I
KINGSLEY KAY Department of National Health, Ottawa, Canada
Air Pollution Review 1956-57 THE period has been marked by the U. S. Public Health Service. Renzetti greatly increased research activity in has analyzed the air near
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Europe, Russia, and America. A voluminous literature on radioactive fallout has built up and constitutes possibly the most important aspect of environmental study in 1956 and 1957. Books and special reports are listed in the bibliography (20, 57, 73, 76, 78, 84, 93, 723, 756, 774, 776, 237, 234, 240). Various organization studies have been made (9, 749, 771,208, 239). Chemical Pollution. A noteworthy report covering 10 years of observation on atmospheric pollution in Great Britain (42, 43), has shown an increase of around 10% in deposited matter as between the 5-year averages 1944-49 and 1949-54. There was an increase in calcium and sulfate ions but a decrease in tar deposit. England and others (56) and Jarvis and Austin (77.5) have reported on surveys of dust deposition in the neighborhood of British power stations. Gilbert and Lindsey (79) have estimated pyrene in snow in England as an index of the amount and distribution of atmospheric smoke pollution. A similar study was carried out at Leningrad (44). Greenburg and Jacobs (86) estimated that 570 of the weight of bituminous coal and residual fuel oil used in New York City is passed into the air as sulfur dioxide, resulting in over 1,500,000 tons of sulfur dioxide per year. Morning maxima during winter ran to 0.8 p.p.m. Levels during inversion were comparable to those fouhd generally in North American urban centers. Cholak and others (24) have estimated levels of oxidant, nitrogen dioxide, sulfur dioxide, and carbon monoxide in Cincinnati from October 21 to July 18, 1956. Carbon monoxide was generally below 1 p.p.m. Rogers (786) reported on nitrogen dioxide and nitric oxide in Los Angeles. A joint city, county, state, and federal study of air pollution in Louisville is to be made (788). Gelman (77) has made analyses for water-soluble chlorides, sulfates, and nitrates in atmospheric dusts from Louisville. A distribution survey of organic vapor sources in Los Angeles County has been made (744) with the finding that around 400 tons are vaporized into the atmosphere daily from an extensive list of operations. Two reports on organic substances in the air of United States cities (23, 225) have now been made from the findings of the air sampling network of
(782) heavy traffic arteries in Los Angeles, finding levels of 4 to 93 p.p.m. carbon monoxide, 0.25 to 2.3 p.p.m. hydrocarbons, and 0.05 to 0.14y0 carbon dioxide. Local contamination by bacterial aerosol from a n animal rendering plant has been found (273). Damage of automobile paint by iron particles from a local industrial operation was described by Fochtman and Langer (68). The human exposure in populated areas from malathion spraying for insect control was estimated by Caplan and others (22) and it was found that hazard was created. Dust exposure during ash removal from incinerators has been measured (758). A detailed study of air pollutants occurring in railway tunnels has been made in Germany by Massmann (753). Greenburg and Jacobs (85) have outlined corrosion effects of air pollution. Meteorological considerations in environmental assessment of pollution have been dealt with by Wanta and associates (733, 247). A recommended standard method for continuing dustfall surveys was prepared by a technical group under the Air Pollution Control Association (7). Radioactive Pollution. An annotated bibliography on radioactive fallout was prepared by Horad and associates (708). The United States Atomic Energy Commission fallout monitoring network was described by Eisenbud (50) in 1956. Eisenbud and Harley (52) have reported on fallout levels obtained to 1955 from network sampling locations covering the United States except that portion within 200 miles of the Nevada test site. I n a further report levels through September 1955 are given (53), covering 62 foreign and 26 domestic stations. Strontium-90 levels to June 1956 have been summarized by Harley and others (94). More recently Eisenbud (57) has discussed global distribution of strontium-90, predicting that an average level of 20 millicuries per square mile may be reached in the latter part of the next decade. Libby observed (738) that natural radioactivity accounts for a dosage of around 150 milliroentgens per year and fallout from nucleqr tests 1 to 5 milliroentgens per year.
Chemical and Physical Studies T h e mechanisms causing eye irritating smog in Los Angeles were discussed,
with the kinetics of particular reactions and with further photochemical explorations (4, 722, 725, 134, 762, 766, 767, 794). Rogers has edited the proceedings of the Conference on Chemical Reactions in Urban Atmospheres held in Los Angeles in February 1956 (4). Additional papers include a study of reactions of NO2 with 2-butene and 3-methylheptane by Miller and others (762), who confirmed previous findings by HaagenSmit. Stephens (277) has established the presence in air of peroxyacyl nitrite formed simultaneously with ozone. This compound is created by the reaction of nitric oxide with organic pollutants. Peroxyacyl nitrite is decomposed by sunlight to form nitrogen dioxide which originally started the cycle. This was confirmed by irradiating auto exhaust. Engine Exhaust Problem. An active research program has delineated many of the factors influencing the contribution of engine exhaust to smog formation in Los Angeles. A status report prepared in 1957 by Rose and Stephan (787) included an extensive bibliography. Chamber experiments and field tests have been conducted by Midwest Research Institute and the Air Pollution Foundation (58, 60, 765, 766). It has been established that eye irritation and oxidant concentration from irradiated exhaust increased as concentration of hydrocarbon was increased. Effects of engine operating conditions on exhaust have been summarized by Faith (58). Morriss and associates (767) showed that lead in gasoline did not contribute materially to smog formation. The impressive results of research by the automotive industry were published last year in monograph form (9). A comprehensive traffic pattern survey by Teague and others indicated the distribution of time of day a t various stages of operation, speed patterns, and other aspects known to influence hydrocarbon emission. Dietrich and a committee studied reduction of hydrocarbon emission during deceleration by induction system devices. It was considered that the principle of the vacuum limiting type of device best approached the need. Exhaust gas treatment by afterburning or catalysis was covered by Nebel and associates. Testing of catalysts by single cylinder engines was dealt with by Carmon, Hill, and Welling, who revealed the difficulty of catalyst poisoning by the lead in gasoline. More recently Nebel and Jackson (768) have found that conVOL. 50,
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centration of nitrogen oxides is highly dependent on air-fuel ratio This was confirmed by Gilbert and others (80). Mader and others (748) have been examining the role of fuel composition on concentration of exhaust constituents. Doyle and Renzetti (46) considered the nfluence of engine operation on aerosol formation. Spindt and others (274) showed that nitrogen oxides in reaction with unsaturated fuel constituents led to formation of engine deposits. Lyn (745) and Fitton (65) in England studied composition of exhaust gases from gasoline and Diesel vehicles. Wilkins (258) measured carbon monoxide in London air during traffic congestion. Guibileo (88) determined carbon monoxide and lead in motor car exhaust and in traffic in Milan. These studies established that in outside air serious levels of contamination were not reached. Renzetti (782)in Los Angeles found high levels of carbon monoxide. Hirschler and coworkers (707) have estimated lead in the air of United States cities to determine whether the vast quantities of leaded gasoline burned are leading to dangerous contamination and found that the lead was well within hygienic limits. Commins and others (27, 28) have analyzed the air inside and outside a London bus garage. Carbon monoxide levels were very low. Only slight differences in 3,4-benzpyrene were noted. Nitrogen dioxide and aldehydes were in the safe range. Tebbens and others (229) have continued to examine in the laboratory the products of incomplete combustion of fuels to identify such products in urban air pollution. Constituents such as nhexane, iso-octane, I-hexene and others were burned. A number of polynuclear aromatic hydrocarbons and their phenolic and carboxylic derivatives were isolated. Temperature and reaction time influenced the nature of the products of combustion. Other Chemical Contributions. Houghton ( 7 70) has studied the composition of fog and cloud water in England. Rain and snow in Sweden have been analyzed at various locations with a view to studying the origin of certain elements important in agriculture (49,55).Miller (764) has presented data on vertical distribution of nitrogen oxides and the nitrate and ammonium ion content of United States rain water. Meetham (757) has estimated the life of a sulfur dioxide molecule to be 6 hours under fog conditions in London. He suggests that in such circumstances conversion of sulfur dioxide to sulfuric acid may be a source of danger to life. Factors influencing the formation of H;?S04 in urban atmospheres have been the subject of further study by Johnstone (720) who has shown that manganese and ferrous nuclei in droplets bring
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about rapid conversion of sulfur dioxide to sulfuric acid. Physical Studies. An annotated bibliography on light scattering by colloid systems has been produced by Fishman (64). Coagulation and flocculation in colloidal systems were the subject of a number of the Dircussions of the Faradaj Society (45). Dautrebande and others (39) have reexamined the phenomenon of agglutination of dust particles by sodium chloride aerosols in a technical study for the United States Atomic Energy Commission. A Russian paper on the subject may be noted (767). Physiochemical factors and the mechanism underlying interaction of dust particles with drops of solution of surface active agents have been dealt with (227, 228). Sleicher and Churchill (799) have examined mathematically, radiant heating of dispersed particles. Equations considered to be reasonably accurate for transient temperature of a dispersion of small particles exposed to a radiant flux were derived. There has been a review by Gordieyeff (82) on unipolarly charged aerosols which are again evoking interest in the fields of meteorology and air pollution. Other work on electrical features of aerosols has been noted (89, 90: 743, 277), including a study by Woessner and Gunn (260) in which the sign and number of‘ elementary charges carried by silica, water, and sulfur aerosols was estimated.
Control of Pollution Legislative and regulatory control of air pollution in the United States has been reviewed by Mallette (750) and Kennedy (726). Purdom (777) has discussed legislative. organizational, and operational aspects of air pollution control. Standardization aspects were the subject of a paper by Speight and Mallette (272). I n the United Kingdom the Clean Air Act of 1956 has opened up a number of new problems, especially in administration by so-called smoke control areas for which the Act provides (747). The Act was the subject of the 1956 Des Voeux lecture delivered by Sir Hugh Beaver (72). Its impact on industry has been reviewed by Strachan (278) and on private dwellings by Branson (77). Sir Ewart Smith (200) has estimated capital costs to meet the requirements of the Act over 15 years at f,625,@0@,00@, a figure not considered to be intolerable as it is around 3y0 of the net annual expenditure on domestic fixed capital formation in 1955. Frenkiel (69) pointed out that in conventional zoning the concern is with use of the land, but for pollution control, it should be with use of the atmosphere. Reviews of Engineering Control.
INDUSTRIAL AND ENGINEERING CHEMISTRY
There have been a number of revielv papers in English on control of air pollution by engineering methods (702, 742, 798, 207, 232). Dallavalle (34)has given an assessment of fields of control in which research is needed. This included aggregation, electrets, thermodeposition, and supercoolants. Hess (703) has also assessed research needs. Smokeless fuel in England was reviewed in 1956 (206). The American Foundrymen’s Society has published material on external foundry discharge ( 7 ) . -4manual on industrial ventilation has been prepared by the American Conference of Governmental Industrial Hygienists ( 6 ) . In England a book on land, air and ocean which deals with air pollution has appeared (73). Histories of air pollution control in Pittsburgh (250) and Los Angeles (276) have been prepared and provide valuable information in view of the extensive programs set up in these two cities. General Meteorological Contributions. Meteorological factors affecting causes and control of air pollution have been dealt with by Hewson (704). Kleinwasser and Wanta (727) discussed development of a forecasting service for pollution control. There have been contriburions by Jehn ( 7 77) and Duffee (48) and two interesting papers on natural ventilation of London’s surface atmosphere (87, 256). Fundamental Dynamics. The fundamental reviews of Hughes and Oppenheim ( 7 7 7 , 772, 770) on fluid dynamics may be noted. Atmospheiic diffusion and turbulence have been treated, mathematically by Csanady (33) in relation to concepts of stream lines. and experimentally in field studies by Cramer and Record (30). Smith (203) reviewed practical applications of diffusion formulas. Friedlander and Johnstone (72) considered deposition of suspended particles from turbulent gas streams in relation especially to particle transfer rate. Theory of behavior of particulates in gas streams has also been considered by Levich (735) and Trappenburg (237). Pressure drop in air-solid flow systems has received study by Mehta and others (759). Low, speed wind tunnel studies on air flow around structures and other aspects of industrial air pollution problems have been attempted (25,279-222),though Collins (25)pointed out that this approach failed to reproduce vertical atmospheric temperature gradients. Frenkiel and Katz (70) have examined turbulent diffusion on a small scale using smoke puffs. Miller and Comings (763) analyzed static pressure distribution in the free turbulent jet. Stack Dispersion. Crozier and Seel? (37) used experimental plumes over a distance of 3 to 22 miles from source. Hewson (705)considered exit gas velocity and stack height. Smith and others (205)carried out experiments with oil I
A I R POLLUTION vapor from a 355-foot stack during temperature inversion and found that Barad's relationship derived for very stable atmospheres (70) applied. Hilst (706) has also experimented during stable conditions, using smoke and fluorescent particles. Vertical distribution was found to depend strongly on Richardson number. Horizontal distribution was adequately expressed by Sutton's classical diffusion model. Vertical temperature profiles and their influence upon pollution have been studied by Jenne (778). Smith (202) and Ozker and Smith (773) considered the dispersion problem under conditions of wind and gustiness. Harris (96) estimated levels of radioactivity in soil in relation to distance from a source, and reviewed the subject of stack dispersion in 1957 (728). Csanady (32) considered the rise of a hot smoke plume and Kayse (724) dealt with the practical problems of high temperature dispersion. Other practical problems in stack dispersion have been the subject of papers (74, 99, 752, 783, 224).
Dry
Centrifugal
Contributions.
Dauphin (37) reviewed earlier theories governing the efficiency of cyclone dust collectors and developed some theoretical modifications. Weber and Keenan (248) have evolved an approach to predicting head loss in flow through cyclone dust separators or vor-' tex chambers. The characteristics of straight-through vortex air cleaners have been investigated by Daniels (35), who found optimum separating length and noted that small particles are reentrained. Design factors for vane-type collectors have been studied by Walker and Cole (245) in relation to tube size, inlet-vanedesign, and utilizationof outlettube vanes. A simple vane cyclone separator has been conceived in India (779). Collins (26) discussed cyclone furnace boilers and flue gas dust loading. Wet Control. Developments in wet collection of effluents continue to be made. Doyle and Brooks (47) in Canada have designed a scrubber based on wet impingement at high gas velocities. Details of the Boucher aerojet system, founded on the mutual action of two aerosols, have been published (76). A multiple Venturi wet collector of unique design has worked successfully on a variety of test aerosols (729). A co-current centrifugal gas absorber was operated with three different gas-water systems and absorption rates were compared (790). A spray tower has been designed which proved comparable to packed towers for removal of halogens, carbon dioxide, and aerosols (747). The economics of the operation of wet collectors using the reverse jet principle has been examined (97). Brink and Contant
(79) have examined the variables in use of a Venturi scrubber for acid mist collection in a statistically designed experiment. Mist particle size was a most important variable. An informative cost estimate of liquid scrubbing for removal of sulfur dioxide from flue gases has been developed by Field and coworkers (67). This covered the nonregenerative limestone, the ammoniacal liquor, and the regenerative sodium sulfite processes. Other chemical processes have been outlined by Tarbutton and others (226) and Lawler (732). The latter described modifications to a n ammonium sulfite-bisulfite system pioneered in Canada. Rendle and Wilsdon (787) in England have carried out research on the effect of the sulfur content of fuel oils on dew point of flue gases and have experimented with reactions which would reduce dew point. The subject has also been considered by Pierce (775). Successful cleaning of cupola gases by Venturi scrubber has been described by Basse ( 7 7 ) . T h e sodium chloride aerosol method for agglutination of air-borne dust developed by Dautrebande has been dealt with in detail in a new book (38). Harris (95) described the method as observed in mines of the Belgian Congo. Walkenhorst (244) discussed its use on coal dust. Electrostatic Precipitation. A 50year review of electrostatic precipitation including discussion of many industrial applications has been contributed by White (255). This author covered particle conductivity factors in another paper (254). Lakey and Bostock (730) have carried out research on re-entrainment of deposited material in relation to resistivity and particle size. The use of electrostatic precipitation in open hearth gas cleaning requires special consideration in relation to factors such as residence time, and uniformity of distribution among others (5). Uniformity was also a subject of consideration in another study where the pipe type unit was found more efficient than dry plate type; small units gave better uniformity and less arcing than large units (233). A British patented development claims that the efficiency of electrostatic precipitation for cleaning flue gases from a pulverized-coal-fired boiler is increased by adding pulverized coal of
