BOREAS TGB-01 NSA SF6 Chamber Flux Data
Summary
The BOREAS TGB-01 team made sulfur hexaflouride (SF6) dark chamber flux
measurements at the NSA-OJP and NSA-YJP sites from 16-May through 13-Sep-1994.
Gas samples were extracted approximately every 7 days from dark chambers and
analyzed at the NSA lab facility. The data are provided in tabular ASCII files.
Table of Contents
* 1. Data Set Overview
* 2. Investigator(s)
* 3. Theory of Measurements
* 4. Equipment
* 5. Data Acquisition Methods
* 6. Observations
* 7. Data Description
* 8. Data Organization
* 9. Data Manipulations
* 10. Errors
* 11. Notes
* 12. Application of the Data Set
* 13. Future Modifications and Plans
* 14. Software
* 15. Data Access
* 16. Output Products and Availability
* 17. References
* 18. Glossary of Terms
* 19. List of Acronyms
* 20. Document Information
1. Data Set Overview
1.1 Data Set Identification
BOREAS TGB-01 NSA SF6 Chamber Flux Data
1.2 Data Set Introduction
Chamber flux measurements were taken at the BOReal Ecosystem Atmosphere Study
(BOREAS) Northern Study Area (NSA) Old Jack Pine (OJP) and Young Jack Pine (YJP)
sites during the summer of 1994. The purpose of these measurements was to
examine the trace gas exchange between the atmosphere and the boreal soils. The
following is a description of the acquisition of data and the final data sets.
1.3 Objective/Purpose
Chamber fluxes were measured at the OJP and YJP sites in the NSA to determine
the soil surface exchange rates of SF6.
1.4 Summary of Parameters
SF6 chamber fluxes were measured at the NSA OJP and YJP sites. Temperatures of
the chamber, 1-cm soil depth, and 10-cm soil depth were recorded at the OJP and
YJP sites.
1.5 Discussion
The chamber flux data included in SF6_flux.txt includes the SF6 tracer study
that was completed at the OJP and YJP aluminum chamber and collar sites.
1.6 Related Data Sets
Other data sets of interest are:
BOREAS team TGB01: CH4 Tower data from OJP : ojp_dat.txt
BOREAS team TGB01: CH4 Tower data from BP : bp_dat.txt
BOREAS team TGB01: CH4 and CO2 profile data: prof1dat.txt, prof2dat.txt, and
prof2dat.txt.
2. Investigator(s)
2.1 Investigator(s) Name and Title
Dr. Patrick M. Crill
Research Associate Professor
University of New Hampshire
2.2 Title of Investigation
Magnitude and Control of Trace Gas Exchange in Boreal Ecosystems
2.3 Contact Information
Contact 1
Dr. Patrick M. Crill
Institute for the Study of Earth, Oceans, and Space
Complex Systems Research Center
University of New Hampshire
Durham, NH
(603) 862-3519
(603) 862-0188 (fax)
Contact 2
Sadredin C. Moosavi
Graduate Student
Institute for the Study of Earth, Oceans, and Space
Complex Systems Research Center
University of New Hampshire
Durham, NH
(603) 862-2927
(603) 862-0188 (fax)
Contact 3
Ruth K. Varner
Research Scientist
Institute for the Study of Earth, Oceans, and Space
Complex Systems Research Center
University of New Hampshire
Durham, NH
(603) 862-2939
(603) 862-0188 (fax)
Contact 4
Sara K. Conrad
Raytheon STX Corporation
NASA/GSFC
Greenbelt, MD
(301) 286-2624
sgolight@pop900.gsfc.nasa.gov
3. Theory of Measurements
Not applicable.
4. Equipment
4.1 Sensor/Instrument Description
SF6 was quantified using a Shimadzu GC-8A Gas Chromatograph (GA) equipped with
an electron capture detector (ECD). The oven temperature during sample analysis
was run at 130 �C and the detector at 300 �C. Ultrahigh-purity 5% CH4/95% Argon
carrier gas was used at a flow rate through the columns of 30 mL/min. Analog
signals (0-1 V) from the detectors were digitized at 10 Hz with a Hewlett
Packard (HP) 35000D A/D board and quantified and logged using HP ChemStation
software. Chamber fluxes were accomplished with aluminum chambers manufactured
at the University of New Hampshire and designed by Patrick Crill.
4.1.1 Collection Environment
The chamber fluxes were collected under ambient conditions. The GC analysis was
completed at the Hayes Road Lab in Thompson, Manitoba.
4.1.2 Source/Platform
Ground.
4.1.3 Source/Platform Mission Objectives
The mission objective was to determine the diffusion rate of SF6 at OJP and YJP.
4.1.4 Key Variables
The key variables measured during the fluxes were SF6 diffusion rate and
temperature.
4.1.5 Principles of Operation
SF6 was quantified using a Shimadzu GC8A equipped with an ECD. When the carrier
gas, CH4-Ar, flows into a cell containing 63Ni, it is ionized by the radiation
from this radioisotope. When a pulsed voltage is applied across the cell
electrodes, an ion current flows.
When the carrier gas brings a sample into contact with the cell, the electron
affinitive compounds in the sample capture the free electrons and become
negative ions. These negative ions combine with positive ions in the flow and
subsequently decrease the ion concentration and therefore the current. This
change is measured by the detector and compared to a reference current, pure
carrier gas (Instruction Manual: GC-8A, Shimadzu Corporation, Kyoto, Japan).
4.1.6 Sensor/Instrument Measurement Geometry
Not applicable.
4.1.7 Manufacturer of Sensor/Instrument
Manufacturer of GC-14A FID/TCD, GC-MINI2, and GC-8A ECD
Shimadzu Scientific Instruments, Inc.
7102 Riverwood Drive
Columbia, MD 21046
(410) 381-1227
4.2 Calibration
Signal peaks from the detectors were quantified with working standards
calibrated against Canadian Atmospheric Environment Services (AES) certified
primary standards acquired by the BOREAS project. Uncertainty in the standards'
analyses on a given day ranged from 0.1 to 0.2%.
4.2.1 Specifications
Not applicable.
4.2.1.1 Tolerance
The sensitivity of the ECD is 0.2 pg for gamma BHC.
4.2.2 Frequency of Calibration
The instrument is calibrated on a daily basis. Standards are run generally
before and after samples on a given day of analysis.
4.2.3 Other Calibration Information
Not applicable.
5. Data Acquisition Methods
The chamber fluxes are determined by analysis of concentration of SF6 in a time
series of grab samples of headspace over the ground surface enclosed by a dark
aluminum chamber. At time zero, 5 mL of SF6 stock were added to the chamber
headspace. The stock mixture is 10 �L SF6 diluted into 60 ml of air so the
mixing ratio is approximately 167 ppmv SF6. The headspace concentration is
equal to about 12 ppbv after the injection of the stock. The volume of the two
aluminum chambers was 0.071 and 0.120 m3 over an area of 0.397 m2. The aluminum
chamber was placed on the trough of an aluminum collar embedded in the ground.
Water was added to the trough of the collar to create an airtight seal. The
volume of the plastic chambers was 0.028 m3 over an area of 0.078 m2. The seal
between the chamber and collar was made using weather stripping or water as
appropriate. Five 60-mL samples were removed from the headspace with
polypropylene syringes and polycarbonate/nylon stopcocks at 4 minute intervals
for 20 minutes (five samples). Samples were returned to the Hayes Road. lab and
analyzed for SF6 using gas chromatography within 12 hours after collection.
6. Observations
6.1 Data Notes
None given.
6.2 Field Notes
None given.
7. Data Description
7.1 Spatial Characteristics
Not applicable.
7.1.1 Spatial Coverage
NSA OJP: (55.92842� N, 98.62396� W)
NSA YJP: (55.89575� N, 98.28706� W)
7.1.2 Spatial Coverage Map
Not applicable.
7.1.3 Spatial Resolution
These are point source measurements.
7.1.4 Projection
Not applicable.
7.1.5 Grid Description
Not applicable.
7.2 Temporal Characteristics
7.2.1 Temporal Coverage
The chamber fluxes were taken approximately every 7 days from 16-May-1994
through 13-Sep-1994.
7.2.2 Temporal Coverage Map
Not applicable.
7.2.3 Temporal Resolution
Not applicable.
7.3 Data Characteristics
Data characteristics are defined in the companion data definition file
(tgb1sfd.def).
7.4 Sample Data Record
Sample data format shown in the companion data definition file (tgb1sfd.def).
8. Data Organization
8.1 Data Granularity
All of the Chamber Flux Data are contained in one dataset.
8.2 Data Format(s)
The data files contain numerical and character fields of varying length
separated by commas. The character fields are enclosed with single apostrophe
marks. There are no spaces between the fields. Sample data records are shown in
the companion data definition file (tgb1sfd.def).
9. Data Manipulations
9.1 Formulae
Rf = Cstd / Astd
Cs = Rf * As
Rf = Response factor
Astd = Average of 10 standard peak areas
Cstd = Concentration of the standard
Cs = Concentration of the sample
As = Peak area of sample
SF6 concentrations were calculated from the average of 10 peak areas of known
SF6 standards. The response factor was calculated as the concentration of the
known standard divided by the average of 10 standard peak areas. The peak area
of the unknown sample was multiplied by the response factor.
The SF6 rate (K) value was calculated by fitting a linear regression to the ln
(natural logarithm) of the concentrations of SF6 versus time. The regressions
of the time series were expected to have an r2 of greater than 0.85.
If -888 is present in the data set, it indicates that a measurement was taken
but discarded for some reason. If -999 is present, then no data were taken.
9.1.1 Derivation Techniques and Algorithms
The K value measured for SF6 is used to determine the rate of diffusion of CH4
and CO2 to the soil surface. The relationship can be seen from the following
equation:
Dsf6/((msf6)1/2) = Di/((mi)1/2)
(Trumbore, 1995 and Rolston, 1991)
Where :
Dsf6 = measured diffusion of SF6
msf6 = molecular weight of SF6 (146 g/mol)
Di = unknown diffusion of substance i (CH4 or CO2)
mi = molecular weight of substance i (CH4 = 16 g/mol; CO2 = 44 g/mol)
From this information, given a known starting concentration of CO2 and CH4, one
can calculate the diffusive flux to the surface:
Di * dCi/dz = Fd
(Trumbore, 1995)
Where:
DCi/dz = soil profile of gas i
Fd = diffusive flux
See Rolston, 1991 and Trumbore, 1995 for more detailed explanation of the
methods and theory.
9.2 Data Processing Sequence
9.2.1 Processing Steps
None given.
9.2.2 Processing Changes
None.
9.3 Calculations
Not applicable.
9.3.1 Special Corrections/Adjustments
Not applicable.
9.3.2 Calculated Variables
Not applicable.
9.4 Graphs and Plots
None.
10. Errors
10.1 Sources of Error
The analytical precision of the GC's is: 0.2% for CH4 and 1% for CO2.
10.2 Quality Assessment
10.2.1 Data Validation by Source
None given.
10.2.2 Confidence Level/Accuracy Judgment
None given.
10.2.3 Measurement Error for Parameters
The analytical precision of the GC's is: 0.2% for CH4 and 1% for CO2.
10.2.4 Additional Quality Assessments
None given.
10.2.5 Data Verification by Data Center
Data were examined for general consistency and clarity.
11. Notes
11.1 Limitations of the Data
The analytical precision of the GC's is: 0.2% for CH4 and 1% for CO2.
11.2 Known Problems with the Data
None given.
11.3 Usage Guidance
None given.
11.4 Other Relevant Information
Not applicable.
12. Application of the Data Set
None given.
13. Future Modifications and Plans
This data set is in its final format.
14. Software
14.1 Software Description
Not applicable.
14.2 Software Access
Not applicable.
15. Data Access
15.1 Contact Information
Ms. Beth McCowan
BOREAS Data Manager
NASA GSFC
Greenbelt, MD
(301) 286-4005
(301) 286-0239 (fax)
beth@ltpmail.gsfc.nasa.gov
15.2 Data Center Identification
See Section 15.1.
15.3 Procedures for Obtaining Data
Users may place requests by telephone, electronic mail, or fax.
15.4 Data Center Status/Plans
These data are available from the Earth Observing System Data and Information
System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive
Center (DAAC). The BOREAS contact at ORNL is:
ORNL DAAC User Services
Oak Ridge National Laboratory
(865) 241-3952
ornldaac@ornl.gov
ornl@eos.nasa.gov
16. Output Products and Availability
16.1 Tape Products
None.
16.2 Film products
None.
16.3 Other Products
Comma separated ASCII files.
17. References
17.1 Platform/Sensor/Instrument/Data Processing Documentation
None.
17.2 Journal Articles and Study Reports
Bubier, J.L., T.R. Moore, L. Bellisario, N.T. Comer and P.M. Crill. 1995.
Ecological controls on methane emissions from a northern peatland complex in the
zone of discontinuous permafrost. Manitoba, Canada. Global Biogeochemical
Cycles 9: 455-470.
Crill, P. M., K.B. Bartlett, R.C. Harriss, E. Gorham, E.S. Verry, D.I. Sebacher,
L. Madzer, and W. Sanner. 1988. Methane flux from Minnesota peatlands. Global
Biogeochemical Cycles, 2, 371-384.
Daubenmire, R.F. 1968. Plant communities: a textbook of plant synecology.
Harper and Row, New York, NY.
Moore, T.R. and N.T. Roulet. 1991. A comparison of dynamic and static chambers
for methane emission measurements from subarctic fens. Atmosphere-Ocean, 29,
102-109.
Rolston, D.E., R.D. Glauz, G.L. Grundman, and D.T. Louie, Evaluation of an in
situ method for measurement of gas diffusivity in surface soils, Soil Science
Society of America Journal, 55, 1536-1542, 1991.
Roulet, N., S. Hardill, and N. Comer. 1991 Continuous measurement of the depth
of water table (inundation) in wetlands with fluctuating surfaces. Hydrological
Processes, 5, 399-403.
Roulet, N.T. 1991. Surface level and water table fluctuations in a subarctic
fen. Arctic and Alpine Research, 23, 303-310.
Sjors, H. 1950. On the relation between vegetation and electrolytes in Swedish
mire waters. Oikos, 2, 241-258.
Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment
Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94).
Sellers, P. and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment
Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96).
Sellers, P. and F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue (in
press).
Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere
Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94).
Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere
Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96).
Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J.
Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J. Ranson, D. Lettenmaier, and D.E.
Wickland. 1995. The boreal ecosystem-atmosphere study (BOREAS): an overview and
earlyresults from the 1994 field year. Bulletin of the American Meteorological
Society. 76(9):1549-1577.
Sellers, P., F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue (in press).
Trumbore, S.E., Use of isotopes and tracers in the study of emissions and
consumption of trace gases in terrestrial environments, in Biogenic Trace Gases:
Measuring Emissions from Soil and Water, edited by P.A. Matson, and R.C.
Harriss, pp. 291-326, Blackwell, Oxford, 1995.
17.3 Archive/DBMS Usage Documentation
None.
18. Glossary of Terms
None.
19. List of Acronyms
AES - Atmospheric Environment Services
BOREAS - BOReal Ecosystem-Atmosphere Study
BORIS - BOREAS Information System
BP - Beaver Pond
CMDL - Climate Monitoring and Diagnostics Laboratory
DAAC - Distributed Active Archive Center
ECD - Electron Capture Detector
EOS - Earth Observing System
EOSDIS - EOS Data and Information System
FID - Flame Ionization Detector
GC - Gas Chromatograph
GSFC - Goddard Space Flight Center
NASA - National Aeronautics and Space Administration
NSA - Northern Study Area
OBS - Old Black Spruce
OJP - Old Jack Pine
ORNL - Oak Ridge National Laboratory
PANP - Prince Albert National Park
SSA - Southern Study Area
TCD - Thermal Conductivity Detector
TGB - Trace Gas Biogeochemistry
URL - Uniform Resource Locator
YJP - Young Jack Pine
20. Document Information
20.1 Document Revision Date
Written:
Last Updated: 20-Jul-1998
20.2 Document Review Date(s)
BORIS Review: 4-Mar-1998
Science Review:
20.3 Document ID
20.4 Citation
20.5 Document Curator
20.6 Document URL
Keywords
Methane flux
Carbon dioxide flux
Trace Gas
TGB01_SF6.doc
08/18/98