BOREAS TF-11 SSA Fen 1996 Water Surface Film Capping Data Summary The BOREAS TF-11 team gathered a variety of data to complement their tower flux measurements collected at the SSA Fen site. The data described in this document were made by the TF-11 team at the SSA Fen site to quantify the effect that the films observed to form on open water surfaces had on the transfer of carbon dioxide and methane from the water to the air. Measurements of fluxes of carbon dioxide and methane were made in 1994 and in 1996 using the chamber flux method. A gas chromatograph and a LI-COR LI-6200 were used to measure concentrations and to calculate the fluxes. The data are stored 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 TF-11 SSA Fen 1996 Water Surface Film Capping Data 1.2 Data Set Introduction This data set was collected by the Tower Flux-11 (TF-11) team at the BOReal Ecosystem-Atmosphere Study (BOREAS) Southern Study Area (SSA) Fen site to quantify the effect that the films observed to form on open water surfaces had on the transfer of carbon dioxide and methane from the water to the air. Measurements of fluxes of carbon dioxide and methane were made in 1994 and in 1996 using the chamber flux method. A gas chromatograph (GC) and a LI-COR LI- 6200 were used to measure concentrations and to calculate the fluxes. 1.3 Objective/Purpose The objectives of this study were to quantify the effect of the film that forms on the water surface of the SSA Fen on fluxes of carbon dioxide and methane and to investigate the growth dynamics of the film after it has been broken up or destroyed. 1.4 Summary of Parameters In this study, fluxes of carbon dioxide and methane were measured as functions of the time since the film was removed from the water surface. These measurements allowed the investigator to determine how much the film inhibited fluxes from the water surface and how quickly it reformed. 1.5 Discussion During the Intensive Field Campaigns (IFCs) of the 1994 BOREAS campaign, the TF- 11 team noticed that an oily-looking film formed on the surface of standing water in the SSA Fen. Initially, this film was very thin and resembled an oil slick. With time, the film grew thicker and lost the rainbow-like interference colors associated with new, thin films. We also noticed during IFC-2 that during periods of rain, the instantaneous concentrations of methane and carbon dioxide showed large spikes, and that after the rain, the fluctuations were much larger than before the rain. This led us to speculate that the film was "capping" the water surface and causing an excess of dissolved gases (compared to a clean surface). The rain caused the film to break up, releasing the excess gas. Further, the agitation of the surface caused by the raindrop impacts caused even more gas to be released to the atmosphere. After the rain, the water surface was clean with no capping film, and gas continued to be released to the atmosphere at a rate in excess of that when a film was present. We attempted to test this hypothesis in 1994, using the components of the chamber flux system that we were employing for other parts of our program. In this experiment, we placed a flux chamber collar in an area of standing water and removed any vegetation above the water surface. The collar was left undisturbed for several days until a thick film had formed in it. We then carefully placed a flux chamber over the collar and collected syringe samples according to our standard sampling protocol. After this first flux measurement, the chamber was removed and the film was gently "blotted" away from the surface with paper towels. The chamber was then replaced on the collar, and a second set of syringe samples was collected. The fluxes of methane and carbon dioxide calculated from these samples indeed showed that the film was affecting the movement of material to and from the surface. In 1996, we mounted a low- intensity effort to further quantify this effect and to explore the regrowth dynamics of the film. A LI-COR LI-6200 portable photosynthesis analyzer and a LI-COR 1-liter soil flux chamber were used to measure carbon dioxide fluxes from the water surface (at the SSA Fen site) as a function of time since removal of the film. A GC was also set up to attempt to measure the effect of the film on methane, but problems with the GC limited this effort to only one set of carbon dioxide and methane fluxes. 1.6 Related Data Sets BOREAS TF-11 SSA Fen Tower Flux and Meteorological Data BOREAS TF-11 SSA Fen Leaf Gas Exchange Data BOREAS TF-11 SSA Fen Soil Surface CO2 Flux Data BOREAS TF-11 SSA Fen 1995 Leaf Area Index Data 2. Investigator(s) 2.1 Investigator(s) Name and Title Dr. David P. Billesbach Center for Laser Analytical Studies of Trace Gas Dynamics University of Nebraska-Lincoln Dr. Shashi B. Verma, Professor Department of Agricultural Meteorology University of Nebraska-Lincoln 2.2 Title of Investigation Field Micrometeorological Measurements, Process-Level Studies and Modeling of Methane and Carbon Dioxide Fluxes in a Boreal Wetland Ecosystem (SSA Fen) 2.3 Contact Information Contact 1 ----------- Dr. David P. Billesbach Center for Laser Analytical Studies of Trace Gas Dynamics Walter Scott Engineering Center University of Nebraska-Lincoln Lincoln, NE (402) 472-7961 (402) 472-4732 (fax) dbillesbach@crcvms.unl.edu Contact 2 ----------- David Knapp Raytheon ITSS NASA GSFC Greenbelt, MD (301) 286-1424 (301) 286-0239 (fax) David.Knapp@gsfc.nasa.gov 3. Theory of Measurements A LI-COR LI-6200 soil chamber was placed on polyvinylchloride (PVC) collars that were mounted in the fen such that the upper lip was just above the water surface. Soft foam tape ensured that a gas-tight seal was maintained. The soil chamber was a metal cylinder that had a volume of 1,149 cubic cm and a cross sectional area of 72.38 square cm. The larger chamber used for the GC measurements was a rectangular parallelepiped formed by aluminum angle pieces. The walls of the chamber were made of transparent Aclar plastic (impervious to carbon dioxide and methane). The chamber was 40.5 cm tall and 31.3 cm x 31.3 cm in cross-section. Like the LI-COR chamber, this too was sealed to a collar planted in the fen by soft foam and spring clamps. A small-diameter plastic tube with a syringe valve that extended through one of the corner structural pieces allowed for gas sampling. 4. Equipment 4.1 Sensor/Instrument Description The instruments used for this experiment were a LI-COR LI-6200 portable photosynthesis analyzer and a Shimadzu GC8 GC equipped with a Flame Ionization Detector (FID), a Shimadzu methanizer, a Shimadzu Chromatopak integrator, and a precision sample injection valve. The LI-6200 was used with a 1-liter soil flux chamber. 4.1.1 Collection Environment Measurements were made between 15:00 and 24:00 Greenwich Mean Time (GMT) (9:00 to 18:00 local time). No measurements were made during periods of rain. Air temperature in the LI-6200 chamber ranged between 17 °C and 27 °C. 4.1.2 Source/Platform The LI-6200 flux chamber was placed on PVC collars anchored into the peat with approximately 2 cm protruding above the water surface. The flux chambers used with the GC-FID instrument were mounted on stainless steel collars that were also fixed into the peat. 4.1.3 Source/Platform Mission Objectives Not applicable. 4.1.4 Key Variables Water surface flux of carbon dioxide and methane. 4.1.5 Principles of Operation The LI-6200 calculates carbon dioxide concentrations by measuring the amount of light absorbed in a narrow band around 4.2 microns. The GC-FID measures concentrations by first separating the components by diffusion through a column, then measuring the number of ions produced in a flame. Fluxes are calculated in both cases by measuring the time rate of change of the density of the component (as calculated from the concentration). 4.1.6 Sensor/Instrumentation Measurement Geometry The LI-6200 collars were located approximately 0.5 meters from either side of the main boardwalk, about 60 meters from the shore. Four collars were used. Collars 1, 2, and 3 were located on the south side of the boardwalk and collar 4 was on the north side. The bottom of collar 1 rested on moss, and the bottoms of the other collars were above the moss surface. Collar 3 was placed in an area where water was observed to flow from north to south. Collar 4 was suspended in deeper water, inside one of the GD-FID flux collars. The two GC- FID flux collars were similarly located, with one on the north side of the boardwalk and one on the south side. All above-surface vegetation was removed from all collars. 4.1.7 Manufacturer of Sensor/Instrument LI-COR, Inc. Environmental Division 4421 Superior Street Lincoln, NE 68504 USA (402) 467-3576 http://www.licor.com/ Shimadzu Scientific Instruments, Inc. 7102 Riverwood Drive Columbia, MD 21046 USA (410) 381-1227 http://www.shimadzu.com/ 4.2 Calibration The LI-6200 was calibrated by first allowing the instrument to warm up for 30 minutes. After this, the soil chamber was placed on a plastic-covered, flat surface to seal it off from the ambient atmosphere. The airflow was switched to pass through a soda lime "scrubber" column, and analyzed. The instrument offset was then adjusted to read zero. The scrubber was then bypassed, and gas from a calibrated cylinder (348.6 ppmv) was introduced into the chamber with a 1/4" diameter tube. The instrument span was then adjusted to match the cylinder concentration value. The procedure was then repeated to verify the calibration. The GC-FID was calibrated by allowing it to warm up for 30 minutes and then injecting calibration gas. The calibration gas used was a 50% mixture of a precision calibration mix (Scott Gases 1% carbon dioxide and 1% methane) with ambient air. The results from two injections were averaged, and calibration coefficients were automatically calculated by the GC-FID system. After this procedure, several injections of the same calibration mixture were measured to ensure instrument stability. 4.2.1 Specifications None. 4.2.1.1 Tolerance The carbon dioxide fluxes measured with the LI-6200 are believed to have error bars of between 10% and 20% of the flux value. 4.2.2 Frequency of Calibration The LI-6200 was calibrated in the morning, before measurements began. At mid- day the calibration was checked and adjusted if necessary. Finally, at the end of the day, the calibration was checked again. The GC-FID was calibrated before sample analysis, and the calibration was checked after all samples had been analyzed. 4.2.3 Other Calibration Information The LI-6200 had been returned to the manufacturer for maintenance and calibration the month prior to the 1996 field experiment. 5. Data Acquisition Methods Carbon dioxide fluxes were measured by setting the LI-6200 soil chamber on a collar and initiating a measurement on the main unit. The chamber was sealed to the collar with a ring of soft foam. Two to five flux measurements were first made with a mature (older than 12 hours), intact film on the water surface. After this, the film was carefully removed from the water surface by blotting it up with a paper towel. Another set of two to five flux measurements was made from this "clean" surface. The ratio of the means of these measurements indicates the amount of "capping" caused by the mature film. After clean surface measurements were made, further measurements were made at fixed time intervals, ranging from 30 seconds to 2 hours. The soil flux chamber was removed from the collar between measurements to prevent the excessive build up of carbon dioxide inside the chamber. In this way, all flux measurements were made at carbon dioxide concentrations that were near ambient levels. Samples for analysis with the GC-FID were collected by clamping the flux chamber to the collar and extracting 60-ml gas samples with a Teflon syringe. Samples were taken every 5 minutes for 30 minutes. Because of the lengthy sampling procedure, only "intact" and "clean" fluxes were measured by this technique. The ratio of intact to clean carbon dioxide fluxes was compared to that obtained with the LI-6200 as a crosscheck of data. 6. Observations 6.1 Data Notes It is believed that data from LI-6200 collar 3 are the most reliable. This is based on better day-to-day reproducibility. 6.2 Field Notes Planned time sequence fluxes were interrupted on 25-Jul-1996, 26-Jul-1996, and 27-Jul-1996. 7. Data Description 7.1 Spatial Characteristics This experiment made point source flux measurements at the SSA Fen site, at essentially four closely spaced locations. 7.1.1 Spatial Coverage The LI-6200 flux measurements were for collar areas of 72.4 square cm. The GC-FID flux measurements were for collar areas of 979.7 square cm. 7.1.2 Spatial Coverage Map Collar locations relative to the boardwalk leading to the tower are described in Section 4.1.6. The North American Datum of 1983 (NAD83) coordinates of the SSA-Fen tower are: Latitude Longitude BOREAS_X BOREAS_Y UTM Northing UTM Easting ------------------------------------------------------------------------- 53.80206N 104.61798W 419.527 330.991 5961566.6 525159.8 7.1.3 Spatial Resolution Not applicable. 7.1.4 Projection Not applicable. 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Data were collected between 24-Jul-1996 and 30-Jul-1996 (middle of IFC-2 in 1996). A single GC-FID measurement was made on 14-Sep-1994 (during IFC-3 in 1994). 7.2.2 Temporal Coverage Map None. 7.2.3 Temporal Resolution Carbon dioxide flux measurements were made with the LI-6200 on time scales that ranged from 30 second intervals to 6 hour intervals. Each GC-FID flux measurement took 30 minutes. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (tf11sflm.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (tf11sflm.def). 8. Data Organization 8.1 Data Granularity All of the SSA Fen 1996 Water Surface Film Capping Data are contained in one data set. 8.2 Data Formats The data file contains 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 (tf11sflm.def). 9. Data Manipulations 9.1 Formulae A.) Fluxes computed by the LI-6200 internal software assumed an area of 1 square cm, and were in units of micromoles/square meter/second. The investigators divided by the actual area of the flux chamber (72.38 square cm) and multiplied by 44 micrograms/micromole to arrive at units of micrograms/square meter/second. BOREAS Information System (BORIS) staff divided these values by 44 to convert the values back to micromoles/square meter/second. B.) Concentrations were calculated by the GC-FID software. A standard least squares linear regression was applied to these points (as a function of time) to calculate the time rate of change of the concentration inside the chamber. 9.1.1 Derivation Techniques and Algorithms A.) Initial fluxes were calculated by the LI-6200 software and were corrected in the Quattro-Pro V4.0 spreadsheet. B.) Concentrations were calculated by the GC-FID software and slopes were calculated both with a hand calculator and in the Quattro-Pro V4.0 spreadsheet 9.2 Data Processing Sequence 9.2.1 Processing Steps WATER SURFACE FILM CONCENTRATION 1. TF-11 collected concentration data from the GC-FID and entered them into a spreadsheet. 2. TF-11 ran a linear regression routine in the data. 3. BORIS received the data from TF-11 and loaded it into the data base. WATER SURFACE FILM FLUX 1. TF-11 collected data from the LI-6200 output files and entered them into a spreadsheet. 2. TF-11 applied correction factors. 3. Averages of the fluxes were calculated. 4. BORIS received the data from TF-11 and loaded them into the data base. 9.2.2 Processing Changes None. 9.3 Calculations 9.3.1 Special Corrections/Adjustments See Section 9.1. 9.3.2 Calculated Variables Carbon dioxide fluxes and average fluxes Time rates of change of methane and carbon dioxide concentration. 9.4 Graphs and Plots None. 10. Errors 10.1 Sources of Error The main source of flux errors in the LI-6200 data come from cracks induced in the film while placing the flux chamber on the collars. The main source of slope errors in the GC-FID data are from errors in the sampling time. 10.2 Quality Assessment 10.2.1 Data Validation by Source The two types of carbon dioxide data (LI-6200 and GC-FID) were validated by comparing the ratios of clean to intact fluxes (or slopes). In addition, the LI-6200 data were validated by repetition. 10.2.2 Confidence Level/Accuracy Judgment The comparison (LI-6200 to GC-FID) of carbon dioxide data showed that the two methods yielded similar results. This leads us to believe that the methane data (from the GC-FID) are also reliable. We found that when we plotted LI-6200 fluxes (from the same collar) as a function of time since cleaning, data from different days fell on the same curve. 10.2.3 Measurement Error for Parameters We believe that carbon dioxide fluxes measured with the LI-6200 are accurate to between 10% and 20%. 10.2.4 Additional Quality Assessments None. 10.2.5 Data Verification by Data Center BORIS loaded the data into the data base and checked for any inconsistencies during loading. 11. Notes 11.1 Limitations of the Data These data are not representative of the entire Fen site. They are from an extremely limited area. 11.2 Known Problems with the Data Not all of the GC-FID samples from 24-Jul-1996 analyzed correctly, although enough did work to obtain slopes that agree with those obtained in 1994. 11.3 Usage Guidance Because of the limited spatial coverage, the flux data should be used only to examine the effect of the film on fluxes. 11.4 Other Relevant Information None. 12. Application of the Data Set These data can be used to better understand the role of oily film on carbon dioxide flux. This oily film is commonly found on the water surface of fens. 13. Future Modifications and Plans None. 14. Software 14.1 Software Description None given. For specific questions regarding the software mentioned in Section 9.1, please contact Dr. David Billesbach. 14.2 Software Access None given. 15. Data Access 15.1 Contact for Data Center/Data Access Information These BOREAS data are available from the Earth Observing System Data and Information System (EOS-DIS) 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 15.2 Procedures for Obtaining Data BOREAS data may be obtained through the ORNL DAAC World Wide Web site at http://www-eosdis.ornl.gov/ or users may place requests for data by telephone, electronic mail, or fax 15.3 Output Products and Availability Requested data can be provided electronically on the ORNL DAAC's anonymous FTP site or on various media including, CD-ROMs, 8-MM tapes, or diskettes. The complete set of BOREAS data CD-ROMs, entitled "Collected Data of the Boreal Ecosystem-Atmosphere Study", edited by Newcomer, J., et al., NASA, 1999, are also available. 16. Output Products and Availability 16.1 Tape Products None. 16.2 Film Products None. 16.3 Other Products These data are available on the BOREAS CD-ROM series. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation Shimadzu GC-8 Users Guide Shimadzu Chromatopak Users Guide LI-COR LI-6200 Users Guide 17.2 Journal Articles and Study Reports Puustjarvi, V. 1952. The Precipitation of Iron in Peat Soils. Acta Agralia Fennica, 78, 1-72. 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., 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 early results from the 1994 field year. Bulletin of the American Meteorological Society, 76(9):1549-1577. Sellers, P.J., F.G. Hall, R.D. Kelly, A. Black, D. Baldocchi, J. Berry, M. Ryan, K.J. Ranson, P.M. Crill, D.P. Lettenmaier, H. Margolis, J. Cihlar, J. Newcomer, D. Fitzjarrald, P.G. Jarvis, S.T. Gower, D. Halliwell, D. Williams, B. Goodison, D.E. Wickland, and F.E. Guertin. 1997. BOREAS in 1997: Experiment Overview, Scientific Results and Future Directions. Journal of Geophysical Research, 102 (D24): 28,731-28,770. 17.3 Archive/DBMS Usage Documentation None. 18. Glossary of Terms None. 19. List of Acronyms ASCII - American Standard Code for Information Interchange BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System DAAC - Distributed Active Archive Center DOY - Day of the Year EOS - Earth Observing System EOSDIS - EOS Data and Information System GC-FID - Gas Chromatograph-Flame Ionization Detector GMT - Greenwich Mean Time GSFC - Goddard Space Flight Center IFC - Intensive Field Campaign NAD83 - North American Datum of 1983 NASA - National Aeronautics and Space Administration ORNL - Oak Ridge National Laboratory PPMV - Parts Per Million by Volume PVC - Polyvinylchloride SSA - Southern Study Area TF - Tower Flux URL - Uniform Resource Locator UTM - Universal Transverse Mercator 20. Document Information 20.1 Document Revision Date Written: 16-Jun-1997 Last Revised: 10-May-1999 20.2 Document Review Date(s) BORIS Review: 25-Apr-1999 Science Review: 20.3 Document ID 20.4 Citation Dr. D.P. Billesbach Center for Laser Analytical Studies of Trace Gas Dynamics University of Nebraska-Lincoln 20.5 Document Curator 20.6 Document URL Keywords: CARBON DIOXIDE METHANE TF11_Surf_Film_Cap.doc 06/09/99