Environ. Sei. Technoi. 1983, 17, 435-439
(3) Galloway, J. N.; Cosby, B. J.; Likens, G. E. Limnol. Oceanogr. 1979,24, 1161-1165. (4) Hansen, D. A.; Hidy, G. M. Atmos. Environ. 1981, 16, 2107-2126. ( 5 ) World Meteorological Organization, “Second Analysis on Reference Precipitation Samples”, May 1978. (6) Bates, R. G. “Determination of pH: Theory and Practice”, 2nd ed.; Wiley: New York, 1973. (7) Eisenman, G., Ed., “Glass Electrodes for Hydrogen and Other Cations: Principles and Practice”; Marcel Dekker: New York, 1967; pp 367 and 449. (8) American Public Health Association, “Standard Methods for the Examintion of Water and Wastewater”, 15th ed.; Washington, D.C., 1980. (9) Environment Canada, “Analytical Methods Manual”, Ottawa, 1979. (10) Fisher Scientific Co. “Instruction Manual: Accument Model 620 Digital pH/Ion Meter”; Pittsburgh, PA. (11) Gran, G. Analyst 1952, 77, 661-671. (12) Kluckner, P. D.; Sandberg, D. K., Project Report P0006; Environmental Laboratory, British Columbia, Canada, 1981. (13) Galloway, J. N.; Likens, G. E.; Edgerton, E. S. Water, Soil Air Pollut. 1976, 6, 423-433.
will be further compounded if adequate facilities, precision equipment, and highly trained technical staff are not available. For these reasons field measurement of pH, for network monitoring, is unlikely to achieve an accuracy of greater than 0.1-0.2 pH units. As shown in this work an accuracy an order of magnitude greater is possible with laboratory measurement. Such accuracy is clearly desirable if trends in acid loading, including subtle changes affecting base-line levels, are to be adequately monitored. It is true that if the sample suffers chemical alteration in transit to the laboratory, the advantages of laboratory measurement may be somewhat obscured. However, samples showing the presence of at least 20 pequiv of Hf/L strong mineral acidity are unlikely to undergo significant change (12). The situation for other samples may require further study, but shipping in coolers and minimizing the time in transit should minimize any chemical alteration affecting pH measurement. Registry No. Water, 7732-18-5.
Literature Cited (1) Tyree, S. Y Atmos. Enuiron. 1981, 15, 57-60. (2) World Meteorological Organization, “Fourth Analysis on Reference Precipitation Samples”, Dec 1981.
Received for review December 20, 1982. Accepted February 18, 1983.
Surface Enrichment of Trace Elements In Electric Steel Furnace Dust Marc J. Van Craen, Erlc A. Denoyer, David F. S. Natusch,+ and F. Adams’ Department of Chemistry, University of Antwerp, 8-26 10 Wilrijk, Belgium
Secondary ion mass spectrometry (SIMS) and laser microprobe mass analysis (LAMMA) have been used to study the surface enrichment of trace elements in dusts emitted from an electric steel making furnace. I t is demonstrated that the elements Na, P, S, C1, K, Cr, Mn, Co, Cu, Zn, and Pb are preferentially enriched on the particle surfaces and that several of these elements are appreciably leachable by water. In several cases the chemical forms of the elements are indicated.
Introduction A number of workers have reported the observation that certain trace elements increase in specific concentration (micrograms per gram) with decreasing particle size in particles emitted to the atmosphere from high-temperature combustion or conversion processes (1-5). The mechanism that gives rise to this phenomenon has not been fully established; however it has been suggested (1,6) that certain trace elements, or their compounds, are volatilized at the elevated temperatures encountered during particle formation and then condense onto the surfaces of coentrained particles during emission. Such a mechanism would give rise to surface enrichment of the volatilized elements, and this has been observed for coal fly ash and for automobile exhaust particles (7, 8). The environmental significance of surface enrichment of potentially toxic species is severalfold. First, if it occurs as a result of the proposed volatilization-condensation mechanism, small particles will contain higher concenill trations of trace elements than large particles, and this w promote emission to the atmosphere, atmospheric en+ Present address: Liquid Fuels Trust Board, Wellington, New Zealand.
0013-936X/83/0917-0435$01.50/0
richment, and pulmonary deposition following inhalation (1, 9). Second, surface enrichment results in enhanced concentrations of potentially toxic species being in immediate contact with the external environment (e.g., body fluids). Finally, if the surface-enriched species are soluble, as is the case for coal fly ash and automobile exhaust particles, then they can be readily mobilized to produce possibly adverse environmental or toxicological effects. In order to explore further the universality of the surface-enrichment phenomenon, we have chosen to study dust derived from an electric steel making furnace. The trace elements present are derived from the original ore used, and the high temperatures (1500 “C) involved in the furnace operation are sufficient to volatilize several of the elements known to be present. The techniques employed include secondary ion mass spectrometric (SIMS) determination of elemental depth profiles in particle conglomerates, laser microprobe mass analysis (LAMMA) of individual particles, and X-ray fluorescence spectrometry (XRF) of the bulk particulate sample. In all cases analyses are performed before and after the particles have been leached with water to determine the extent of solubility of surface-enriched species.
Experimental Section Materials. The dust samples were collected in bulk from a baghouse used to control the furnace emissions of a standard electric steel making furnace. The baghouse temperature was 200-246 OC. The feed was scrap iron, and the furnace produces steel ingots and/or bullets for further processing. No attempts were made to separate the dust samples with respect to particle size. Under electron microscopic examination it was found that individual fly ash particles range in size from 0.01 to
0 1983 American Chemical Society
Environ. Sci. Technol., Voi. 17,No. 7, 1983 435
Table I. Mean Surface Concentrations or Range of Concentrations Found for the Electric Furnace Dust Using SIMS element Na A1 Si
c1
K Ca Ti V Cr Mn Fe
co
cu Zn Ba Pb
concentration, % wt surf ace bulk 1.25 f 0.55 0.57 f 0.14 2.1 f 0.1 2.0 f 0.35 0.34 i 0.12 5.0 i: 0.3 0.019 i 0.004 0.057 f 0.020 0.22 f 0.04 8.4 1.8 51 f 4 4.9 f: 1.7 0.12 f 0.02 2-7 0.0097 f 0.0018 3.8 f 0.8
0.10 f 0.05 0.60 f 0.15 3.0 f 0.15 1.3 It 0.25 5.0 f 0.3 0.027 f 0.006 0.041 f 0.015 0.15 f 0.03 4.2 f 0.9
