>EPA
United States
Environmental Protection
Agency
Environmental Sciences Research EPA-600 3-79-010
Laboratory February 1 979
Research Triangle Park NC 27711
Research and Development
Non-Urban
Hydrocarbon
Concentrations in
Ambient Air
North of
Houston, Texas
>A/600/3-79/010
r r
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-79-010
February 1979
NON-URBAN HYDROCARBON CONCENTRATIONS
IN AMBIENT AIR NORTH OF HOUSTON, TEXAS
By
Robert L. Seila
Atmospheric Chemistry and Physics Division
Environmental Sciences Research Laboratory
Research Triangle Park, North Carolina 27711
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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DISCLAIMER
This report has been reviewed by the Environmental Sciences Research
Laboratory, U.S. Environmental Protection Agency, and approved for publication.
Mention of trade names or commercial products does not constitute endorse-
ment or recommendation for use.
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ABSTRACT
In January 1978, a study was undertaken at Jones State Forest, 38 miles
north of Houston, Texas, to determine the concentrations of non-methane
hydrocarbons, methane, and carbon monoxide; to detail the composition of
hydrocarbons (especially of the vegetation); and to discover the sources of
non-methane hydrocarbons. Thirteen 3-hour integrated Tedlar bag samples
and five grab samples using stainless steel cans were collected over a
39-hour period. The samples were returned to the Research Triangle Park
laboratory for analysis, where the can samples showed lower non-methane
hydrocarbon concentration values that did the bag samples. Sources of
paraffins (72% of the non-methane hydrocarbons) and the other hydrocarbons
were found to be: vehicular exhaust (35%), the forest's vegetation (2%),
the city of Houston (22%), and the region between Houston and the forest
(32%). Isoprene and alpha-pinene were the vegetative hydrocarbons noted,
with the latter showing a destinctive 24-hour cycle of concentration
variation.
This report covers a period from January to April 1978 and work was
completed as of December 1978.
111
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CONTENTS
Abstract ill
Figures vi
Tables vii
Acknowledgement viii
1. Introduction , 1
2. Conclusions 2
3. Recommendations 3
4. Experimental 4
Location 4
Sampling Methods 4
Analysis Methods 8
5. Results and Discussion 11
NMTHC, CH , CO Results 11
Bag/Can Differences 11
Composition of Jones State Forest NMTHC 16
Natural Gas Composition 16
Sources of Jones State Forest NMTHC 17
Source Analysis Results 19
Vegetative Hydrocarbons 21
o /
References
Appendices
A. Detailed Hydrocarbon, CO Data Summary 26
B. Source Contribution Calculations 28
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FIGURES
Number Page
1 Location of Jones State Forest 5
2 Sampling sites at Jones State Forest 6
3 Sequential ambient air sampler 7
4 Hydrocarbon analysis chromatographic system 10
5 Jones State Forest NMTHC, CH,, and CO concentration
results for January 4-6, 1978 12
6 Acetaldehyde concentration versus storage time in
stainless steel cans and Tedlar bags 15
7 Hydrocarbon-to-acetylene ratios of Houston vehicular
emissions, Houston downtown air, and Jones State Forest
air 17
8 Diurnal variation of a-pinene, ethane, and wind speed at
Jones State Forest, January 4-6, 1978 23
vi
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TABLES
Number Page
1 GC Columns and Methods for Hydrocarbon Analyses 9
2 Comparison of NMTHC and CO Measurements in JSF 11
3 Detailed Comparison of JSF Can and Bag Samples 13
4 Oxygenate Concentrations of JSF Can Samples Compared with
the Previous Samples from the Same Cans 14
5 Hydrocarbon Composition of JSF on the Afternoon of
January 5, 1978 16
6 Composition of Houston Commercial Natural Gas 16
7 Sources of Jones State Forest NMTHC 20
8 Comparison of Houston and North Houston Light Paraffin/
Ethane Ratios to those of Natural Gas and Refinery Emissions... 21
A-l Jones State Forest Hydrocarbon and Carbon Monoxide Data 27
vii
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ACKNOWLEDGEMENT
The author acknowledges the assistance of Mr. James A. Reagan,
Environmental Sciences Research Laboratory, for assistance with the
statistical methods and Mr. William A. Lonneman, Environmental Sciences
Research Laboratory, for general technical assistance.
viii
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SECTION 1
INTRODUCTION
The importance of vegetative hydrocarbons in the photochemical production
of ozone is an ongoing subject of controversey and debate. The issue has
been defined and discussed by Dimitriades and Altshuller (1) and reviewed
and analyzed by Coffey and Westberg (2,3). The data concerning photochemical
reactivities, emission rates, and ambient concentrations of vegetative hydro-
carbons are the evidence upon which analyses and opinions are based. This
report concerns the ambient concentration component of the issue.
Whitehead and Severs reported a mean ambient non-methane total hydro-
carbon (NMTHC) concentration of 8.7 ppm for 35 morning samples collected at
W.G. Jones State Forest (JSF), a 1700 acre tract located in Montgomery County
38 miles north of Houston, Texas. They concluded that the "high NMTHC levels
observed were produced by the forest vegetation" (4). The results of White-
head and Severs seem to run counter to the prevailing evidence concerning
ambient vegetative hydrocarbon concentrations. Westberg reviewed the avail-
able ambient concentration data and concluded that natural hydrocarbon con-
centrations are of the order of a few ppb carbon (ppbC) , even in forested
regions (5). The ambient alpha-pinene concentrations measured by this
laboratory at a loblolly pine plantation in central North Carolina were only
a few ppbC, ranging from 0.6 to 13 for over 300 samples collected above the
canopy during midday. The highest concentration observed within the canopy
itself was 55 ppbC during night inversion conditions. Even when limbs were
enclosed in Teflon bags - a method for determining vegetative emission rates
(6) - the NMTHC concentrations rarely exceeded 8.7 ppm.
Since Whitehead and Severs used a total hydrocarbon analyzer for their
investigation, they had no means for determining the specific hydrocarbons
contributing to their NMTHC values. In order to determine the specific
hydrocarbons and their contributions to the NMTHC burden at JSF a three-day
sampling program was undertaken. This report presents the results of that
study.
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SECTION 2
CONCLUSIONS
The conclusions herein concern the ambient air concentrations, com-
position, and sources of hydrocarbons at JSF. Because of the limited nature
of the sampling program, the conclusions are valid only for the period of
the study when the wind was from a southerly direction.
The NMTHC concentrations at JSF ranged from 0.1 to 0.5 ppm and consist
primarily of paraffins. The NMTHC composition during this study was 72%
paraffin, 18% aromatic, 6% olefin, 2% acetylene, and 2% vegetative.
The vast majority of NMTHC in the air of JSF, 89% in this study were
transported there from outside sources. The sources can be divided into
two main categories: vehicular and non-vehicular. In this study, vehicular
sources accounted for 35% and non-vehicular sources accounted for 54% of
Jones State Forest NMTHC. Of the non-vehicular hydrocarbons 41% were due
to Houston sources, and 59% were due to sources north of Houston. Refinery
and natural gas emissions appear to account for most of the non-vehicular
hydrocarbons.
The vegetative hydrocarbon concentrations at JSF were low; they were less
than 10 ppbC and represented only 2% of the NMTHC burden.
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SECTION 3
RECOMMENDATIONS
Background sampling at JSF when the wind is from the northwest is
desirable in order to better ascertain the effects of Houston on JSF NMTHC.
Sampling of geogenic oil and natural gas seeps in the Houston area is
suggested in order to estimate the magnitude of natural petroleum emissions.
Sampling of gaseoline, refinery emissions, and commercial and geogenic
natural gas in the Houston area is recommended in order to perform a thorough
source reconcilation for Houston similar to that done for Los Angeles by
Mayrsohn and Crabtree (7).
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SECTION 4
EXPERIMENTAL
LOCATION
Jones State Forest is located one mile west of Interstate Highway 45 on
Farm to Market Road (FM) 1488, and five miles southwest of Conroe, the
nearest town. Figure 1 shows its location relative to Houston. It is
operated hy the Texas Forest Service for research and recreation (picnicking
and camping). The predominant vegetation is loblolly pine.
SAMPLING METHODS
The JSF sampling consisted of diurnal sampling using bags, and grab
sampling using steel cans. Thirteen, 3-hour integrated samples were collected
in Tedlar bags from January 4 to January 6, 1978. Five grab samples were
collected in stainless steel cans on January 5. In addition to the JSF
sampling, two samples of commercial natural gas from the Houston Medical
Center were collected in cans during March 1978.
Samples were collected at two sites within JSF (Figure 2). All of the
thirteen diurnal samples and three of the can samples were collected at a
picnic area about 100 meters from FM 1488. This site was the only location
with electricity for operating a continuous sampling system, yet it was not
an ideal site because of the close proximity of FM 1488, a rural paved road
with moderate traffic. However, southerly winds kept the road downwind of
the picnic site during the entire study, which minimized the impact of local
automobile pollution. The second site was deeper in the forest away from
the potential impact of the road. Two can samples were collected there by
means of a battery operated pump.
Diurnal sampling was performed from 1500 CST, January 4, to 0600 CST,
January 6, 1978. A sequential sampler as diagrammed in Figure 3 was used to
collect 3-hour integrated samples in 10 liter capacity 2 mil Tedlar bags;
construction of the bags is described elsewhere (8). The bags were leak-
tested by evacuation prior to shipment to Houston, and by subsequent visual
inspection just before use. If air had leaked into a bag it was not used.
Just prior to attachment to the sampler, each bag was spiked with 15 ml of a
38 ppm mixture of nitric oxide in nitrogen to destroy any ozone present in the
air being sampled, in order to prevent reaction with the hydrocarbons in the
samples. Only 5 liters of sample were collected to allow for expansion
during the return flight to Research Triangle Park. Upon return three very
deflated bags were presumed to have leaked and were not analyzed.
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LOCATION OF JONES STATE FOREST
JONES
STATE
FOREST
BEAUMONT HIWAY
CHANNELVIEW DRIVE
MB
10
SOUTHWEST
FREEWAY /59\ |
/
0 5 10
KILOMETERS
0 5
I I
MILES
10
Figure 1. Location of Jones State Forest.
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s
2500
— PAVED
---. UNPAVED
• SAMPLING SITE
PARK BOUNDARY
WATER
Figure 2. Sampling sites at Jones State Forest.
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SAMPLE
INLET
BAGS
QUICK CONNECTS
NEEDLE VALVES
PUMP
Figure 3. Sequential ambient air sampler.
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Five internally electropolished 4.5 liter stainless steel cans were
used for the grab samples to provide a comparison with the bag samples.
The cans were purged with approximately 50 liters of pre-purified nitrogen
before shipment to Texas. Three can samples were collected at the picnic
site and two at the interior site. All were collected by purging the cans
with ambient air for five minutes and then pressurizing them to approx-
imately 15 psig, using a Teflon diaphragm dc pump energized by a 12-volt
car battery.
ANALYSIS METHODS
The JSF samples were analyzed for methane, carbon monoxide, and CL to
Cin individual hydrocarbons. The Houston natural gas samples were analyzed
for GI to C,. hydrocarbons.
The C- to GIQ analyses were performed using three columns equipped with
flame ionization detectors; each sample was analyzed once per column. Prior
to injection on each column, 400 ml of sample were concentrated by a cryogenic
preconcentration step. Table 1 lists the columns, cryogenic traps, and
injection technqiues used for the C? to Cin analyses; a schematic of the GC
system is shown in Figure 4. Each analysis required two steps: cryogenic
trapping and injection. When value V.. (Figure 4) was actuated, sample air
was routed from the bag through a cryogenic trap into the 2.5 liter tank,
where the pressure difference was used to fix the volume of air trapped.
Liquid oxygen was the cryogen. Actuation of value V? routed carrier gas
through the trap for the injection. The trap substrates and injection
techniques were determined by the nature of the compounds to be analyzed.
Methane and carbon monoxide determinations were performed on a Beckman
6800 air quality chromatograph.
The natural gas analyses were performed on the same silica gel column
that was employed for the ambient C to C aliphatics analyses. However,
cryogenic preconcentration was not required for the natural gas analyses.
All GC detector outputs were recorded on strip chart recorders, while a
Hewlett Packard digitizer was used to measure peak areas and heights from
the strip chart chromatograms. Response factors determined from analyses of
known concentration compounds were used to convert the area or height
measurements to concentrations. Detailed results of the analyses are con-
tained in Appendix A.
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TABLE 1. GC COLUMNS AND METHODS FOR HYDROCARBON ANALYSES
Analysis
GC Column
Cryogenic Trap
Injection Technique
C2 to C5
and
natural gas
2.4 m X 3 ram SS
with 60/80,
nitric acid
washed, grade 58.
silica gel at room
temperature. He
carrier gas
30 cm X 3 iran SS
with 10% carbowax
1540 on 60/80 Gas
Chrom Z
Front flush trap at
room temperature for
two minutes
C to C
4 8
91 m X 1.5 mm i.d.
open tubular copper
column coated with
dibutylmaleate at
ice water tempera-
ture. He carrier
gas
30 cm X 3 mm SS
with 10% carbowax
1540 on 60/80 Gas
Chrom Z
Front flush trap in
room temperature water
for 25 seconds
C6 to C10
91 m X 1.5 mm i.d.
open titular copper
column coated with
a mixture of m-bis
(m-phenoxy phenoxy)
benzene (MBMA) and
Apiezon L grease at
65 C. He carrier
gas
30 cm X 3 mm SS
with 60/80 glass
beads
Back flush trap in hot
(90°C) water for 45
seconds
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TEDLAR BAG
CARRIER GAS, He
VACUUM PUMP
Figure 4. Hydrocarbon analysis chromatographic system.
10
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SECTION 5
RESULTS AND DISCUSSION
This section of the report discusses the following questions: What are
the CH,, NMTHC, and CO concentrations in JSF and how do they compare with the
measurements of Whitehead and Severs? Do the bag and can sample results
differ? What is the NMTHC composition at Jones State Forest? What are the
sources of JSF NMTHC? and What are the vegetative hydrocarbon concentration
levels in Jones State Forest?
NMTHC, CH , CO RESULTS
A summary of the NMTHC, CH, and CO results of this study is presented
graphically in Figure 5. The NMTHC concentrations were derived by summing
the individual hydrocarbon concentrations. The comparison of the results
of this study and those of Whitehead and Severs are shown in Table 2.
Although the CO measurements of the two studies agree quite closely, the
NMTHC values are very disparate.
TABLE 2. COMPARISON OF NMTHC AND CO MEASUREMENTS IN JSF
„ n.. _ Mean Concentration, ppm
Pollutant 7=-:—: -T— f rr_. .
Whitehead and Severs This study
CO 0.60+0.15 0.63+0.16 (bags)
0.47 + 0.14 (cans)
NMTHC 8.7 0.306+0.096 (bags)
0.184 + 0.069 (cans)
BAG/CAN DIFFERENCES
Observation of Figure 5 suggests that although the CH and CO differences
between the bag and can samples are minimal, the can NMTHC values seem signif-
icantly lower than those of the bags. All but one of the can NMTHC concentra-
tions were lower than the lowest bag NMTHC value. A more detailed examination
of the differences between the bags and cans is provided by Table 3, which
compares the bag and can median concentrations for various groups and indi-
vidual hydrocarbons. Most of the hydrocarbons, though not all, were much
higher in the bags than the cans. Ethane, propane, alpha-pinene, and other
aromatics showed no significant difference, while the oxygenates (acetaldehyde,
11
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o
a
a
o
CH4
CO-
500
400
u
.a
a.
300
200
— INTEGRATED BAG SAMPLES FROM PICNIC AREA
O CAN SAMPLES FROM PICNIC AREA
a CAN SAMPLES FROM FOREST INTERIOR
NMTHC-
D
O
100
1500
2400
1200
2400
TIME OF DAY, CST
Figure 5. Jones State Forest NMTHC, CH4, AND CO concentration results
for January 4-6, 1978.
12
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TABLE 3. DETAILED COMPARISON OF JSF CAN AND BAG SAMPLES
Compound
Ethane
Propane
Isobutane
N-butane
Isopentane
N-Pentane
Cyclopentane
2-Methylpentane
3-Methylpentane
N-hexane
Other paraffins
Ethylene
Propylene
C-4 olefins
C-5 olefins
Toluene
Xylene
Ethylbenzene
Other Aromatics
Acetylene
Alpha-pinene
Acetaldehyde
Propionaldehyde
Acetone
Carbon monoxide
Median
5 Can samples
27.3
17.5
6.2
9.7
5.9
3.6
0.6
1.2
0.9
1.6
11.4
4.2
1.0
1.9
0.6
4.7
5.3
1.0
13.1
2.6
3.0
10.7
14.2
6.9
420
Concentration, ppbC
10 Bag samples
27.6
21.6
13.5
20.2
14.8
11.1
1.4
4.3
3.2
4.1
42.1
8.9
5.1
10.6
1.2
10.9
10.9
2.8
16.8
3.6
3.2
7.9
n.d.
5.7
570
13
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acetone, propionaldehyde) were considerably greater in the cans than the bags.
The oxygenate concentrations in the cans were so great that they were probably
not representative of their true values in JSF.
The median oxygenate concentration for can samples was 33 ppbC, while
the median concentration for bags was 12.3 ppbC. A review of the results of
previous samples stored in the same five cans that were used at JSF is shown
in Table 4. The median oxygenate concentration of previous samples was also
a high 35 ppbC. One can in particular showed very high oxygenate concentrations,
103 and 82 ppbC, for the two samples suggesting an oxygenate artifact effect
which might vary from can to can. Further experiments were conducted to in-
vestigate this phenomenon.
TABLE 4. OXYGENATE CONCENTRATIONS OF JSF CAN SAMPLES COMPARED
WITH THE PREVIOUS SAMPLES FROM THE SAME CANS
E Oxygenates, ppbC
Can number Jones State Forest Previous sample
1
2
3
4
5
Median + s
21
103
49
33
10
- 33+40
23
82
36
35
32
35 + 25
When zero grade nitrogen was stored in the cans no buildup of oxygenates
was observed; however, when ambient air was stored in two cans and two Tedlar
bags, all containers showed a significant buildup of oxygenates over a ten
day storage period (acetaldehyde results are graphed in Figure 6). This
evidence suggests that the JSF oxygenate determinations were biased high and
should not be included in the NMTHC summations. These findings concerning
the oxygenates however do not help to explain the fact that the NMTHC values
were higher in the bags than the cans.
The NMTHC difference must be due to the loss of hydrocarbons on the can
surfaces, the addition of hydrocarbons to the bags by permeation or leaks, or
a combination of the two. Surface deposition should be evidenced by an in-
creasing difference between the bag and can concentrations as the molecular
weights increase, but the data of Table 3 do not show such a trend. The
minimal differences that the bags and cans show in alpha-pinene and the other
aromatics suggest that these hydrocarbons are not deposited onto surfaces.
With the lack of clear surface deposition evidence, it must be concluded that
the bags were contaminated through leaks or permeation (probably permeation
of fuel vapors during the return flight), indicating that the bag results are
an overestimate of NMTHC, and that can results minus oxygenate concentrations
are the best estimates of Jones State Forest NMTHC.
14
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TEDLAR BAGS i
10
Figure 6. Acetaldehyde concentration versus storage time in stainless steel cans and Tedlar bags.
15
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COMPOSITION OF JONES STATE FOREST NMTHC
Table 5 shows the breakdown of the Jones State Forest NMTHC into hydro-
carbon structure categories, of which the paraffins dominate.
TABLE 5. HYDROCARBON COMPOSITION OF JSF AIR ON THE
AFTERNOON OF JANUARY 5, 1978
Category
Paraffins
Aromatics
Olefins
Acetylene
Vegetative hydrocarbons
Total
Composition
72%
18%
6%
2%
2%
100%
Median concentration,
89
22
7
3
3
124
ppbC
NATURAL GAS COMPOSITION
The percentage composition of Houston commercial natural gas was com-
puted from the analysis results of two samples (Table 6). These natural gas
data are used in the later discussion of the sources of Jones State Forest
NMTHC.
TABLE 6. COMPOSITION OF HOUSTON COMMERCIAL NATURAL GAS
Compound
Percentage
Methane
Ethane
Propane
N-Butane
Isobutane
N-Pentane
Isopentane
90.19 + 0.41
5.61+0.36
2.40 + 0.12
0.78 + 0.05
0.47 + 0.04
0.28 + 0.03
0.28 + 0.02
16
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SOURCES OF JONES STATE FOREST NMTHC
An analysis was performed based upon the hydrocarbon to acetylene
(C9H_) ratios within JSF, Houston ambient air, and two Houston tunnels to
determine the sources of Jones State Forest NMTHC. If two assumptions are
made: that vehicular emissions are the only significant source of C«H_ and
that C9H? is unreactive in the atmosphere, then C?H_ can be used to trace
both auto exhaust and the Houston urban plume. The appropriate ratio of
source hydrocarbon to C H multiplied by the Jones State Forest C?H con-
centration yields the hydrocarbon concentration in JSF due to the particular
source. Similar C.H ratioing techniques have been used by others in the
past (9,10,11).
For this analysis to be valid the wind during and somewhat prior to
the sampling period at Jones State Forest had to be from the general
direction of Houston which is to the south. The wind was indeed from a
southerly direction during the entire three-day study; when the can samples
were collected on January 5, the mean hourly average wind direction from
10:00 to 16:00 CST was 192° + 5° at the Texas Air Control Board's Aldine
station. The mean hourly average wind speed during the same eight hour
period was 21.4 4 + 1.7 m sec (12).
The data for the analysis of the hydrocarbon to C-H,., ratios were from
two sources: the can sample results of this report, and Houston metro-
politan area and tunnel (Baytown and Washburn) data reported by Lonneman
et al. (13) This earlier study consisted of two tunnel samples and 19
ambient samples distributed between Jacinto City to the north, Baytown to
the east, Pasadena to the south and the I-45/I-10 interchange to the west.
Seven of the ambient samples were collected on a very stagnant day; their
NMTHC values ranged from 2.9 to 9.1 ppm.
The hydrocarbon to C_H? ratios of the most abundant compounds observed
in JSF were determined for Houston ambient and tunnel air, and JSF air. The
methods of the ratio calculations are shown in Appendix B, while the ratios
themselves are plotted in bar graph form in Figure 7. The three bars under
each group or individual compound represent, from left to right, the compound
to acetylene ratio in Houston tunnel air (vehicular emissions), Houston
metropolitan air, and JSF air. This bar graph provides a visual basis for
explaining the qualitative relationships between the various ratios and the
hydrocarbon sources.
If diluted vehicular emissions were totally responsible for the hydro-
carbons in JSF then the three lines under each compound would be of nearly
equal height. While the paraffins and aromatics do not show this relationship,
the olefinic compounds do, suggesting that the predominant source of olefins
in JSF is vehicular emissions. The slightly decreasing olefin/acetylene
trend indicates that the olefins have reacted somewhat during transport to
JSF.
17
-------
15
14
13
12
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-------
Hydrocarbon sources other than vehicles would be revealed by lines
(hydrocarbon/C H ratios) higher than the corresponding auto exhaust ratios.
The increased ratios of all of the paraffins and aromatics of Houston air
relative to the tunnel air indicate that there are sources of these com-
pounds in Houston other than auto exhaust. In addition, the fact that the
ratios of some of the paraffins (ethane, propane, isobutane) are higher
in JSF air than in Houston air indicates that the sources of these paraffins
are other than Houston or auto exhaust. These sources must be located
between the Houston and JSF sampling areas. This area will be referred
to hereinafter as "north Houston" and defined as the area between 1-610
and the JSF boundary.
The previous graphical analysis suggests three sources for Jones State
Forest NMTHC: vehicles, Houston and north Houston. However, fourth source,
JSF vegetation, can also be added. The contribution of vegetative sources
was determined by direct measurement of the natural hydrocarbons in the JSF
samples. The contributions of each of the other three sources were determined
by calculations based upon hydrocarbon to CLH_ ratios. The Houston and north
Houston sources were further subdivided into individual and grouped hydro-
carbon contributions. One should note that the Houston and north Houston
categories do not include vehicular emission compounds from those areas;
these compounds are from sources other than vehicles. The methods of the
calculations and error estimation are described in detail in Appendix B; the
results are presented in Table 7.
SOURCE ANALYSIS RESULTS
Vehicular emissions comprise 35% of Jones State Forest NMTHC. This
percentage is only slightly higher than the vehicular contributions to
C to C,. hydrocarbons determined by McMurray, et al. (14) and Westberg (15)
for several sites in the Houston metropolitan area itself.
The Houston metropolitan area hydrocarbons from sources other than
vehicles are primarily light paraffins - ethane, propane, butane, pentane.
There were also some heavier paraffins and aromatics present. The sources
of these compounds could be refinery/industry and/or natural gas. Although
the light paraffins are compounds in natural gas, the percentage of the
ethane and propane components of the Houston non-vehicular NMTHC of Jones
State Forest is too low to represent much natural gas. If the assumption
were made that all of the non-vehicular ethane in JSF due to Houston (3.6
ppbC) were from natural gas, then the natural gas concentration in JSF due
to Houston would be 3.6 * 0.57 = 6.3 ppbC, where 0.57 is the ratio of ethane
to NMTHC in Houston natural gas. Of the non-methane hydrocarbons in Houston
other than vehicular emissions, no more than 22% (6.3 ^ 29.1) can be due to
natural gas emissions; the rest must be due to refinery/industry sources.
The non-vehicular hydrocarbons emitted between Houston and Jones State
Forest (north Houston) are also primarily light hydrocarbons—ethane, propane,
isobutane—and some aromatics. In this case the proportions of ethane and
propane suggest that the natural gas component of non-vehicular NMTHC in
north Houston is higher than in Houston air.
19
-------
TABLE 7. SOURCES OF JONES STATE FOREST NMTHC
Concentrations+estimated
standard error, ppbC
Sources
Vehicles
*
Compounds
Individual Total
46.0+8.8
Percent
34.6
Houston
North Houston
n-butane
propane
ethane
isobutane
n-pentane
isopentane
other paraffins
aromatics
Total
ethane
propane
isobutane
aromatics
Total
Vegetative
hydrocarbons
All
2,
2.
.5
.7
7.7+1.9
4.0+1.0
3.6+0.9
.0+0.
.0+0.
1.4+1.2
2.7+2.2
5.7+2.2
23.1+5.9
13.3+3.7
3.5+0.9
2.9+4.3
29.1+9.7
42.8+8.8
21.9
32.2
3.0+0.4 2.2
120.9+12.7 90.9
Measured
NMTHC
Unspecified
NMTHC
133.0+15.4 100.0
12.1+20.0
9.1
Excluding vehicular emissions
Again, the assumption that natural gas is the source of all ethane leads to
a computation that 95% of the non-vehicular NMTHC in JSF from north Houston
is natural gas. The use of propane or isobutane for the same computation
yields values over 100%. This is strong evidence of very significant
natural gas emissions from the north Houston area.
An alternative view of these relationships is to compare the relative
compositions of refinery emissions and natural gas to those of Houston and
north Houston non-vehicular hydrocarbons. Table 8 compares the light
paraffin/ethane ratios of the aforementioned sources. The natural gas
ratios were computed from the samples of this study, while the refinery
ratios were computed from ambient hydrocarbon concentration data reported
20
-------
by Westberg, et ai_. (16) . The Houston ratios more closely resemble
refinery ratios, while the north Houston ratios more closely resemble
natural gas ratios; hence, the primary sources of Houston non-vehicular
hydrocarbons in these two areas appear to be refinery emissions and
natural gas emissions, respectively.
TABLE 8. COMPARISON OF HOUSTON AND NORTH HOUSTON LIGHT
PARAFFIN/ETHANE RATIOS TO THOSE OF NATURAL GAS AND REFINERY EMISSIONS
Sources
Compound
Ethane
Propane
n-Butane
i-Butane
n-Pentane
i-Pentane
Ref inery
1.0
2.7
3.1
1.3
1.1
1.5
Houston
1.0
1.1
2.1
0.6
0.6
0.4
north
Houston
1.0
0.6
0.1
natural
gas
1.0
0.4
0.1
0.08
0.05
0.05
There is evidence of industrial activity north of Houston which could be
a source of natural gas. The carbon monoxide to acetylene ratio in JSF is
much higher than either the vehicular or Houston CO to C«H? ratios, indicating
there are sources of CO other than vehicles (e.g. industrial combustion).
The hydrocarbon measurements of Westberg, et al. in 1976 at a site north of
Houston showed "high aromatic content" (17) which further suggests industrial
activity. The concentration of ethane in Jones State Forest unaccounted for
by dilution of Westberg's north site air was computed to be 15 ppbC. This
suggest that there are considerable sources of ethane between Westberg's
north site and Jones State Forest. The source of this ethane could be
natural gas emissions.
Although there is strong evidence of natural gas in JSF, the sources
are not precisely known. The evidence of industrial activity suggests in-
dustrial sources. However geogenic oil and natural gas seeps are known
to exist along the east coast of Texas (18), which suggests that the
possibility of some geogenic natural gas being present in JSF cannot be
excluded.
VEGETATIVE HYDROCARBONS
Jones State Forest is predominantly a loblolly pine forest, but some
hardwoods, primarily oak and sweetgum are also present. Alpha-pinene and
isoprene are the major emissions of loblolly pine and hardwoods, respectively
(19) . These are the natural hydrocarbons one would most expect to see.,at
JSF. Lesser emissions one might expect are d-limonene, beta-pinene, A -carene,
and beta-phellanderene (20).
21
-------
The results of this study were no exception to previous findings by this
and other laboratories that ambient concentrations of natural hydrocarbons
were in the low ppb carbon range. Only alpha-pinene and isoprene were
observed in any of the samples: Isoprene in two and alpha-pinene in fourteen
(all but one). The two isoprene measurements were 0.4 and 1.2 ppbC; the mean
alpha-pinene concentration (from a range of less than 0.1 to 7.7 ppbC) was
3.6 + 0.5 ppbC. As Table 6 shows, the natural hydrocarbon contributed to
Jones State Forest NMTHC was only 2%.
The diurnal variation of alpha-pinene compared to that of ethane and
the wind speed is plotted in Figure 8. The plot shows that the alpha-pinene
concentration increases rather sharply at sunset as the nocturnal inversion
sets in marked by lowered wind speed. The concentration begins to decrease
during the night as the mixing height above ground rises and decreases further
during the day after the inversion has broken and wind speed has increased.
This diurnal behavior is precisely that which one would expect from a local
source such as the pine trees in JSF. In contrast, the ethane concentration
shows generally the opposite behavior of alpha-pinene. Its concentration falls
as the nocturnal inversion begins, but rises during the day when there is
considerable mixing from above. This behavior indicates that the source of
ethane is not local, but exists outside of JSF. The peculiar rise of ethane
and drop of alpha-pinene during the last 3-hour sampling period was probably
due to a breakup of the nocturnal inversion by rain in the night. The diurnal
behavior of alpha-pinene indicates that meterological conditions influence
the concentration of vegetative hydrocarbons. Daytime meterological con-
ditions of full sun and good mixing render very remote the possibility of
vegetative hydrocarbon concentrations rising to levels of photochemical
significance.
2?
-------
40
35
u 30
•a
o
p
K
O
CJ
25
20
15
20
15
UJ
35
a
i 10
ETHANE
— BAG SAMPLES
0 CAN SAMPLES
CJ
.Q
CL
a.
O
P 5
cr
h-
UJ
CJ
Z
O
a
PINEN
E
______
'
1800 2400 0600
i
M^MB«
1200
isfrJ
/
I I
I I
I
1800 2400
TIME OF DAY (CST) hrs.
Figure 8. Diurnal variation of a-pmene, ethane, and wind speed at Jones State Forest,
January 4-6, 1978.
23
-------
REFERENCES
1. Dimitriades, B. and A. P. Altshuller. International Conference on
Oxidant Problems: Analysis of the Evidence/Viewpoints Presented.
Part I. Definition of Key Issues. J. Air Poll. Control Assoc.
27(4): 299 (1977).
2. Dimitriades, B. and A.P. Altshuller. International Conference on
Oxidant Problems: Analysis of the Evidence/Viewpoints Presented.
Part II. Evidence/Viewpoints on Key Issues. J. Air Poll. Control
Assoc. 28(3): 207-212, 1978.
3. Coffey, P.E. and H. Westberg. International Conference on Oxidants,
1976: Analysis of Evidence and Viewpoints. Part IV. The Issue of
Natural Organic Emissions. EPA-600/3-77-116, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina, 1977.
51 pp.
4. Whitehead, L., and R.K. Severs. Background Hydrocarbon Levels in East
Texas. In: Proceedings of American Institute of Chemical Engineers
83rd National Meeting, Houston, Texas, March, 1977.
5. Coffey and Westberg, p. 42.
6- Zimmerman, P.R. Testing of Hydrocarbon Emissions from Vegetation and
Development of a Methodology for Estimating Emission Rates from Foliage.
Draft Final Report for EPA contract number DU-77-C063, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina, 1978. 97 pp.
7. Mayrsohn, H. and J.H. Crabtree. Source Reconciliation of Atmospheric
Hydrocarbons. Atmos. Environ. 10(2): 137-144, 1976.
8. Seila, R.L., W.A. Lonneman and S.A. Meeks. Evaluation of Polyvinyl
Fluoride as a Container Material for Air Pollution Samples. J. Environ.
Sci. Health-Environ. Sci. Eng., All(2): 121-130, 1976.
9. Lonneman, W.A., S.L. Kopczynski, P.E. Darley, and F.D. Sutterfield.
Hydrocarbon Composition of Urban Air Pollution. Environ. Sci. Technol.,
8(3): 229-236, 1974.
10. Stephens, E.R., and F.R. Burleson. Distribution of Light Hydrocarbons
in Ambient Air, J. APCA, 19(12): 929-936, 1969.
11. McMurry, J.R., R.E. Flannery, L.H. Fowler, and D.J. Johnson. Ambient
Sampling for Stationary and Mobile Source Hydrocarbons in Houston, Texas
24
-------
Presentation: 68th Annual Meeting of the Air Pollution Control Association,
Boston, MA, June, 1975.
12. Driscoll, T. Texas Air Control Board Aldine Station continuous monitoring
data. Private Communication, February 1978.
13. Lonneman, W.A., G.R. Namie, and J.J. Bufalini, Hydrocarbons in Houston
Air. In publication.
14. McMurray, et al., p. 8.
15. Westberg, H., K. Allwine, and E. Robinson. Measurement of Light Hydro-
carbons and Oxidant Transport - Houston Area 1976. EPA-600/3-78-062, U.S.
Environmental Protection Agency, Research Triangle Park, NC, 1978, p. 39.
16. Westberg, H.H., K.J. Allwine, and E. Robinson. Ambient Hydrocarbon
and Ozone Concentrations Near a Refinery Lawrenceville, Illinois -
1974. EPA-600/7-77-049, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, 1977.
17. Westberg, .et.'fL-L* Measurement of Light Hydrocarbons and Oxidant Transport
Houston Area 1976, p. 24,35.
l8- Davis, J.B., Petroleum Microbiology, Elsevier Publishing Company,
New York, 1967, p. 98.
19. Coffey and Westberg, p. 39.
2Q. Zimmerman, pp. 51-52.
21. Dean, R.B. and W.J. Dixon. Simplified Statistics for Small Numbers of
Observations. Anal. Chem. 23(4): 636-638, 1951.
22. Baird, D.C., Experimentation: An Introduction to Measurement Theory
and Experiment Design. Prentice-Hall, Inc. Englewood Cliffs, New
Jersey, 1962, pp. 48-69.
23. Cochran, W.G. Sampling Techniques, John Wiley and Sons, New York,
1963, p.31.
25
-------
APPEOTIIX A
DETAILED HYDROCARBON, CO DATA SUMMARY
Table Al gives a complete summary by time and location.of the Jones
State Forest detailed hydrocarbon, methane, and carbon monoxide data. The
blank spaces in the non-methane hydrocarbon section of the table indicate
the concentrations below the detection limit of 0.1 ppbC. The CH, , CO
data for the 1/05, 16-18 sample are blank because a lack of sample pre-
vented the analysis. The "1" under location indicates the picnic sampling
site, while the "2" indicates the forest interior sampling site (see Figure
2).
26
-------
Table A1. JONES STATE FOREST HYDROCARBON
AND CARBON MONOXIDE DATA
) •. 1 1 , i)?.;
n ii , C',T
ACt 1'YLr'IL
CT 1AM.
P R o P \ n.
1 MM1'!, r \h. 1.
IMJPI.I.TANE
.-!>!. HT A,. L
C\C LOl'LM \.i !.
2-MLT'lYl.PniTAtlE
J-MLTHYLPhlJrAt.E
4-METilYLPENT4t.E
1ILTHYLC YCl.OrCNTAJ.l-
UNKNOWN C6
.\-HEXANL
I'JI.OOUN C6
CYCLOHtXAKE
JUKI. OWN C6
2,3 DIMLIHYLPEKTA.'IE
2,4 DIMETrtYLPENTASE
1C3 l)I-!FTIlYLCYCLOPL..TAta
1T3 DI'lfcTHYLCYCLOPL.ITAI.E
2-Ml.T'iYLHEXANE
3-SILTHYI.IIEXAJL
'JM.i.OWN C7
1ETHYLCYCLOHEXANE
2,2,4 TRIMbTIIYLPENTANE
J-DECANfc
ETHYLENE
PROPYLEHt
ISOBUTYLENE
T-BUTENE-2
C-BUTENE-2, BUTADIENE
2-METHYLBUTEHE-l
2-METI1YLBUTEME-2
PENTENE-I
T-PENTEIiE-2
C-PENTUIE-2
HEXENE-1
T-HEXENE-3
C-IIEXENE-2
TOLUENE
UNKNOWN C7
UNKNOWN C8
ET11YLBENZENE
I'-xYLE'.E
M-XYLENE
0-XYLLNE
UNKNOWN C8
ISOPKOPYLBE.'IZE.SE
UNKNOWN C9
N-PROPYLBEMZEIIL
3,4 ETIlYLTOLUEf.E
UNKNOWN C9
1,3,5 TRI'IF.TIIYEBEHZENE
1,2,4 TRIMETHYLBENZENE
0-ETHYLTOLUEME
U'il.NOWN C9
ACLTALHEilYDE
ACbTONL
pRopiotutncHvrnr
I S 0 P k E N" L
ALP11A-P INI. 'I1:
SUM M1HC
METHANE (PP 1 )
CARBO'J MO'.O-anf: (PPM)
I/
1 i-
2 7
16
1.1
14
9
3
1
3
1
3
1
1
2
4
1
3
3
1
5
16
7
4
5
2
10
4
1
3
1
5
2
1
3
1
8
7
3
257
J4
1 S
1
6
3
. 3
f)
.9
. 1
. 1
n
.i
.2
. 1
ft
.2
. 5
.3
. 5
.5
.2
. 2
.6
.1
.6
.1
.1
.4
.0
7
. 4
. 5
.0
.5
.0
.0
. 7
. 1
.9
. 1
. 3
09
51
I/
1 Lt-
3
26
1 .)
1 2
')
4
,
!
:
1
2
5
4
1 1
4
2
1
6
5
1
3
5
1
6
205
) 4
2 1
1
. 0
/,
. j
. 9
ft
. 3
ft
.2
. 1
, 0
9
ft
5
0
.5
.6
•>
. 7
. 6
8
5
T
. 1
.1
.2
. 3
.3
. 7
0
.4
. 5
. 8
. 3
. 5
. 7
. 7
.9
. 9
. 4
10
55
1 /04
21-2-.
1
9 . 2
'2.2
32.0
14.,
3 I; . 4
14. 7
'j. 7
1 . 1
3. 7
9. d
1 . 1
3. 6
. 1
1 . 4
1. 5
1.9
2.9
1. 5
2. 7
13.8
8.4
3.4
.2
.4
9.4
4.2
3.3
1 . 3
4.4
3. 1
. 1
3.0
3.6
2. 1
3. 3
8. 5
16.0
6. 3
301 . 9
2.11
. 65
1 /05
03-06
1
5.0
>:( . 3
17.1
23.4
1 5.0
12.9
1 . 7
3.0
3.9
1 . 8
5. 9
.2
1 . 7
. 4
1 . 7
3.6
3.9
. 7
.6
•> . i
a. 9
6.6
2. 7
.1
.6
.2
. 1
9. 1
3.5
1.8
1 . 0
3. 3
.6
1. 5
1 . 1
1.5
. 1
.8
7. 2
2. 9
5 . 9
246. 6
2.12
1/Ji
09-12
1
[JAG bA
6. 2
24.4
12.2
22.0
14.1
9.9
1 . 3
4. 5
4. 1
.2
4.4
1 . 3
5.6
. 1
3 . 3
I . 5
.9
2 . 7
4.5
5. 3
l.U
1 .0
15. 6
6.4
4.9
.3
.4
.3
. 1
. 1
10.0
4. 1
2.4
1 .4
4. 2
.8
.8
2.0
1 . 1
2. 1
1.0
16.9
7. 1
2 . 7
272.6
2.24
. 82
12-1 5
1
1 [' 1. h S
2. 5
38.4
I2.'l
9. b
13.6
7. 6
3.6
1 . 8
2.0
3. 1
1 . 9
2.9
9 . 6
2 . 6
2.1
1.3
2.0
2. 1
.9
2 . 8
4.0
I. 9
1 . 7
.3
.2
. 2
.4
9.2
3.8
1.6
. 8
3.0
1 .4
1.9
1 .4
2.2
1.0
1.0
.2
7.0
5. 7
1.3
211.1
2.23
. 55
I/
1 '. -
ur,<
3
3.1
1 ft
1 r,
1 0
17
1
3
3
2
3
1
1
4
1
5
2
1
25
6
6
1
8
3
1
1
15
19
3
304
18
1
' T
. 6
n
. i
. 6
.9
. 5
1
.4
.1
. 1
1
. 1
. 1
ft
7
.2
.6
.0
. 8
.6
.0
.0
4
.2
.3
. 1
.4
.5
.8
.0
.0
. 1
. 3
.4
. 8
.0
. 7
. 4
. 4
.5
1 / J5
lfc-21
1
•ATI >:
2 . 3
23.4
I 2. S
31.6
21.9
21.8
4 . 1
19.5
14. 9
.5
6. 7
3. 5
17.7
1.2
3. 1
.6
3. 1
1 . 1
1.4
6. 4
.6
6.3
4.4
1.0
4 . 3
3.8
3.2
2 . 4
1 . 1
1.6
.8
3.8
. 1
1.4
1.3
25.6
5.8
1 . 7
2.9
2.0
6.4
2.3
2.5
1.4
1. 5
1 .4
1.0
18. 7
3.0
7. 7
356.9
2.06
.57
1/05
21-24
1
, P P B C
1 . 2
17.0
15.0
7 . 6
49.6
40.6
16.0
6 . 1
10. 0
1. 2
7.4
2 . 8
8. 5
2.6
I . 1
1.8
11.5
10. 6
.9
. 7
6.0
16. 7
1.8
8.9
1.6
4. 6
7. 1
1 .5
2.8
1.7
.1
1.9
3.3
14.0
2.7
2.3
1 . 7
6.0
.4
1.4
. 3
.8
. 1
7.0
4. 7
1 . 7
361 . 3
1 . 97
.39
1/06 1/05
00-03 1440
1 1
2.8
27.2
IB. 8
15.2
12.0
15.0
12.2
1 . 1
2 . 5
2.4
. 4
2. 7
1 . 1
4.3
1.2
1.8
2. 0
.9
1 . 0
1.0
2 . 8
5.0
1.0
1.0.0
1.5
11.1
27 7
10.4
5.6
6. 5
5
.6
.4
2. 1
1.4
.2
.8
91.9
4.0
1 i
10.4
16.1
48. 3
4.4
17.2
12.8
34.7
5.7
4.4
3.0
1. 2
530. 9
1 .99
.88
1.8
27. 3
18.4
6. 2
11.2
5.9
4. 7
1 . 2
.9
2.1
1.5
. 5
.5
1 . 2
2.7
1.0
. j
4. 7
3.8
1.0
. 2
2.7
.9
. 3
1.6
.5
12.0
5.4
3.9
1 . 7
138.9
2.13
.69
1/05
160i)
1
CA1I
3. 1
35.4
18. 1
6 . 6
8.6
5.8
3. 3
1 .0
1.5
1 . 1
. 4
1.4
.5
6.3
1.0
. 7
.1
.1
. 1
. 1
4.2
2.2
1. i
. 3
1.3
.1.8
.3
.3
.6
10.7
7.9
14.2
. 4
3.6
165.8
2. 20
. 39
1/05
1620
1
1 530
2
SAMPLES
4.0 2.6
24.1 21.7
14.5 17.5
7.6 ft 9
10.4
5.4
3.4
1.0
. 5
1.6
. 9
.2
. 4
.7
2.4
.3
.6
3.7
1.0
. 6
.1
. 1
.1
.4
4.3
.4
1.0
.6
2.1
2.8
.2
.2
. 4
.4
3.4
4.9
1.8
3.0
123.9
2. 19
.48
9. 7
7.0
4. 6
. 9
. 3
2.2
.7
, 3
.6
.3
.3
16.9
.6
1. 1
7.2
6.8
. 4
1.5
.2
9.4
14.6
2.2
.8
. 2
.9
2.4
5. 3
. 9
. 1
1.8
.1
.3
9.5
56.2
7.0
39.9
2. 7
297. 2
2.15
. 37
1/05
1540
2
2.0
27.6
15.8
8.2
6.0
3.6
.9
1.5
1 0
.6
.3
3.8
1.8
.8
4.2
1.0
.1
.1
.1
.4
9.8
1.9
.6
1.6
. 8
2.7
2.2
.9
1.2
.3
.4
7.4
6. 9
34. 3
3.4
193.2
2.14
.42
27
-------
APPENDIX B
SOURCE CONTRIBUTION CALCULATIONS
In this appendix the methods are shown for the calculations of the
source contributions to JSF and their standard errors (see Table 7) .
The vehicular and Houston hydrocarbon to acetylene ratios, R, were
estimated by the formula:
where [he] is hydrocarbon concentration and [ac] is acetylene concentration.
The JSF ratios were estimated by the formula:
R - {Iff (Eq. 2)
where [he] was the median of the five can samples. Since the number of samples
was small, it was decided that the median rather than the mean, in this case
was a better measure of central tendency (21).
The vehicular component of JSF air was determined by multiplying the
mean tunnel NMTHC/C-H^ ratio times the JSF mean C-H^ concentration:
[NMTHC]V = Rvtac]J (Eq. 3)
The Houston component for individual hydrocarbons was determined in like
manner:
[hc]R = RjjEaclj (Eq. 4)
The non-vehicular contribution due to Houston was determined by sub-
traction:
[hc]RjNV = [hc]R - [hc]y (Eq. 5)
28
-------
= Vac]/" Rytaclj (Eq. 6)
* 7)
The non-vehicular contribution due to north Houston was
- 8>
Equations (3), (7), and (8) were the working equations for the source
contribution calculations of Table 7.
The standard errors of the source calculations were determined by prop-
agation of errors methods described by Baird (22) . The variances of hydro-
carbon contributions were estimated from the variances of the hydrocarbon/
acetylene ratios and the mean acetylene concentration. Determination of
the variances of the hydrocarbon/acetylene ratios was by the formula:
- 2RZ([hcHac]) + R2£[ac]2
- __ o
R n(n-l)[ac]
which is a rearrangement of Cochran's formula 2.34 (23). The variance of the
mean acetylene concentration is
VAc = Z([ac]i - Uc])2
n(n-l)
The variance of the product of R times [ac]is
VHC *
and the estimated standard error is
SHC - (V
29
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
DEPORT NO
EPA-600/3-79-010
3. RECIPIENT'S ACCESSIOr*NO.
ri_E A\D SUBTITLE
NON-URBAN HYDROCARBON CONCENTRATIONS IN AMBIENT
AIR NORTH OF HOUSTON, TEXAS
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
R. L. Seila
8. PERFORMING ORGANIZATION REPORT NO.
5 REPORT DATE
February 1979
PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Sciences Research Laboratory-RTF, NC
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Fark, North Carolina 27711
10. PROGRAM ELEMENT NO.
1AA603 AD-06 (FY-78)
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Sciences Research Laboratory-RTF, NC
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Tn-hniigQ 1/7ft-A/7«
14. SPONSORING AGENCY CODE
EPA/600/09 -
15. SUPPLEMENTARY NOTES
16. ABSTRACT
In January 1978, a study was undertaken at Jones State Forest, 38 miles
north of Houston, Texas, to determine the concentrations of non-methane
hydrocarbons, methane, and carbon monoxide; to detail the composition of
hydrocarbons (especially of the vegetation); and to discover the sources of
non-methane hydrocarbons. Thirteen 3-hour integrated Tedlar bag samples
and five grab samples using stainless steel cans were collected over a
39-hour period. The samples were returned to the Research Triangle Park
laboratory for analysis, where the can samples showed lower non-methane
hydrocarbon concentration values that did the bag samples. Sources of
paraffins (72% of the non-methane hydrocarbons) and the other hydrocarbons
were found to be: vehicular exhaust (35%), the forest's vegetation (2%),
the city of Houston (22%), and the region between Houston and the forest
(32%). Isoprene and alpha-pinene were the vegetative hydrocarbons noted,
with the latter showing a destinctive 24-hour cycle of concentration
variation.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COSATl Field/Group
* Air pollution
* Hydrocarbons
Chemical analysis
* Vegetation
13B
Q7C
Q7D
06C
06F
18 DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19 SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
38
20 SECURITY CLASS (This page/
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
30
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