BOREAS TGB-10 Volatile Organic Carbon Data over the SSA Summary: The BOREAS TGB-10 team collected several trace gas data sets in their efforts to determine the role of biogenic hydrocarbon emissions with respect to boreal forest carbon cycles. This data set contains measured VOC concentrations. These data were obtained at the SSA Old Jack Pine site from May to September 1994. 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 TGB-10 Volatile organic Carbon Data over the SSA 1.2 Data Set Introduction The BOReal Ecosystem-Atmosphere Study (BOREAS) Trace Gas Biogeochemistry (TGB) team #10 collected volatile organic carbon (VOC) concentration data at the Southern Study Area (SSA) old jack pine (OJP) site during the growing season of 1994. The equipment used included teflon bags, 6 liter passivated stainless steel canisters, and a gas chromatograph. A combination of branch enclosures and gradient and relaxed Eddy Accumulation (REA) methods were used to make the needed measurements. 1.3 Objective/Purpose Emission/deposition rates of biogenic hydrocarbons (or volatile organic carbon, VOC) were measured along with ambient concentrations of biogenic hydrocarbons. We will use these data to examine (a) the role of biogenic hydrocarbon emissions with respect to carbon cycles in the boreal forest, (b) the chemical fate of boreal biogenic emissions, (c) the hypothesis that biospheric volatile organic carbon (VOC) emissions contribute to peroxide formation, and (d) the deposition rates of hydrogen peroxide and organic peroxides. 1.4 Summary of Parameters Investigations of biogenic hydrocarbon emissions and tropospheric concentrations of hydrogen peroxide and organic hydroperoxides in a boreal forest. 1.5 Discussion None given. 1.6 Related Data Sets TGB-08 Tower monoterpene Data over the SSA BOREAS TGB-08 Starch Data over the SSA BOREAS TGB-08 Tower Photosynthesis Data over the SSA BOREAS TGB-09 Above Canopy Non-Methane Hydrocarbon Data over the SSA 2. Investigator(s) 2.1 Investigator(s) Name and Title Dr. Hal Westberg Washington State University Dr. Nick Hewitt Lancaster University 2.2 Title of Investigation Measurement of Biogenic Hydrocarbon Fluxes 2.3 Contact Information TGB-10a: Biogenic Hydrocarbon Emissions Contact 1: Biogenic Hydrocarbon Emissions Dr. Hal Westberg Dept. of Civil and Environmental Engineering Washington State University Pullman, WA (509)-335-1529 (509)-335-7632 (Fax) westberg@mail.wsu.edu Contact 2: Deposition of Hydrogen Peroxide Brad Hall (Dr. Candis Claiborn) Dept. of Civil and Environmental Engineering Washington State University Pullman, WA (509)-335-5553 (509)-335-7632 (Fax) bhall@lar.ce.wsu.edu claiborn@wsu.edu Contact 3: Hydrogen Peroxide and Hydroperoxides Andrea V. Jackson (Dr. Nick Hewitt) Environmental Science Division Institute of Environmental and Biological Sciences Lancaster University Lancaster United Kingdom (44-1524)-843854 (Fax) andrea@lec.leeds.ac.uk n.hewitt@lancaster.ac.uk Contact 4 Sara Conrad Raytheon STX Corporation NASA GSFC Greenbelt, MD (301)286-2624 (301)286-0239 (fax) Sara Golightly@gsfc.nasa.gov 3. Theory of Measurements Three different methods were employed to measure biogenic VOC fluxes in the BOREAS SSA. A branch enclosure technique provided individual branch-level emission estimates. Tower-based gradient and relaxed eddy accumulation (REA) methods yielded canopy scale biogenic hydrocarbon fluxes. Enclosure Method ---------------- Hydrocarbon emission rates were determined using a dynamic enclosure technique. The emission rate was calculated from the following expression: E = C*Q/B (g C/g/s) where C (gC/m3) (gC(g C/m3) (g C is grams carbon) is the concentration of a specific hydrocarbon, Q (m3/s) is the flow rate of air through the chamber, and B (g) is the dry leaf (needle) biomass of the enclosed branch. Gradient Method: Canopy-scale biogenic hydrocarbon fluxes and hydrogen peroxide deposition velocities were determined by the flux-gradient technique, in which the flux is expressed as the product of an eddy exchange coefficient and the concentration gradient. The biogenic VOC flux (F) can be derived from the eddy exchange coefficient and the measured gradient. F = K*(dC/dz) (g C/m2/s) where K (m2/s) is an eddy diffusion coefficient and concentration is measured in gC/m3. The deposition velocity (Vd) of hydrogen peroxide is found from the eddy exchange coefficient and the normalized gradient. Vd = K*(dC/dz)/C (m/s) where concentration is measured in ppbV. Relaxed Eddy Accumulation (REA) Method Canopy-scale fluxes of biogenic hydrocarbons were determined by the REA method at the Old Black Spruce site. These measurements were carried out in cooperation with Dr. Elizabeth Pattey (BOREAS team TF-07). In this method, air is sampled at a constant rate and partitioned into one of two containers, contingent upon whether the vertical velocity component was positive (upward) or negative (downward). The flux is computed from the following expression: F = b*sw*(C2 - C1) (gC/m2/s)(g C/ m2/s) where b (dimensionless) is a weak function of stability (determined by eddy correlation measurements of heat, water vapor, or CO2 flux), sw (m/s) is the standard deviation of vertical wind speed, and C2 and C1 (gC/m3) are the concentrations in the "upward" and "downward" containers respectively. For a more complete description of the REA method, one should consult the TF-7 documentation. Hydrogen Peroxide Measurements (TGB-10b): Hydrogen peroxide (BOREAS team TGB-10b) was measured by the continuous, enzyme- catalyzed, fluorometric method (Lazrus et al, 1986). An incoming air stream (2 L/min) was split equally into two parts. Each gas stream was passed through a glass stripping coil in which peroxides were dissolved into a buffer solution at pH 5.8 (0.5 ml/min, 0.004M potassium hydrogen phthalate). To each liquid stream (A and B), horseradish peroxidase (8,000 units/L, type II, Sigma Chemical), 0.004M p-hydroxyphenylacedic acid (POPHA), 0.004M ethylenediamine tetraacetic acid (EDTA), and 0.0005M formaldehyde (HCHO) solutions were added. Prior to the addition of the peroxidase and POPHA, bovine-liver catalase, which destroys hydrogen peroxide, was added to stream B. The catalase concentration is adjusted until approximately 90% of the H2O2 in channel B is destroyed. In both channels, peroxidase catalyzes the reaction of peroxides with POHPA to form a fluorescent dimer with excitation and emission wavelengths of 320 and 400 nm respectively. The resulting signals, generated by photo multiplier tubes, are proportional to the peroxide concentration in each photo cell. Hydrogen peroxide concentration is the difference in signal between channels A and B. Air was sampled at each height through a 4 meter section of 1/4" PFA Teflon tubing connected to a PFA Teflon-coated 2-way valve (Furon). From there, the air was drawn through 40 m of PFA Teflon line to the analytical system, located inside the instrument hut. At this point, the air stream was separated into two streams by a PFA Teflon tee. One stream was sent to the hydrogen peroxide instrument and the other to the ozone analyzer. The valve was switched at 18 minute intervals, sequentially sampling air at both levels. Hydrogen Peroxide and Organic Hydroperoxide Measurements (TGB-10c): Ambient hydrogen peroxide and organic hydroperoxides concentrations were determined by high performance liquid chromatography (HPLC) with fluorometric detection. The detection method is similar to that described in the previous section. Air was drawn at 4 L/min from the inlet (24 m height) on the TF tower through 1/4" TFE Teflon tubing to the tower base, where a gas-phase scrubber was used to scrub peroxides from the air stream. Samples were collected in 5 ml deionized water. HPLC analysis was performed immediately after sample collection. HPLC separation was achieved on a Absorbosphere MF Plus C18 column (Altech) with an eluent of 0.001M sulfuric acid with 0.0001M EDTA delivered by a Merck-Hitachi L-6200 Intelligent HPLC pump at a flow rate of 0.6 mL/min. After separation, the peroxides were derivatized by addition of 0.026M p-hydroxyphenylacetic acid with 10,000 units/L of horseradish peroxidase (type II Sigmal Chemical) in 0.5M potassium hydrogen phthalate buffer at pH 5.8. The reaction of the fluorescence reagent with the separated hydroperoxides takes place in a Teflon coil to ensure adequate mixing. Following this, the pH of the resulting solution is raised to above 10 to convert the dimer to its fluorescent anionic form using a membrane reactor constructed of Nafion (DuPont) tubing immersed in 30% ammonium hydroxide solution. Fluorescence measurements were made using a Merck-Hitachi spectrophotometer with excitation and emission wavelengths of 310 and 405 nm respectively. The HPLC analytical system was located in the instrument hut. Formaldehyde Monitoring: The reaction of formaldehyde with dinitrophenylhydrazine (DNPH) was the basis for the measurement procedure used during this study. A DNPH/silica cartridge was connected to the inlet end of a 1/4" stainless steel tube extending to 3 m above the ground. The sample flow (1 L/min) was generated with a small pump and monitored with a Matheson flowmeter. A calibrated Tylan digital totalizer was used to record the total volume sampled. The cartridges were exposed to the ambient air for nominal durations of 2, 4, or 6 hours. Cartridges were brought back to WSU for analysis. Sample and blank cartridges were eluted with 3 ml acetonitrile. Hydrazone concentrations in the eluent were determined by reverse-phase HPLC. The HPLC analysis was performed using a LKB modular system consisting of two pumps (LKB #2150), a 190-600 nm ultraviolet/visible wavelength detector (LKB #2151) operated at 360 nm, and an LC gradient controller (LKB # 2152). A Brownlee-Rainin 10 cm OD-MPS column (or comparable) with a hydrophobic, non-polar stationary phase (bonded on 5 micrometer spheres), preceded by a similar guard column was used for peak separation. A gradient elution, beginning with a 50:50 water:acetonitrile ratio was used, changing to a 30:70 water:acetonitrile ratio over a period of 21 minutes. The column flow rate was 0.5 ml/min and the sample loop volume was 20 microliters. 4. Equipment: 4.1 Sensor/InstrumentDescription Biogenic VOCs:Description Biogenic VOC samples were analyzed on an Hewlett Packard HP5890 gas chromatograph fitted with a cryogenic accessory and two flame ionization detectors. A freeze- out trap was used with a six-port gas sampling valve for pre-concentrating the sample prior to injection. A 30 m DB-1 fused silica column was used in a temperature-programmed mode (-50 deg C to 150 deg C at 4 deg/min) to separate VOCs in the C5 to C10 range. Compound identities were determined through retention time comparisons and mass spectral analysis. Sample volume was measured with a vacuum system employing an evacuated vessel of known volume and a digital vacuum gauge (Validyne). Sample volumes range from 100 to 1000 cm^3 depending upon the expected VOC concentration. Gradient samples for biogenic VOCs were collected in 6 liter passivated stainless steel canisters. The sample containers were cleaned prior to field deployment by heating under reduced pressure, and then flushed with humidified, hydrocarbon- free air at room temperature. REA samples were collected in Teflon bags. Immediately after filling, the contents of the bag were transferred to a stainless steel canister for transport to the analytical laboratory. Hydrogen Peroxide: Hydrogen peroxide (TGB-10b) was measured by the dual-channel, enzyme-catalyzed, fluorometric method. The instrument was constructed at Washington State University, following the procedure outlined by K&K Instruments; Boulder, Colorado (Lazrus et al., 1986). Ozone was measured with a Dasibi 1003-AH ozone sensor. 4.1.1 Collection Environment Tower-based measurements were conducted under ambient atmospheric conditions. Enclosure-based biogenic VOC measurements were conducted under near-ambient conditions, but at slightly elevated temperatures. 4.1.2 Source/Platform All biogenic VOC, peroxide, and ozone measurements were made from ground or tower mounted instruments. 4.1.3 Source/Platform Mission Objectives The missions of these experiments were to obtain canopy-scale fluxes of biogenic VOCs and peroxides, and branch-scale fluxes of biogenic VOCs in a boreal environment. 4.1.4 Key Variables Emissions and/or ambient concentrations of the following trace gases were measured: isoprene alpha-pinene beta-pinene limonene monoterpenes hydrogen peroxide methylhydroperoxide hydroxymethlyhydroperoxide ozone 4.1.5 Principles of Operation (see section 3.0) 4.1.6 Sensor/Instrument Measurement Geometry Enclosure Sampling: The instruments used for enclosure sampling were mounted on a battery-powered portable cart. The bag enclosure was mounted on a tripod base, allowing access to branches 1-3 meters from the ground. Biogenic VOC analysis: The gas chromatograhic system was housed in the WSU mobile lab, located at the Torch Camp site (highway 120, near the Torch River). This central location served to minimize the storage time for VOC samples. Gradient Sampling: Inlets were located on beams protruding 1 m off the west sides of the TF towers. With winds predominately from the south, west, or north, the samples usually contained unperturbed air. The inlet heights (above the forest floor) are summarized below. OA 27.5 m and 37.5 m OBS 12.4 m and 23.3 m OJP 16.5 m and 23.8 m IFC-1, IFC-2 OJP 17.2 m and 23.8 m IFC-3 The lower inlet at the Old Jack Pine site was raised prior to IFC-3 to alleviate possible influences of the roughness sublayer. 4.1.7 Manufacturer of Sensor/Instrument HP5890 Gas Chromatograph Hewlett Packard 15815 SE 37th St. Bellevue, WA 98006 Dasibi 1003-AH ozone analyzer Dasibi Environmental 616 E. Colorado St. Glenedale, CA 91205 HP-3396A integrator Hewlett Packard 15815 SE 37th St. Bellevue, WA 98006 The hydrogen peroxide system was custom-built at WSU: WSU Technical Services Washington State University Pullman, WA 99164-2801 HPLC system (TGB-10c): Merck Ltd. Merck House Poole, Dorset BH15 1TD, England Data handling systems: Labtech 400 Research Dr. Wilmington, MA 01887 VG Data Systems St. Georges Court Hanover Business Park Altrincham, Cheshire WA14 5UG England 4.2 Calibration 4.2.1 Specifications Hydrogen Peroxide: The H2O2 gradient measurements were occasionally subject to bias. It was extremely difficult to maintain clean sampling conditions at all times. Inlet filters cannot be used due to the potential for severe H2O2 loss on filter surfaces. Periods of unacceptable bias were encountered during the first IFC when the jack pine trees were pollenating, and occasionally during IFC-2 and IFC-3 when bugs would collect in the sample lines. The sample lines were sequentially flushed with methanol, water, and dry air periodically to remove dirt, pollen, and bugs. Ozone: Calibration of the gas chromatograph was achieved by measuring instrument response to a known concentration of 2,2-dimethylbutane in air (Scott Environmental Technology; cylinder # A-11). The resulting calibration curves have been compared to a propane standard that is traceable to the National Institute of Standards and Technology (NIST, formerly NBS) (3.08 ppm propane; ID# M3281665). Daily span checks were performed during each field campaign using the 0.204 ppm 2,2-dimethylbutane standard. Formaldehyde: High-purity formaldehyde-hydrazone was prepared by conventional methods for use as a master standard. The master standard was diluted to concentrations of 0.2, 0.5, 1.0, 2.0, and 5.0 ppm to establish calibration curves. Sensors for the peripheral environmental measurements were calibrated at WSU prior to the field sampling program. Mass flow meters were tested against a precision wet-test meter at several flow rates. The thermocouples and amplifiers were calibrated against a NIST traceable mercury thermometer by measuring the response with all sensors immersed in a stirred ice-water bath slowly warmed to approximately 45 deg C. The humidity sensor was compared to calculated values for air passed through a temperature controlled water bath. All of the sensor calibrations were performed using the PC laptop data system employed in the field. 4.2.1.1 Tolerance None given. 4.2.2 Frequency of Calibration Calibrations were performed before and after each IFC. Bias checks for peroxide gradients were performed every few days during IFC-2 and IFC-3. No bias checks were performed during IFC-1. 4.2.3 Other Calibration Information Hydrogen peroxide (TGB-10b): The continuous hydroperoxide system was calibrated twice daily with liquid standards of hydrogen peroxide in deionized water. The standards were prepared at the 10-8M level by serial dilution of a 30% H2O2 reagent (Fisher). The concentration of the primary reagent was determined by titration against KMnO4, which was then titrated against a NIST-traceable sodium oxalate solution. Line losses through the PFA Teflon tubing were measured before and after each IFC. A gas-phase H2O2 generation system was used to produce a sample stream with near-ambient levels of H2O2. Line losses were determined by sampling this stream with and without the tower sampling line. A critical aspect of the peroxide gradient system is the potential for bias introduced in the two separate inlet sections. Care was taken to ensure that bias introduced by the valve and 4 m inlet sections was well-known and correctable. Relative bias was determined every few days by placing both inlets at the same height and sampling ambient air for several hours. Subsequent gradients were corrected for bias, which ranged from -1 to 9%. When the bias surpassed 7%, samples were rejected and the valve and sample lines were cleaned with methanol, deionized water, and peroxide-free air. After cleaning, bias was reduced to a non-detectable level. Hydroperoxides (TGB-10c): Peak identities were confirmed by comparison with retention times of authentic standards. Quantification was based on system response to hydrogen peroxide, as the same fluorescent dimer is formed for all hydroperoxides. Calibration was carried out twice daily and was found to be linear over the range 8x10-8M to 5x10-6M. The limit of detection has been determined to be less than 50 pptv. Ozone: The Dasibi ozone monitor was calibrated against a Dasibi ozone source/monitor model 1008-PC (serial #3226). 5. Data Acquisition Methods Enclosure Method The enclosure consisted of a cylindrical 30 liter Teflon film bag supported externallysupported on a metal frame. Hydrocarbon-free zero air (from a compressed gas cylinder) was swept through the Teflon bag at a controlled rate. The zero air ësweep gasí was introduced through a perforated annular ring at one end and exhausted through a port at the other end. he sweep gas was humidified by bubblingBubbling through a water bath, maintained at ambient temperature, humidified the sweep gas. Carbon Dioxide was added to yield near-ambient CO2 concentrations (360 +/- 10 ppm) in the sweep gas. Gradient Method Ambient concentrations of biogenic hydrocarbons were measured at two heights (see section 4.1.6) above the OBS, OA, and OJP forests. Hydrogen peroxide was measured at two heights above the OJP forest. For biogenic hydrocarbons, 30 minute average concentrations were determined by simultaneously filling two stainless steel canisters. Each canister was connected to a PTFE Teflon line running from a location on the tower (above the canopy) to the tower base. For hydrogen peroxide, the concentration at each height was measured sequentially at 18 minute intervals. The average concentrations observed during each interval were used to compute the concentration gradient. Eddy exchange coefficients for heat and water vapor were determined by simultaneously measuring the fluxes (by eddy correlation) and the gradients of heat and water vapor. The respective TF groups will provide these data. Relaxed Eddy Accumulation (REA) Method Canopy-scale fluxes of biogenic hydrocarbons were determined by the REA method at the Old Black Spruce site. In this method, air is sampled at a constant rate and partitioned into one of two containers, contingent upon whether the vertical velocity component was positive (upward) or negative (downward) Signals from the hydrogen peroxide and ozone instruments (TGB-10b) were stored as 1 minute averages via PC computer. Data acquisition software from Labtech was used to record signals (voltages). The gas chromatograph was interfaced to a pair of HP-3396A integrators for peak integration. Raw signals were also stored via PC computer for data reprocessing. The HPLC system for hydroperoxides was interfaced with a VG Data Systems Minichrom data acquisition system for chromatography. The connection of the HPLC to the data system was achieved using a chromatography server. 6. Observations 6.1 Data Notes Hydrogen peroxide: Periods of unacceptable bias were encountered during the first IFC, when the jack pine trees were pollenating, and occasionally during IFC-2 and IFC-3 when bugs would collect in the sample lines. Ozone: Some problems with the electronic zero were detected during IFC-1. An offset of - 6 ppb relative to the data acquisition system was discovered. This offset was easily measured on a daily basis, and remained essentially unchanged throughout the experiment.None Given. 6.2 Field Notes TGB-10b Peroxide data were deemed questionable (QC = 2) or unacceptable (QC = 3) during the following periods: C *** QUALITY CONTROL (based local TIME and DOY) IF (DOY .EQ. 145) QC = 2 poor calibration IF (DOY .EQ. 146) QC = 2 Ï Ï IF (DOY .EQ. 147) QC = 2 Ï Ï IF (DOY .EQ. 155) QC = 3 extreme pollen event IF (DOY .EQ. 156) QC = 3 Ï Ï IF (DOY .EQ. 157) QC = 2 moderate pollen event IF (DOY .EQ. 160) THEN IF (TIME .GT. 17.) QC = 2 bias unknown ENDIF IF (DOY .EQ. 206) THEN IF ((TIME .GT. 8.0) .AND. (TIME .LT. 12.0)) QC = 2 poor calibration ENDIF IF (DOY .EQ. 212) THEN IF ((TIME .GT. 3.0) .AND. (TIME .LT. 9.0)) QC = 3 high noise level ENDIF IF (DOY .EQ. 216) QC = 2 None Given. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage Biogenic VOC fluxes were determined at three tower sites in the Southern Study Area (OA, OBS, OJP).Area. Peroxide and ozone concentrations were measured only at the OJP site. The North American Datum 1983 (NAD83) coordinates for the sites are: SSA-OA 53.62889N, 106.197779W SSA-OBS 53.91634N, 104.69203W SSA-OJP 53.98717N, 105.11779W 7.1.2 Spatial Coverage Map Not available. 7.1.3 Spatial Resolution These data represent point source measurements at the given locations. 7.1.4 Projection Not applicable. 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Biogenic VOC samples were collected for 30 minute periods. Sampling was usually performed from sunrise to sunset, to capture the diurnal variability. Some overnight sampling was performed at the OA site during IFC-3. Ambient biogenic VOC and oxidation products were measured at the Torch Camp (near Candle Lake, Saskatchewan) during each IFC. These measurements were meant to supplement those obtained at the tower sites. Peroxide and ozone concentrations were measured continuously during daylight hours. In addition, many overnight sampling periods were obtained. 7.2.2 Temporal Coverage Map Not available. 7.2.3 Temporal Resolution No regular intervals of data collection resulted at the sites; however, data were collected on several days during the growing season of 1994 at each location. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (tgb10voc.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (tgb10voc.def). 8. Data Organization 8.1 Data Granularity All of the Volatile Organic Carbon 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 (tgb10voc.def). 9. Data Manipulations 9.1 Formulae The peroxide gradient was computed from 3 successive measurements of peroxide concentration at two levels (10-18 minutes at each level). Peroxide_gradient = (C2 - 0.5*(C1+C3))/delta_Z where C1 = concentration measured at lower level (period t) C2 = concentration measured at upper level (period t+1) C3 = concentration measured at lower level (period t+2) special note: If the standard error associated with C1,C2,or C3 was greater than 0.05%,the peroxide gradient was deemed unacceptable. This procedure was performed in order to screen periods of highly variable concentration, which might suggest unsteady-state conditions (gusts or large eddies) which are not conducive to K-theory. 9.1.1 Derivation Techniques and Algorithms None given. 9.2 Data Processing Sequence 9.2.1 Processing Steps BORIS processed the data by: 1) Reviewing the initial data files and loading them on-line for BOREAS team access, 2) Designing relational data base tables to inventory and store the data 3) Loading the the data into the relational data base tables, 4) Working with the HYD-06 team to document the data set, and 5) Extracting the standardized data into logical files. 9.2.2 Processing Changes None given. 9.3 Calculations Emission rate: E = C*Q/B where C is the concentration of a specific VOC, Q is the flowrate of air through the chamber, and B is the dry leaf (needle) biomass of the enclosed branch. Biogenic VOC flux (F): F = K*(dC/dz) Deposition velocity (Vd): Vd = K*(dC/dz)/C 9.3.1 Special Corrections/Adjustments None given. Peroxide Bias adjustment: C1 = C1*fb C3 = C1*fb where fb = bias relative to upper sampling level (range 0.99 to 1.07 for H2O2, 0.99 to 1.02 for ROOH) 9.3.2 Calculated Variables None given. 9.4 Graphs and Plots None. 10 Errors 10.1 Sources of Error Hydrogen Peroxide (TGB-10b): The following sources of error are those that are not easily identified, and may affect the data record despite efforts to identify and correct all errors. - irregularities in sample line loss (condensation, dirt, bugs) - contamination of the switching valve due to bugs, dirt, pollen, etc. - irregular signal drift, possibly due to extreme temperature fluctuations - interference due to smoke particles Hydroperoxides (TGB-10c): - fluctuations in air flow rate - error in preparing sample volume - fluctuations in sample collection efficiency with temperature - possible condensation in sample lines - interference due to smoke particles - error associated with the serial dilution of H2O2 standards None given. 10.2 Quality Assessment 10.2.1 Data Validation by Source 10.2.2 Confidence Level/Accuracy Judgment Hydrogen peroxide concentrations are good to approximately 30%. Total organic peroxide concentrations have not been corrected for collection efficiency. Reported total organic peroxide concentration may be underestimated by as much as 60%. Individual deposition velocity measurements are subject to 50-80% uncertainty due to uncertainties in the measured gradient, the measured eddy diffusivity, and the natural variability of a turbulent atmosphere. Ozone concentrations are good to +/- 5 ppb for IFC-1, and +/- 3 ppb for IFC-2 and IFC-3. 10.2.3 Measurement Error for Parameters None given. 10.2.4 Additional Quality Assessments None given. 10.2.5 Data Verification by Data Center BORIS processed the data by: 1) Reviewing the initial data files and loading them on-line for BOREAS team access, 2) Designing relational data base tables to inventory and store the data 3) Loading the the data into the relational data base tables, 4) Working with the TGB-10 team to document the data set, and 5) Extracting the standardized data into logical files. 11. Notes 11.1 Limitations of the Data Peroxide deposition velocities at OJP are subject to some uncertainty (factor of 2) simply because we do not know for certain that the application of Kh is appropriate for peroxide transport. The eddy diffusivity for water vapor over OJP was lower than that of heat. Therefore, average peroxide deposition velocities should probably be taken as an upper limit. 11.2 Known Problems with the Data None given. 11.3 Usage Guidance Peroxide deposition rates are extremely difficult to measure in the field. Individual measurements of peroxide deposition velocity hold little significance due to the uncertainties mentioned in section 10.2. However, because of the large amount of data collected, these deposition rates are a valuable component of the peroxide budget. Vd data should be used to assess average deposition rates to a rough, boreal pine forest. 11.4 Other Relevant Information None given. 12. Application of the Data Set None given. 13. Future Modifications and Plans None. 14. Software: 14.1 Software Description All software used to gather data were off-the-shelf, standard scientific scientific packages. 14.2 Software Access None given. 15. Data Access 15.1 Contact Information Ms. Beth Nelson 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-10 VOC 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 Tabular ASCII files. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation None given. 17.2 Journal Articles and Study Reports Guenther, A.and others, (1996), Isoprene fluxes measured by enclosure, relaxed eddy accumulation, surface layer gradient, mixed layer gradient, and mixed layer mass balance techniques, Journal of Geophysical Research, 101, 18555- 18567. Hall, B.D., and Claiborn, C.S., (1997) Measurements of the dry deposition of peroxides to a Canadian boreal forest, Journal of Geophysical Research, in press. Lazrus, A.L, G.L. Kok, S.N. Gitlin, J.A. Lind, B.G. Heikes, R.E. Shetter, (1986). Automated fluorometric method for hydrogen peroxide in air. Anal. Chem. 58, 594-597. Kok, G.L., S.E. McLaren, and T.A. Staffelbach, (1995) HPLC determination of atmospheric organic hydroperoxides, J. Atmos. Ocean Tech., 12, 282-289. Sellers, P., F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). Sellers, P., F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96). Sellers, P., F. Hall, K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94). Sellers, P., F. Hall, 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. 17.3 Archive/DBMS Usage Documentation None. 18. Glossary of Terms None. 19. List of Acronyms 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 HPLC - High Performance Liquid Chromatography IFC - Intensive Field Campaign NASA - National Aeronautics and Space Administration NIST - National Institute for Standards and Technology OA - Old Aspen OBS - Old Black Spruce OJP - Old Jack Pine ORNL - Oak Ridge National Laboratory REA - Relaxed Eddy Accumulation URL - Uniform Resource Locator VOC - Volatile Organic Compound (or Carbon) 20. Document Information 20.1 Document Revision Dates Written: 17-Nov-1994 Last Updated: 02-Jul-1998 20.2 Document Review Dates BORIS Review: 12-Jun-1998 Science Review: 20.3 Document ID 20.4 Citation 20.5 Document Curator 20.6 Document URL Keywords Oxidant Volatile Organic Carbon Peroxide Isoprene TGB10_VOC.doc 07/07/98