(9) Grimsrud, E. P., Westberg, H. H., Rasmussen, R. A,, Int. J . Chem. Kinet., Symp. No. 1,183-95 (1975). (10) Went, F. W., Proc. Natl. Acad. Sci. U.S.A., 51, 1259-67 (1964). i l l ) Went. F. W.. Slemmons. D. B.. Mozineo. H. N.. Proc. Natl. Acad. Sci. U.S.A., 58,69-74 (1967). (12) Rimerton, L. A., Jeffries, H. E., Worth, J. B., Enuzron. Sci Technil., 5,246-8 (1971). (13) Lillian, D., Adu. Chern. Ser., No. 113,211-18 (1972). (14) Stephens, E. R., Price, M. A., in “Aerosols and Atmospheric Chemistry”, G. M. Hidy, Ed., pp 167-81, Academic Press, New York, N.Y., 1972. (15) Pitts, J. N., Winer, A. M., Darnall, K. R., Lloyd, A. C., Doyle, G. J., in “International Conference on Photochemical Oxidant Pollution and Its Control, Proceedings”, B. Dimitriades, Ed., Vol. 11, pp 687-704, EPA 600/3-77-001b,1977. (16) Haagen-Smit, A. J., Wayne, L. G., in “Air Pollution”, A. C. Stern, Ed., 3rd ed, Vol. I, pp 235-88, Academic Press, New York, N.Y., 1976.
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Figure 1. Effect of wind speed on expected canopy concentration of monoterpenes
erature on natural NO and NO2 sources, I remain skeptical of their significance for two simple reasons. Natural background ozone levels, while subject to argument as to sources, are clearly low. There is also abundant evidence of visible injury to vegetation produced by relatively low ozone levels. Thus, I can only conclude that photochemical smog is clearly a product of modern technology. In this regard, the NO and NO:! produced by combustion processes may be a t least as important as hydrocarbon emissions from anthropogenic sources. I would also conclude that while terpene emissions can be a significant hydrocarbon source (and need to be recognized when formulating smog control strategies), this does not in any way mean they are “the cause” of observed smog levels.
Literature Cited (1) Lonneman, U’.A., Seila, R. L., Bufalini, J. J., Enuiron. Sci. Technol., 12,459-63 (1978). (2) Zimmerman, P., “Procedures for Conducting Hydrocarbon Emission Inventories of Biogenic Sources and Some Results of Recent Investigations”, presented at EPA Emission Inventory/ Factor Workshop, Raleigh, N.C., Sept 1977. (3) Zimmerman, P., “The Determination of Biogenic Hydrocarbon Emissions”, presented a t Pacific Northwestern International Section, Air Pollution Control Association Meeting, Nov 1977. (4) Zimmerman, P., Air Pollution Research Section, Washington State University, Pullman, Wash., private communication. (5) Turrell, F. M., Garber, M. J., Jones, W. W., Cooper, W. C., Young, R. H., Hilgardia, 39,428-45 (1969). (6) Went, F. W., Proc. Natl. Acad. Sci. U.S.A., 46,212-21 (1969). (7) Groblicki, P. cJ., Nebel, G. J., in “Chemical Reactions in Urban Atmospheres”, C!. S. Tuesday, Ed., p p 241-67, American Elsevier, New York. N.Y.. 1971. (8) Ripperton, L. A.,Jeffries, H. E., White, O., Adu. Chem. Ser., No. 113,219-31 (1972). 0013-936X/79/09 13-0235$01 .OO/O
@
1979 American Chemical
Society
SIR: Lonneman et al. ( 1 ) recently presented data concerning the abundance of natural hydrocarbons in the Florida atmosphere and advanced the conclusion that natural sources are not significant. Our review of this paper indicates that because of limitations in their sampling, storage, and analytical systems, this conclusion is not justified and further work is required to determine the true abundance of natural emissions. Contrary to the authors’ reasoning as to why terpenes and other natural organic compounds were not detected in the field samples, our calculations indicate that because these compounds are not stable under the conditions imposed by the sampling and storage system, substantial concentrations could have existed in the ambient atmosphere. The samples which best indicate such storage loss are those taken in the orange grove, samples G-2 and G-3. Based on the authors’ assumption that the emissions in the orange grove should include the volatile constituents of orange oil [composition >97% d-limonene, 1-3% myrcene, and a trace of a-pinene (2, 3)]one would expect to find d-limonene and possibly myrcene in the samples. However, calculations of the d-limonene and myrcene storage loss in the Tedlar bags in the same manner as used by the authors for a-pinene show that in the 5 h allotted for reaction with ozone, 98.7% of the d-limonene and 99.98% of the myrcene would have been destroyed. These calculations are based on ozonolysis rate constants of 0.016 and 0.031 ppm-l s-l for d-limonene and myrcene, respectively (4). Obviously, there is a very high probability that these important terpenes were completely destroyed by storage in the Tedlar bags and were never delivered to the GLC for analysis. Our calculations also show that the initial bag concentrations of these terpenes could have been as high as 77 ppbC (parts per billion of carbon) d-limonene and 90 ppbC myrcene. Considering that substantial losses of these terpenes would also be expected during sampling when ozone was also present, it is evident that very high ambient concentrations of these terpenes could have existed. Another problem with the storage loss position taken by the authors is the fact that no data were presented for the terpene laboratory storage test. Based on the ozonolysis rate given, it is assumed that a-pinene was used in this test. Ripperton, Jeffries, and White ( 5 ) have reported that a-pinene reacts much faster with ozone than calculated by the first-order kinetics used by the authors. Ripperton and co-workers postuVolume
13, Number 2,
February 1979 235
_ _ _ _ ~
~~
~~
Table 1. Volatiles from Oranges. Reprinted with Permission from Journal of Food Science (29 (6), 790-5 (1964)); Copyright 1964 by Institute of Food Technologists Peak
1
> 3 4 5
Peak no.
Sullrtance
no.
Methane ’ Methyl chloride’ .4crtaldrhyde ( Ethanol ‘ Acetone ’
1
28R 29 29A
3-Hexen-1-01 2-Hrxcn-1-01 e
Diethyl ether
6
Ethyl Iorniate
7
2-Xlcthylpmtane *
7A
11-Rutyraldchyde \ 3-Metliylpentane ’ 1 Methyl ethyl ketone *
8
Subrtanct
Ethyl hutanoate ’ Ethyl hrnrme’ p-Sylcnc and/or m-Xylcne ’
27
30 35
o-Xylene ’
38
Myrcetie 1 Ethyl hcxatioate Limotictie
40P
Methyl 3-hydroxy-~icxanuate‘ ti-(
ktanol
9P
I-Propanol
42
/ p-lsol)rol)enyltoluene
9
10 11
ri-Hexane Ethyl acetate 2- M etliyl-3-buten-2-ol ’
44 47
12
Methyl cyclopetitane
52
13 14 15
Benzene ‘ Ethyl sec-butyl ether Cycloliexane ’ \ ],I-Diethoxy ethane * I4-Methyl-Z-pentanone 3-Methyl-I-butanol Toluene ‘ ti-Hexanal
53 54
58
Linalool Ethyl 3-hydroxy-hexanoate Terpinen-4-olb Ethyl Octanoate * a-terpineol ’ Decanal Octyl acetate Citronellol
59
Carvone’
6oP 60
Citral Perillaldehyde ’ Biphenyl’
23 24 25 26
’
51
68
I
’
‘
’ Source unknown, perhaps from solvent used to apply resin to the fruit.
’ Previously reported as an orange volatile with identification by classical or spectral methods. Solvent used in present work. ‘ Previously suggested as an orange volatile or tentatively identified. Newly found orange volatile. Fungistat from packaging material.
‘
C ~ hydrocarbons. O Table I (from ref. 8) lists over 30 compounds which might be expected to be present in the orange grove ambient samples and which would be expected to exhibit significant loss in extended Tedlar bag storage. In addition to these compounds, oxygenated and other compounds formed by the atmospheric reactions of the directly emitted natural hydrocarbons would also be expected not to store well in Tedlar bags. Related to this is the question as to whether the GLC system used by the authors was calibrated to detect the higher molecular weight oxygenated compounds such as are shown in Table I. Since only Cp and C3 oxygenates are included in the analytical listings shown in the Lonneman paper, it is assumed that the analysis of these higher molecular weight compounds was not attempted. In summary, our calculations and the work of others show that the results presented by Lonneman are consistent with use of a sampling and storage system in which large losses of natural emissions and their atmospheric reaction products would be expected. To determine the extent of these emissions requires a sampling/storage/analytical system which will handle not only the reactive hydrocarbons and oxygenates which are directly emitted from natural sources, but also the volatile atmospheric reaction products of these compounds as well. This is a complex and difficult problem which requires more sophisticated and advanced techniques than have yet been developed and applied by the authors. Until such techniques are developed and applied, the results presented by Lonneman et al. cannot be interpreted to indicate that natural emission sources are not significant. In the meantime, the statiddynamic enclosure technique developed by Zimmerman (9) minimizes the sampling/storage loss problems associated with ambient sampling methods and appears to provide the most reliable emission data for trees, shrubs, and other natural sources. Literature Cited
lated that a product from the reaction between a-pinene and ozone was rereacting with a-pinene, as one of the steps which leads to aerosol formation. These investigators report that the ratio of a-pinene/Os reacting varies from 2 to 5.5 depending upon initial reactant concentrations. Since under the conditions of the field sample storage, the ozone concentration is probably greater than that of the a-pinene, an enhanced loss of a-pinene over that calculated would be expected. Furthermore, other trace atmospheric constituents such as NO,, SO,., HpO, particulate matter, etc., may react with the a pinene (and other terpenes) and adversely affect storage stability. Experiments to assess these possibilities are necessary before concluding that a-pinene and other terpenes are stable when stored in Tedlar bags for long periods. A further concern with the storage system is the expected loss of oxygenated compounds arising from natural sources, to the walls of the Tedlar bags during storage. While Lonneman et al. show that Tedlar bags are strong sources for some of these compounds, viz. acetaldehyde and acetone, the bags would be expected to be strong sinks for others. Polasek and Bullin (6) have shown that carbon monoxide, stored in Tedlar bags, exhibits an average 42% loss in a 100-h period. This period of time is comparable to the 4 to 5 days that Lonneman et al. stored their samples in Tedlar bags prior to analysis. More reactive oxygenated compounds would be expected to show even greater storage loss. To further complicate matters, Denyszyn and co-workers (7) have indicated that Tedlar bags are sources of significant concentrations (1-2 ppmC) of FID responsive species in the C g to Cl0 range. These authors have also shown that a-pinene and P-pinene, a t the 10-ppbC level, stored in stainless steel containers, exhibit a 400h loss in 2 days and a 100% loss in 1 week. They considered stainless steel containers superior to Tedlar bags for storage of most Cg to 236 Environmental Science & Technology
(1) Lonneman, W. A., Seila, R. L., Bufalini, J. J., Enuiron. Sci.
Technol, 12,459-63 (1978). (2) Kirk-Othmer, “Encyclopedia of Chemical Technology”, 2nd ed, Vol. 14, Wiley, New York, N.Y., 1967. (3) Swisher, H. E., Drug Cosmet. Ind., 90(4),415 (1962). (4) Coffey, P. E., Westberg, H., “International Conference on Oxidants 1976-Analysis of Evidence and Viewprints. Part IV. Issue of Natural Organic Emissions”, Report EPA 600/3-77-116, Research Triangle Park, N.C., Oct 1977. (5) Ripperton, L. A,, Jeffries, H. E., White, O., Adu. Chem. Ser., No. 113 (1972). (6) Polasek, J. C., Bullin, J. A,, Enuiron. Sci. Technol., 12(6),708 (1978). (7) Denyszyn, R. B., Hardison, D. L., Harden, J. M., McGaughey, J. F., Sykes, A. L., “Evaluation of Various Hydrocarbon Sampling Devices”, presented at NBS Symposium on Trace Organic Analysis, Gaithersburg, Md., April 10-13, 1978. (8) Schultz, T. H., Teraniski, R., McFadden, W. H., Kilpatrick, P. W., Corse, J., J . Food Sei., 29, 790 (1964). (9) Zimmerman, P., “Procedures for Conducting Hydrocarbon Emission Inventories of Biogenic Sources and Some Results of Recent Investigations”, Washington State University Report to EPA Emission Inventory/Factor Workshop, Raleigh, N.C., Sept 13-15, 1977.
Kenneth H. Ludlum Bruce S. Bailey Environmental Protection Department Texaco Inc. P.O. Box 509 Beacon, N.Y. 12508
SIR: The correspondence of Sculley agrees in general with the conclusions made in our paper (Enuiron. Sci. Technol., 12,459 (1978)).Although using a different approach, Sculley
This article not subject to U.S. Copyright. Published 1979 American Chemical Society
