34 research outputs found
Bacterial Mutagenicity of Urban Organic Aerosol Sources in Comparison to Atmospheric Samples
The bacterial mutagenicity of a comprehensive set of urban
particulate air pollution source samples is examined using
the Salmonella typhimurium forward mutation assay.
Each of the combustion source samples examined, including
the exhaust from catalyst-equipped autos, noncatalyst
autos, heavy-duty diesel trucks, plus natural gas, distillate oil, and wood combustion sources, is mutagenic in this assay, with a response per microgram of organic carbon in these samples generally greater than that of cigarette smoke aerosol. The noncombustion source samples tested generally are not mutagenic at the levels examined. The specific mutagenicity (mutant fraction per microgram of
organic carbon) of ambient aerosol samples collected in
southern California is compared to a weighted average of
the specific mutagenicity of the primary source samples
assembled in proportion to their emission rates in the Los
Angeles area. In most cases where a comparison can be
made, the specific mutagenicity of the source composites
and the ambient samples are of similar magnitude, with
the exception that the -PMS mutagenicity of the aerosol
at Long Beach, CA, during the first half of the calendar
year 1982 and at Azusa, CA, during the April-June 1982
period is much higher than can be explained by direct
emissions from the sources studied here
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Effects of Catalytic Mineral Matter on CO/CO sub 2 ratio, Temperature and Burning Time for Char Combustion
In this program we are measuring the CO{sub 2}/CO ratio for both catalyzed and uncatalyzed chars over a wide range of temperature. These results will then be used to develop predictive models for char temperature and burning rates. In this report progress on modeling particle temperature under conditions where ignition occurs is reported. A comparison of preliminary modeling results with experimental results is also reported. 11 refs., 4 figs
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Effects of catalytic mineral matter on CO/CO[sub 2] ratio, temperature and burning time for char combustion
We have extended our recently reported method for determining the surface area of single microporous particles, Dudek et al., 1989 using an electrodynamic chamber (EDC) by increasing the operating pressures from 1 at to 25 at. The value of total surface area is determined from adsorption measurements of CO[sub 2] assuming monolayer adsorption. Measurements of CO[sub 2] desorption were also carried out to yield a point to point difference from the adsorption measurements of about 1%. Adsorption-desorption cycles were carried out for 10 particles to yield a scatter of less than 5% in the measured value for saturation adsorption. The major advantage of using high pressure measurements for evaluating the saturation value for CO[sub 2] adsorption is the improved accuracy of the extrapolation procedure. Previous measurements with the EDC at atmospheric pressure, Dudek, et al., 1989, yielded values for the surface area for similar particles of comparable value with a relative error of about 15%. The results of the high pressure measurements are however bounded with an error of about 3%. Also, the equilibrium adsorption-desorption coefficient was found with a high accuracy, whereas from atmospheric measurements it was not practical to obtain an accurate value
Bacterial Mutagenicity of Urban Organic Aerosol Sources in Comparison to Atmospheric Samples
The bacterial mutagenicity of a comprehensive set of urban
particulate air pollution source samples is examined using
the Salmonella typhimurium forward mutation assay.
Each of the combustion source samples examined, including
the exhaust from catalyst-equipped autos, noncatalyst
autos, heavy-duty diesel trucks, plus natural gas, distillate oil, and wood combustion sources, is mutagenic in this assay, with a response per microgram of organic carbon in these samples generally greater than that of cigarette smoke aerosol. The noncombustion source samples tested generally are not mutagenic at the levels examined. The specific mutagenicity (mutant fraction per microgram of
organic carbon) of ambient aerosol samples collected in
southern California is compared to a weighted average of
the specific mutagenicity of the primary source samples
assembled in proportion to their emission rates in the Los
Angeles area. In most cases where a comparison can be
made, the specific mutagenicity of the source composites
and the ambient samples are of similar magnitude, with
the exception that the -PMS mutagenicity of the aerosol
at Long Beach, CA, during the first half of the calendar
year 1982 and at Azusa, CA, during the April-June 1982
period is much higher than can be explained by direct
emissions from the sources studied here
Fuel oil atomization
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1943.Vita.Includes bibliographical references (leaf [167]).by John Ploeger Longwell.Sc.D
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Effects of catalytic mineral matter on CO/CO[sub 2] temperature and burning time for char combustion
The high temperature oxidation of char is of interest in a number of applications in which coal must be burned in confined spaces. These include: the conversion of oil-fired boilers to coal using coal-water slurries, the development of a new generation of pulverized-coal-fired cyclone burners, the injection of coal into the tuyeres of blast furnaces, the use of coal as a fuel in direct-fired gas turbines in large-bore low-speed diesels, and entrained flow gasifiers. In addition, there is a need to better understand the temperature history of char particles in conventional pulverized-coal-fired boilers in order to better understand the processes governing the formation of pollutants and the transformation of mineral matter. The temperature of a char particle burning in an oxygen containing atmosphere is the product of a strongly coupled balance between particle size and physical properties, heat transfer from the particle, surface reactivity, CO/CO[sub 2] ratio and gas phase diffusion in the surrounding boundary layer and within the particle. In addition to its effects on burning rate, particle temperature has major effects on ash proper-ties and mineral matter vaporization. Measurements of the temperature of individual burning char particles have become available in recent years and have clearly demonstrated large particle to particle temperature variations which depend strongly on particle size and on panicle composition. These studies, done with pulverized coal, do not allow direct determination of the CO/CO[sub 2] ratio produced at the char surface or the catalytic effects of mineral matter in the individual char particles and it has generally been assumed that CO is the only product of the carbon-oxygen reaction and that CO[sub 2] is formed by subsequent gas phase reaction More recent work, however, has pointed out the need to take CO[sub 2] Production into consideration in order to account for observed particle temperatures