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Chemical variability of mainstream cigarette smoke as a function of aerodynamic particle size
Dynamics and measurement of ultrafine aerosols
233
aerodynamic diameter is a progressive rising function, which value amounts to 1 at 0.2 #m and to 3.4 at 5 pro. Similar factors were determined to correct for particle losses due to the deposition in the edge layers of the foil and the filter present in the exhaust of the spiral duct. Semi-monodisperse triphenyl phosphate aerosols generated with a condensation nuclei generator were used for the size range 0.3-1/am; magnesium sulphate aerosols in the size range above 1/am. The correction factor for losses in the edge layers is maximal for particles with an aerodynamic diameter of 0.7/am and amounts to about 1.7. Above this diameter the factor decreases and attains a value of 1.05 at 5/am. For diameters smaller than 0.7/am the factor decreases up to 1.4 at 0.45/am. The correction factor for losses in the exhaust declines from 1.6 at 0.4/am to 1 at 1.6/am and is constant for aerodynamic diameters larger than 1.6/am. REFERENCE Strber, W. and Flachsbart, H. (1969) Envir. Sci. Tech. I, 1280.
COAGULATION
OF AEROSOLS
BY BROWNIAN
MOTION
C. N. DAvI~S Department of Chemistry, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, U.K. Experiments show that up to Kn ~ 15 the coagulation coefficient of aerosols is equal to 4kTC/3~h where C is the Cunningham-Knudsen-Weber-Millikan factor. The Fuchs ~ factor is erroneous and is not required. For Kn > 15 a new factor is proposed which shows how the coagulation coefficient attains the gas-kinetic value, K~c, at Knudsen number i> Kn~. The value of the latter rises as the particle size decreases. REFERENCES Davies, C. N. (1979) J. Aerosol Sci. 10, 151, Rooker, S. J. and Davies, C. N. (1979) J. Aerosol Sci. 10, 139.
CHEMICAL VARIABILITY OF MAINSTREAM SMOKE AS A FUNCTION OF AERODYNAMIC
CIGARETTE PARTICLE SIZE
Philip Morris Research Centre, Richmond, Virginia, U.S.A. and HERMANN FLACHSBARTand WERNER STOBER Institut f'tir Aerobiologie der Fraunhofer gesellschaft, Miinster, West Germany It appears to be obvious that different thermolytic breakdown processes occur in a burning cigarette and give rise to different chemical compounds. Theseindividual chemical differences should manifest themselves in aerosol particles of different size, because the growth and residence times in the hot environment may be quite different. There have been a few attempts to measure whether chemical differences do exist between the various particle sizes in mainstream smoke, but most have suffered from the comparison of chemical concentrations and the total mass separated. The total mass is subject to interferences of unknown magnitude from inorganics and water present in the smoke aerosol. Described here is a different approach to these problems, incorporating the use of the combination of radiolabelled materials and the separation of the labelled aerosol particles by a spiral centrifuge. In order to avoid the major pitfalls incurred by others using the concentration of a selected component vs total weight of condensate per region of interest, the measurement of specific radioactivity of each separated particle size zone was employed. The specific activity measurements are a direct measure of the ratio of radiocarbon present to total carbon ( t4C/1 zC ). These techniques are chemically independent of the amo ant of water or the inorganic composition of the particles. The non-volatiles were chosen for study to minimize any chemical compositional changes due to evaporative losses. The cigarettes used were made up individually of z4C-Bright, t4C-Burley and t4C-Oriental tobaccos, t4Cglycerol, t4C-invert sugar, t'tC-Bright stems, t4C-paper (cellulose) and t4C-dotriacontane. With the exception of dotriacontane, the cigarettes were made up to the exact weight percentages of each cigarette component as is present in the 1RI cigarette. The smoke was generated by a conventional reverse puffing technique. As soon as the smoke exited the cigarette, it was diluted 200 to I with air and separated in the centrifuge. The separated smoke was then assayed for total carbon (carbon-12 + carbon-14) and radioactivity (carbon-14). The data, thus, generated gave the specific activity of each particle size range in question. A quantitative recovery of all of the material in a particular size range was not required. Only enough material was needed to determine the L~C/12C ratio. Background values for both t4C and IzC were determined and properly subtracted. The analytical precision of the overall technique for the measurement of specific activity was determined to be 5.8Y. at two-sigma. The larger particles (greater than 0.5 #m) show no chemical differences due to coagulation effects on the smoke prior to separation. The small particles show definite differences in chemical composition and these values are shown as plots of relative specific activity vs particle size. In order to better understand the contribution of each of the ingredients of the IRl cigarette to each particle size range, the specific activity data was multiplied by the average contribution of each cigarette ingredient to the total MS TPM (carbon mass balance). This resulted in the actual contributions (F.) of each individual IRI cigarette component to each size fraction of mainstream TPM. The data is presented in the form of histograms for each particle size range.
233
aerodynamic diameter is a progressive rising function, which value amounts to 1 at 0.2 #m and to 3.4 at 5 pro. Similar factors were determined to correct for particle losses due to the deposition in the edge layers of the foil and the filter present in the exhaust of the spiral duct. Semi-monodisperse triphenyl phosphate aerosols generated with a condensation nuclei generator were used for the size range 0.3-1/am; magnesium sulphate aerosols in the size range above 1/am. The correction factor for losses in the edge layers is maximal for particles with an aerodynamic diameter of 0.7/am and amounts to about 1.7. Above this diameter the factor decreases and attains a value of 1.05 at 5/am. For diameters smaller than 0.7/am the factor decreases up to 1.4 at 0.45/am. The correction factor for losses in the exhaust declines from 1.6 at 0.4/am to 1 at 1.6/am and is constant for aerodynamic diameters larger than 1.6/am. REFERENCE Strber, W. and Flachsbart, H. (1969) Envir. Sci. Tech. I, 1280.
COAGULATION
OF AEROSOLS
BY BROWNIAN
MOTION
C. N. DAvI~S Department of Chemistry, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, U.K. Experiments show that up to Kn ~ 15 the coagulation coefficient of aerosols is equal to 4kTC/3~h where C is the Cunningham-Knudsen-Weber-Millikan factor. The Fuchs ~ factor is erroneous and is not required. For Kn > 15 a new factor is proposed which shows how the coagulation coefficient attains the gas-kinetic value, K~c, at Knudsen number i> Kn~. The value of the latter rises as the particle size decreases. REFERENCES Davies, C. N. (1979) J. Aerosol Sci. 10, 151, Rooker, S. J. and Davies, C. N. (1979) J. Aerosol Sci. 10, 139.
CHEMICAL VARIABILITY OF MAINSTREAM SMOKE AS A FUNCTION OF AERODYNAMIC
CIGARETTE PARTICLE SIZE
Philip Morris Research Centre, Richmond, Virginia, U.S.A. and HERMANN FLACHSBARTand WERNER STOBER Institut f'tir Aerobiologie der Fraunhofer gesellschaft, Miinster, West Germany It appears to be obvious that different thermolytic breakdown processes occur in a burning cigarette and give rise to different chemical compounds. Theseindividual chemical differences should manifest themselves in aerosol particles of different size, because the growth and residence times in the hot environment may be quite different. There have been a few attempts to measure whether chemical differences do exist between the various particle sizes in mainstream smoke, but most have suffered from the comparison of chemical concentrations and the total mass separated. The total mass is subject to interferences of unknown magnitude from inorganics and water present in the smoke aerosol. Described here is a different approach to these problems, incorporating the use of the combination of radiolabelled materials and the separation of the labelled aerosol particles by a spiral centrifuge. In order to avoid the major pitfalls incurred by others using the concentration of a selected component vs total weight of condensate per region of interest, the measurement of specific radioactivity of each separated particle size zone was employed. The specific activity measurements are a direct measure of the ratio of radiocarbon present to total carbon ( t4C/1 zC ). These techniques are chemically independent of the amo ant of water or the inorganic composition of the particles. The non-volatiles were chosen for study to minimize any chemical compositional changes due to evaporative losses. The cigarettes used were made up individually of z4C-Bright, t4C-Burley and t4C-Oriental tobaccos, t4Cglycerol, t4C-invert sugar, t'tC-Bright stems, t4C-paper (cellulose) and t4C-dotriacontane. With the exception of dotriacontane, the cigarettes were made up to the exact weight percentages of each cigarette component as is present in the 1RI cigarette. The smoke was generated by a conventional reverse puffing technique. As soon as the smoke exited the cigarette, it was diluted 200 to I with air and separated in the centrifuge. The separated smoke was then assayed for total carbon (carbon-12 + carbon-14) and radioactivity (carbon-14). The data, thus, generated gave the specific activity of each particle size range in question. A quantitative recovery of all of the material in a particular size range was not required. Only enough material was needed to determine the L~C/12C ratio. Background values for both t4C and IzC were determined and properly subtracted. The analytical precision of the overall technique for the measurement of specific activity was determined to be 5.8Y. at two-sigma. The larger particles (greater than 0.5 #m) show no chemical differences due to coagulation effects on the smoke prior to separation. The small particles show definite differences in chemical composition and these values are shown as plots of relative specific activity vs particle size. In order to better understand the contribution of each of the ingredients of the IRl cigarette to each particle size range, the specific activity data was multiplied by the average contribution of each cigarette ingredient to the total MS TPM (carbon mass balance). This resulted in the actual contributions (F.) of each individual IRI cigarette component to each size fraction of mainstream TPM. The data is presented in the form of histograms for each particle size range.