James W. Smith

Occupational Exposure to Airborne Dust, Respirable Quartz and Metals Arising from Refuse Handling, Burning and Landfilling

Industrial hygiene investigations were conducted in 1983 at a refuse derived fuel (RDF) burning plant, a refuse transfer station and three municipal landfill sites. The field surveys were conducted during the warmer and drier seasons of the year. The investigations included air sampling for total dust, respirable quartz and airborne metals. Bulk samples of soil cover, precipitator/boiler ash and transfer station baghouse fines were analyzed for quartz, elements, asbestos and polychlorinated biphenyls (PCBs) content. Asbestos and PCBs were not detected in any of the bulk samples taken. Quartz content of the bulk samples varied from 8% to 31%. Except for the boiler grate inspector and the precipitator cleaner at the RDF burning plant, exposure to airborne metals was not excessive at the sites tested. One personal sample (at landfill site A) for total dust exceeded 10 mg/m3 out of a total of eighteen personal and area samples. Significant exposure to respirable quartz was found at all the sites (up to 0.20 mg/m3). Respirable quartz exposures in excess of the NIOSH criteria concentration of 0.05 mg/m3 were found in three out of seven personal samples at the RDF burning plant, two out of three personal samples at the refuse transfer station and six out of nine personal samples taken at the three landfill sites.

Comparison of the Effectiveness of Bubble Coalescence and Foamed Surfactant in Controlling the Acid Mist Formed by Electrowinning Cells

During the electrowinning of metals such as copper and zinc, an acid mist is produced by gas bubbles bursting at the electrolyte surface. The bubbles eject droplets of the acidic electrolyte into the atmosphere above the cells. The particles range in size from 0.5 to 30 µm, and each studies have shown emission rates of about 1.6 mg H2SO4/sec·m2. Two methods for controlling this acid mist are compared. The first is addition of a surfactant to the electrolyte to produce a foam layer. Under field conditions, however, the surfactant is costly, reduces curve efficiency, and may not he as effective as in the laboratory because of the foam being swept aside by large bubble streams. The second met is the use of a coalescence device, developed at the University of Toronto, which reduces the acid emissions by coalescing the bubbles collecting the droplets that are ejected. It was found that the surfactant, which produced a foam layer about 20-mm thick, reduced the aer emissions by 98%, and the coalescence device by...

Instability of two‐phase flow in vertical cylinders

The stability of two‐phase flow in a vertical cylinder is considered. The liquid phase is assumed to flow past the cylinder surface in a thin layer, assuming no mixing with the core gas flow. The complete system of Navier–Stokes and continuity equations for both phases is treated analytically, using a perturbation procedure based on expansion in powers of small wavenumbers. The results of the first approximation determine the phase velocity of waves developed on the liquid‐gas interface. The second approximation reveals the complete pattern of hydrodynamical stability of two‐phase flow over the entire range of gas‐flow velocities. The topological features of stability curves are depicted. The effects of surface tension, cylinder radius, and interface curvature on the two‐phase flow stability are revealed.

Review and Evaluation of Models Estimating the Minimum Atmospheric Dilution of Gases Exhausted Near Buildings

Abstract In this study, eleven mathematical models estimating the minimum possible atmospheric dilution of rooftop exhaust gases around buildings are evaluated and reviewed using data obtained from 72 full-scale tracer tests at two buildings. Quantities measured were the stack height, stack-to-intake distance, stack diameter, wind speed and direction, exhaust flux, and the stack-to-intake dilution. These models are all based on wind-tunnel simulations and are designed to account for a worst-case scenario so that they can be used to provide a conservative safeguard for design of new stacks or for modification purposes. Although none of the models gave outstanding performance relative to the others, Halitsky’s model, derived from the prism tests and Clinical Center data incorporating the exhaust momentum ratio, gave particularly good predictions. Further, all models led to very conservative estimates of the dilution in the case of gases exhausted close to a receptor, suggesting that the models reviewed here...

A Non-Toxic Diffusional Dosimeter for Sulfur Dioxide

Diffusional (passive) dosimeters are often required for the determination of time-weighted average concentrations of sulfur dioxide under relatively severe workplace conditions. The method developed here combined the use of a diffusional dosimeter and a relatively non-toxic buffered formaldehyde absorbing solution. The dosimeter was found to give reproducible results using two lots of General Electric single-backed dimethyl silicone membranes; sampling times from 1 to 7 hr; sampling temperatures from 25°C to 38°C; and at face velocities from 0–600 ft/min (0–3 m/s). Concentrations as low as 0.05 ppm were determined over a maximum sampling time of 7 hr, yielding a sensitivity better than 0.35 ppm·hr. Fluctuating concentrations from 0.5,1.0 or 2.0 ppm background to 10.0 ppm for 1/2 hr were shown to result in no significant error.

A Simple Compact System for the Extraction of Radon from Water Samples

Radon is the radioactive decay product of radium. This gaseous element and its progeny are major contributors to the population dose produced by environmental radioactivity. Radon enters the environment by exhalation from soil and rock and by effusion from ground and surface waters. Effusion or exhalation into poorly ventilated spaces can produce significant airborne concentrations of radon and its progeny. This paper describes a compact system for the extraction of radon from water samples for subsequent quantitation. The system can accommodate samples having different volumes. The volumes tested ranged from 130 to 455 mL. The limit of detection of the 155 mL sample, based upon a counting time of 1000 min, is 0.034 Bq/L (0.91 pCi/L) of water.

Industrial ventilation — a review and update

Industrial ventilation is an engineering discipline which has been badly neglected for a long period of time. With the recent emphasis on improving conditions in the in-plant workplace environment, more advanced techniques are required and are being developed to solve difficult and complex industrial ventilation problems. The paper reviews the technical progress being made in the industrial ventilation field by different investigators throughout the world. The scope of the field reviewed and updated includes natural ventilation, local exhaust ventilation, specialized ventilation techniques (dilution, air jets and air curtains, recirculation of filtered air, exhaust of open surface tanks, tracers for ventilation studies), and mine ventilation. Typical applications of the new technology to solving industrial ventilation problems are presented. Important areas requiring further research and development work are identified.

Cross‐language perception of Russian plain/palatalized laterals and rhotics.

A number of studies investigating factors in non‐native speech perception have focused on discrimination and identification of English /l/ and /r/ by listeners whose native languages do not have the relevant phonemic contrast. Relatively little work, however, has been done on non‐native perception of lateral/rhotic contrasts in other languages and particularly on the perception of palatalized laterals or rhotics. This paper presents results of an AX discrimination experiment where 84 listeners, native speakers of Cantonese, English, Japanese, Korean, Mandarin, and Russian, were presented with stimuli containing intervocalic consonants /l/, /lj/, /r/, and /rj/ produced by a Russian native speaker. The results revealed significant differences in the perception of the lateral/rhotic contrasts across the listener groups, with relatively good discrimination of the contrasts by Korean and English listeners (yet less accurate compared to Russian listeners), and much poorer discrimination by the other groups of n...

Evaluation of the performance of ‘Electrocaps’ under simulated industrial conditions

ABSTRACT Electrocaps were developed at the University of Toronto to reduce the emission of the acid mist that is produced during the electrowinning of metals such as copper or zinc. During electrowinning, bubbles of hydrogen and oxygen, produced at the cathodes and anodes respectively, burst at the electrolyte surface and eject droplets of the acidic electrolyte into the atmosphere above the cells. The Electrocaps reduced the acid emissions by coalescing the bubbles and by collecting by impaction and diffusion the droplets that were ejected. It was thought that the presence, under industrial conditions, of a suspension of manganese dioxide and a foam layer due to a surfactant would affect the effectiveness of the Electrocaps. The acid mist formation was simulated by bubbling air through a cell containing the electrolyte; the bubble size used was comparable to that found in electrowinning cells. Parameters studied to determine their effect on the emission rate and size distribution included the addition of fine MnO2 particles, a surfactant, and the Electrocaps to the system. It was found that MnO2 generally increased the emission rate, that the Electrocaps and the surfactant both reduced the emissions, and that the sufactant increased the effectiveness of the Electrocaps. Depending on the conditions, at least 94% of the acid mist was eliminated.

A Course in Applied Chemistry at a Third World University

Summaries English An outline is given of a programme in applied chemistry within a classical chemistry department of a university located in a Third World country with certain specific needs. The curriculum has been specifically designed to provide students with the knowledge and skills used by chemists in Jamaican industry. Industry personnel were invited to participate fully in the development of the curriculum as well as in actual instruction. In this way, an attempt was made to bridge the gap between the ‘academic’ and the ‘real’ world. The Third World has experienced a perennial shortage of skilled professional scientists, including chemical engineers. The role of the applied chemist, as envisaged by the authors, has assumed greater importance in the light of this shortage. The programme outlined can probably serve as a basis for discussion in other developing countries contemplating similar programmes.