Literature Cited (1) Potter, A. E.; Harrington, R. E.; Spaite, P. W. Air Eng. 1968,10, 12-26. (2) Potter, A. E. Am. Ceram. SOC.Bull. 1969,48, 855-8. (3) Borgwardt, R. H.; Harvey, R. D. Environ. Sci. Technol. 1972,6, 350-60. (4) Falkenberry, H. L.; Slack, A. V. Chem. Eng. Prog. 1969, 69, 62-6. (5) Coutant, R. W.; Barrett, R. E.; Lougher, E. H. Trans. ASME 1970, 113. (6) Siegel, S.; Fuchs, L. H.; Hubble, B. R.; Nelsen, E. L. Enuiron. Sci. Technol. 1978,12, 1411-6. (7) Kito. M.: Wen, C. Y. AIChE Symp. Ser. 1974, No. 147, 119-25. (8) Pigford, R. L.; Sliger, G. Ind. Eng. Chem. Process Des. Deu. 1973, 12, 85-91. (9) Hartman, M.; Pata, J.; C o u g h , R. W. Ind. Eng. Chem. Process Des. Deu. 1978,17, 411-9. (10) Chen, Tan-Ping; Saxena, S. C. Fuel 1977,56, 401-11. (11) Best, R. J.; Yates, J. G. Ind. Eng. Chem. Process Des. Dev. 1977, 16, 347-52. (12) Leyko, J. Przem. Chem: 1956,35, 257-64; Chem. Abstr. 1959, 53, 2571-h. (13) Simon, A.; Thummler, Fr.; Klugel, E., Silikattechnik 1955,4, 101-4; Chem. Abstr. 1954,48, 1128-e. (14) Cismaru, D. Reu. Chim., Acad. Repub. Pop. Roum. 1957, 2, 267-78. (15) Hedvall, J. A.; Nordengren, S.; Liljegren, B. Acta Polytech., Chem. Incl. Metall. Ser. 1955,4, 7; Chem. Abstr. 1956,50, 6238. (16) Hedvall, J. A.; Nordengren, S.; Liljegren, B. Chalmers Tek. Hoegsk. Handl. 1955, No. 158; Chem. Abstr. 1955,49, 8719. (17) Shargorodskii, S. D. Ukr. Khim. Zh. (Russ. Ed.) 1950,16, 310-9; Chem. Abstr. 1952,46, 5411-i.
(18) Cismaru. D. Stud. Cercet. Chim. 1958,6, 539-46; Chem. Abstr. 1959,53, 17446. (19) Ginstling, A. M.; Volkov, A. D. Zh. Prikl. Khim. (Leningrad) 1960,33, 274-9; Chem. Abstr. 1960,54, 10618. (20) Weychert, S.; Milewshi, J. Przem. Chem. 1957,13, 690-6; Chem. Abstr. 1958,52, 8495. (21) Osmani. R.: Datar. D. S. J . Indian Chem. SOC.Ind. News Ed. 1957,20, 1-5; Chem. Abstr. 1958,52, 2629. (22) Akerman, K.; Zmudzinski, B.; Orman, Z.; Musieko, Z. Arch. Hutn. 1956,1, 319-39; Chem. Abstr. 1957,51, 12383. (23) Bischoff, F. V. Z. Anorg. Allg. Chem. 1942,250, 10-22. (24) Briner. E.: Knodel. Ch. Helu. Chim. Acta 1944, 27, 1406-14; Chem. Abstr.’ 1945,39, 2923-7. (25) Zinzen, A. Forsch. Geb. Ingenieurwes 1943,14B, 89-104; Chem. Abstr. 1945,39, 1746. (26) Zinzen. A. Z. Ver,Dtsch. Ing. 1944,88,171-8; Chem. Abstr. 1945, 39, 401. (27) Fuji, K. Gypsum 1952, I, 320-3; Chem. Abstr. 1953,47, 4778. 128) Feigl. F. “SDot Tests in Inorganic Analysis”; Elsevier: Amster‘ dam,f958. (29) Lau. K. H.: Cubicciotti, D.; Hildebrandt, D. L. J. Chem. Phys. 1977,66,4932-9. (30) Wheelock, T. D.; Boylan, D. R. Ind. Eng. Chem. 1960, 52, 215-8. (31) Montagna, J. C.; Lene, J. F.; Vogel, G. J.; Jonke, A. A. Ind. Eng. Chem. Process Des. Dev. 1977,16, 230-6. (32) Shewmon, P. G. “Diffusion in Solids”; McGraw-Hill: New York, 1963. (33) Deer, W. A.; Howie, R. A.; Zussman, J. “Rock-FormingMinerals”; Wiley: New York, 1964; Vol. 3. ~~
I
Received for review May 24, 1979. Accepted November 12,1980
Airborne Plume Study of Emissions from the Processing of Copper Ores in Southeastern Arizona Mark Small,+ Mark S. Germani,* Ann M. Small,t and William H. Zoller” Department of Chemistry, University of Maryland, College Park, Maryland 20742
Jarvis L. Moyers Department of Chemistry, University of Arizona, Tucson, Arizona 8572 1
Air-filter samples were collected with a light, twin-engine aircraft in the plumes of five copper smelters in southeastern Arizona and analyzed for 37 elements. Abundances of many volatile and chalcophilic elements are greatly enriched compared to the crustal abundance pattern for those elements. Comparisons of average results for each smelter showed marked differences in the abundance pattern of trace elements on particles released from different smelters. These unique abundance patterns could possibly be used as “fingerprints” to determine contributions of material from various plants at a specific impact point.
Introduction In recent years there has been increased public concern about the potential health effects caused by atmospheric particulate material released by anthropogenic activities. Before the impact of major emission sources on any region can be evaluated, the compositions of particles released from the sources must be known. Considerable work has been done on various industrial and fossil-fuel combustion processes. A t Present address: Midwest Research Institute, Kansas City, MO 64110. Present address: Chemistry Department, Arizona State University, Tempe, AZ 85281.
*
major type of anthropogenic source that has received only limited attention is nonferrous metallurgy processes, particularly the processing of copper ores. Previous studies have shown increased concentrations of many chalcophilic elements in the vicinity of other types of nonferrous metal smelters. For example, Ragaini et al. ( I ) performed studies near a lead smelter complex in Kellogg, ID, and found elevated concentrations of chalcophilic trace elements in soil, grass, and ambient aerosols. Children living in that area have up to 20 times as much lead in their hair as their urban counterparts (2). In an extensive study of a lead smelter in southern Missouri, Jennett et al. ( 3 )found high concentrations of Pb, Zn, Cd, and Cu in the particulate emissions. Jacko et al. ( 4 ) observed high concentrations of Zn, Cd, Ni, Cu, As, and Hg in stack emissions from a zinc smelter. Unfortunately, both of these studies focused on only a few elements. However, they did show that several chalcophilic elements in addition to the major one being processed are released in high concentrations during the processing of nonferrous metal ores. Studies of copper smelters have generally concentrated on only sulfur and arsenic species (5, 6), although a study by Parungo et al. (7) showed that many trace elements emitted from copper smelters are borne by small particles which can be transported long distances and can be deposited efficiently in the lungs.
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The composition of particulate emissions from the processing of copper ores is quite important because >lo% of the world-wide production is concentrated in small areas of the southwestern United States (9).As natural resources become scarce, this area may become more affected by increased energy and nonferrous metallurgical processes. We have determined the elemental composition of particulate material released during copper ore processing by detailed analyses of samples collected in the plumes of several copper smelters. This paper presents the results of the aircraft studies of five smelters near Tucson, AZ, and the companion paper by Germani et al. (8) gives compositions of stack and process samples from the smelters studied.
*
Sites Studied The copper smelters associated with the porphyry deposits of southwestern North America were selected as the best location to conduct the study. The porphyr'y copper deposits are locally disseminated, hydrothermal deposits without any common source bed. Although the deposits are located close together, each ore body was independently formed with variations in both mineral and trace-metal content. Sulfide mineralization is prominent with varying degrees of oxides in each deposit (9). The deposits contain mostly low-grade copper (0.5-1.0%), making it economically desirable to locate the process plants as close as possible to their respective mines to minimize shipping costs. The five smelters studied, all within a 150-km radius of Tucson, account for the majority of copper production by the seven smelters in Arizona. They are located in rural areas with the only nonsmelter anthropogenic sources being those which arise from emissions and dust associated with employees' housing and transportation. Variations in the ore composition, processing techniques, and emission-control technology exist among the different smelters.
Sample Collection A modified, light, twin-engine aircraft (Piper Aztec) was used to sample the plumes. The electrical output of the aircraft was increased to provide 3 kW of power at 24 and/or 110 V to operate sampling equipment. A modification of the aircraft vacuum system allowed one of the engine vacuum pumps to provide vacuum for sampling. Since all sampling was carried out at an aircraft speed of 120 knots, the pumping system was calibrated for isokinetic flow through the filters at conditions similar to those encountered in the field. Two separate and independent particle collection systems were installed. The main sampling system (Figure 1)consisted of a 3-m long by 15-cm i.d. stainless-steel sampling probe. The probe extended from in front of the propellers to a hatch door installed on the roof of the aircraft. The probe was tested at the University of Maryland Wind Tunnel. Tests a t wind speeds and conditions simulating sampling showed that a 9-cm core in the center of the probe contained laminar flow unaffected by the probe wall. All sample collections from the probe were made in this center core. Filters were placed in sealed polyethylene filter holders which had a 2-cm diameter exhaust and a 2-cm diameter intake opening. Filter holders were placed externally on a hatch door and changed in flight by opening the hatch door and changing the entire holder assembly. A nozzle calibrated for isokinetic air flow, at the aircraft sampling speed of 120 knots, was threaded onto the intake opening of the filter holder before use. The nozzle extended from the filter holder to a point 15 cm inside the main sampling probe, being positioned in the center core of the probe. The exhaust end of the filter holder was connected by Tygon tubing to the aircraft vacuum system and the flow regulators. This sampling system and the one described below both have the advantage that there are no 294
Environmental Science & Technology
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Frmt S o d o r
Figure 1. Diagram of Aztec sampling aircraft showing the main sampling
probe and the filter holder assemblies. '
bends in the sampling train ahead of the filters, which might cause deposition of particles in the tubes. The second sampling system was installed in the front baggage compartment of the aircraft. The intake manifold for this system was a 1.0-m long by 2.0-cm i.d. Teflon tube which extended from a point 10 cm in front of the aircraft through the nose of the aircraft and into the baggage compartment. A nozzle of the size appropriate for isokinetic sampling was placed on the front of the intake manifold. Filters in the nose compartment were changed by remote control, allowing up to three filters to be collected by this system per flight. The vacuum for these filters was provided by a 24-V vacuum pump installed in the rear of the aircraft. A detailed description of the entire aircraft sampling system is given by Small (10). Samples were collected on Nuclepore filters of 0.4-pm pore diameter and on Fluoropore filters of 0.4- and 1.0-pm pore diameter. Both types of filters had diameters of 110 mm. A comparison of the blank values obtained from the analysis of Fluoropore and Nuclepore filters revealed large differences in the blank concentrations of trace elements for these two types of filters. Since some elements with high blank values on one type of filter were low on the other, both types were used so that each element could be measured on one or the other. All filters were mounted in polyethylene filter holders that remained sealed until just before use. All intake tubing, nozzles, and filter holders were constructed of Teflon or polyethylene to minimize trace-metal contamination of the filters. After collection, filter samples were stored in plastic petri dishes which were brought to a clean room at the University of Maryland where they were prepared for analysis. Instruments that measured total sulfur, condensation nuclei (CN), NO and NO,, total hydrocarbons, and 0 3 were used as plume monitors (SOZ: Meloy Laboratories, Model SA16OR sulfur analyzer; CN: Environment One Corp., Model Rich 100 condensation nucleus monitor; NO,: Monitor Labs., Inc., Model 8440 nitrogen oxides analyzer; 03:Monitor Labs., Inc., Model 8410A ozone analyzer). Sample air for the analyzers was supplied from the main sampling probe through a port in the hatch door. All instrument outputs were monitored on chart recorders. The plume was usually visible over the entire sampling pattern as a white cloud. On some occasions visibility was reduced to zero in the region directly over the stack where very high SO2 concentrations were detected. Quantitative plume-gas measurements were made by the gas analyzers. Concentrations of SOz and condensation nuclei above ambient levels were found at distances more than 100 km downwind of the plants. Continuous monitoring of these species enabled us to detect and follow the plume for large distances from the
plant. The rapid response time of the NO, and the O3 analyzer made the monitoring of these species the best way to determine plume boundaries near the stack so that corrections could be made for the total time in the plume and in background air. All samples were collected between 6 a.m. and 11a.m., as the early morning flights provided the calmest winds (5-10 knots) and the strongest temperature inversions, optimizing plume conditions for sampling. Night sampling was too dangerous because of the rough terrain and limited visibility. Afternoon flying was avoided because of high gusty winds which would rapidly disperse the plumes. Flight patterns for sample collections were a modified figure eight parallel to the center axis of the plume and crisscrossing over the stack of the smelter. Sampling was usually confined to the first 8-km region of the plume to ensure sufficient particle loading on the filters for a detailed chemical analysis. The downwind turn was made completely in the plume and the upwind turn out of the plume. In general, sampling flights remained in the plume for -7040% of the time. Aircraft speeds during sampling varied from 200 to 230 km/h.
Sample Analysis Concentrations of most elements were determined by instrumental neutron activation analysis (INAA) using procedures similar to those described by Zoller and Gordon ( 1 1 )and Ondov et al. (12).Either one-half of a filter or the entire filter was folded and placed in a polyethylene bag, which was heat sealed. These bags were placed in heat-sealed polyvials along with standards containing known amounts of the elements to be measured. The polyvials were irradiated with neutrons in the National Bureau of Standards reactor. Each sample analysis consisted of two neutron irradiations and the collection of four y-ray spectra which were taken by using lithium-drifted germanium [Ge(Li)]detectors coupled to 4096channel pulse-height analyzers. Areas under the peaks of prominent lines of the species of interest were calculated by using a minicomputer fitting procedure. Procedures were checked by analysis of the National Bureau of Standards’ coal standards SRM 1632a and 1635 (13).Lead analyses were done by atomic absorption spectroscopy at the University of Maryland. The filters were digested in H N 0 3 to remove the lead before analysis. Results and Discussion Direct Plume Measurements. Typical records of the S02, condensation nuclei, 03,NO, and NO, concentration profiles across the plume are shown in Figure 2. All of the smelters emitted large amounts of S02. Concentrations of SO2 within 200 m of the stacks exceeded 10 ppm for all smelters except smelter 5, which had SO2 levels of -1 ppm. These lower concentrations of SO2 at smelter 5 were detected on two different sampling days and demonstrate the effectiveness of the emission control devices. Concentrations of SO2 decreased rapidly with distance from the stack but usually remained above 100 ppb a t a distance of 8 km. Condensation nuclei counts exceeding 300 000 CN/cm3 were generally found in the region around the stack, along with near-zero visibility. These high CN concentrations can probably be attributed to the formation of sulfuric acid mist, which acts as nuclei for condensation (7). Both SO2 and CN concentrations were found to be in excess of ambient levels over 100 km downwind of the smelters. Composition and Variability of Plume Particles. At least two in-plume whole-filter samples collected a t each of five smelters were analyzed for trace elements. Results of the analysis of a representative filter from each smelter, as well as the average of all background concentrations, are given in Table I. The plume data represent the blank- and back-
NO
Figure 2. Examples of a typical aircraft traverse of a copper smelter plume 8 km downwind of the source.
ground-corrected concentrations of the suspended particulate material. The error given is the analytical error associated with each measurement including blank subtraction. Average background trace-element concentrations were determined from samples collected while flying to and from the smelters. These collections were made at altitudes ranging from 600 to 2000 m above sea level and 150 to 1000 m above the local terrain. We were unable to make background collections directly upwind of each smelter because of mountainous terrain and complex wind patterns which could have resulted in the inadvertent sampling of old plume material instead of collecting true background particles. Ambient concentrations of trace elements were generally much lower than concentrations observed in the plumes. There are significant differences in the elemental compositions of particles from plumes of the various smelters. Some differences in the absolute concentrations of samples are due to variations in plume densities, meteorological parameters, collection times, or other variables that are independent of a smelter’s operation. Removal of fluctuations in absolute concentrations is necessary before comparisons can be made of the distribution patterns of elements in samples collected at different times and from different smelters. For this reason we define the enrichment factor (EF) as the ratio of a given element to a reference element in the suspended particulate material divided by the same ratio for crustal material (14). We chose A1 as the reference element because of its high concentration in crustal material and in ambient and plume aerosols, the reliability with which it can be analyzed by INAA, and its low volatility, allowing us to assume that it is not vaporized in high-temperature sources. Thus, the enrichment factor is calculated as follows: where Cx and CAIare concentrations of the trace element of interest and Al, respectively, in the plume sample or average crustal material. If plume material were simply average crustal material, EFs for all elements would be unity. Elements with values less than unity are depleted in the plume with respect to the crust while those with EFs greater than unity are enriched. At the outset of this study there was considerable uncertainty as to the variations that there would be in compositions Volume 15, Number 3, March 1981 295
Table 1. Typical Concentrations a of Elements Observed in Plumes from Several Copper Smelters smelter 1
550 f 80 370 f 260 2200 f 290 280 f 32 1300 f 240 1.6f 0.3 0.38f 0.06 180 f 50 59 f 8 6.5f 2.6 39 f 3 1.8f 0.1 3.7f 0.6 3.2f 0.3 0.34f 0.11 2.0f 0.1 920 f 10 17f4 1.6f 0.7 190 f 20 1.5f 0.1 80 f 5 6f6 0.45f 0.20 14f8 1.9f 0.3 lfl 70 f 45 6.7f 0.9 320 f 20 0.34f 0.02 5.1f 1.0
smelter 2
700 f 300
