BOREAS TGB-09 Above-canopy NMHC at SSA-OBS, SSA-OJP and SSA-OA Sites

Summary

THE BOREAS TGB-09 team collected data in order to inventory and quantify the 
anthropogenic and biogenic NMHCs over the BOREAS study areas.  This data set 
contains concentration and mixing ratio values for several NMHCs collected at 
the BOREAS SSA from 27-MAY-1994 to 15-SEP-1994.  The data are provided in tabular 
ASCII files.

Table of Contents

   *  1 Data Set Overview
   *  2 Investigator(s)
   *  3 Theory of Measurements
   *  4 Equipment
   *  5 Data Acquisition Methods
   *  6 Observations
   *  7 Data Description
   *  8 Data Organization
   *  9 Data Manipulations
   *  10 Errors
   *  11 Notes
   *  12 Application of the Data Set
   *  13 Future Modifications and Plans
   *  14 Software
   *  15 Data Access
   *  16 Output Products and Availability
   *  17 References
   *  18 Glossary of Terms
   *  19 List of Acronyms
   *  20 Document Information

1. Data Set Overview

1.1 Data Set Identification

BOREAS TGB-09 Above-Canopy NMHC at SSA-OBS, SSA-OJP, and SSA-OA Sites

1.2 Data Set Introduction

BOReal Ecosystem-Atmosphere Study (BOREAS) Trace Gas Biogeochemistry Team 9 (TGB-
09) measured non-methane hydrocarbon (NMHC) data at the Southern Study Area 
(SSA)-Old Black Spruce (OBS), Old Jack Pine (OJP), and Old Aspen (OA) sites.

1.3 Objective/Purpose

The mission objective was twofold:  1) to provide a quantitative inventory of 
NMHCs, both anthropogenic and biogenic, at the SSA-OBS, SSA-OJP and SSA-OA tower 
flux sites; and 2) to provide ambient concentration data for biogenic 
hydrocarbons suitable for calculating the flux of biogenic hydrocarbons at the 
tower flux sites using the gradient method.

1.4 Summary of Parameters

Concentrations in the parts per trillion by volume (pptv) - parts per billion by 
volume (ppbv) range are reported for a variety of biogenic and anthropogenic 
NMHCs. Local sources and transport from distant sources contribute to the NMHCs 
inventory in the boreal forest region. A quantitative inventory of ambient 
hydrocarbon concentrations can aid in identification of sources important to the 
boreal atmosphere. In particular, gradient measurements allow biogenic emissions 
from the forest itself to be quantified.

1.5 Discussion

Each sample was analyzed on two separate Gas Chromatograph (GC) Flame Ionization 
Detector (FID) systems. In one, the column and temperature program were chosen to 
optimize quantitation of C2-C6 hydrocarbons. In the other, the column and 
temperature program were chosen to optimize quantitation of C5-C10 hydrocarbons.

Samples collected at the SSA sites were transported to the laboratory in Toronto 
for analysis.  The time between collection and analysis varied greatly over the 
course of the study.  The earliest samples were analyzed within 1 month of 
collection, whereas some of the latest samples were not analyzed until 6 months 
after collection.  Extensive experience with such samples has demonstrated that 
these samples are stable over such long periods of time. 

1.6 Related Data Sets

BOREAS TGB-10 Oxidant Concentration Data over the SSA
BOREAS TGB-10 Oxidant Flux Data over the SSA

2. Investigator(s)

2.1 Investigator(s) Name and Title

Professor Hiromi Niki (deceased April 1995)

2.2 Title of Investigation

Ambient Measurements of Non-Methane Hydrocarbons 

2.3 Contact Information

Contact 1
---------
Byron Kieser
Centre for Atmospheric Chemistry
006A Steacie Science Library
York University
North York, ON  Canada
(416) 736-5410
(416) 736-5411 (fax)
bnkieser@helios.sci.yorku.ca

Contact 2
---------
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

Estimates of the hydrocarbon flux above the canopy by the gradient method require 
measurement of the hydrocarbon concentration gradient. To accomplish this, 
simultaneous samples were collected at two heights above the canopy and analyzed 
for a range of hydrocarbons. The flux of any particular hydrocarbon (HC) can then 
be determined by the following relationship.

FLUX(HC) = k(z) ? ([HC]" - [HC]') / (z" - z')

where ([HC]" - [HC]') is the difference in [HC] between the two heights z" and 
z'. The eddy diffusivity coefficient k(z) should be obtained from other 
researchers performing simultaneous measurements at the same sites. Measurements 
of the hydrocarbon concentrations are made by collecting whole air samples over a 
30-minute period in evacuated, electropolished stainless steel canisters that are 
then transported to the laboratory for analysis. Before being shipped to 
Saskatchewan for sample collection, the canisters were heated to 80 C and 
evacuated to 10-6 Torr for 2 hours.

4. Equipment

4.1 Sensor/Instrument Description

a. The sample collection system filled two sample canisters simultaneously over 
30 minutes.  The system consists of:

(i) Two electropolished stainless steel sample canisters (Biospherics Research 
Corp., Oregon, U.S.A.), 3- or 6- liter volume, evacuated, sealed by a Nupro metal 
bellows valve, and having a Swagelock connection on the inlet.

(ii) Two mass flow controllers, Tylan FC-260V, 0 - 500 sccm.

(iii) 12V DC 1.5 A KNF Neuberger metal bellows pump UN05 ATI.

(iv) Stainless steel tubing and fittings between components.

b.  The sample analysis system for identification and quantification of 
hydrocarbons.  The system consisted of:

(i) Hewlett Packard (HP) 5890II GC-FID with DB-1 100 m x 0.25 mm ID x 0.5 
micrometer film column, electronically programmable pressure control inlet, and 
HP PC-ChemStation v. 1.01 software, primarily for C5-C10 hydrocarbons.

(ii) HP 5890II GC-FID with Al2O3/KCl PLOT 50 m x 0.32 mm ID column and HP PC-
ChemStation v. 1.01 software, primarily for C2-C6 hydrocarbons.

(iii) HP 5890 GC with SPB-5 30 m x 0.25 mm ID x 0.25 micrometer film column, HP 
5970 MSD, HP 5970 GC-MS Workstation v. 3.2 software, and in-house constructed 
cryogenic sample prefocusing system.

(iv) Cryogenic sample preconcentration system, one per GC system, constructed in-
house.

(v) Modified Tekran Cryotherm-100 cryogenic sample prefocusing system, one per 
GC-FID system.  Tekran cryofocusers were modified by replacing all internal 
nickel tubing with stainless steel tubing. The prefocusing system for the GC-MSD 
was constructed in-house.

4.1.1 Collection Environment

Samples were collected at each of the SSA-OBS and SSA-OJP sites during Intensive 
Field Campaign (IFC)-1, IFC-2, and IFC-3. Samples were collected at the SSA-OA 
site during IFC-2 and IFC-3.  Samples were collected regardless of the prevailing 
weather conditions.

4.1.2 Source/Platform

a. A portable sampling system mounted on a backpack frame and placed at the base 
of the tower. Sampling was through Teflon lines mounted on the tower. Full sample 
canisters were shipped to the laboratory for analysis.

b.  Benchtop systems in the laboratory at York University as described above.

4.1.3 Source/Platform Mission Objectives

The objective of the tower was to provide a place to mount instrumentation for 
measurements. The objective of the backpack was to allow transport of equipment 
to measurement sites. The lab benchtop provided an area to use to analyze the 
samples.

4.1.4 Key Variables

Concentration of individual NMHCs in air.  Compounds that are measured (not all 
are included in this data set): ethylene,  acetylene,  ethane,  propene,  
propane,  propyne,  isobutane,  iso-butene,  1,3-butadiene,  n-butane,  t-2-
butene,  2,2-dimethylpropane,  1-butyne,  c-2-butene,  2-methylbutane,  1-
pentene,  2-methyl-1-butene,  n-pentane,  isoprene,  t-2-pentene,  c-2-pentene,  
2-methyl-2-butene,  2,2-dimethyl-butane,  4-methyl-1-pentene,  3-methyl-1-
pentene,  cyclopentane,  2,3-dimethyl-butane,  c-4-methyl-2-pentene,  2-
methylpentane,  t-4-meth-2-pentene,  3-methylpentane,  2-ethyl-1-butene,  1-
hexene,  n-hexane,  t-2-hexene,  c-3-methyl-2-pentene,  c-2-hexene,  t-3-methyl-
2-pentene,  2,2-dimethylpentane,  methylcyclopentane,  2,4-dimethylpentane,  
2,2,3-trimethylbutane,  benzene,  cyclohexane,  2-methylhexane,  2,3-
dimethylpentane,  3-methylhexane,  1-heptene,  2,4,4-trimeth-pentan,  t-3-
heptene,  heptane,  t-2/c-3-heptene,  c-2-heptene,  methylcyclohexane,  2,2-
dimethylhexane,  2,5-dimethylhexane,  2,4-dimethylhexane,  2,3,4-trimethylpenta,  
toluene,  2-methylheptane,  4-methylheptane,  3-methylheptane,  c-1,3-
dimethylcycloh,  t-1,4-dimethylcycloh,  2,2,5-trimethylhexane,  1-octene,  n-
octane,  t-2-octene,  t-1,3-dimethylcycloh,  c-2-octene,  c-1,2-dimethylcycloh,  
ethylbenzene,  m-xylene,  p-xylene,  styrene,  o-xylene,  1-nonene,  n-nonane,  
iso-propylbenzene,  benzaldehyde,  alpha-pinene,  3,6-dimethyloctane,  n-
propylbenzene,  camphene,  3-ethyltoluene,  4-ethyltoluene,  1,3,5-
trimethylbenze,  sabinene,  2-ethyltoluene,  b-pinene,  myrcene,  1,2,4-
trimethylbenze,  t-butylbenzene,  n-decane,  2-carene,  iso-butylbenzene,  sec-
butylbenzene,  3-carene,  a-terpinene,  1,2,3-trimethylbenze,  p-cymene,  
limonene,  indan,  1,3-diethylbenzene,  1,4-diethylbenzene,  n-butylbenzene,  g-
terpinene,  1,2-dieth-benz,  undecane

Other compounds may be identified at a later date.  Contact the investigators for 
further information.

4.1.5 Principles of Operation

a.  Sample collection system

Whole air samples were simultaneously collected at constant flow rates for 30 
minutes (typically) into stainless steel canisters, from two heights on a flux 
tower during IFC-1, IFC-2, and IFC-3 at each of the SSA-OBS, SSA-OJP, and SSA-OA 
sites.  Air was pumped from the sampling site on the tower through a Teflon line 
into a sample canister. The mass flow controller held the pumping rate constant 
as the can filled to a final pressure of about 20 pounds per square inch (psi). 
Two pumping systems (mounted on the same backpack) with inlets at different 
points on the tower were used in order to fill two cans simultaneously with air 
from different heights above the canopy.

b.  Sample analysis

The collected samples were transported to the laboratory for analysis using GC 
techniques. Permissible injection volumes for capillary GC are below 1 cc (gas). 
Typical concentrations for the hydrocarbon species being measured are in the 
range of 10 pptv to 10 ppbv, which, for isoprene as example, gives an analyte 
range of 0.06 to 60 fg/cc. The constraint on injection volume for capillary GC 
combined with the low concentrations of analyte requires that the samples be 
preconcentrated prior to GC analysis. Sample preconcentration is accomplished by 
passing a known volume of the air sample through a trap filled with fine glass 
beads cooled to -180 C.  Volatile hydrocarbons are retained on the beads.  The 
bulk air constituents (nitrogen and oxygen) are collected in an evacuated 
reference volume. From the final pressure of the reference volume, the total 
volume of air that passed through the preconcentration system may be calculated. 
This volume is used to calculate the mixing ratio of each compound in the 
original air sample after GC analysis. The sample trapped cryogenically on the 
glass beads is thermally desorbed into a stream of ultrapure helium and retrapped 
on the surface of a fine stainless steel capillary cooled to -180 C. This second 
cryogenic trapping stage "focuses" the sample into a small linear section of 
tubing. Electrical resistance ballistically heats the cold stainless steel 
capillary, and the cryofocused sample quickly desorbs into the helium stream and 
is transferred to the chromatographic column. 

The volatile components of the sample are carried through the GC column by the 
mobile phase, the ultrapure helium. Capillary GC columns are typically a long 
(10-100m) section of fused silica capillary (0.18-0.53 mm inner diameter, I.D.). 
The inside surface of the column has a thin (0.05-5 m) coating of a stationary 
phase designed to interact with the components of a mixture passing through the 
column. For any individual hydrocarbon, the amount of time taken to traverse the 
length of the column (retention time) is determined by the component's affinity 
for the stationary phase, which, in turn, is a function of the chemical nature of 
the component. This differential affinity of various species for the stationary 
phase makes it possible for the GC column to separate a complex mixture as it 
travels through the column. Controlled variation of column temperature over the 
course of the analysis (temperature program) also affects the separation of the 
compounds, the retention time for each compound, and the total analysis time for 
the sample. Compounds are identified by their characteristic retention times. 

Compounds eluting from the end of the column are detected using an FID, in which 
the column effluent is introduced into a hydrogen-air diffusion flame. An 
electrical charge applied a potential across the flame collects species formed 
through radical reactions in the flame and the current is amplified by a 
sensitive electrometer. The FID displays a linear response to carbon atoms over a 
large dynamic range. The FID is very sensitive to hydrocarbons, but is 
insensitive to water or carbon dioxide.

In addition to the FID detector, some of the samples are analyzed using a mass 
selective detector (MSD). The MSD produces mass spectra of the species eluted 
from the column. The MSD is less sensitive than the FID, but provides a more 
certain identification of the species eluted by relying not only on the retention 
time, but also on the mass spectrum of the effluent. The column separates 
components, they are introduced to a high-energy stream of electrons, and a 
fraction of the molecules are converted to ions. The ions are electrically 
accelerated into a quadrupole mass filter and passed to an electron multiplier. 
The electron multiplier counts the number of ions that strike it. By scanning a 
range of mass-charge ratios, the MSD can construct a mass spectrum for each 
compound exiting the column. The pattern and abundance of ions produced are 
characteristic of the chemical structure of a compound, and thus may be used to 
identify species eluting from the column. The MSD results are used to 
qualitatively identify unknown compounds, while the FID results provide 
quantitative data. 

Unlike the FID, the MSD is sensitive to water and carbon dioxide.  Water and 
carbon dioxide are present in ambient air in amounts several orders of magnitude 
larger than any of theNMHCs.  Although small amounts will not affect FID 
operation, typical ambient concentrations do pose chromatographic problems and 
problems with the MSD operation. Water and carbon dioxide have a detrimental 
effect on the chromatographic separation of hydrocarbons. Because of its polar 
nature, water interferes with the interaction between the hydrocarbons and the 
stationary phase of the column. Water can also clog the glass bead trap, cryo-
focuser, or column during the analysis, and may extinguish the FID flame. In the 
MSD, high water and carbon dioxide signals increase the background signals for 
other ions such that the detection limit is raised to an unsuitable level. In 
order to avoid these problems, water and carbon dioxide are removed from the air 
samples prior to preconcentration. A cold trap (-20 to -60 C) removes water in 
sufficient amounts to allow chromatographic analysis to proceed without any 
clogging or FID quenching. A potassium carbonate trap at 80 C removes carbon 
dioxide. These traps were tested extensively to ensure that the concentrations of 
the hydrocarbons of interest are not affected.

4.1.6 Sensor/Instrument Measurement Geometry

The Teflon sampling tubes are mounted on the main tower at each site. The height 
of the inlet above the ground, in meters, is given for each sample. Both inlets 
are above the mean canopy height.

4.1.7 Manufacturer of Sensor/Instrument

a. The sampling system was assembled by the investigators. All tubing was 
chromatographic-grade stainless steel.

(i)  Stainless steel canisters were manufactured by:

Biospherics Research Corp.
1121 N.W. Donelson Street
Hillsboro, OR  97124
(503) 690-1077

(ii)  Mass flow controllers were manufactured by:

Tylan Corporation
Torrance, CA  90501 

(iii)  The metal bellows pump was manufactured by:

KNF Neuberger, Inc.
Princeton, NJ  
(609) 799-4350

b.  Analysis system

(i,ii,iii) GC and GC-MSD was manufactured by:

Hewlett-Packard (Canada)
5150 Spectrum Way H80
Mississauga, ON L4W 5G1 
(905) 206-4725

(iv)  The cryogenic sample preconcentration system was assembled by the 
investigators.

(v)  The cryogenic sample prefocusing system for the GC-FIDs was manufactured by:

Tekran, Inc.
Toronto, ON

The cryogenic sample prefocusing system for the GC-MSD was assembled by the 
investigators

4.2 Calibration

a.  Sampling system

The sampling system flow rate was calibrated using a soap bubble flow meter.

b.  Hydrocarbon analysis

GC-FID systems were calibrated with standard mixtures from Environment Canada, 
National Center for Atmospheric Research (NCAR), Scott Specialty Gases, as well 
as standard mixtures prepared in the laboratory (Dr. Daniel Wang, Environment 
Canada, 351 St. Joseph Blvd., Hull, PQ K1A 0H3;   Dr. Eric Apel, NCAR, 1850 Table 
Mesa Drive, Boulder, CO 80303;  Scott Specialty Gases, 6141 Easton Road, 
Plumsteadville, PA 18949-0310), and checked with secondary standards mixed in the 
laboratory. 

Calibration of the GC systems was accomplished using prepared gas mixtures in air 
of known concentration to determine the characteristic retention time and FID 
response for each compound in the mixture. Measured FID responses were checked 
against the expected response based on the number of carbon atoms in each 
compound, since the FID response is linear over a large range, and is essentially 
mass responsive to carbon atoms.

4.2.1 Specifications

4.2.1.1 Tolerance

a.  Sampling system: Constant flow rate of 500 50 sccm air at STP.

b.  Hydrocarbon analysis: Detection limits and precision:

NMHC analysis detection limit:   5 pptv

NMHC Precision: 
+/-5pptv for [HC] < 0.1ppbv
+/-5% for 0.1ppbv < [HC] < 1.0ppbv
+/-1% for [HC] > 1.0ppbv

NMHC GC-MSD analysis detection limit:   0.1-0.5 ppbv (depending on compound)

Precision:  not used for quantitative analysis

4.2.2 Frequency of Calibration

a.  Sample collection system calibration was checked weekly.

b.  NMHC analysis system was checked weekly for all components reported using 
standards from NCAR and/or Environment Canada and/or laboratory- prepared 
mixtures. 

4.2.3 Other Calibration Information

For NMHC analysis, the two samples in each pair were run consecutively on the 
same day by the same operator on the same GC. Before the project began, each 
operator demonstrated that he could achieve the precision quoted in Section 
4.2.1.1 for multiple runs of the same sample. Each day, one sample was repeated 
by another operator on the same GC to test reproducibility between operators. The 
concentration of isoprene obtained from the two GCs was compared for each sample.  
Several samples from each IFC were analyzed more than once to monitor the system 
performance, as well as track any sample stability problems.

5. Data Acquisition Methods

The two outlets of the pumping system were connected to evacuated stainless steel 
canisters. The inlets of the pumping system were connected to Teflon lines 
mounted on a tower so that air could be sampled simultaneously from two heights 
above the forest canopy. The flow rate for the mass flow controllers was set such 
that each can would fill to a pressure of about 20 psi during 30 minutes of 
sampling. The cans were sealed by shutting the valve, and the full cans were then 
shipped to the laboratory for analysis.

Approximately 500 - 700 mL (at standard temperature and pressure) of sample was 
used for GC-FID analysis. The sample handling procedure is described in more 
detail in Section 4.

6. Observations

6.1 Data Notes

None given.

6.2 Field Notes

SSA-OBS:  The mean canopy height was 9 m. Sampling inlets were placed at 12.4 m 
and 23.3 m above ground level.  A path about 50 m wide was made from the road to 
the tower. Data taken when the wind was from the direction of the road may be 
suspect because of the removal of trees to create the path.

7. Data Description

7.1 Spatial Characteristics

7.1.1 Spatial Coverage

Samples were collected only from the tower at each site. Each sample may be 
considered as an ambient sample whose spatial coverage could be determined by 
back-trajectory analysis for the 30-minute sampling period.  The North American 
Datum 1983 (NAD83) coordinates of the measurement sites are:

SSA-OBS: 53.98717N, 105.11779W
SSA-OJP: 53.91634N, 104.69203W
SSA-OA:  53.62889N, 106.19779W

7.1.2 Spatial Coverage Map

Not available.

7.1.3 Spatial Resolution

The resolution, for gradient calculations, is no better than the footprint of 
forest considered in flux measurements. As ambient measurements, the spatial 
resolution is subject to the meteorological conditions at the time the 
measurements were made.

7.1.4 Projection

Not applicable.

7.1.5 Grid Description

Not applicable.

7.2 Temporal Characteristics

7.2.1 Temporal Coverage

Samples were collected at the three SSA tower flux sites during the IFCs from 27-
May to 15-Sep-1994.

7.2.2 Temporal Coverage Map

Note: Sample refers to a pair of upper- and lower-level samples.

SSA-OJP 27-May-1994, 4 samples 
SSA-OJP 07-Jun to 12-Jun-1994, 33 samples 
SSA-OJP 27-Jul to 02-Aug-1994, 30 samples
SSA-OJP 09-Sep to 11-Sep-1994, 8 samples
SSA-OJP 15-Sep-1994, 4 samples

SSA-OBS 31-May to 05-Jun-1994, 25 samples
SSA-OBS 20-Jul to 24-Jul-1994, 32 samples
SSA-OBS 01-Sep to 07-Sep-1994, 32 samples

SSA-OA  04-Aug to 08-Aug-1994, 20 samples
SSA-OA  12-Sep to 14-Sep-1994, 21 samples

7.2.3 Temporal Resolution

On the dates listed in Section 7.2.2., samples were typically collected at 1-hour 
intervals, usually from late morning to evening.  On several occasions, samples 
were collected over a 24-hour period, when there was no precipitation.

7.3 Data Characteristics                                                        

Data characteristics are defined in the companion data definition file 
(tgb9nmhc.def).

7.4 Sample Data Record

Sample data format shown in the companion data definition file (tgb9nmhc.def).

8. Data Organization

8.1 Data Granularity

All of the Above-canopy NMHC at SSA-OBS, SSA-OJP and SSA-OA Sites 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 (tgb9nmhc.def).

9. Data Manipulations

9.1 Formulae

[Sample] = ((sample pk area) x (Response Factor) / (sample vol))

Where:

[Sample] is the mixing ratio of the NMHC of interest in the sample.

(sample pk area) is the area in area counts of the chromatogram peak that 
corresponds to NMHC of interest in the sample.

Reponse Factor is the FID response in area counts per ppbv of the NMHC of 
interest per cc of sample.

(sample vol) is the volume of sample analyzed in cc.

9.1.1 Derivation Techniques and Algorithms

Calculations were performed by HP-ChemStation software.

9.2 Data Processing Sequence

9.2.1 Processing Steps

1. HP-ChemStation integrates each peak in chromatogram.

2. Operator verifies that software chose reasonable baseline and limits for peaks 
and manually sets baseline and limits if necessary.

3. Peaks are identified by comparison to retention times found using standard 
mixtures.

4. Operator transfers area count data to spreadsheet program for concentration 
calculations.

9.2.2 Processing Changes

None.

9.3 Calculations

Peak areas were converted to concentrations (mixing ratios) by formula in Section 
9.1.

9.3.1 Special Corrections/Adjustments

Data Below Detection Limit: When the NMHC of interest is not detected by the GC-
FID system, it is assigned a concentration of 0.002 ppbv, which is approximately 
the average between the detection limit of 0.005 ppbv and 0.000 ppbv.

Conversion to Greenwich Mean Time (GMT): Time at start of sampling was originally 
noted in local Saskatchewan time. This was converted to GMT by adding 6 hours.

9.3.2 Calculated Variables

None.

9.4 Graphs and Plots

None.

10. Errors

10.1 Sources of Error

The user is advised to check meteorological data carefully before using these 
data to calculate fluxes by the gradient method and to know the limitations of 
this method. Because compound identification is based on retention time, it is 
possible to misidentify a compound that is present in a real sample but not 
present in the calibration standard. The temperature programs have been adjusted 
to achieve good separation for the compounds in the calibration standards, but 
additional species present in real samples may co-elute. This is unlikely to 
cause problems for the C2-C6 data, because the calibration standard for light 
hydrocarbons is comprehensive, but there may be interferences in the C5-C10 data.

10.2 Quality Assessment

Laboratory analysis of the air samples was conducted, and the samples were 
examined for outliers. When an outlier was spotted, the original chromatogram was 
checked for correct integration and quantification.

10.2.1 Data Validation by Source

Time series plots for each hydrocarbon and hydrocarbon distribution plots were 
analyzed. Samples were collected in evacuated stainless steel canisters and 
shipped to the laboratory in Toronto, ON, for analysis by GC-FID. Concentrations 
in the pptv-ppbv range are reported for a variety of biogenic and anthropogenic 
NMCs. The measurements are sufficiently precise for use in calculating fluxes by 
the gradient method. They are also valuable as a record of the ambient trace gas 
concentrations present in the region.

10.2.2 Confidence Level/Accuracy Judgment

The investigators are quite confident in the C2-C10 data.   Compound 
identification is made primarily by retention time only.  This may lead to 
improper identifications, particularly for the larger hydrocarbons, such as C10.  
Users are cautioned that although the identifications are likely correct, they 
are not guaranteed.

10.2.3 Measurement Error for Parameters

Absolute concentrations are considered accurate within 20%, limited primarily by 
the uncertainty in the concentrations in the calibration standards. Uncertainty 
in gradients calculated from these concentrations is determined by the precision 
of the analysis, which is quoted in section 5.2.1.1.

10.2.4 Additional Quality Assessments

As data from other investigators become available, these results will be compared 
with theirs and the data and documentation updated as necessary.

10.2.5 Data Verification by Data Center

Data were examined for general consistency and clarity.

11. Notes

11.1 Limitations of the Data

None given.

11.2 Known Problems with the Data

Three samples in this data set contain unusually high levels of anthropogenic 
hydrocarbons:

     12.4m 02-Jun-94 13:25
     12.4m 02-Jun-94 14:35
     23.3m 04-Jun-94 12:00.

This is not a problem with the GC analysis; values from the two GC-FID systems 
for C6 hydrocarbons agree well. The high concentrations of light hydrocarbons 
such as ethane and propane indicate that contamination of the canisters is not a 
factor; these species are removed very effectively by the cleaning procedure. In 
fact, 23.3m 04-Jun-94 12:00 was collected in a new canister purchased for this 
project. The investigators suggest referring to other measurements of trace gas 
concentrations at these times to determine whether a significant, transient, 
local anthropogenic source existed.

11.3 Usage Guidance

Not all species identified are included in this data set.  Researchers interested 
in specific compounds should contact the investigators directly for further 
information about the data.

11.4 Other Relevant Information

None given.

12. Application of the Data Set

These data are intended for use in the study of atmosphere-biosphere 
interactions, and the atmospheric chemistry of biogenic and anthropogenic 
hydrocarbons.  The data have been used in conjunction with other data collected 
at the sites by other researchers for the calculation of biogenic hydrocarbon 
emissions from the various sites.  

13. Future Modifications and Plans

None given.

14. Software

14.1 Software Description

HP 5970 GC-MS Workstation v. 3.2 software
HP PC-ChemStation v. 1.01 software

14.2 Software Access

Not applicable.

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 Section 15.1

15.3 Procedures for Obtaining Data

Users may place requests by telephone, electronic mail, or fax.

15.4 Data Center Status/Plans

The TGB-09 NMHC data are available from the Earth Observing System Data and 
Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed 
Activ Archive Center (DAAC).  The BOREAS contact at ORNL is:

ORNL DAAC User Services
Oak Ridge National Laboratory
(865) 241-3952
ornldaac@ornl.gov
ornl@eos.nasa.gov

16. Output Products and Availability

16.1 Tape Products

None.

16.2 Film Products

None.

16.3 Other Products

Comma-delimited American Standard Code for Information Interchange (ASCII) text 
files.

17. References

17.1 Platform/Sensor/Instrument/Data Processing Documentation

Sample analysis is performed by standard chromatographic techniques. No knowledge 
specific to the GC-FIDs used is required in order to assess or interpret the 
data. Any analytical instrumentation text should give the user sufficient 
information about GC-FID.

17.2 Journal Articles and Study Reports

A comprehensive review of sample analysis and data analysis in the laboratory may 
be found in the Ph.D. dissertation of Byron Kieser and the Ph.D. dissertation of 
Bertram Thomas Jobson:

Kieser, B. 1997. Measurements of Biogenic Hydrocarbon Emissions from the Boreal 
Forest. Department of Chemistry, York University.

Jobson, B.T. 1994. Seasonal Trends of Non methane Hydrocarbons at a Remote Boreal 
and High Arctic Site in Canada Department of Chemistry York University.

Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment 
Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). 

Sellers, P.and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan. 
Version 1996-2.0, NASA BOREAS Report (EXPLAN 96). 

Sellers, P.and F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue.

Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere 
Study: 1994 Operations. NASA BOREAS Report (OPSDOC 94). 

Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere 
Study: 1996 Operations. NASA BOREAS Report (OPSDOC 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. 

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
    EOS     - Earth Observing System
    EOSDIS  - EOS Data and Information System
    FID     - Flame Ionization Detector
    GC      - Gas Chromatograph(y)
    GMT     - Greenwich Mean Time
    GSFC    - Goddard Space Flight Center
    HP      - Hewlett Packard
    IFC     - Intensive Field Campaign
    MSD     - Mass Selective Detector
    NASA    - National Aeronautics and Space Administration
    NMHC    - Non-Methane Hydrocarbons
    NSA     - Northern Study Area
    OA      - Old Aspen
    OBS     - Old Black Spruce
    OJP     - Old Jack Pine
    ORNL    - Oak Ridge National Laboratory
    PANP    - Prince Albert National Park
    ppbv    - Parts Per Billion by Volume
    pptv    - Parts Per Trillion by Volume
    psi     - Pounds Per Square Inch
    SSA     - Southern Study Area
    TGB-09  - Trace Gas Biogeochemistry Team 9
    URL     - Uniform Resource Locator

20. Document Information

20.1 Document Revision Date

Written:       22-Nov-1994
Last updated:  02-Jul-1998

20.2 Document Review Date(s)
BORIS Review:  02-Jul-1998
Science Review: 

20.3 Document ID

20.4 Citation

20.5 Document Curator

20.6 Document URL

Keywords

Nonmethane hydrocarbons
Carbon flux
TGB09_NMHC_DATA.doc
07/07/98