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 ßC and the detector at 300 ßC. 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 µL 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: (55.92842ß N, 98.62396ß W) NSA YJP: (55.89575ß N, 98.28706ß 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