(4) Federal Water Quality Administration, Office of Operations,
Technical Support Division, “Hazards of arsenic in the environment with Darticular reference to the aquatic environment”, 38 pp, August i970. (5) . . Chansler. J. F.. Pierce, D. A,, “Bark beetle mortality in trees injected with cacodylic acid (herbicide)”, J . Econ. Entomol., 59 (6), 1357-9 (1966). (6) McGhehey, J. H., Nagel, W. P., “Bark beetle mortality in precommercial herbicide thinnings of Western hemlock”, ibid., 60 (6). 1572-4 (1967). (7) Stelzer, M. A,, “Mortality of I p s lecontei attracted to Ponderosa pine trees killed with cacodylic acid”, ibid., 63 (3), 956-9 (1970). (8) Buffam, P. E., “Spruce beetle suppression in trap trees treated with cacodylic acid”, ibid., 64 (4), 958-60 (1971). (9) Frye, R. H., Wygant, N. D., “Spruce beetle mortality in cacodylic acid-treated Engelmann spruce trap trees”, ibid., pp 91116. (10) Newton, M., Holt, H. A., “Scolytid and Buprestid mortality in Ponderosa pines injected with organic arsenicals”, ibid., pp 952-8. (11) Price, D. K., Roberts, W. O., Glass, H. B., Klopsteg, P. E., Commoner, B., Hoagland, H., Holton, G., Rees, M. S., Rieser, L. M., Steinbach, H. B., Thimann, K. V., Wolfe, D. (Editorial), “On the use of herbicides in Vietnam”, Science, 161,235-54 (1968). (12) Wheeler, J. A., “Herbicides in the perspective of 20 months and 20 years”, ibid., 160, 255-6 (1968). (13) Tschirley, F. H., “Defoliation in Vietnam”, ibid., 163, 779-86 (1969).
(14) Pfeiffer, E. W., “Ecological effects of the Vietnam war”, Sci. J., 5 (2), 33-8 (1969). (15) Orians, G. H., Pfeiffer, E. W., “Ecological effects of the war in Vietnam”, Science, 168,544-54 (1970). (16) Constable, J., Meselson, M., “The ecological impact of large scale defoliation in Vietnam”, pp 4-9, T h e Sierra Club Bull., (April 1971). (17) Westing, A. H., “Agent Blue in Vietnam”, N.Y. Times, 120 (41 442), 27 (July 12,1971). (18) Malone, C. R., “Responses of soil microorganisms to nonselective vegetation control in a fescue meadow”, Soil Biol. Biochem., 3,127-31 (1971). (19) Malone, C. R., “Effects of a non-selective arsenical herbicide on plant biomass and community structure in a fescue meadow”, Ecology, 53 (3), 507-12 (1972). (20) Finney, D. J., “Probit Analysis-a Statistical Treatment of the Sigmoid Response Curve”, 318 pp, Cambridge University Press, 1952. (21) Schroeder, H. A,, Balassa, J. J., “Abnormal trace metals in man: Arsenic”, J . Chronic Dis., 19,85-106 (1966). (22) Van Hook, R. I., “Energy and nutrient dynamics of spider and orthopteran populations in a grassland ecosystem”, Ecol. Mon. 41,l-26 (1971).
Received for review January 24, 1974. Resubmitted J u n e 12, 1975. Accepted November 10, 1975. Work supported by the U.S. Energy Research and Development Administration under contract with the Union Carbide Corp. A.P. W . supported by a n Oak Ridge Associated Universities Traineeship for the duration of the study.
Analysis of Carbonaceous Materials in Southern California Atmospheric Aerosols Bruce R. Appel’, Paul Colodny’, and Jerome J. Wesolowski State of California, Department of Health, Air and Industrial Hygiene Laboratory, Berkeley. Calif. 94704
A technique is described for estimating the contributions of elemental carbon and primary organic and secondary organic materials to atmospheric particulate matter collected in California’s South Coast Air Basin. The technique employs a combination of solvent extractions and carbon determinations; primary organics are estimated from the carbon solubilized in cyclohexane and secondary organics by the carbon solubilized by successive extraction with benzene and methanol-chloroform minus the primary organics. At the same time an upper limit estimate of the elemental carbon is obtained from the carbon remaining insoluble after the two-step extraction. Support for this technique is provided for samples collected at four locations.
The carbonaceous material present in atmospheric aerosols is a combination of elemental carbon, organic (including polymeric), and inorganic compounds (e.g., carbonate salts). When considering the origins of atmospheric aerosols, the organic fraction may be further divided into “primary” and “secondary” materials ( I ) . The former term indicates material introduced into the atmosphere directly in the particle state. Materials which, because of their low vapor pressure, condense shortly after introduction into the atmosphere from a n elevated temperature source are also considered “primary”. Secondary refers t o particles formed as the result of homogeneous or heterogeneous reactions in the atmosphere. Present address, MCA Disco-Vision Inc., 1640 W. 228th St., Torrance. Calif. 90511.
While considerable research effort has been devoted t o determining the concentrations and origins of organic particulate constituents known to be hazardous (e.g., polynuclear aromatics), less effort has been devoted to characterizing the nature and origins of carbonaceous material more generally. Even the proportion of the elemental carbon present remains a matter of speculation. Previous studies of carbonaceous matter have primarily examined organic solvent-soluble fractions and include the work of Mader e t al. ( Z ) , Dubois e t al. ( 3 ) ,Ciaccio e t al. ( 4 ) , and Cukor e t al. ( 5 ) . The latter group analyzed solvent extracts from suspended particulate matter collected near a major intersection in New York City. They concluded that the organics strongly resembled used automobile lubricating oils (i.e., were “primary” in origin). Mueller e t al. reported a technique for determining carbonate and noncarbonate carbon (6). Their work in analyzing aerosols from Pasadena, Calif., demonstrated that carbonate carbon was consistently less than 5% of the total carbon present and that noncarbonate carbon (including both elemental and organic carbon) represented from 1844% of the total suspended particulate matter. Recent work includes studies by Grosjean and Friedlander (7) and Grosjean (8).Grosjean compared the ability of various solvents and solvent mixtures t o extract organic carbon. For atmospheric particulate matter collected in Pasadena, Calif., the extraction efficiency of the polar solvents, ethanol and acetone, increased with the ozone concentration measured during the time of particle collection while, for t h e solvents isooctane and methylene chloride, no change was observed. Although Grosjean did not use these results t o quantitate primary and secondary organics, it is Volume 10, Number 4, April 1976 359
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clear from these results that solvent extraction might be so used. As part of the work sponsored by the California Air Resources Board in the Aerosol Characterization Experiment (ACHEX), we have sought methods to determine ambient air concentrations of elemental carbon as well as primary and secondary organics. As in Reference 6, carbonates were again shown to represent less than 5% of the total carbon present and have, therefore, been ignored. Numerous techniques were explored, including column chromatography, high resolution mass spectroscopy, thermal analysis, and multiple solvent extraction with total carbon analyses of the various solvent extracts. We present here a discussion of the latter technique since, thus far, it has proved to be the most useful. The basis of this technique is to equate primary organics in atmospheric aerosols to those organics soluble in cyclohexane and total organics, to those solubilized by successive extraction with benzene followed by methanol-chloroform. An upper limit estimate to the elemental carbon present is obtained from the carbon remaining insoluble after the two-step extraction. The secondary organics are obtained by difference between total and primary organics. All determinations are based upon carbon analyses rather than total weight to avoid errors resulting from solubilization of inorganic salts (e.g., N H ~ N O B ) . The techniques for estimating primary and secondary organics will be supported by comparisons with ozone data obtained during sample collection and used to indicate the extent of photochemical (Le., secondary) organic particle production expected. The technique was applied to samples collected on filters at four locations within California's South Coast Air Basin. Sampling locations for the study are shown in Figure 1. These include a site adjacent to a complex of chemical plants and refineries, Dominguez Hills (DH), and three receptor sites with respect to photochemical smog, West Covina (WC), Pomona (PO), and Rubidoux (RB). As indicators of levels of air pollution on the days sampled, Table I lists maximum values observed for ozone and the lightscattering coefficient (bscat) ( 9 ) , as well as the total suspended particulate matter and particulate carbon averaged over the sampling period shown. The episodes include days of light, intermediate, and heavy photochemical smog. Experimental
Materials. Cyclohexane, benzene, and 1:2 v/v methanolchloroform were Eastman Spectrograde having a nonvolatile residue less than 0.001%. For the 85 ml of each solvent used for extractions, this represents
