EPA/600/ A-96/081
96-RP128.02
Hourly Measurements of VOCs by AutoGC
at the New Hendersonville, TN Southern
Oxidants Study Site - June 17-27,1995
William A. McClenny
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina
E. Hunter Daughtrey, Jr., Keith G. Kronmiller, Jeffrey R. Adams and K.D. Oliver
ManTech Environmental Technology, Inc.
Research Triangle Park, North Carolina
Air & Waste Management
ASSOCIATION
~
Since 1907
For Presentation at the
89th Annual Meeting & Exhibition
Nashville, Tennessee
June 23-28, 1996
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Hourly Measurement of VOCs by AutoGC
At The New Hendersonville. "FN Southern Oxidants Study Site
June 17-27. 1995
William A. McClenny
U.S. EPA
79 Alexander Drive
Research Triangle Park, NC 27711
E. Hunter Daughtrey, Jr.
Keith G. Kronmiller
Jeffrey R. Adams
K.D. Oliver
ManTech Environmental Technology, Inc.
2 Triangle Drive
Research Triangle Park. NC 27709

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96-RP 128.02
INTRODUCTION
The North American Research Strategy for Tropospheric Ozone (NARSTO) program has
sponsored the development oi' advanced measurement tools for monitoring organic atmospheric
compounds related to the formation of tropospheric ozone. Some of these compounds are known
to be emitted from anthropogenic sources, others originate from biogenic sources, and some are
created by reactions in the ambient air. Many compounds are reactive so that the transport and
conditioning of the air sample must be undertaken with care to avoid loss of .sample integrity.
New autoGC instrumentation was demonstrated over a ten day period as part of the NARSTO
contribution to the summer 1995 Southern Oxidants Study (SOS) at the New Hendersonville. TN
site, northeast of Nashville. This was a rural site although within a mile of a major highway and
close to residential subdivisions. The site was approximately 15 miles from downtown
Nashville. T his presentation documents the capabilities of the new autoGC by showing some of
the interesting compound variations that were observed when monitoring with hourly updates.
EXPERIMENTAL
The autoGC system was comprised of a XonTech Model 930 sample concentrator, a XonTech
Model 940 cryogenic concentrator, and a Varian STAR 3700 GC with a Saturn II ion trap. The
reader is referred to the companion presentation by Daughtrey et al.; for details of the system and
its operational characteristics. The system is designed to reduce the water content of air samples
while retaining water-soluble compounds. This is done in three ways, first during sample
concentration onto a multisorbent packing when approximately 2/3 of the water vapor breaks
through the packing and then during a dry purge of the packing with He when another 50% of
the water vapor is lost. Finally the sample is split during transfer to the GC column so that only
20% is analyzed. The total reduction in water is estimated as greater than 90%.
At the New Hendersonville site, sample air was channeled at a rapid rate through large diameter
tubing from the top of a 30m tower. A heated secondary tubing was used to route air from the
tower tube to a heated manifold equipped with a sample port leading past the inlet to the sample
concentrator. A second ten day study was performed near the EPA facility in the Research
Triangle Park. NC using the same secondary tubing (heated) but elevated only approximately 10
m above the ground. Some of the interesting types of observations made in the Nashville field
study were made again.
RESULTS AND DISCUSSION
As expected, the extent of diurnal variations from different compounds depended on wind
direction. Generally rural areas to the north contributed a higher biogenic mixture at the site than
did the area to the south and southwest in the direction of Nashville. Significant differences in
concentration levels for trace VOCs were found in the Research Triangle Park. NC as compared
to the New Hendersonville. TN site.

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96-R PI 28.02
Isoprene, Alpha and Beta Pinene
Some typical diurnal variations obtained for compounds generally identified as biogenic
emissions were seen at the New Hendcrsonville site as shown in the f igures la&b. figure la
shows the typical diurnal variation of the compound isoprene over the ten day study period. The
estimates of concentration are based on a calibration using a reference standard obtained from
Alphagaz (Walnut (.'reek, C'A). The patterns are well defined as repetitive, systematically
varying changes with one dominant concentration peak per day occurring in the time span
between noon and early evening. Similar patterns have been noted in Atlanta. Georgia2.
although the peak concentrations are much more pronounced in the data from New
Hendersonville. figure lb shows the diurnal patterns of alpha pinene. indicating a pattern of
concentration that generally peaks at the same time as isoprene. Concentration levels arc based
on calibrations made by dynamic dilution of a 10 ppmv standard gas mix from Alphagaz. When
alpha pinene is plotted versus beta pinene, as in Figure 2a, the two are shown to be linearly
related, a fact that suggests that the two are driven by the same mechanism. When this
experiment was repeated at the Research Triangle Park. NC. the same linear relationship was
noted between the two compounds although a factor of forty increase in average concentrations
was noted. This may be the result of emissions from the different types of trees in the Research
Triangle as compared to Nashville. Nashville has primarily deciduous trees while the Research
Triangle Park is dominated by varieties of southern pine.
Higher Aldehydes
Throughout this study and in other studies in rural Alabama near Mobile and at a site in the semi-
rural environment of the Research Triangle Park. NC. a number of higher molecular weight
aldehydes are present and often dominate in chromatograms of samples from the ambient air. As
an example of this. Figure 1c shows the apparent pronounced diurnal variations of decanal at the
New Hendersonville site, with a peak in concentration at noon (central daylight saving time).
Similar variations were observed for nonanal and lower molecular weight aldehydes. The
variations arc superimposed on what appears to be a monotonicallv decreasing background
concentration (note trend of lowest nonzero concentration) during the course of the study.
Values of concentrations, although high and easily observed on the chromatograms, are subject
to unresolved uncertainties associated with the method of calibration and cannot be specified
accurately at this point; the values shown are therefore shown as a percentage of the maximum.
However, as with the case of alpha and beta pinene. the concentrations of decanal and nonanal
are linearly related as noted in Figure 2b. and appear to be driven by the same mechanism,
possibly temperature. The observation of these aldehydes in Japan as reported by Yokouchi and
coworkers-' and in Italy as reported by Ciecioli and coworkers4 seem to confirm these
observations. The same type of diurnal concentrations patterns were noted at the Research
Triangle Park and nonanal and decanal concentrations were again observed to be linearly related.

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96-RP128.02
The investigation of possible artifact formation of aldehydes during samnle transport and
conditioning must still be completed before accepting these data as what actually occurs m the
ambient air. In the present case the adsorbent Tenax GR was the first adsorbent in the sample
concentrator trap and must still be examined for potential artifacts due to the reaction of
atmospheric compounds, most notably ozone. In previous research Helmig and Greenberg^
report that n-aldehyde species observed in their ambient air sampling with Tenax and Tenax GR
are unlikely to be due to adsorbent and system contaminants.
Benzene, Toluene, and o-Xylcnc
Anthropogenic sources of the BEX (benzene, toluene, and xylene) compounds were evident in
the patterns observed when plotting wind direction versus concentrations. As noted in Figure 3
for benzene, toluene and o-xylene versus wind direction, the patterns indicate pronounced
common sources of the three at 220-230 degrees from north and a source of only toluene at 30-40
degrees. Traffic activity from the general direction of downtown Nashville would explain the
common source of BEX. We have noted such patterns in previous field studies and have
suggested their use to locate emission sources and to spot departures from toxic release
inventories on a presence/absence basis 6.
CONCLUSION
The new type of autoGC system used in this study was highly effective in producing an
essentially complete, hourly update of VOC concentrations from the ambient air. The results
promise to provide a database rich in information on the prevalence and variation of both
biogenic and anthropogenic compounds. While the demonstration of monitoring techniques was
the main objective of this study, a brief review of the data indicates the presence of potentially
important information on the prevalence of aldehydes and pinenes. and the factors affecting their
diurnal variations. Due to the hourly updating of the data, abrupt changes in concentration of
toluene, benzene and other compounds are immediately evident in plots of concentration versus
wind direction and can be used to identify the effect of local sources on the VOC database.
DISCLAIMKR
The information in this document has been funded wholly or in part by the United States
Environmental Protection Agency (EPA) under contract 68-D0-0068 to Man Tech Environmental
Technology. Inc. It has been subjected to Agency review and approved for publication. Mention
of trade names or commercial products does not constitute endorsement or recommendation for
use.
4

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96-RP 128.02
REFERENCES
1.	E.H. Daughtrey. Jr.. K..G. Kronmiller, J.R. Adams, C.R. Fortune. K.I). Oliver, and W.A.
McClenny. Interpretation and Data Quality Evaluation for Hourly Measurements of Target
VOCs at the New Hendersonville, I N. Southern Oxidants Study Site. June 17-27. 1995. Paper
96-RP 128.03. 1996 A&WMA Annual Meeting. Nashville. TN.
2.	The State of the Southern Oxidants Study: Policy-Relevant Findings in Ozone Pollution
Research, 1988-1994. prepared by W.L. Chameides and E.B. Cowling, c/'o Southern Oxidants
Study, College of Forest Resources, NC State University. Raleigh, NC, April 1995.
3.	Y. Yokouchi. H. Mukai, K. Nakajima. and Y. Ambe, "Semi-volatile aldehydes as
predominant organic gases in remote areas," Atmos. Environ. 24A: 439 (1990).
4.	P. Ciccioli, E. Brancaieoni, F. Massimiliano. A. Cecinato and A. Brachetti, " Ubiquitous
occurrence of semi-volatile carbonyl compounds in tropospheric samples and their possible
sources", Atmos. Environ. 27A(12): 1891 (1993).
5.	D. Helmig and J.P. Greenberg, "Automated in situ chromatographic-mass spectrometric
analysis of ppt level volatile organic trace gases using multistage solid-adsorbent trapping", J.
Chromatogr. A 677:123 (1994).
6.	W.A. McClenny, K.D. Oliver, and J.D. Pleil. "A field strategy for sorting volatile organics
into source-related groups," Environ. Sci. & Technol. 23: 1373 (1989).
NOTE TO EDITORS
Under the new federal copyright law,
publication rights to this paper are
retained bv the author(s).

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site: (a) benzene; (b) toluene; and (c) o-xylene.
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Replacement Figure 2(a) Plot of a- versus P-pinene at the New Hendersonville Site.
For Presentation: Hourly Measurement of VOCs by AutoGC at the New Hendersonville,
TN Southern Oxidants Study Site, June 17-27,1995 - Paper 96-RP128.02 by McClenny, et
al.
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TECHNICAL REPORT DATA
1. REPORT HO.
EPA/600/A-96/081
2.
3.RECIPII
4. TITLE AND SUBTITLE
Hourly Measurement of VOCs by AutoGS at the New
Hendersonvilie, TN Southern Oxidants Study Site June
17-127, 1995
5.REPORT DATE
6 . PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
W.A. McClenny; OSEPA & E.H. Daughtrey, Jr., K.G.
Kronmiller, J.R. Adams and K.D. Oliver; Mantech
8.PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Mantech Environmental
Research Triangle Park, NC
10.PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-DO-0106
12. SPONSORING AGENCY NAME AND ADDRESS
US Environmental Protection Agency
Research Triangle Park, NC 27711
13.TYPE OF REPORT AND PERIOD COVERED
publication of proceedings
14 , SPONSORING AGENCY CODE
EPA/600/09
IS. SUPPLEMENTARY NOTES
16. ABSTRACT
The North American Research Strategy for Tropospheric Ozone (NARSTO) program has
sponsored the development of advanced measurement tools for monitoring organic
atmospheric compounds related to the formation of tropospheric ozone. Some of these
compounds are know to be emitted from anthropogenic sources, other originate from
biogenic sources, and some are created by reactions in the ambient air. Many compounds
are reactive so that the transport and conditioning of the air sample must be
undertaken with care to avoid loss of sample integrity. New autoGC instrumentation was
demonstrated over a ten-day period as part of the NARSTO contribution to the summer
1995 Southern Oxidants Study (SOS) at the New Hendersonvilie, TN site, northeast of
Nashville. This was a rural site although within a mile of a major highway and close
to residential subdivisions. The site was approximately 15 miles from downtown
Nashville. This presentation documents the capabilities of the new autoGC by showing
some of the interesting compound variations that were observed when monitoring with
hourly updates.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/ OPEN ENDED
TERMS
c.COSATI



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RELEASE TO PUBLIC

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