O2 concentration determined from optode	umol/kg	O2
O2_Arsat	O2/Ar supersaturation measured directly but nominally = ((O2/Ar)actual / (O2/Ar)equil - 1)*100	percentage	no_bcodmo_term
Net_O2_community_production_based_on_prior_O2_Ar	NOP = kw * O2/Arsat * [O2]equil * density	mmol O2 /m2/d	no_bcodmo_term
weighted_gas_exchange_coefficient_used_for_productivity_calcs	kw	m/d	no_bcodmo_term
mixed_layer_depth_used_for_gas_exchange_weighting	mixed layer depth for determining kw	meters	depth_mixed_layer

Database

Contribute Data

Dataset: Underway O2 Ar
Deployment: RB-08-02

Dataset acquisition description

Dataset Processing Description

Database

Contribute Data

Dataset: Underway O2 ArDeployment: RB-08-02

Dataset acquisition description

Dataset Processing Description

Dataset: Underway O2 Ar
Deployment: RB-08-02