(18) Hicks, S. D., Limnol. Oceanogr., 4, 316-27 (1959). 119) Weisberg. R. H., Sturees, W., “The Net Circulation in the West Passage of NarragansettBay”, University of Rhode Island Tech-
Report No. 55, Coastal Resources Center, University of Rhode Island, 1977. (8) Schultz, D. M., Ph.D. Thesis, University of Rhode Island, Kingston, R.I., 1974. (9) Wade, T. L., Quinn, J. G., Mar. Enuiron. Res., in press. (10)Mills, G. L., Quinn, J. G., Chem. Geol., in press. (11) Menzel, D. W., Vaccaro, R. F., Limnol. Oceanogr., 9, 138-42 (1964). (12) Van Vleet, E. S., Quinn, J. G., J . Fish. Res. Board Can., 35, 536-43 (1978). (13) Rhode Island Department of Health, Division of Water Supply and Pollution Control,listing of discharges to accompany present water quality condition map, 1975. (14) Hyland, J. L., EPA Ecological Research Series, EPA-600/3-
nical Report 3-73, 1973. (20) Meyers, P. A,, Quinn, J. G., Nature (London), 244, 23-4 (1973). ~ - . --,
(21) Goldberg, E. E., Gamble, E., Griffin, J. J., Koide, M., Estuarine Coastal Mar. Sci., 5, 549-61 (1977). (22) McMaster, R. L., Science 83, 261-7 (1967). (23) Rhoads, D. C., Oceanogr. Mar. Riol. Annu. Reu., 12, 263-300
(1974).
(24) Wade, T. L., Quinn, J. G., Org. Geochem., in press. (25) Youngblood, W. W., Blumer, M., Geochim. Cosmochim. Acta,
39,1303-14 (1975).
77-064, 1977. (15) Hoffman, E. J., Quinn, J. G., in “Proceedings of the ARGO MERCHANT Symposium”,University of Rhode Island, 1978, pp 80-8. (16) Kremer, J. N., Nixon, S. W., “ A Coastal Marine Ecosystem: Simulation and Analysis”, Ecological Studies 24, Springer-Verlag, N.Y., 1978. (17) McMaster, R. L., J . Sediment. Petrol., 30,249-74 (1960).
(26) Farringtan, J. W., Frew, N. M., Gschwend, P. M., Tripp, B. W.,
Estuarine Coastal Mar. Sci., 5 , 793-808 (1977). (27) Thompson, S., Eglinton, G., Geochim. Cosmochim. Acta, 42, 199-207 (1978). Received for reuieu September 22, 1978. Accepted February 21, 1979. This study uas supported by a research grant (04715844088)from the National Sea Grant Program.
Generation of Respirable Aerosols of Power Plant Fly Ash for Inhalation Studies with Experimental Animals Otto G. Raabe”, Kenneth D. McFarland, and Brian K. Tarkington Radiobiology Laboratory and California Primate Research Center, University of California, Davis, Calif. 95616
Methods and equipment have been developed and used for the laboratory generation of fly ash aerosols that simulate respirable particles in effluents from coal-burning power plants. Size-classified fly ash particles smaller than 5 pm in aerodynamic diameter were dispersed with a Wright dust feed mechanism and passed through a specially built cyclone separator to remove agglomerates and large particles. An s5Kr discharger reduced the aerosol electrostatic charge distribution to Boltzmann equilibrium. The resulting aerosol was introduced into a 3.5-m3 exposure chamber suitable for exposure of rodents or nonhuman primates. During a 180-day exposure period, aerosol samples collected by electrostatic precipitation and examined by both transmission and scanning electron microscopy had an average count median diameter of 0.68 pm (0.02 pm SE), with an average geometric standard deviation of 1.54 (0.02 SE). Aerodynamic size distributions, determined with a cascade impactor, had an average mass median aerodynamic diameter of 1.98 pm (0.02 pm SE), with an average geometric standard deviation of 1.65 (0.02 SE). The mean mass concentration was 4.2 mg/m3 (1.4 mg/m3 SD). The methods described are suitable for use in laboratory studies requiring reaerosolization of collected fine particulate matter. During the combustion of coal in power plant furnaces, small particles of aluminosilicate and other products of fusion or sintering of mineral residues are carried with the exhaust gases as fly ash. Concurrently, volatile coal constituents, including hydrocarbons, polycylic organic compounds, and inorganic compounds, can be vaporized and undergo chemical transformations. These fly ash aerosols and various gases flow with the effluent stream to the exhaust treatment systems, where particle collection devices, such as electrostatic precipitators, remove most of the fly ash. However, a small fraction of the mass of fly ash may escape the collection devices and be released to the atmosphere via the smoke stack. These released aerosols contain a higher proportion of the smaller 836 Environmental Science & Technology
respirable particles than found in untreated exhaust gases. Because particles larger than approximately 5 pm in aerodynamic (resistance) diameter (D,,) have relatively high settling speeds (greater than 5 cm/min) and are not usually carried long distances, the respirable particles smaller than about 5 pm D,, are the most likely to form stable aerosols in the atmosphere. The larger particles settle rapidly and are unstable in the air. As the effluent cools in the plant exhaust ducts, in the smoke stack, and finally upon release to the atmosphere, organic and metallic compounds can diffuse to and collect on fly ash surfaces; the smaller, more respirable particles will have a higher relative mass concentration of these compounds. Studies of such aerosols need to emphasize these respirable particles. To examine the potential health hazard associated with these fly ash aerosols, we have developed an improved method for generating laboratory aerosols of fly ash that are representative of the respirable aerosols released from coalburning power plants.
Experimental Collection of Fly Ash. Fly ash was obtained from a power plant in the western United States, burning coal with a relatively low sulfur content. The power plant was equipped with electrostatic precipitators (ESP) operating a t about 110 “C. Fly ash samples were collected either a t the breeching of the smoke stack downstream of the plant’s electrostatic precipitators or from the ESP hoppers. Because of the limited availability of this stack ash, it has been used only for short acute exposures, and hopper ash has been used for the chronic exposure system whose detailed description follows. The stack ash, collected by McFarland et al. ( 1), was classified in situ as four size fractions. The smallest size fraction had a volume median (physical) diameter (VMD) of 2.2 pm (geometric standard deviation, crg = 1.9) and a count median diameter (CMD) of 0.92 pm (og = 1.5). This fraction would have a mass median aerodynamic (resistance) diameter (MMAD,,) ( 2 ) of about 3.6 pm if a uniform particle density 0013-936X/79/0913-0836$01 .OO/O
@ 1979 American Chemical Society
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