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 �sweep gas� 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 � �
IF (DOY .EQ. 147) QC = 2 � �
IF (DOY .EQ. 155) QC = 3 extreme pollen event
IF (DOY .EQ. 156) QC = 3 � �
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