BOREAS TGB-12 222Rn Activity data over the NSA Summary: The BOREAS TGB-12 team made measurements of soil carbon inventories, carbon concentration in soil gases, and rates of soil respiration at several sites to estimate the rates of carbon accumulation and turnover in each of the major vegetation types. Sampling strategies for soils were designed to take advantage of local fire chronosequences, so that the accumulation of C in regrowing mosses could be determined. All the data are used to (1) calculate the inventory of C and N in moss and mineral soil layers at NSA sites (2) determine the rates of input and turnover (using both accumulation since the last stand-killing fire and radiocarbon data) and (3) link changes in soil respiration rate to shifts in the 14C content of soil CO2 to determine the average 'age' respired CO2. These 222Rn activity data were collected from 15-NOV-1993 to 16-AUG-1994 over the NSA sites. The data in this data set 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 TGB-12 222Rn Activity data over the NSA 1.2 Data Set Introduction This dataset contains seasonal variations in the 222Rn soil gas concentrations. The data presented represent sampling from the fall of 1993 to the summer of 1994. 1.3 Objective/Purpose The objective of these data are to estimate rates of carbon input, turnover, and accumulation in the soils of each of the major vegetation types at the BOREAS study sites. In addition, the data will be used to relate the estimates of soil carbon dynamics to ecosystem models of the carbon cycle, other measures of C cycling dynamics, regional models of soil carbon accumulation, and spatial and temporal models of soil moisture and drainage. 1.4 Summary of Parameters 222Rn Activity and soil depth were measured over the BOReal Ecosystem Atmosphere Study (BOREAS) Northern Study Area (NSA). 1.5 Discussion Carbon inventories together with 14C data determine C storage and the accumulation rate of C (in non-steady state systems), or the turnover rate of C (in systems where C turnover rate is less than soil or disturbance age). These data may be verified using the isotopic composition of respired CO2 (which will reflect the 14C content of root respiration and decomposing organic matter), and by the soil C inputs and losses. 1.6 Related Data Sets BOREAS TGB-12 CO2 Flux Data over the NSA BOREAS TGB-12 Soil Carbon Isotope Data over the NSA BOREAS TGB-05 Fire History Map in Raster Format BOREAS TE-18 LandSat Level 3 Land Cover Classification of NSA BOREAS AFM-12 Land Cover Classification from AVHRR BOREAS Regional Soils Data in Raster Format and AEAC Projection BOREAS Soils Data over the SSA in Raster Format and AEAC Projection BOREAS TGB-01 Soil CH4 and CO2 Profile Data over the NSA 2. Investigator(s) 2.1 Investigator(s) Name and Title Susan Trumbore Department of Earth System Science UC Irvine Jennifer Harden US Geological Survey Menlo Park, CA Eric Sundquist US Geological Survey Woods Hole, MA 2.2 Title of Investigation Input, Accumulation and Turnover of Carbon in BOREAS NSA soils (TGB-12) 2.3 Contact Information Contact 1 Jennifer Harden US Geological Survey Menlo Park, CA Phone: 415-329-4949 FAX: 415-329-4936 e-mail: harden@usgs.gov Contact 2 Susan Trumbore Department of Earth System Science University of California Irvine, CA Phone: 714-824-6142 FAX: 714-824-3256 e-mail: setrumbo@uci.edu Contact 3 Eric Sundquist US Geological Survey Woods Hole, MA Phone: 508-457-2397 e-mail: sundquist@nobska.wr.usgs.gov Contact 4 Greg Winston US Geological Survey Woods Hole, MA Contact 5 Sara K. Conrad Raytheon STX Corporation NASA/GSFC Greenbelt, MD (301)286-2624 (301)286-0239 (fax) Sara.Golightly@gsfc.nasa.gov 3. Theory of Measurements Special pits were instrumented with thermistors (for monitoring soil temperature), TDR probes (for monitoring soil water content), and soil gas probes (1/8" stainless steel tubing, perforated at one end and inserted 50 to 100 cm laterally into the soil pit wall, capped with 1/8" swagelock union fittings sealed with a septum). Further details are given in Winston et al. (submitted), and in section 4, below. 222Rn gas samples were obtained using gas-tight syringes, 60 cc, were dried (by passing through drierite), then allowed to fill an evacuated counting cell coated with phosphor scintillant and decay counted. A Description of radon sampling and analysis procedures is given in Davidson and Trumbore (1995). 4. Equipment: 4.1 Sensor/Instrument Description As all of the equipment used in this project is common to many other projects and no special procedures were used, we have minimized description detail in this section, and refer the reader to appropriate publications. Field equipment for soil collection was minimal, excepting the pH test kit (LaMotte). Drying ovens were supplied by the BOREAS project for the NSA labs. We brought our own scale, which was frequently checked using a calibration weight. Radon measurements were made using Pylon alpha scintillation counters. 4.1.1 Collection Environment Samples were collected under all environmental conditions. 4.1.2 Source/Platform Soil. 4.1.3 Source/Platform Mission Objectives The objective was to determine the soil 222Rn Activity. 4.1.4 Key Variables The key variables measured were 222Rn Activity and soil depth. 4.1.5 Principles of Operation None given. 4.1.6 Sensor/Instrument Measurement Geometry Not applicable. 4.1.7 Manufacturer of Sensor/Instrument None given. 4.2 Calibration Radon cell efficiencies were determined in the lab using background air and 226Ra of known activity absorbed to manganese fibers and sealed in a tube. Counting cell backgrounds were determined using ambient air (see Davidson and Trumbore, 1995, for details of radon measurement methods). 4.2.1 Specifications None given. 4.2.1.1 Tolerance None given. 4.2.2 Frequency of Calibration None Given. 4.2.3 Other Calibration Information None. 5. Data Acquisition Methods None Given. 6. Observations 6.1 Data Notes None given. 6.2 Field Notes None Given. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage The North American Datum 1983 (NAD83) coordinates of the sites were: Site Latitude Longitude ------ --------- ---------- NSA-OBS: 55.88007N 98.48139W NSA-OJP: 55.92842N 98.62396W NSA-YJP: 55.89575N 98.28706W NSA-Gillam Road: 55.9055 N 97.70872W 7.1.2 Spatial Coverage Map Not available. 7.1.3 Spatial Resolution None given. 7.1.4 Projection Not applicable. 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Soil gas flux and concentration measurements were made from Nov 1993 to Aug 1994. 7.2.2 Temporal Coverage Map Not applicable. 7.2.3 Temporal Resolution The temporal resolution of the measurements was variable. Some sites were visited once and other were visited multiple times. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (tgb12rad.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (tgb12rad.def). 8. Data Organization 8.1 Data Granularity All of the BOREAS TGB-12 222Rn Activity data over the NSA data are contained in one dataset. 8.2 Data Format(s) The 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 (tgb12rad.def). 9. Data Manipulations 9.1 Formulae 9.1.1 Derivation Techniques and Algorithms Methods for calculating radon and radiocarbon data are given in Davidson and Trumbore (1995) and Trumbore (1995). 9.2 Data Processing Sequence None given. 9.2.1 Processing Steps None given. 9.2.2 Processing Changes None given. 9.3 Calculations None given. 9.3.1 Special Corrections/Adjustments None given. 9.3.2 Calculated Variables None given. 9.4 Graphs and Plots None given. 10. Errors 10.1 Sources of Error Sources of error include inaccuracies in soil collection, instrument errors during running of samples. 10.2 Quality Assessment 10.2.1 Data Validation by Source Analyzing known-value standards as unknowns assesses errors in laboratory procedures. The accuracy of measurement is defined as the standard error of the mean of the analyses. Errors for bulk soil analyses are harder to estimate. The most uncertain terms are bulk density (largely due to uncertainties in horizon thickness). The calculation of grams/cm2 is therefore less prone to error than grams/cm3. We estimate the uncertainty in bulk density at approximately 10%, but it is difficult to ascertain as lateral and vertical heterogeneity is large (therefore a 'replicate' sample cannot truly be taken in the field). The error in bulk density will propagate through to other values, such as volumetric moisture content. There are many sources of error in flux measurements. The ones associated with our methods are detailed in Stephens et al (submitted). Errors involved in soil gas sampling include: the volume of soil air space sampled (500 cc to 1 liter) represents a far larger volume of soil. Thus the depth assigned to a soil gas sample (i.e. the depth of the probe) may not represent the average for the interval integrated in the gas sample taken from it (that is, air may be pulled down from above or up from below). We give only analytical errors in our data sets 10.2.2 Confidence Level/Accuracy Judgment For radon measurements, accuracy is 10% of the measured value, with most of the error due to uncertainty in the efficiency of the counting cell. 10.2.3 Measurement Error for Parameters For radon measurements, accuracy is 10% of the measured value, with most of the error due to uncertainty in the efficiency of the counting cell. 10.2.4 Additional Quality Assessments None. 10.2.5 Data Verification by Data Center Data was examined for general consistency and clarity. 11. Notes 11.1 Limitations of the Data None given. 11.2 Known Problems with the Data None given. 11.3 Usage Guidance None given. 11.4 Other Relevant Information None. 12. Application of the Data Set The data can be used for estimation of soil gas exchange rates from 222Rn data (or testing of soil gas exchange rates derived from models). 13. Future Modifications and Plans None given. 14. Software 14.1 Software Description Calculations of fluxes for radon used linear regression from programs like Microsoft Excel and Kaleidograph. 14.2 Software Access Software sold by Licor and Campbell was used with the IRGA and data loggers. 15. Data Access 15.1 Contact Information Ms. Beth Nelson BOREAS Data Manager NASA GSFC Greenbelt, MD (301) 286-4005 (301) 286-0239 (fax) Elizabeth.Nelson@gsfc.nasa.gov 15.2 Data Center Identification See 15.1. 15.3 Procedures for Obtaining Data Users may place requests by telephone, electronic mail, or FAX. 15.4 Data Center Status/Plans The TGB-12 Radon activity data are available from the EOSDIS ORNL DAAC (Earth Observing System Data and Information System) (Oak Ridge National Laboratory) (Distributed Active Archive Center). 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 with text delimited by single quotes (Î). 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation Not applicable. 17.2 Journal Articles and Study Reports Donahue, D. J., T. W. Linick and A. J. T. Jull, Isotope-ratio and background corrections for accelerator mass spectrometry radiocarbon measurements, Radiocarbon 32: 135-142 (1990). Goh, K. M., Carbon dating, chapter 8 (pp. 125 - 145), in, D. C. Coleman and B. Fry, Carbon isotope techniques, Academic Press, San Diego (1991). ONeill, K. P., J. W. Harden, S. E. Trumbore, H. Veldhuis, 1995. U S Geological Survey Open File Report. Harden, J. W., K. P. O'Neill, S. E. Trumbore, H. Veldhuis, and B. J. Stocks, submitted. Accumulation and Turnover of carbon in soils of the BOREAS NSA 2. Carbon balance in soils of a mature black spruce stand (BOREAS NSA OBS). submitted for JGR Atmospheres special BOREAS issue. Southon, J., R., J. S. Vogel, S. E. Trumbore and others, Progress in AMS measurements at the LLNL spectrometer, Radiocarbon 34: 473 - 477 (1992). Stuiver, M. and H. Polach., Reporting of 14C data. Radiocarbon 19: 355-363 (1977). Stuiver, M. and R. Kra, 1993. Radiocarbon v. 35 No 1. Calibration Issue. Taylor, R. E., A. Long, and R. Kra, eds., Radiocarbon after Four Decades: An interdisciplinary perspective, Springer-Verlag, NY,596 pp. (1992). Trumbore,S. E., Comparison of carbon dynamics in two soils using measurements of radiocarbon in pre-and post-bomb soils. Global Biogeochemical Cycles 7:275- 290 (1993). Trumbore, S. E. and J. W. Harden, submitted. Accumulation and Turnover of carbon in soils of the BOREAS NSA 1. Methods for determining soil C balance in surface and deep soil. submitted for JGR Atmospheres special BOREAS issue. Trumbore, S. E. Measurement of cosmogenic isotopes by accelerator mass spectrometry: applications to soil science, p. 311-340 in Mass Spectrometry of Soils, T. Boutton and S. Yamasaki, eds, Marcel Dekker (New York) (1996). Verardo, D., Froelich, P.N. and McIntyre, A., 1990. Determination of organic carbon and nitrogen in marine sediments using the Carlo-Erba-N!-1500 Analyzer. Deep-Sea Research, Part A - Oceanographic Research Papers 37:157-165. Davidson, E. A. and S. E. Trumbore. Gas diffusivity and production of CO2 in deep soils of the eastern Amazon, Tellus. 47B: 550-565 (1995). Mathieu, G. G. P. E. Biscaye, R. A. Lupton and D. E. Hammond, 1988. System for measurement of 222Rn at low levels in natural waters. Heath Physics 55:989-992. Stephens, B. B. and E. T. Sundquist, submitted. Measurements of soil surface gas fluxes using closed chamber techniques. (contact authors for status - Stephens is now a student at Scripps Institution of oceanography) Winston, G. C., E. T. Sundquist, B. B. Stephens and S. E. Trumbore, submitted, Winter CO2 fluxes in a boreal forest; submitted for JGR Atmospheres special BOREAS issue. 17.3 Archive/DBMS Usage Documentation None. 18. Glossary of Terms None given. 19. List of Acronyms AMS - Accelerator Mass Spectrometry BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System DAAC - Distributed Active Archive Center EOS - Earth Observing System EOSDIS - EOS Data and Information System GSFC - Goddard Space Flight Center NASA - National Aeronautics and Space Administration NSA - Northern Study Area ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park SSA - Southern Study Area URL - Uniform Resource Locator 20. Document Information 20.1 Document Revision Date Written: 14-Nov-1997 Last Updated: 05-Aug-1998 20.2 Document Review Date(s) BORIS Review: 10-Jul-1998 Science Review: 20.3 Document 20.4 Citation For soils data, the USGS open file reports (see references, 17.2) should be cited. For interpretations, cite submitted JGR papers (see references, 17.2). Other citations should refer to the BORIS data set. 20.5 Document Curator 20.6 Document URL Keywords 14C, 13C, 222Rn, CO2, CH4, Flux, Soil gas concentration TGB12_RadonActivity 08/20/98