Airborne Sources Research Articles

Aerosols Generated by Accidents: Pressurized Liquid Release Experiments

Safety assessments and environmental impact statements for facilities require an estimation of airborne releases from accidents. Aerosols generated by accidents are being investigated to develop the source terms for these releases. One example of a severe accidental release event is a pressurized liquid release. Pressurized liquid release experiments performed in static air measured the mass airborne as a function of source size and containment pressure. Pressurized releases with the containment breach above the liquid level were investigated. For this configuration, only containment presure at the time of release was found to be a significant parameter. Releases in static air can be estimated using the relationships developed in this work. Weight percent of the airborne source ranged from 4×10−4 to 0.15%. All of the pressurized releases produced a significant fraction of respirable particles.

Synthetic aperture radar observations of ocean and land

A brief history of synthetic aperture radar (SAR) from early radar ideas to recent satellite systems is presented. Properties of electromagnetic radar measurement that are fundamental to SAR systems are presented and discussed by the use of example SAR images derived from airborne and Seasat satellite sources. The next decade of activity in radar satellites is outlined.

Viable sampling for airborne bacteria in a poultry processing plant

Air was sampled for viable bacteria in the shackling room of a poultry processing plant. Large numbers of bacteria were isolated from the workers’ breathing zone, and gram‐negative organisms were characterized. The probable source of airborne gram‐negative bacteria and their endotoxins was identified as the birds’ feces. These data suggest a potential health risk for workers due to inhalation of viable bacteria.

In Situ Methods for Quantifying Gamma-Radiation Levels and Radionuclide Concentrations

Small perturbations of the environmental radiation field by artificial radionuclides have been successfully quantified using high pressure ionization chambers and in situ semiconductor detector gamma-ray spectra. The calibration and use of these instruments for the detection of ground-deposited and airborne sources of activity is described and general methods for data interpretation are discussed. Specific examples are given in which the exposure rate from fallout radionuclides deposited on the soil surface and from noble gases released by nuclear facilities are determined and unambiguously separated from variations in the underlying background.

Effects of Indoor Residence on Radiation Doses from Routine Releases of Radionuclides to the Atmosphere

Dose reduction factors from indoor residence during routine releases of radionuclides to the atmosphere were studied using models that are suitable for application to arbitrary source terms. Dose reduction factors for internal exposure to inhaled radionuclides account for air ventilation and deposition on inside building surfaces. Estimated internal dose reduction factors are approx. 0.2 to 0.8 for particulates and 0.07 to 0.4 for radioiodine. Dose reduction factors for external photon exposure from airborne and surface-deposited sources are based on the point-kernel integration method. Values for source terms from a fuel reprocessing plant and a hypothetical reactor accident are within a factor of 2 of the value 0.5 adopted by the US Nuclear Regulatory Commission (NRC) for population dose assessments. For the release at Three Mile Island nuclear station, however, the external dose reduction factor may be an order of magnitude less than the value adopted by the NRC.

Wound Infections in Patients Undergoing Total Hip Arthroplasty

Ultraviolet (UV) irradiation (1,537 A) during total hip arthroplasty will effectively reduce risk of airborne bacterial contamination of the operative field. An air sampling study at the operative site compared 28 total hip arthroplasties with UV lights on and 19 operations with UV lights off. The use of UV irradiation significantly reduced the average number of airborne bacteria over the operative site, although the results indicate that the number of airborne bacteria collected at the operative site in each conventional operating room without UV irradiation was quite low. Data confirmed the fact that airborne bacteria are a reflection of operating room personnel and their activities. With UV light, the rate of infection from possible airborne sources was 0.15% for 1,322 total hip patients. Thus, emphasis is now placed on those causes of infection that are not airborne.

The determination of nicotine in biological fluids at picogram levels by selected ion recording

Using a combined gas chromatographic-mass spectrometric-selected ion recording technique it has been possible to achieve detection, identification, and quantitation of nicotine in biological fluids in amounts as low as 25 pg. Employing the deuterated variant nicotine-5′,5′- d 2 both as an internal standard and as a carrier in an inverse isotope dilution method, an accurate, sensitive, and specific method for picogram level quantitation of nicotine is obtained. Careful precautions were necessary to prevent positive “blank” values at low levels due to extraneous nicotine, which were found to arise both from the solvents used in the extractions and from airborne sources.

Noise cancelling microphone

A microphone unit comprises a pair of like electroacoustic transducers each having sound-responsive elements in the form of identical diaphragms which are parallel to each other and mounted in a common housing that is open at at least one end for the reception of desired sounds in a direction perpendicular to the diaphragms. The diaphragms are spaced apart a distance no greater than one-quarter of the shortest wavelength of the range of frequencies of the noises to be cancelled; and the housing has further apertures that open into the housing in directions parallel to the planes of the diaphragms, these further apertures being disposed at least one on each side of each diaphragm and the interior ones of said further apertures being spaced apart from their associated diaphragm a distance no greater than one-eighth of the shortest wavelength of the range of frequencies of the noises to be cancelled. The noise sources and channels that the microphone may be exposed to are 1. air-borne ambient noises; 2. air-borne noises due to reflection and echoes; 3. direct vibration transmitted to the microphone housing through non-air channels by contact and/or mounting; and 4. microphony effects of the housing, that is, vibration produced by the housing due to all air-borne sources. Air-borne ambient noises, direct vibrations, and microphony noises will be cancelled by the arrangement of the transducers; while echoes, and reflections, as well as ambient noises, will be attenuated by the presence of the further apertures.

The assessment of air-inlet filters for intravenous infusions in glass bottles

Glass infusion bottles require the influx of air into the containers to replace fluid during administration. A non-absorbent cotton wool plug, situated in the air-inlet set, acts as a filter to remove airborne micro-organisms. an enclosed air space artificially contaminated with viable bacterial spores was used to assess the contamination of intravenous infusions from an airborne source. Only small numbers of spores gained access to the infusion fluids when containers were used with commercially made air-inlet sets. Removal of the filter permitted the entry of spores, the numbers being related to the concentration present in the external air. The efficiency of cotton wool plugs was related to the weight of cotton wool in the air-inlet set. The compression applied to the cotton wool also significantly influenced filter efficiency. Although air-inlet sets were challenged with much higher levels of airborne contamination than would be expected in a hospital environment, results indicate that the air-inlet set should contain sufficient cotton wool. The compression of the filter material should also be considered.

Geographical Distribution of Fluorides in Forage Using a Bioindicator

AbstractFluoride levels in leaves of black locust (Robinia pseudoacacia L.) collected in late summer were used to predict geographical distributions of average seasonal pasture forage and hay fluoride levels near a source of airborne fluorides.Simple linear regression models with various logarithmic transformations were tested. Greatest proportions of the total variation were explained by the linear regression model for second‐cutting hay (81%) and by a logarithmic transformation of the dependent variable for average pasture forage (63%). None of the models tested were found adequate for predicting fluoride levels in first‐cutting hay. Isopleth maps based on predicted fluoride values compared favorably with those derived from direct measurements.The use of black locust foliage as a quantitative bioindicator of geographical forage fluoride levels can provide considerable savings in material and personnel in long term fluoride surveys.

High-frequency model for sound transmission from an airborne source into the ocean : MEECHAM W. C., 1976. J. acoust. Soc. Am., 60 (2): 339–342

High-frequency model for sound transmission from an airborne source into the ocean : MEECHAM W. C., 1976. J. acoust. Soc. Am., 60 (2): 339–342

High-frequency model for sound transmission from an airborne source into the ocean

The problem of the transmission of sound from an airborne source into the ocean, through the rough ocean surface, is considered. A high-frequency approximation is adopted, requiring for its validity that the sound wavelength in air be (much) less than typical radii of curvature and than typical displacements of the ocean surface. This condition is approximately met in many applications. Attention is focused on observation directions with small grazing angles. The result is approximately unaffected by surface roughness when the grazing angle is greater than the rms surface slope, and approaches a limit (proportional to the variance of the surface slope) when the grazing angle is less than the slope. The result is independent of the source height, under the stated approximations, as is also the case for the transmission through a plane surface. The enhancement due to surface roughness, even at moderate wind speed, ranges up to 10 dB. Subject Classification: [43]30.25.

Directivity as a discriminant in monitoring of air-acoustic environmental noise

Directivity is useful in the automatic monitoring of air-acoustic environmental noise because discrimination is possible not only between ground and airborne sources, but between different ground sources as wall. The experimental program compared omnidirectionals, gradients, cardioids, donuts, cardonuts, and second-order donuts as vertical discriminators between ground and airborne sources. DIFAR, DARAS, and CODAR arrays were the means examined for resolving ground sources. The data were gathered in flat, sandy, scrub-pine woods (New Jersey) and under a 50-ft jungle canopy (Panama). Nineteen different microphones were mounted at zero, 10- and 40-ft heights. Each height contained an omnidirectional, downward-looking cardioid and pair of horizontally crossed gradients. The 10-ft level included separate DIFAR, 2-ft baseline DARAS, and 75-ft CEDAR arrays. Vertical directivity discriminated between ground and airborne sources provided the microphone pattern nulled both upward and downward to attenuate the multipath. Cardonuts and second-order donuts were most effective, flyover noise being reduced 25 dB even in the presence of severe ground reflectivity. DIFAR and DARAS gave bearing angles to vehicles consistently within a few degrees in spite of the multipath. CODAR was not useful. Adaptive DIFAR enhanced capability by improving or rejecting bad bearings.

Heavy-metal Pollution in the Sudbury Mining and Smelting Region of Canada, I. Soil and Vegetation Contamination by Nickel, Copper, and Other Metals

Soil, vegetation, and rainfall, have been collected in the vicinity of a nickel–copper smelter at Sudbury, Ontario. The region is a major producer of many metals, and the large areas of forest desolation in the vicinity have been ascribed to sulphur dioxide fumigations over the past 80 years. In the present study, attention has been focused on potentially toxic heavy metals. Very elevated soil levels of nickel and copper were found, with values up to 5,104 ppm Ni and 2,892 ppm Cu within 1.1 km of the smelter. The concentrations decreased with distance to 49.8 km in one direction. Surface soils were the most contaminated, and a decline through the soil profile was found. Other metals such as iron, cobalt, and silver, showed a similar pattern of distance and depth, suggestive of an airborne source. Analyses of the foliage of three plant species also showed excessive levels of nickel and copper, as well as of aluminium. The levels declined with distance from the smelter.The relative possibilities of soilversusaerial uptake are considered. The soils within 2–3 km of the smelter were markedly more acidic than those from farther away, and this was paralleled by their increased conductivity. Dustfall–rainfall collections and analyses of the soluble heavy metals indicated that a major aerial source of metals existed, and that the problem of metallic emissions is not merely one of the past. Heavy metals are persistent in soils, and the ecological consequences to date have perhaps only been masked around Sudbury by the sulphur dioxide damage, and the particular importance attached to it in the past.

Air pollution control at Cape Kennedy.

Abstract Larger missiles and the increased use of toxic propellants require effective planning and operations to prevent the development of major air pollution problems. At Cape Kennedy Air Force Station, large-scale air-borne sources are of an instantaneous rather than a continuous nature. Significant air contamination sources include missile exhaust, aborts, spills of volatile propellants, disposal of toxic materials, and normal industrial or transportation activities. Abatement techniques incorporating equipment design, operations support, and environmental studies are discussed. Special emphasis is given controls, test data, and problems associated with the Titan II missile program.

The Application of Inertia Navigation Systems to Civil Air Transport

Navigation by the use of inertial information is now an accepted technique for military aircraft and for missiles. In civil aircraft the application of inertial techniques are, as yet, limited to defining the vertical and providing a memory of azimuth direction; that is, as aids to flight rather than a primary or even sole navigational aid. Although the principles applied—the inertial properties of matter and the laws of gravitation—are the same, the accuracy of the inertial sensors differs by some three orders of magnitude, and the cost by some two orders, between these two extremes.Mr. A. Stratton of the Royal Aircraft Establishment first of all presents in perspective the range of application of inertial techniques that are available for civil use and suggests how the information obtained by inertial means can be related to that from other airborne sources. He shows that even if the expense of an accurate inertial platform of ‘navigational’ quality should not be justified, considerable advantage over existing sources obtains in terms of accurate attitude reference, and instantaneous velocity and acceleration, by the use of a lower-grade platform in conjunction with other navigation aids.

I—The Inertial Reference Platform in Civil Aviation

The objects of this paper are to present in perspective the range of application of inertial techniques that are available for civil use and to suggest how the information that can be obtained by this means relates to that from other airborne sources.

Noise Control for Reciprocating Compressors

Reciprocating compressors, as used in many air-conditioning systems, have long been recognized as potential major sources of airborne and structureborne noise. However, in many installations, some of the noise paths are overlooked either because of incomplete information, ill-defined criteria, or haphazard consideration of the problems. In this paper, the need for effective noise-control measures for both the airborne and structureborne path is illustrated by several case histories involving reciprocating compressors. It is shown, however, that adequate noise-control measures can usually be provided within the framework of “normal” construction techniques.

Atmospheric Attenuation of Sound from an Elevated Source

Experimental data were given in a previous paper at the October, 1957, meeting of the Acoustical Society of America on the effects of weather parameters on the attenuation of sound propagated from an airborne source to ground. These results have been analyzed in greater detail and improved procedures have been developed for predicting attenuation. The residual attenuation, defined as that in excess of spherical divergence and molecular absorption, does not vary systematically with any of the measured weather parameters for source elevations of 10° or higher and for altitudes above a few hundred feet. Its average value in this region may be expressed by α0=0.11f12 db/1000 ft, where f is the frequency in cps. At lower source elevations and altitudes, the attenuation is increased by an amount depending on frequency, source elevation, wind velocity and direction, and temperature gradients. Comparison of upwind with downwind propagation for source elevations of 2°, 5°, 10°, and 15° shows a significant difference only for 2°. The statistical data for upwind propagation are compared with theory applicable to shadow formation. (This research was supported by Wright Air Development Center.)

Sound Propagation through the Atmosphere

The propagation of sound from an airborne source to the ground has been studied. The source was a propeller type airplane flown at altitudes up to 4800 ft and distances up to 9600 ft. Angles of elevation of the source with respect to the earth's surface were 2°, 5°, 15°, 30°, and 90°. The weather varied to include typical year-round conditions in the Chicago, Illinois, area and winter in Phoenix, Arizona. The noise propagated to the earth was analyzed to determine the variation in attenuation as a function of frequency and the relative position of the noise source. A statistical analysis was made to determine the effects of various weather parameters on propagation of the sound. Average values of sound attenuation were obtained. In addition, the effects of temperature, temperature gradient, humidity, wind, and wind gradient are given in an empirical formula. Propagation does not vary significantly for elevation angles between 5° and 90°, but for the 2° angle there is evidence of ground surface effects. The most important factor for minimizing the noise on the ground on a particular day was wind direction. Other meteorological conditions do not appear to be significant for controlling noise from flight operations around an airport. (Sponsored by the Aero Medical Laboratory, WCRDB, Wright-Patterson Air Force Base, Ohio.)