Saulius Trakumas - Academia.edu (original) (raw)
Papers by Saulius Trakumas
Http Dx Doi Org 10 1080 15298660108984633, Jun 4, 2010
The overall filtration efficiency of a vacuum cleaner traditionally has been tested by placing th... more The overall filtration efficiency of a vacuum cleaner traditionally has been tested by placing the vacuum cleaner in a test chamber and measuring aerosol concentrations at the chamber inlet and outlet. The chamber test method was refined and validated in this study. However, this chamber test method shows an overall filtration efficiency of close to 100% for most of the industrial vacuum cleaners and for most of the newly developed household vacuum cleaners of midprice range or higher because all these vacuum cleaners have a high-efficiency particulate air (HEPA) or other highly efficient filter installed at the exhaust. A new test method was therefore developed through which the vacuum cleaner was probed in various internal locations so that the collection efficiency of the individual components could be determined. For example, the aerosol concentration upstream of the final HEPA filter can thus be measured, which permits one to estimate the life expectancy of this expensive component. The probed testing method is particularly suitable for field evaluations of vacuum cleaners because it uses compact, battery-operated optical particle size spectrometers with internal data storage. Both chamber and probed tests gave the same results for the aerosol filtration efficiency. The probed testing method, however, also gives information on the performance of the individual components in a vacuum cleaner. It also can be used to determine the dust pickup efficiency and the degree of reaerosolization of particles collected in the vacuum cleaner.
Http Dx Doi Org 10 1080 15428110208984756, Jun 4, 2010
This study evaluated a new method that uses an optical aerosol photometer for dynamically monitor... more This study evaluated a new method that uses an optical aerosol photometer for dynamically monitoring dust pickup efficiency during vacuuming. In the first stage of this study the new method was compared with built-in dirt sensors installed by vacuum cleaner manufacturers. Through parallel testing it has been shown that the widely available built-in dirt sensors are not sensitive enough to register small (< 53 microm) dust particles. Therefore, only the optical photometer was used in the rest of the experiments of this study to monitor the dust pickup efficiency while the vacuum cleaner was operated with different nozzles on clean and soiled carpet and vinyl sheet flooring. This method also was used to monitor dust pickup efficiency when vacuuming carpets originating from lead-contaminated homes. The dust pickup efficiencies obtained with the optical aerosol photometer have been compared with the surface lead concentrations found during different stages of cleaning. Results indicate that the dust mass concentration registered with the optical aerosol photometer at the nozzle outlet correlates well with the dust mass collected in the vacuum cleaner filter bag and with the surface lead level. Therefore, dynamic dust pickup monitoring can provide valuable information about the efficiency of cleaning when a vacuum cleaner is used. This suggests that a small aerosol photometer similar to a light-scattering smoke detector would be beneficial in vacuum cleaners used for cleaning surfaces contaminated with leaded dust and biological particles (including allergens).
Atmos Environ, 1994
The evolution of urban aerosol size distribution growing by heterogeneous reactions has been obse... more The evolution of urban aerosol size distribution growing by heterogeneous reactions has been observed in winter fog. Particle diameter growth rates from such data are presented. The functional dependence of the growth rates on particle diameter infer clues about chemical mechanisms of heterogeneous interaction. The data are consistent with aerosol formation in winter fog resulting from condensation of low vapor pressure species formed by gas phase reactions and droplet phase reactions.
Atmospheric Research, 1996
Continental aerosol particle size distributions were measured as a function of time at the backgr... more Continental aerosol particle size distributions were measured as a function of time at the background station Aisetas and in the suburb of Vilnius, Marine aerosol particle formation was studied in outdoor photochemical chamber experiments performed on the coast of the Baltic sea. The functional dependence of the particle diameter growth rate on the particle size was calculated from the aerosol particle size distribution data and was compared with the theoretical predictions for the particle growth due to vapor condensation or due to the adsorption of aerosol precursor gases on the particle surface or within an airborne droplet. It was shown that during summer months condensation of low pressure vapors formed by gas phase homogeneous chemical reactions was predominant mechanism of the continental aerosol particle growth. While in winter growth of a submicrometer continental aerosol particle was frequently governed by two competing processes: condensation of low pressure vapors and heterogeneous oxidation of aerosol precursor gases inside the liquid droplet. Ozone was found to be an active oxidant in the heterogeneous aqueous phase chemical reactions. The outdoor photochemical chamber experiments showed that aqueous phase chemical reactions were responsible for the formation of marine sulfuric acid aerosol particles from the dimethylsulfide. After these particles were partially neutralized by ammonia to the ammonium sulfate or bisulfate, their further growth was observed to be surface limited.
AIHAJ : a journal for the science of occupational and environmental health and safety
In this study, methods were developed for comparative evaluation of three primary dust collection... more In this study, methods were developed for comparative evaluation of three primary dust collection methods employed in vacuum cleaners: filter bag, cyclonic, and wet primary dust collection. The dry collectors were evaluated with KCl test aerosols that are commonly used in filter testing. However, these aerosols cannot be used for evaluating wet collectors due to their hygroscopicity. Therefore, the wet collectors were evaluated with nonhygroscopic test particles. Both types of test aerosol indicated similar collection efficiencies in tests with dry collectors. The data show that high initial collection efficiency can be achieved by any one of the three dust collection methods: up to 50% for 0.35 microm particles, and close to 100% for 1.0 microm and larger particles. The degree of dependence of the initial collection efficiency on airflow rate was strongly related to the type and manufacturing of the primary dust collector. Collection efficiency decreased most with decreasing flow r...
Aihaj a Journal For the Science of Occupational and Environmental Health and Safety, Jul 1, 2001
Industrial vacuum cleaners with final high-efficiency particulate air (HEPA) filters traditionall... more Industrial vacuum cleaners with final high-efficiency particulate air (HEPA) filters traditionally have been used for cleanup operations in which all of the nozzle-entrained dust must be collected with high efficiency, for example, after lead-based paint abatement in homes. In this study household vacuum cleaners ranging from 70to70 to 70to650 and an industrial vacuum cleaner costing more than $1400 were evaluated relative to their collection efficiency immediately after installing new primary dust collectors in them. Using newly developed testing technology, some of the low-cost household vacuum cleaners equipped with a final HEPA filter were found to have initial overall filtration efficiencies comparable to those of industrial vacuum cleaners equipped with a final HEPA filter. The household vacuum cleaners equipped with a final HEPA filter efficiently collect about 100% of the dry dust entrained by the nozzle. For extensive cleaning efforts and for vacuum cleaning of wet surfaces, however, industrial vacuum cleaners may have an advantage, including ruggedness and greater loading capacity. The methods and findings of this study are applicable to field evaluations of vacuum cleaners.
AIHAJ : a journal for the science of occupational and environmental health and safety
The overall filtration efficiency of a vacuum cleaner traditionally has been tested by placing th... more The overall filtration efficiency of a vacuum cleaner traditionally has been tested by placing the vacuum cleaner in a test chamber and measuring aerosol concentrations at the chamber inlet and outlet. The chamber test method was refined and validated in this study. However, this chamber test method shows an overall filtration efficiency of close to 100% for most of the industrial vacuum cleaners and for most of the newly developed household vacuum cleaners of midprice range or higher because all these vacuum cleaners have a high-efficiency particulate air (HEPA) or other highly efficient filter installed at the exhaust. A new test method was therefore developed through which the vacuum cleaner was probed in various internal locations so that the collection efficiency of the individual components could be determined. For example, the aerosol concentration upstream of the final HEPA filter can thus be measured, which permits one to estimate the life expectancy of this expensive compo...
AIHAJ : a journal for the science of occupational and environmental health and safety
The 1995 Department of Housing and Urban Development (HUD) Guidelines for the Evaluation and Cont... more The 1995 Department of Housing and Urban Development (HUD) Guidelines for the Evaluation and Control of Lead-Based Paint Hazards in Housing discusses using interior and exterior wall enclosures for lead hazard control. Leaded dust may be aerosolized inside enclosures and released through gaps and cracks into a room. The effects of airflow and mechanical disturbances on dust release were studied using a laboratory wall enclosure model with dust collected from homes with lead-based paint hazards. Airflows relevant to residences were blown down the enclosure and out a 4-, 6-, or 8-mm horizontal gap at its bottom, simulating potential enclosure failure. Then, low-frequency mechanical vibrations also were applied to the enclosure. No significant dust release was found when blowing air down the enclosure even at 37 cm/sec (representing extremely high flow); release occurred only with this high flow and 3 Hz mechanical disturbances. Dust was released primarily from the floor area immediate...
AIHAJ, 2002
This study evaluated a new method that uses an optical aerosol photometer for dynamically monitor... more This study evaluated a new method that uses an optical aerosol photometer for dynamically monitoring dust pickup efficiency during vacuuming. In the first stage of this study the new method was compared with built-in dirt sensors installed by vacuum cleaner manufacturers. Through parallel testing it has been shown that the widely available built-in dirt sensors are not sensitive enough to register small (< 53 microm) dust particles. Therefore, only the optical photometer was used in the rest of the experiments of this study to monitor the dust pickup efficiency while the vacuum cleaner was operated with different nozzles on clean and soiled carpet and vinyl sheet flooring. This method also was used to monitor dust pickup efficiency when vacuuming carpets originating from lead-contaminated homes. The dust pickup efficiencies obtained with the optical aerosol photometer have been compared with the surface lead concentrations found during different stages of cleaning. Results indicate that the dust mass concentration registered with the optical aerosol photometer at the nozzle outlet correlates well with the dust mass collected in the vacuum cleaner filter bag and with the surface lead level. Therefore, dynamic dust pickup monitoring can provide valuable information about the efficiency of cleaning when a vacuum cleaner is used. This suggests that a small aerosol photometer similar to a light-scattering smoke detector would be beneficial in vacuum cleaners used for cleaning surfaces contaminated with leaded dust and biological particles (including allergens).
Journal of Environmental Monitoring, 2003
The objective of this study was to determine if there is an exposure gradient in particulate matt... more The objective of this study was to determine if there is an exposure gradient in particulate matter concentrations for people living near interstate highways, and to determine how far from the highway the gradient extends. Air samples were collected in a residential area of Greater Cincinnati in the vicinity of two major highways. The measurements were conducted at different distances from the highways by using ultrafine particle counters (measurement range: 0.02-1 mm), optical particle counters (0.3-20 mm), and PM2.5 Harvard Impactors (0.02-2.5 mm). The collected PM2.5 samples were analyzed for mass concentration, for elemental and organic carbon, and for elemental concentrations. The results show that the aerosol concentration gradient was most clearly seen in the particle number concentration measured by the ultrafine particle counters. The concentration of ultrafine particles decreased to half between the sampling points located at 50 m and 150 m downwind from the highway. Additionally, elemental analysis revealed a gradient in sulfur concentrations up to 400 m from the highway in a residential area that does not have major nearby industrial sources. This gradient was qualitatively attributed to the sulfate particle emissions from diesel engine exhausts, and was supported by the concentration data on several key elements indicative of traffic sources (road dust and diesel exhaust). As different particulate components gave different profiles of the diesel exposure gradient, these results indicate that no single element or component of diesel exhaust can be used as a surrogate for diesel exposure, but more comprehensive signature analysis is needed. This characterization is crucial especially when the exposure data are to be used in epidemiological studies.
Journal of Aerosol Science, 1997
Dimethylsulfide, particle growth rate, water uptake In despite of a number of publications devote... more Dimethylsulfide, particle growth rate, water uptake In despite of a number of publications devoted to marine aerosol studies [1,2], there remains a big gap in the knowledge about water uptake by marine aerosol particles. The goal of this work was to consider the influence of diffusion-coagulation of photochemically generated marine aerosol particles with the preexisting accumulation mode particles on the water uptake by last ones.
Journal of Aerosol Science, 1995
Journal of Aerosol Science, 1994
Journal of Aerosol Science, 2001
We have investigated the parameters a!ecting the magnitude and polarity of the electric charges c... more We have investigated the parameters a!ecting the magnitude and polarity of the electric charges carried by biological particles in the airborne state. A recently developed experimental setup through which we analyzed the electric charges imposed on airborne particles by a means of induction charging (Mainelis et al. (Aerosol Sci. Technol. 2001, submitted for publication)) was utilized for this research. In this study, the microorganisms were aerosolized under controlled conditions and an electric mobility analyzer extracted particles of speci"c electric mobility. The extracted microorganisms were then analyzed by an optical particle size spectrometer. The amount of electric charge carried by airborne microorganisms was found to depend on the dispersion method and can be more than 10,000 elementary electric charges. This "nding contrasts with the low electric charge levels carried by non-biological particles. Our data show that repeated pneumatic dispersion of sensitive bacteria a!ects their structural integrity, which, in turn, changes the magnitude of electric charges carried by these bacteria. We have concluded that the amount of electric charge carried by aerosolized bacteria may be used as an indicator of mechanical stress. It was also found that the electrical conductivity and the pH level of a bacterial suspension increase during aerosolization from a Collison nebulizer. Thus, these two parameters may be used as indicators of the mechanical stress, injury and loss in viability, endured by bacteria during aerosolization, i.e., measuring the electrical conductivity and pH level of bacterial suspensions may be a simple and convenient method for monitoring the`wear and teara of the bacteria suspended in deionized water.
Journal of Aerosol Science, 1997
Abstracts detection systems. The rate coefficient was determined at 294 K to (7.4 + 2.6) x lo-i4 ... more Abstracts detection systems. The rate coefficient was determined at 294 K to (7.4 + 2.6) x lo-i4 cm3 molecule-' s-i. The lifetime of DMHg with respect to reaction with NOa is less than 4 h at a radical concentration of 1 x lo9 molecu-lescmm3. The carbon balance obtained during the product studies showed that all carbon initially present in dimethyl mercury was transformed into gas-phase organic species, The organic compounds were formaldehyde, methanol and methyl peroxynitrate.
Journal of Aerosol Science, 1997
Abstracts 1107 than 1 pm. Bitumen particles have a mean aerodynamic diameter of 1.4 pm and are al... more Abstracts 1107 than 1 pm. Bitumen particles have a mean aerodynamic diameter of 1.4 pm and are also predominant in the fine fraction mode (< 2 pm). Soil concentrations in the vicinity of a highway indicate exponential decrease in bitumen concentrations with increasing distance from the road. Constant values are reached after about 20 m. Constant values are reached sooner for tire particles which comply with the impactor measurements:
Journal of Aerosol Science, 1995
Journal of Aerosol Science, 1999
Http Dx Doi Org 10 1080 15298660108984633, Jun 4, 2010
The overall filtration efficiency of a vacuum cleaner traditionally has been tested by placing th... more The overall filtration efficiency of a vacuum cleaner traditionally has been tested by placing the vacuum cleaner in a test chamber and measuring aerosol concentrations at the chamber inlet and outlet. The chamber test method was refined and validated in this study. However, this chamber test method shows an overall filtration efficiency of close to 100% for most of the industrial vacuum cleaners and for most of the newly developed household vacuum cleaners of midprice range or higher because all these vacuum cleaners have a high-efficiency particulate air (HEPA) or other highly efficient filter installed at the exhaust. A new test method was therefore developed through which the vacuum cleaner was probed in various internal locations so that the collection efficiency of the individual components could be determined. For example, the aerosol concentration upstream of the final HEPA filter can thus be measured, which permits one to estimate the life expectancy of this expensive component. The probed testing method is particularly suitable for field evaluations of vacuum cleaners because it uses compact, battery-operated optical particle size spectrometers with internal data storage. Both chamber and probed tests gave the same results for the aerosol filtration efficiency. The probed testing method, however, also gives information on the performance of the individual components in a vacuum cleaner. It also can be used to determine the dust pickup efficiency and the degree of reaerosolization of particles collected in the vacuum cleaner.
Http Dx Doi Org 10 1080 15428110208984756, Jun 4, 2010
This study evaluated a new method that uses an optical aerosol photometer for dynamically monitor... more This study evaluated a new method that uses an optical aerosol photometer for dynamically monitoring dust pickup efficiency during vacuuming. In the first stage of this study the new method was compared with built-in dirt sensors installed by vacuum cleaner manufacturers. Through parallel testing it has been shown that the widely available built-in dirt sensors are not sensitive enough to register small (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 53 microm) dust particles. Therefore, only the optical photometer was used in the rest of the experiments of this study to monitor the dust pickup efficiency while the vacuum cleaner was operated with different nozzles on clean and soiled carpet and vinyl sheet flooring. This method also was used to monitor dust pickup efficiency when vacuuming carpets originating from lead-contaminated homes. The dust pickup efficiencies obtained with the optical aerosol photometer have been compared with the surface lead concentrations found during different stages of cleaning. Results indicate that the dust mass concentration registered with the optical aerosol photometer at the nozzle outlet correlates well with the dust mass collected in the vacuum cleaner filter bag and with the surface lead level. Therefore, dynamic dust pickup monitoring can provide valuable information about the efficiency of cleaning when a vacuum cleaner is used. This suggests that a small aerosol photometer similar to a light-scattering smoke detector would be beneficial in vacuum cleaners used for cleaning surfaces contaminated with leaded dust and biological particles (including allergens).
Atmos Environ, 1994
The evolution of urban aerosol size distribution growing by heterogeneous reactions has been obse... more The evolution of urban aerosol size distribution growing by heterogeneous reactions has been observed in winter fog. Particle diameter growth rates from such data are presented. The functional dependence of the growth rates on particle diameter infer clues about chemical mechanisms of heterogeneous interaction. The data are consistent with aerosol formation in winter fog resulting from condensation of low vapor pressure species formed by gas phase reactions and droplet phase reactions.
Atmospheric Research, 1996
Continental aerosol particle size distributions were measured as a function of time at the backgr... more Continental aerosol particle size distributions were measured as a function of time at the background station Aisetas and in the suburb of Vilnius, Marine aerosol particle formation was studied in outdoor photochemical chamber experiments performed on the coast of the Baltic sea. The functional dependence of the particle diameter growth rate on the particle size was calculated from the aerosol particle size distribution data and was compared with the theoretical predictions for the particle growth due to vapor condensation or due to the adsorption of aerosol precursor gases on the particle surface or within an airborne droplet. It was shown that during summer months condensation of low pressure vapors formed by gas phase homogeneous chemical reactions was predominant mechanism of the continental aerosol particle growth. While in winter growth of a submicrometer continental aerosol particle was frequently governed by two competing processes: condensation of low pressure vapors and heterogeneous oxidation of aerosol precursor gases inside the liquid droplet. Ozone was found to be an active oxidant in the heterogeneous aqueous phase chemical reactions. The outdoor photochemical chamber experiments showed that aqueous phase chemical reactions were responsible for the formation of marine sulfuric acid aerosol particles from the dimethylsulfide. After these particles were partially neutralized by ammonia to the ammonium sulfate or bisulfate, their further growth was observed to be surface limited.
AIHAJ : a journal for the science of occupational and environmental health and safety
In this study, methods were developed for comparative evaluation of three primary dust collection... more In this study, methods were developed for comparative evaluation of three primary dust collection methods employed in vacuum cleaners: filter bag, cyclonic, and wet primary dust collection. The dry collectors were evaluated with KCl test aerosols that are commonly used in filter testing. However, these aerosols cannot be used for evaluating wet collectors due to their hygroscopicity. Therefore, the wet collectors were evaluated with nonhygroscopic test particles. Both types of test aerosol indicated similar collection efficiencies in tests with dry collectors. The data show that high initial collection efficiency can be achieved by any one of the three dust collection methods: up to 50% for 0.35 microm particles, and close to 100% for 1.0 microm and larger particles. The degree of dependence of the initial collection efficiency on airflow rate was strongly related to the type and manufacturing of the primary dust collector. Collection efficiency decreased most with decreasing flow r...
Aihaj a Journal For the Science of Occupational and Environmental Health and Safety, Jul 1, 2001
Industrial vacuum cleaners with final high-efficiency particulate air (HEPA) filters traditionall... more Industrial vacuum cleaners with final high-efficiency particulate air (HEPA) filters traditionally have been used for cleanup operations in which all of the nozzle-entrained dust must be collected with high efficiency, for example, after lead-based paint abatement in homes. In this study household vacuum cleaners ranging from 70to70 to 70to650 and an industrial vacuum cleaner costing more than $1400 were evaluated relative to their collection efficiency immediately after installing new primary dust collectors in them. Using newly developed testing technology, some of the low-cost household vacuum cleaners equipped with a final HEPA filter were found to have initial overall filtration efficiencies comparable to those of industrial vacuum cleaners equipped with a final HEPA filter. The household vacuum cleaners equipped with a final HEPA filter efficiently collect about 100% of the dry dust entrained by the nozzle. For extensive cleaning efforts and for vacuum cleaning of wet surfaces, however, industrial vacuum cleaners may have an advantage, including ruggedness and greater loading capacity. The methods and findings of this study are applicable to field evaluations of vacuum cleaners.
AIHAJ : a journal for the science of occupational and environmental health and safety
The overall filtration efficiency of a vacuum cleaner traditionally has been tested by placing th... more The overall filtration efficiency of a vacuum cleaner traditionally has been tested by placing the vacuum cleaner in a test chamber and measuring aerosol concentrations at the chamber inlet and outlet. The chamber test method was refined and validated in this study. However, this chamber test method shows an overall filtration efficiency of close to 100% for most of the industrial vacuum cleaners and for most of the newly developed household vacuum cleaners of midprice range or higher because all these vacuum cleaners have a high-efficiency particulate air (HEPA) or other highly efficient filter installed at the exhaust. A new test method was therefore developed through which the vacuum cleaner was probed in various internal locations so that the collection efficiency of the individual components could be determined. For example, the aerosol concentration upstream of the final HEPA filter can thus be measured, which permits one to estimate the life expectancy of this expensive compo...
AIHAJ : a journal for the science of occupational and environmental health and safety
The 1995 Department of Housing and Urban Development (HUD) Guidelines for the Evaluation and Cont... more The 1995 Department of Housing and Urban Development (HUD) Guidelines for the Evaluation and Control of Lead-Based Paint Hazards in Housing discusses using interior and exterior wall enclosures for lead hazard control. Leaded dust may be aerosolized inside enclosures and released through gaps and cracks into a room. The effects of airflow and mechanical disturbances on dust release were studied using a laboratory wall enclosure model with dust collected from homes with lead-based paint hazards. Airflows relevant to residences were blown down the enclosure and out a 4-, 6-, or 8-mm horizontal gap at its bottom, simulating potential enclosure failure. Then, low-frequency mechanical vibrations also were applied to the enclosure. No significant dust release was found when blowing air down the enclosure even at 37 cm/sec (representing extremely high flow); release occurred only with this high flow and 3 Hz mechanical disturbances. Dust was released primarily from the floor area immediate...
AIHAJ, 2002
This study evaluated a new method that uses an optical aerosol photometer for dynamically monitor... more This study evaluated a new method that uses an optical aerosol photometer for dynamically monitoring dust pickup efficiency during vacuuming. In the first stage of this study the new method was compared with built-in dirt sensors installed by vacuum cleaner manufacturers. Through parallel testing it has been shown that the widely available built-in dirt sensors are not sensitive enough to register small (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 53 microm) dust particles. Therefore, only the optical photometer was used in the rest of the experiments of this study to monitor the dust pickup efficiency while the vacuum cleaner was operated with different nozzles on clean and soiled carpet and vinyl sheet flooring. This method also was used to monitor dust pickup efficiency when vacuuming carpets originating from lead-contaminated homes. The dust pickup efficiencies obtained with the optical aerosol photometer have been compared with the surface lead concentrations found during different stages of cleaning. Results indicate that the dust mass concentration registered with the optical aerosol photometer at the nozzle outlet correlates well with the dust mass collected in the vacuum cleaner filter bag and with the surface lead level. Therefore, dynamic dust pickup monitoring can provide valuable information about the efficiency of cleaning when a vacuum cleaner is used. This suggests that a small aerosol photometer similar to a light-scattering smoke detector would be beneficial in vacuum cleaners used for cleaning surfaces contaminated with leaded dust and biological particles (including allergens).
Journal of Environmental Monitoring, 2003
The objective of this study was to determine if there is an exposure gradient in particulate matt... more The objective of this study was to determine if there is an exposure gradient in particulate matter concentrations for people living near interstate highways, and to determine how far from the highway the gradient extends. Air samples were collected in a residential area of Greater Cincinnati in the vicinity of two major highways. The measurements were conducted at different distances from the highways by using ultrafine particle counters (measurement range: 0.02-1 mm), optical particle counters (0.3-20 mm), and PM2.5 Harvard Impactors (0.02-2.5 mm). The collected PM2.5 samples were analyzed for mass concentration, for elemental and organic carbon, and for elemental concentrations. The results show that the aerosol concentration gradient was most clearly seen in the particle number concentration measured by the ultrafine particle counters. The concentration of ultrafine particles decreased to half between the sampling points located at 50 m and 150 m downwind from the highway. Additionally, elemental analysis revealed a gradient in sulfur concentrations up to 400 m from the highway in a residential area that does not have major nearby industrial sources. This gradient was qualitatively attributed to the sulfate particle emissions from diesel engine exhausts, and was supported by the concentration data on several key elements indicative of traffic sources (road dust and diesel exhaust). As different particulate components gave different profiles of the diesel exposure gradient, these results indicate that no single element or component of diesel exhaust can be used as a surrogate for diesel exposure, but more comprehensive signature analysis is needed. This characterization is crucial especially when the exposure data are to be used in epidemiological studies.
Journal of Aerosol Science, 1997
Dimethylsulfide, particle growth rate, water uptake In despite of a number of publications devote... more Dimethylsulfide, particle growth rate, water uptake In despite of a number of publications devoted to marine aerosol studies [1,2], there remains a big gap in the knowledge about water uptake by marine aerosol particles. The goal of this work was to consider the influence of diffusion-coagulation of photochemically generated marine aerosol particles with the preexisting accumulation mode particles on the water uptake by last ones.
Journal of Aerosol Science, 1995
Journal of Aerosol Science, 1994
Journal of Aerosol Science, 2001
We have investigated the parameters a!ecting the magnitude and polarity of the electric charges c... more We have investigated the parameters a!ecting the magnitude and polarity of the electric charges carried by biological particles in the airborne state. A recently developed experimental setup through which we analyzed the electric charges imposed on airborne particles by a means of induction charging (Mainelis et al. (Aerosol Sci. Technol. 2001, submitted for publication)) was utilized for this research. In this study, the microorganisms were aerosolized under controlled conditions and an electric mobility analyzer extracted particles of speci"c electric mobility. The extracted microorganisms were then analyzed by an optical particle size spectrometer. The amount of electric charge carried by airborne microorganisms was found to depend on the dispersion method and can be more than 10,000 elementary electric charges. This "nding contrasts with the low electric charge levels carried by non-biological particles. Our data show that repeated pneumatic dispersion of sensitive bacteria a!ects their structural integrity, which, in turn, changes the magnitude of electric charges carried by these bacteria. We have concluded that the amount of electric charge carried by aerosolized bacteria may be used as an indicator of mechanical stress. It was also found that the electrical conductivity and the pH level of a bacterial suspension increase during aerosolization from a Collison nebulizer. Thus, these two parameters may be used as indicators of the mechanical stress, injury and loss in viability, endured by bacteria during aerosolization, i.e., measuring the electrical conductivity and pH level of bacterial suspensions may be a simple and convenient method for monitoring the`wear and teara of the bacteria suspended in deionized water.
Journal of Aerosol Science, 1997
Abstracts detection systems. The rate coefficient was determined at 294 K to (7.4 + 2.6) x lo-i4 ... more Abstracts detection systems. The rate coefficient was determined at 294 K to (7.4 + 2.6) x lo-i4 cm3 molecule-' s-i. The lifetime of DMHg with respect to reaction with NOa is less than 4 h at a radical concentration of 1 x lo9 molecu-lescmm3. The carbon balance obtained during the product studies showed that all carbon initially present in dimethyl mercury was transformed into gas-phase organic species, The organic compounds were formaldehyde, methanol and methyl peroxynitrate.
Journal of Aerosol Science, 1997
Abstracts 1107 than 1 pm. Bitumen particles have a mean aerodynamic diameter of 1.4 pm and are al... more Abstracts 1107 than 1 pm. Bitumen particles have a mean aerodynamic diameter of 1.4 pm and are also predominant in the fine fraction mode (< 2 pm). Soil concentrations in the vicinity of a highway indicate exponential decrease in bitumen concentrations with increasing distance from the road. Constant values are reached after about 20 m. Constant values are reached sooner for tire particles which comply with the impactor measurements:
Journal of Aerosol Science, 1995
Journal of Aerosol Science, 1999