moke and Fume Investigations A HISTORICAL REVIEW ROBERT E. SWAIN Stanford University, C a l i f .
A
few outstanding cases of injury to animal and plant life by emanations from industrial plants-at Ducktown, Tenn., Anaconda, Mont., Salt Lake City, Utah, and Trail, B. C.-are cited in a historical survey of atmospheric pollution and the steps that have been taken ta prevent and combat i t .
J
IYST at the turn of this century a young student rode a bicycle through Germany on his way to Strassburg to work with Hofnieister in biochemistry. One day he wheeled into Leipzig, where the laboratory of Wilhelm Ostwald was then a magnet for young American chemists. A seminar was held that evening in the lecture hall, presided over by Ostwald, with van’t Hoff, who had come down from Charlottenburg, as the speaker. There were found Fred Cottrell and Harry Morse, both candidates for the doctorate a t t,he University of Leipzig and friends of earlier student days out west, one a t the University of California and the other at Stanford. Leaving Leipzig for Dresden, the student rode through the smoky cities of Chemnitz and Freiberg and spent the night in the village of Tharandt. On the way, he observed t’hat the forests of pine and spruce fringing those industrial cities were scant in foliage, with bare sterns in the younger growth a t t8hetop. Learning that a forest academy was located in Tharandt, he rode past it the next morning and accidentally met the director, the genial, scholarly Professor Wislicenus, who enthusiastically showed him his fumigation cabinets and told the young novice, who knew nothing whatever about the subject, of the menacing evil of injury t,o crops and forests caused by indust,rial smoke. Those were unforgettable days. I n Leipzig there mas Fred Cottrell, who later was to direct his genius and unbounded energy t,o t)hephenomenal process which bears his name for the electrical precipitation of solids and mists from industrial emanatiom En route to Tharandt there was a first look a t areas of serious forest injury by sulfur dioxide from metallurgical operations; and a t the other end of the line, Wislicenus, widely known for his work on injury to plant life by air-borne industrial wastes. One of those two men was a ripe scholar, reflect’ing in his personality the traditions of culture and broad training along scholarly lines of the German professor of his day; and the other, Cottrell, born and brought up in the West, a real front,iersman, unshackled by tradition and full of the spirit of adventure, had a career of great distinct,ion ahead of him in America. I t was my good fortune to be that young stutient. Wislicenus and his eo-workers a t Tharandt turned out a long series of monographs which, because of their historical interest, have R place in the reference files of every worker in this field; and befoye them and cont,emporaneously with them, some connected wit’ii the academy a t Tharandt, some even students of Liebig, onc of the founders of agricultural chemistry, were St’ockhardt, Schroeder, Freytag, Wieler, Ost, Haselhoff, Adam Smith, and many others whose contributions to the early history of atmospheric pollution are widely known (5, 18). I n the light of later developments, arising from new lines of approach t,o the general problem, and more refinement in ap-
paratus and technique, much of t,he work of these earlier investigators has been considerably revised. Fifty years from now, the same thing will happen t’omuch of t,he work of today. ATMOSPHERIC POLLUTION IN GERMANY AND ENGLAND
Long before the end of the nineteenth century atmospheric pollution was a live subject not only in laboratory and field invest’igations but in legislative halls. In Germany metallurgical smoke with sulfur dioxide as the chief offender held the center of the stage, while in England coal smoke and chemical plants were the chief troublemakers. To a marked degree this is reflected in the earlier scientific work done in these countries on atmospheric pollution. For the more important work on the oxides of sulfur and smelter smoke in general, one turns particularly t,o German investigators; in studies on products of the incomplete combustion of coal, especially soot and tarry produck, England took the lead. I n 1306 a royal proclamation in the reign of Edward I prohibited the use of ”sea coales” by artificers in their furnaces and set up a commission of inquiry to seek out violators and punish them “with great fines and ransomes.” I n Zwickau, Germany, 40 years later, metal plants werc denied the use of coal as fuel through whose smoke “die Lust aerpestet werde.” I n the middle of the sixteenth century Queen Elizabeth, “greatly grieved and annoyed by the smoke of sea coales,” issued a proclamation forbidding the burning of coal in London while Parliament was in session-an exhibition of class favoritism which today would be shocking. Through the ensuing three centuries, the hornc chimney with its plume of black smoke and the soot carted away by the chimney sweeps were reminders to all of a common responsibility for badly polluted atmospheres. From t’he cradle to the grave human beings lived in smoky air in all the larger cit,ies. It was just s o m e thing to be endured. Then late in the ninet,eenth century the consumption of coal in industrial operations rose rapidly and from that timeson smoke damage and abatement have been topics of nat’ionwide interest. There is good reason lor the emphasis on pollution due t o soot, tarry material, and fly ash which runs all through the smoke literature of England. There coal runs high in volatile matber; the dull, murky weather, with long periods of high relative humidity and local fogs, impedes rapid atmospheric dispersion and aggravates the trouble; and they have no natural gas or hydroelcctric power of any consequence to share the energy load, This does not mean that sulfur dioxide hay been neglected or overlooked as an injurious agent. Chemical plants in general h a w been kept under rigid inspection and control since the passage of the Alkali et cetera Works Regulat,ion I c t in 1881, and where
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damage is done, smelters are required to take every reasonable step to abate the trouble. Their smelters operate usually in smaller units than ours, and waste sulfur dioxide is a t a premium, owing t o the demand for sulfur for making sulfuric acid. The evil of coal smoke in England has been with them for centuries, and, as in most other countries, relief measures have barely kept up with the increase in coal consumption due to an expansion in industry. One has only to look around in London to find abundant evidence of this. The massive monuments on Trafalgar Square, the carved balustrades and cornices of Westminster Abbey, and old stone structures everywhere give mute testimony to a long exposure to the destructive action of acid smoke and high humidity ( 1 , 8, 9). SMELTER SMOKE
b
The first decade of this century is an important one in the story o f atmospheric pollution in America, and i t dealt particularly with smelter smoke. Our smoke troubles have been more conspicuous because of our flair for operations on a colossal scale, which began to assert itself about that time. European case studies were on relatively small plants. A11 the smelters operating in the lower Hare Mountains treated annually a total of 63,000 tons of ore in 1899. The Anaconda smelter alone a few years later treated much more than that amount every week. Three areas of injury in particular, widely separated geographically, came into prominence in that period-Ducktown, Tenn., Anaconda, Mont., and Salt Lake City, Utah. A fourth, that of the great smelter at Tiail, €3. C., came to public attention two decades later. Ducktown. There were two copper smelters near Ducktown, erected in a sparsely settled area. Over the years these ran thc entire gamut of injury to vegetation from the early days of heap roasting on through to furnace roasting and low stacks, then to tall stacks, and finally to sulfur dioxide recovery as sulfuric acid. Their ores carried no arsenic. Sulfur dioxide was the offender, running wild a t first, as the barren and gullied slopes near by, denuded even to the grass roots, clearly showed; then reaching further out as all air-borne emanations were discharged from low stacks. Later on, with high stacks, i t left its trail for 30 miles across the broad-leafed forests of northern Georgia, and finally was brought to the roundup by the largest lead chamber installation of all time. The smelters are located in Tennessee just over the Georgia border. A crisis came when Georgia brought suit against Tennessee to compel i t to cancel the franchise of the smelting companies. This case went directly to the United States Supreme Court and the Federal Government began an investigation. The outcome was plain; the fact of widespread injury was beyond dispute. Out of this came a great industrial achievement-the design, erection, and successful operation of a n adaptation of the lead chamber process to convert sulfur dioxide from copper smelting operations to sulfuric acid. The enormous volumes of furnace gases treated, their high temperature, fluctuating composition, and high percentage of carbon dioxide-a new factor to be dealt with-were hurdles to get over. When this process came into full production the plants were turning out around 1000 tons of sulfuric acid daily, most of i t going to the phosphate plants of the South. There was a time when the income from the sulfuric acid produced by these smelters out of the sulfur dioxide once thrown away actually took first place and copper dropped to the status of a by-product. That may still hold today. Anaconda. With the installation at the Anaconda smelter in 1910 of an enormous Cottrell system for electrical precipitation of solids, one of the most remarkable cases of injury to livestock by smelter smoke ever recorded passed into history. The emissions from the low stacks of an old plant operated at a neighboring location had killed all vegetation, and losses of livestock by arsenical poisoning had been heavy over the near-lying area. Y e m after the plant was dismantled, the top soil of a large area
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centering at the old site was stripped off, sent through concentrators, and smelted at the new plant with a reported recovery of over $1,000,000 in copper and other metals. Then the new smelter was erected, the largest of its kind in the world, and a marvel of engineering skill in design and operation. When its four 200-foot stacks failed to abate losses in livestock, a new stack, 30 feet in diameter, 300 feet tall, and located on a spur of the Rocky Mountains 700 feet above the roasting furnaces and 1100 feet above the floor of the Deer Lodge Valley, was erected as a common outlet. Its great height, the buoyancy of its hot gases, and 6,000,000 cubic feet of settling chamber and flu? space were the reply to the challenge. But i t failed. Little was known then about particle size and rates of subsidence of suspended solids. When it passes from the vapor phase by cooling to around 190 ' C. arsenic trioxide forms particles of very small size, down to B radius of a few microns and even to the submicron range. That explains the unexpected failure of the settling chambers and the widespread atmospheric dispersion of arsenic-plainly traceable for 35 miles from the smelter along the path of prevailing winds According to investigations made at that time, there were discharged into the atmosphere from this stack daily over three billion cubic feet of gases, measured at stack conditions, 2300 tons of sulfur dioxide, 200 tons of sulfur trioxide, 30 tons of arsenic trioxide, 3 tons of zinc, and over 2 tons each of copper, lead, and antimony trioxide (3). I n spite of the height a t which it was discharged, the smoke, swept downward by the cold air from the snowy mountains to the south, often struck the valley floor within a half mile from the stack, while on calm days it rose high and hung'as a haze over the valley. Arsenical poisoning was confined almost entirely to horses, cows, and sheep feeding on hay and range grasses. Typical arsenical ulcers were common in the no+ trils of horses and sheep due to the action of arsenical dust from hay and pasture feeding. Arsenic in grass and hay ran up to 400 p.p.m. or more and dust collected from hay or manger bottoms ran from 400 to 9000 p.p.m. (4, I d ) . One wonders what would have been the outcome at, Anaroiida if Frederick Cottrell had not been curious enough to try out the experiment of Sir Oliver Lodge made 20 years before; in 1905 he demonstrated the phenomenon of electrical precipitation of airborne dusts and fumes and put it into commercial operation. That was the answer, and the only one for Anaconda, foi the degree of fineness of material which this process will collect exceeds that of any other commercial method. For example, tobacco smoke, chiefly a tar fog, has a particle size of 0.01 to 0.15 micron, with around 5,000,000 particles of tar fog per ml. I n the visible cloud from a cigaret the instantaneous precipitation of this smoke makes a spectacular laboratory demonstration of the process. Salt Lake City. The situation around Salt Lake City was more complicated. The advantages of an abundant water supply, the M ide fringe of salt-infiltrated marshland around the shore of Great Salt Lake as a place for waste disposal, and close proximity to ore bodies and transcontinental railway lines led to the erection of four smelters on the border of the fertile Jordan River Valley. It was in fact a treacherous location for smelters, for it was a region of many small farms and pasture lands with a great variety of crops sensitive to sulfur dioxide. Two of these smelters ultimately were sent to the scrap heap and two survived. The controversy over these was long and bitter, running practically through the first two decades of this century. Injury to horses by lead poisoping, as well as to vegetation b y sulfur dioxide, was claimed. Finally, in 1921, a threatened permanent injunction against these smelters was relieved by the acceptance by Judge Tillman D. Johnson, of the Federal Court, of certain stipulations remmmended by an appointed commissioner after an extended study of field conditions and plant operation carried out under his supervision. These placed no limitation upon the amount of orc treated. Each plant was to discharge its gases through a stacli a t least 450 feet in height; give buoyancy to escaping gases by
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maintaining throughout the growing season for vegetation in that area, between sunrise and sunset, a difference in temperature of a t least 75” C. between the stack gases and the outside air; and subject all emanations from smelting operations to electrical precipitation by the Cottrell process, bag filtration, or any other process of equal efficiency for the removal of suspended solids and mists. So far as the writer is aware there has been no injury to plant and animal life by emanations from these two smelters since these regulations were put into effect. Contributions of Research. The second decade of this century was a notable one for contributions made by research to the broad question of smelter smoke injury. The Selby Smelter Commission, appointed in 1913 to investigate and report on a claimed violation of an injunction issued against the Selby Smelting and Lead Company whose plant was located on San Francisco Bay near Crockett, made a thorough investigation through an able assisting staff. This report (?‘) is one of the classics of the smelter smoke controversy. A review of its 500 pages is impossible here, but a few contributions are worthy of particular mention. The hlarston-Wells method was developed for the estimation of sulfur dioxide in the air. Through it an accurate determination could be made within a few minutes on a sample collected instantaneously by opening the stopcock of a partially evacuated 24-liter bottle. The importance of a rapid quantitative method for the determination of sulfur dioxide in the field is apparent, inasmuch as the concentration of a gas in the smoke stream from any plant is variable, owing t o changes in the direction, velocity, and turbulence of the wind, and other factors. This method was widely used until superseded in 1929 by the Thomas recorder. A new method for controlled fumigation of plants was developed. This was the first instance in which a stream of air was used in fumigation work on field plots with movable cabinets and with the gas under study mixed with the air, not within the cabinet, but outside of it. Thus equipped, field plots were subjected t o sulfur dioxide fumigations of high and low concentrations, durations long and short even through the entire life of the plants, in sunlight and in shadow, and a t varying humidity and temperature. The question of invisible injury was studied but no evidence of any such condition was found. Mild fumigations up to the point of slight foliar markings, carried out over long periods of time, caused no appreciable loss in yield. Plants were found to be far more sensitive to sulfur dioxide than t o sulfur trioxide. Dusts and acid mists discharged from smelter stacks are negligible as agents of injury t o vegetation. These are only a few of the results of this investigation. O’Gara and Fleming (22, 27) followed this up over a period of 9 years with an investigation of the smoke problem around the Murray smelter near Salt Lake City. An experimental farm provided field plots for fumigation work on many varieties of plants and thousands of determinations of sulfur dioxide in the smoke stream were made by men trained in a modified Marston-Wells method. A few phases of these investigations are of especial interest. A correlation of gas concentrations and injury t o vegetation in the Murray smelter area showed that sulfur dioxide injury could occur there only when four weather conditions were coincidental: a temperature above 5’ C.; a relative humidity above 70%; daylight; and wind prevalent as to direction for 3 hours or more. The first three bear directly on stomata opening, and thus on the rate a t which the gas may find its way inside the leaf; the last on the important factor of duration of exposure. I n fact, the rate of absorption of sulfur dioxide in a given plant system shows remarkable variations under different environmental conditions. An exposure which would result in severe foliar injury under one set of conditions might be entirely harmless under another. It is concentration of gas, duration of fumigation, and rate of a b s o r p tion, a11 together, which count, as later work by Thomas and Hill (14)has clearly shown. A careful review of weather records over several years revealed
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that every injurious fumigation in the district had been precisely accompanied by the above weather conditions. It was thus a p parent that, during the growing season injury could be avoided by having a man on duty a t the plant weather station who, when these four conditions coexisted, telephoncd thc superintendent’s office to shut down the roasters, the chief source of sulfur dioxide. This order held until the wind changed, relative humidity fell off, or darkness came on, when roasting operations could begin again. This came t o be known as the “sea-captain theory,” arising from the often-quoted reply of the general manager who, when told of the discovery, indignantly asked “DOyou want me to get a sea captain to run my plant?’’ Of the effectiveness of this remedy there was no doubt; but the rare, yet occasional, shutdown of the roasters was its undoing. This was pioneering work in a field which in recent years has claimed much attention-the relation of meteorological eonditions to smoke troubles. Certainly, a variable wind and high turbulence are of first importance in gas diffusion. The smoke stream plays over a wide sector, periods of exposure by a given plant are short, and, when the ground level is reached, the gas concentration is low. Where weather conditions can be tied in promptly with an elastic control of gas emission a t the source, as has long been done a t Trail, it may afford a highly successful remedy.
AN INTERNATIONAL PROBLEM The third decade of this century was not particularly eventful on the smoke question, although the general atmospheric pollution difficulties were mounting in many large cities and a number of notable studies were in progress. These are outside the scope of this paper. However, during the last decade another case arose, international in its range and important in its scientific aspects. This involved the smelter of the Consolidated Mining and located on the Columbia River Smelting Company a t Trail, B. about 9 miles north of the international boundary. It is the largest of its kind in the British Commonwealth, with a daily output of around 1000 tons of zinc and lead. Through the 20’s the emission of sulfur dioxide increased to 600 tons per day and serious complaints of injury to crops and forests were made by residents of the State of Washingt,on, chiefly along the narrow, steep-walled Columbia River Valley and its tributaries. These resulted in damage claims against the company which were settled in 1932 after lengthy hearings by the International Joint Boundary Commission. I n that year the company installed recovery measures and erected a large by-product plant, designed to recover two thirds of the waste sulfur dioxide. It now operates six sulfuric acid units using the vanadium catalytic process, with a total capacity of 1200 tons of acid, and produces 240 tons of ammonia. These are intermediates which chiefly find their way out as phosphate and other fertilizers. A stand-by plant, which operated for several years, will convert 300 tons daily of sulfur dioxide to elementary sulfur by reduction in coke furnaces whenever the market favors it. An outstanding development there is a huge installation for recovering and utilizing sulfur dioxide from furnace gases, in which it is present in very low concentrations. This is a modification of the Guggenheim process. The gases are sent through Cottrells to remove dusts and fumes, and then to enormous scrubbing towers, through which circulates an ammonium sulfite solution which passes over to the bisulfite as sulfur dioxide is absorbed. As the bisulfite reaches maximum values in the last tower it is drawn off and treated with sulfuric acid. The pure sulfur dioxide released goes to the sulfuric acid plant, or t o reduction to elementary sulfur, and the ammonium sulfate goes to the fertilizer plant. Additions of 30% ammonia solution t o the scrubbers make up for the amount removed as sulfate. This deserves to be put down as one of the mileposts in the march of industry toward the recoveryofsulfur dioxide from gases in which it is present in highly dilute form. Three years later further claims of damage made across the
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border led to a convention between the two governments to refer the issue to an international tribunal. This was composed of Jan F. Hostie of Belgium, chairman, Judge Charles Warren of the United States, and Chief Justice R. A. E. Greenshields of Canada. After extended hearings, a decision was rendered in 1938 awarding damages amounting to $78,000. At the same time the tribunal retained jurisdiction until October 1, 1940, and instructed its technical consultants to organize an assisting staff and make an investigation of all phases of the situation, with a view to the formulation of a regime which would assure relief from injury in the future. Most of the material of scientific interest in this case has been published ( d , 6 , l O ) . A detailed record, in book form, of investigations carried on under the auspices of the National Research Council of Canada, and presented as evidence during the hearings, is a noteworthy contribution to the literature of the smoke problem in its wide scope and the high quality of the work done. The final judgment of the tribunal was rendered in March 1941. The operating regime laid down involves a regulation of the amount of sulfur dioxide issuing from the Dwight and Lloyd roasting furnaces, in accordance with certain conditions, among which are wind direction and velocity, atmospheric turbulence, time of day or night, and the readings of a Thomas sulfur dioxide recorder at Columbia Gardens located down the Columbia River near the International Boundary. A central control office a t the plant receives all these records continuously by self-recording devices and from it go out orders to shut down one or more of the eleven Dwight and Lloyds or to resume full operation, depending upon the specific stipulations of the regime. This program functioned successfully, even through the war years, when the plant was operated at far above normal production. Diurnal Fumigation. A remarkable phenomenon revealed in this case is that of the so-called “diurnal fumigation.” During the hearings the readings of a number of Thomas recorders located at stations down the Columbia River for about 40 miles were presented in evidence. I n reviewing this record involving hundreds of feet of recorder strips, after the hearings were over but before the tribunal made its decision, the startling observation was made that many of the fumigations recorded were actually simultaneous at all stations. These must have come, not from a smoke stream moving down-river at the ground level, tapping each station in turn as it advanced, but from the descent of a continuous air stratum containing sulfur dioxide, like a blanket, over t h e entire stretch of 40 miles or more. These uaique fumigations are evidently due to the formation, under favorable atmospheric conditions, of an isothermal atmospheric stratum, low in turbulence, high above the valley floor. Into this the hot gases from t h e tall stacks of the smelter rise, and especially during the night time are carried by it slowly down-river. After sunrise the heat from the morning sun, which is fairly uniform along the valley, but more intense on the steep-walled west side than on the shaded east side, leads to increased turbulence, a change in lapse rate, and a descent of the gas-carrying air to the ground. There t h e long line of Thomas recorders picked it up, automatically recording the sulfur dioxide present and the exact time and date. This type of fumigation appears in the morning usually a few hours after sunrise, or, less often, after sundown. It is rare in winter, being limited almost entirely to the warm growing season for crops. It is a part of the duty of the control office promptly to spot the weather conditions which herald an oncoming fumigation of this type and throttle it at once by shutting down the roasters. There are, of course, nondiurnal fumigations of the usual type, which may occur at any time weather conditions favor them. These are kept under proper control by similar measures.
CONCLUSIONS This review has been deliberately limited to the citation of a few outstandiag cases of injury to animal and plant life by
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emanations from industrial plants, what happened, what was done about it, and something of what was learned from them in regard t o the handling of air-borne wastes and the detection and appraisal of injury done. These run through four decades of this century. Each had injured neighboring property and faced the emergency of an injunction, and the plant management had found itself on the brink of decisions which called for courage, wisdom, and an enormous expenditure of funds. At Anaconda the dilemma rapidly became two-pronged as injury by sulfur dioxide began t o appear on the red fi and lodgepole pine of the national forest reserve far back on the slopes of the Continental Divide. What could the smelters a t Ducktown, or out in Montana, do with a daily output of a thousand tons or more of sulfuric acid? It could not be stockpiled nor dumped, but had promptly to be disposed of as i t was produced. The situation of the lead smelters in Utah was not so baffling. Lead and sulfur trioxide fumes were soon put under complete control by liming and bag filtration, and by electrical precipitation. However, sulfur dioxide was causing occasional damaging fumigations and the new copper smelter at Garfield Beach, 15 miles away, was clearly within range of a prosperous farming area. The situation at Trail developed later but was perhaps the most difficult of all. The smelter was located in an isolated mountainous region, far from any Canadian city, on a branch railway. The nearest known phosphate beds of good quality were several hundred miles away across the international boundary in Montana; and the controversy was an international one. All found their way to a successful solution of the local issue of smoke injury, and all turned out to be profitable business investments. The Ducktown development put new life into the use of phosphate fertilizer, especially on the southern plantations, many of which had been abandoned except by sharecroppers owing to the exhaustion of soil nutrients. The story at Trail was in many ways more dramatic. Experts were sent abroad to study every known process for sulfur dioxide recovery and for making sulfuric acid and ammonia. About $13,000,000 were finally invested in recovering air-borne wastes and converting them to marketable by-products. These were tied together into a smoothly operating system and soon phosphate fertilizers of several types, ammonium sulfate, and sulfur were being produced on a large scale. Before this, another stage had to be set. Canadian farmers were not fertilizer-minded. The once rich, virgin soils of Alberta, Saskatchewan, and Manitoba were slowly being exhausted but were still producing fair crops. Because ordinary advertising would not work quickly there, a wellknown authority on soil fertilization was engaged and sent across the prairies, meeting groups of farmers in villages over the great wheat belt. He proposed a t each stop to substantiate his recommendations by giving fertilizer free to certain farmers who would agree to add a prescribed amount to their seed drills in adjacent strips a t seeding time. Soon carloads of fertilizer were shunted onto railway sidings, and i t was drilled in with the seed. When the crop matured the striking differences in height and yield were a convincing demonstration of soil deficiency and the way to correct it. The time of crop maturity was notably advanced in the fertilized strips-an important matter in northern climes, where there is always grave danger of frost injury to late ripening wheat. This was one of the means of settling the question of marketing the products of a new plant which leaped into full production on short notice to meet the emergency of smoke relief. The initial output of around 400 tons per day is now more than doubled, and still the demand for their fertilizers is not being fully met. Here again, sulfur dioxide was made to reverse its notorious behavior, and become a benefactor of agriculture. The solution at the Murray smelter, owned by the American Smelting and Refining Company, did not lead immediately to any substantial returns in by-product recovery, as it was accomplished chiefly through improved atmospheric dispersion. However, the
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establishment and generous support by this company of its Laboratory for Agricultural Research near Salt Lake City were equally important. For over three decades this research group has not only kept the company fully advised on atmospheric pollution and remedial measures a t its many plants over the country, but has published many papers, covering research in plant fumigation and the development of procedures of the highest accuracy in experimental work in that field. The recorder, developed by Thomas ( I S ) of that group, is now widely employed in sulfur dioxide determinations. This remarkable analytical robot makes a determination of sulfur dioxide and records it, automatically, every 20 minutes with an accuracy of a fraction of a part in a million parts of air, and requires servicing only once aweek for replenishing solutions and exchanging recording charts. Later designs (15, 16) record a determination every 10 or 15 seconds and are adapted also to the estimation of total gaseous sulfur compounds in the air. The fifth decade of the half-century or so since the smoke problem came across the Atlantic to plague us is fully covered b y the ensuing papers in this symposium. Research in our universities, research institutes, and industrial research laboratories is finding more lines of approach, more tools to work with, more ideas, than ever before. Most of our large cities are attempting to work out sound measures of inspection and control. I n the West, especially, there is a rapid increase in the use of hydroelectric power in private homes and industry, and the use of natural gas, rapidly becoming nationwide, is a big step forward. Thus there is promise that the pendulum will soon be swinging toward less polluted atmospheres in iimerica. Coal smoke and slums have much in common. Both promote squalor, cut out the
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sunshine, cultivate gloom and uncleanlniess, and set up conditions which in general are bad. There i s n o aubsfitute for clean air in any human environment.
LITERATURE CITED Cohen, J. B., and Rushton, A, G,,Smoke, A Study of Town 2nd ed., London, E. Arnold & Co., 1925. Dean, R. S.,and Svain, R. ElsI C.7- S . Bur. Mines, Bull. 453 (1944).
Harkins, W. D., andswainsR,. E,, .Ic Am, Chem. SOC.,29,970--98 (1907) Ibid., 30,928-46 (1908) e
~
Haselhoff, E., and Lindau, G., ””DieBeschadigung der Vegetatioa, durch Rauch,’nBerlin, Bosntriiger, 1903, Hewson, E. W., IND.EKG.CHERI.,36, 195-201 (1944). Holmes, J. A., Franklin, E. C., and Gould, R. A,, U.S.B~rut.. M i n e s , Bull. 98 (1915).
Meller, H. B., IND. EXG.CHEM.,27, 949 (1935). Meller, H. B., and Sisson, L. B., Ibid., 27, 1309 (1935). National Research Council of Canada, Ottawa, Associate Co~rrmittee, “’Effect of Sulfur Dioxide on Vegetation,” 1939. O’Gara, P. J., and Fleming, E. P.,J. IND.ENG.CHEM.,14, 744 (1922). Swain, R.E., and Harkins, 11‘.J - ) ~ .lo , A m , Chem. Soc., 30, 915--2in (1908) * Thomas, &I. D., I X D . ER’G.C H E M , , B K a L . E D . , 4,253-6 (1932). Thomas, M. D., and Hill, G . R.. Jr., Plant Phys., 10, 291-302 (1935) Thomas, M. D., Ivie, J. O., Abersolde, J. N., and Hendricks, 11, I N D . EXG.CEEM., ) \ N I L . ED., 15, 28‘7-90 (1943). Thomas, D., Ivie, J, O., and Fitt, T. C., Ibid., 18, 383-95 (1946). Wells, A. E., J. IKD. ENG.CHEM.,9,640-59 (1917). Weler, 4.,“Cntersuchungeu uber die Einwirkung schwofligoSaure auf die PflanzenPs’Revlin, Rorutrager, 1905. e
w.,
K c c ~ n - mMarch 7, 1040.
Dust and Fume Stand LOUIS C. MCCABE, A. H. ROSE, W. 9. HAMMING,
AND
F. H. WETS
2.0s Angeles County Air Pollution Control D i s t r i c t , Los Angeles, Calif.
T
HE meteor ologicalfactors
T h e average weight of the hourly charge of materials Atmospheric contamiriainfluencing air pollution used in a process determines the amount of solids (dusts tion may be caused by liquids, ( g ) , the technical aspects of and fumes) that may be released from stacks in Los Ansolids, or gases, but the standgeles County. Data from nonferrous, steel, gray iron, and ards discussed here are conthe smog problem ( 3 ) , and the nature of industrial dusts electric iron industries were used in developing the “masscerned only with solids, which and fumes in the Los Anpeles rate” standard which has been in use since March 1949, are further classified as dusts area ( 4 ) have been discussed and fumes. They are definrd in the regulations as folloa i: by others. These studies Fumes (1)are solid particles commonly generated by the condemonstrate the necessity for limiting the amount of pollution densation of vapors of solid matter after volatilization from the entering the atmosphere from industrial and other sources. Durmolten state. They may be generated by sublimation, distill%ing the past year, the Los Angeles County Air Pollution Control tion, calcination, or chemical reaction, whenever such procemcw District and the industries that release dust and fumes in their create air-borne particles. stack effluents have studied the nature and quantity of the mateDusts (1) are solid particles released to the air by natural rials that contribute to air contamination. The development of forces, or generated by mechanioal processes such as crushings thc dust and fume standards discussed herein is based largely on grinding, milling, drilling, demolition, bagging, sweeping, and these tests. shoveling. More than half of the 100 tons of industrial dusts released to Over a period of several months, dust and fume data from furthe atmosphere daily is of submicron size. Below one micron, nace operations were collected, tabulated, and analyzed (Table l the particles are most effective in scattering light and, therefore, They represent the various metallurgical installations in the Los ontribute to low visibility. They do not settle unless washed Angeles area, correlate well, and are of sufficient accuracy for use out by rain and there is normally no effective removal in this manin dust and fume standards. ner except in the winter and early spring months. Temperature Initially, attempts were made to develop standards of emission inversion, the low average wind velocity, and the topography of based on the opacity of the stack effluent or on the total process the area prevent easy dispersion and removal from the basin. As enthalpy. These were of little practical value, but the concept the natural agencies hinder thorough cleansing of the atmosphere, of total process enthalpy led to the use of total process weight as a the standards described here have been incorporated in the rules basis for establishing the weight of solids that may be released t o and regulations of the Los Angeles Air Pollution Control District the atmosphere. This ignores the relationship between the volto cause the maximum collection of dust and fumes a t the source, ume of effluent gases and the weight of solids discharged from a consistent with the availability of equipment for the purpose.
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