Joakim Pagels | Lund University (original) (raw)

Papers by Joakim Pagels

Research paper thumbnail of Direct Deposition of Gas Phase Generated Aerosol Gold Nanoparticles into Biological Fluids - Corona Formation and Particle Size Shifts

PLoS ONE, 2013

An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the ri... more An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the risks associated with nanoparticle inhalation has led to the emergence of Air-Liquid interface toxicology. As a step in this process, this study explores the evolution of particle characteristics as they move from the airborne state into physiological solution. Airborne gold nanoparticles (AuNP) are generated using an evaporation-condensation technique. Spherical and agglomerate AuNPs are deposited into physiological solutions of increasing biological complexity. The AuNP size is characterized in air as mobility diameter and in liquid as hydrodynamic diameter. AuNP:Protein aggregation in physiological solutions is determined using dynamic light scattering, particle tracking analysis, and UV absorption spectroscopy. AuNPs deposited into homocysteine buffer form large gold-aggregates. Spherical AuNPs deposited in solutions of albumin were trapped at the Air-Liquid interface but was readily suspended in the solutions with a size close to that of the airborne particles, indicating that AuNP:Protein complex formation is promoted. Deposition into serum and lung fluid resulted in larger complexes, reflecting the formation of a more complex protein corona. UV absorption spectroscopy indicated no further aggregation of the AuNPs after deposition in solution. The corona of the deposited AuNPs shows differences compared to AuNPs generated in suspension. Deposition of AuNPs from the aerosol phase into biological fluids offers a method to study the protein corona formed, upon inhalation and deposition in the lungs in a more realistic way compared to particle liquid suspensions. This is important since the protein corona together with key particle properties (e.g. size, shape and surface reactivity) to a large extent may determine the nanoparticle effects and possible translocation to other organs.

Research paper thumbnail of Air contaminants in a submarine equipped with air independent propulsion

Journal of Environmental Monitoring, 2006

The Swedish Navy has operated submarines equipped with air independent propulsion for two decades... more The Swedish Navy has operated submarines equipped with air independent propulsion for two decades. This type of submarine can stay submerged for periods far longer than other non-nuclear submarines are capable of. The air quality during longer periods of submersion has so far not been thoroughly investigated. This study presents results for a number of air quality parameters obtained during more than one week of continuous submerged operation. The measured parameters are pressure, temperature, relative humidity, oxygen, carbon dioxide, hydrogen, formaldehyde and other volatile organic compounds, ozone, nitrogen dioxide, particulate matter and microbiological contaminants. The measurements of airborne particles demonstrate that air pollutants typically occur at a low baseline level due to high air exchange rates and efficient air-cleaning devices. However, short-lived peaks with comparatively high concentrations occur, several of the sources for these have been identified. The concentrations of the pollutants measured in this study do not indicate a build-up of hazardous compounds during eight days of submersion. It is reasonable to assume that a substantial build-up of the investigated contaminants is not likely if the submersion period is prolonged several times, which is the case for modern submarines equipped with air independent propulsion.

Research paper thumbnail of Laboratory evaluation of a gasifier particle sampling system using model compounds of different particle morphology

Biomass Conversion and Biorefinery, 2011

Research paper thumbnail of Saturation Vapor Pressures and Transition Enthalpies of Low-Volatility Organic Molecules of Atmospheric Relevance: From Dicarboxylic Acids to Complex Mixtures

Research paper thumbnail of On-line particle density measurements of combustion aerosols with the DMA-APM system and comparison with aggregation theory

Research paper thumbnail of Development of a High Temperature Aerosol Particle Sampling Probe for Field Measurements in Thermochemical Conversion of Biomass

Research paper thumbnail of Formation of highly hygroscopic soot aerosols upon internal mixing with sulfuric acid vapor

Journal of Geophysical Research, 2009

The hygroscopic properties of submicron soot particles during internal mixing with gaseous sulfur... more The hygroscopic properties of submicron soot particles during internal mixing with gaseous sulfuric acid have been investigated using a combined tandem differential mobility analyzer (TDMA) and differential mobility analyzer–aerosol particle mass analyzer (DMA-APM) technique. Fresh particles exhibit no change in mobility size and mass at subsaturated conditions, whereas particles exposed to gaseous sulfuric acid (109–1010 molecule cm−3, 12 s contact

Research paper thumbnail of Experimentally Determined Human Respiratory Tract Deposition of Airborne Particles at a Busy Street

Environmental Science & Technology, 2009

Traffic is one of the major sources of harmful airborne particles worldwide. To relate exposure t... more Traffic is one of the major sources of harmful airborne particles worldwide. To relate exposure to adverse health effects it is important to determine the deposition probability of the inhaled particles in the human respiratory tract. The sizedependent deposition of 12-580 nm particles was measured with a novel setup in 9 healthy subjects breathing by mouth on the windward side of a busy street in Copenhagen, Denmark. The aerosol was characterized both at the curbside and, to obtain the background concentration, at rooftop level. Particle hygroscopicity, a key parameter affecting respiratory tract deposition, was also measured at the same time of exposure. The total deposition fraction of the curbside particles in the range 12-580 nm was 0.60 by number, 0.29 by surface area, and 0.23 by mass. The deposition fractions of the "traffic exhaust" contribution, calculated as the hydrophobic fraction of the curbside particles, was 0.68, 0.35, and 0.28 by number, surface area, and mass, respectively. The deposited amount of traffic exhaust particles was 16 times higher by number and 3 times higher by surface area compared to the deposition of residential biofuel combustion particles investigated previously (equal inhaled mass concentrations). This was because the traffic exhaust particles had both a higher deposition probability and a higher number and surface area concentration per unit mass. To validate the results, the respiratory tract deposition was estimated by using the well-established ICRP model. Predictions were in agreement with experimental results when the effects of particle hygroscopicity were considered in the model.

Research paper thumbnail of Methodology for Studies on Respiratory and Cardiovascular Effects of Humans at Occupational Exposure to Airborne Nanoparticles

In production environments, airborne particles have been a threat to workers' health for several ... more In production environments, airborne particles have been a threat to workers' health for several hundred years. In 1713 the Italian physician Ramazzini published De Morbis Artificum with descriptions of health hazards in a number of different occupations. He observed, for example, that many workers who were exposed to airborne mineral particles (e.g. stone-cutters and quarrymen) got the disease we today know as silicosis.

Research paper thumbnail of A Potential Soot Mass Determination Method from Resistivity Measurement of Thermophoretically Deposited Soot

Aerosol Science and Technology, 2011

Research paper thumbnail of Methodology for Sampling and Characterizing Internally Mixed Soot-Tar Particles Suspended in the Product Gas from Biomass Gasification Processes

Energy & Fuels, 2011

When biomass is used to produce fuels and green products by thermochemical conversion, the abilit... more When biomass is used to produce fuels and green products by thermochemical conversion, the ability to handle or remove the fine particle phase in the product gas is crucial. The product gas from biomass gasification contains relatively volatile organic compounds ("tar") condensed on nonvolatile cores of, for example, aggregated soot particles and char. The problems are, for example, that particles will poison catalysts used for upgrading of the gas and loss of thermal energy occurs when carbonaceous particles are being formed. The aim of the work is to design and use novel methodologies to characterize the particles in the product gas stream. A methodology has been developed to sample and characterize fine particles by a sampling probe connected to either a denuder or a packed bed device. The system was designed to avoid condensation of organic compounds when diluting the sample and decreasing the temperature. A flame soot generator connected to a condensationÀevaporation unit was used to produce internally mixed model particles, i.e., particles consisting of a core of soot with an outer layer of condensed volatile compounds. A scanning mobility particle sizer (SMPS) and a differential mobility analyzer followed by an aerosol particle mass analyzer (APM) were used to characterize the particles. Because of the agglomerated structure of soot, the SMPS system was not adequate to fully characterize the mass of volatiles condensed onto the soot core, and therefore the DMA-heater-APM technique was used to determine the mass fraction of the condensed phase on the soot particles. The two different configurations were studied, and the sampling system was shown to work at a high load of organic mass. In both cases, the organic removal efficiency was >99.5%. Minor condensation of organics on the sampled soot was found for the denuder but not the packed bed. On the other hand, the particle losses were substantially higher for the packed bed compared to the denuder. The results showed that the tested sampling methodology can be used to get sufficient characterization of particles in the product gas and to evaluate the performance of biomass product gas cleaning systems at high temperature.

Research paper thumbnail of Direct Deposition of Gas Phase Generated Aerosol Gold Nanoparticles into Biological Fluids - Corona Formation and Particle Size Shifts

PLoS ONE, 2013

An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the ri... more An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the risks associated with nanoparticle inhalation has led to the emergence of Air-Liquid interface toxicology. As a step in this process, this study explores the evolution of particle characteristics as they move from the airborne state into physiological solution. Airborne gold nanoparticles (AuNP) are generated using an evaporation-condensation technique. Spherical and agglomerate AuNPs are deposited into physiological solutions of increasing biological complexity. The AuNP size is characterized in air as mobility diameter and in liquid as hydrodynamic diameter. AuNP:Protein aggregation in physiological solutions is determined using dynamic light scattering, particle tracking analysis, and UV absorption spectroscopy. AuNPs deposited into homocysteine buffer form large gold-aggregates. Spherical AuNPs deposited in solutions of albumin were trapped at the Air-Liquid interface but was readily suspended in the solutions with a size close to that of the airborne particles, indicating that AuNP:Protein complex formation is promoted. Deposition into serum and lung fluid resulted in larger complexes, reflecting the formation of a more complex protein corona. UV absorption spectroscopy indicated no further aggregation of the AuNPs after deposition in solution. The corona of the deposited AuNPs shows differences compared to AuNPs generated in suspension. Deposition of AuNPs from the aerosol phase into biological fluids offers a method to study the protein corona formed, upon inhalation and deposition in the lungs in a more realistic way compared to particle liquid suspensions. This is important since the protein corona together with key particle properties (e.g. size, shape and surface reactivity) to a large extent may determine the nanoparticle effects and possible translocation to other organs.

Research paper thumbnail of Detection of Soot Using a Resistivity Sensor Device Employing Thermophoretic Particle Deposition

Research paper thumbnail of Nano-objects emitted during maintenance of common particle generators: direct chemical characterization with aerosol mass spectrometry and implications for risk assessments

Journal of Nanoparticle Research, 2013

Nanotechnology gives us materials with enhanced or completely new properties. At the same time in... more Nanotechnology gives us materials with enhanced or completely new properties. At the same time inhalation of manufactured nano-objects has been related to an array of adverse biological effects. We characterized particle emissions, which occurred during maintenance of common metal nanoparticle generators and contrasted the properties of the emitted particles with those originally produced by the generators. A new approach using online aerosol mass spectrometry, for time and size resolved measurements of the particle chemical composition, was applied in combination with more conventional techniques for particle sampling and analysis, including electron microscopy. Emissions during maintenance work, in terms of mass and surface area concentration in the size range of 0.02-10 µm, were dominated by large agglomerates (1-5 µm). With aerosol mass spectrometry we show that the particle composition depends on both generator type and maintenance task being performed and that the instrument can be used for highly time resolved selective studies of metal nanoparticle emissions. The emitted agglomerates have a relatively high probability to be deposited in the lower respiratory tract, since the mean particle diameter coincided with a peak in the lung deposition curve. Each of these agglomerates consisted of a very high number (10 3 -10 5 /agglomerate) of nanometer sized primary particles originating from the particle synthesis process. This made them possess large surface areas, one of the key properties in nanotoxicology. Similar agglomerates may be emitted in a wide range of processes when nanoparticles are manufactured or handled. The fate of such agglomerates, once deposited in the respiratory tract, is unknown and should therefore be considered in future particle toxicological studies. Our results highlight the importance of including micrometer sized particles in exposure and emission assessments.

Research paper thumbnail of Size-Resolved Respiratory-Tract Deposition of Fine and Ultrafine Hydrophobic and Hygroscopic Aerosol Particles During Rest and Exercise

Inhalation Toxicology, 2007

Particle size distributions and hygroscopic growth were studied in a town in Sweden with extensiv... more Particle size distributions and hygroscopic growth were studied in a town in Sweden with extensive emissions from wood combustion. The average deposited fraction of particle number, surface area and volume dose in the human respiratory tract was estimated using the data set, as well as the typical deposition pattern of the two dominant particle source types: wood combustion and traffic exhaust. As far as we know, this is the first report on the deposited fraction and hygroscopicity of ambient particles from domestic wood combustion in the literature. The use of PM 2.5 as a substitute for the deposited dose was also tested. Source/receptor modeling and the hygroscopicity measurements showed that wood combustion and traffic exhaust are dominant sources, and that these particles have a low water uptake. Number fractions of 38 and 69% of the wood combustion and traffic particles, respectively, were deposited in the respiratory tract, and 53% of the particles were deposited as an average for the whole period. The deposited fraction of the surface area and volume dose was also calculated for wood combustion particles, with the result being 22% for both parameters. The results also revealed that the PM 2.5 average over more than 10 hours correlated well (r 2 > 0.80) with the deposited surface area and volume dose. This means that PM 2.5 can be used as proxy for the deposited dose when examining health effect relationships during short-term exposure studies if the averaging time is sufficient, while a PM 2.5 proxy is not recommended for shorter averaging times.

Research paper thumbnail of Tandem Measurements of Aerosol Properties—A Review of Mobility Techniques with Extensions

Aerosol Science and Technology, 2008

When multiple instruments are used in tandem it is possible to obtain more complete information o... more When multiple instruments are used in tandem it is possible to obtain more complete information on particle transport and physicochemical properties than can be obtained with a single instrument. This article discusses tandem measurements in which submicrometer particles classified according to electrical mobility are then characterized with one or more additional methods. Measurement combinations that are summarized here include mobility

Research paper thumbnail of Hygroscopic Behavior of Aerosol Particles Emitted from Biomass Fired Grate Boilers

Aerosol Science and Technology, 2005

This study focuses on the hygroscopic properties of submicrometer aerosol particles emitted from ... more This study focuses on the hygroscopic properties of submicrometer aerosol particles emitted from two small-scale district heating combustion plants (1 and 1.5 MW) burning two types of biomass fuels (moist forest residue and pellets). The hygroscopic particle diameter growth factor (Gf ) was measured when taken from a dehydrated to a humidified state for particle diameters between 30-350 nm (dry size) using a Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA). Particles of a certain dry size all showed similar diameter growth and the Gf at RH = 90% for 110/100 nm particles was 1.68 in the 1 MW boiler, and 1.5 in the 1.5 MW boiler. These growth factors are considerably higher in comparison to other combustion aerosol particles such as diesel exhaust, and are the result of the efficient combustion and the high concentration of alkali species in the fuel. The observed water uptake could be explained using the Zdanovski-Stokes-Robinson (ZSR) mixing rule and a chemical composition of potassium salts only, taken from ion chromatography analysis of filter and impactor samples (KCl, K 2 SO 4 , and K 2 CO 3 ). Agglomerated particles collapsed and became more spherical when initially exposed to a moderately high relative humidity. When diluted with hot particle-free air, the fractallike structures remained intact until humidified in the H-TDMA. A method to estimate the fractal dimension of the agglomerated combustion aerosol and to convert the measured mobility diameter hygroscopic growth to the more useful property volume diameter growth is presented. The fractal dimension was estimated to be ∼2.5.

Research paper thumbnail of Fine-particle emissions from solid biofuel combustion studied with single-particle mass spectrometry: Identification of markers for organics, soot, and ash components

Research paper thumbnail of Measurement Techniques for Respiratory Tract Deposition of Airborne Nanoparticles: A Critical Review

Journal of Aerosol Medicine and Pulmonary Drug Delivery, 2013

Determination of the respiratory tract deposition of airborne particles is critical for risk asse... more Determination of the respiratory tract deposition of airborne particles is critical for risk assessment of air pollution, inhaled drug delivery, and understanding of respiratory disease. With the advent of nanotechnology, there has been an increasing interest in the measurement of pulmonary deposition of nanoparticles because of their unique properties in inhalation toxicology and medicine. Over the last century, around 50 studies have presented experimental data on lung deposition of nanoparticles (typical diameter £ 100 nm, but here £ 300 nm). These data show a considerable variability, partly due to differences in the applied methodologies. In this study, we review the experimental techniques for measuring respiratory tract deposition of nano-sized particles, analyze critical experimental design aspects causing measurement uncertainties, and suggest methodologies for future studies. It is shown that, although particle detection techniques have developed with time, the overall methodology in respiratory tract deposition experiments has not seen similar progress. Available experience from previous research has often not been incorporated, and some methodological design aspects that were overlooked in 30-70% of all studies may have biased the experimental data. This has contributed to a significant uncertainty on the absolute value of the lung deposition fraction of nanoparticles. We estimate the impact of the design aspects on obtained data, discuss solutions to minimize errors, and highlight gaps in the available experimental set of data.

Research paper thumbnail of Particulate PAH Emissions from Residential Biomass Combustion: Time-Resolved Analysis with Aerosol Mass Spectrometry

Environmental Science & Technology, 2014

Time-resolved emissions of particulate polycyclic aromatic hydrocarbons (PAHs) and total organic ... more Time-resolved emissions of particulate polycyclic aromatic hydrocarbons (PAHs) and total organic particulate matter (OA) from a wood log stove and an adjusted pellet stove were investigated with high-resolution time-of-flight aerosol mass spectrometry (AMS). The highest OA emissions were found during the addition of log wood on glowing embers, that is, slow burning pyrolysis conditions. These emissions contained about 1% PAHs (of OA). The highest PAH emissions were found during fast burning under hot air starved combustion conditions, in both stoves. In the latter case, PAHs contributed up to 40% of OA, likely due to thermal degradation of other condensable species. The distribution of PAHs was also shifted toward larger molecules in these emissions. AMS signals attributed to PAHs were found at molecular weights up to 600 Da. The vacuum aerodynamic size distribution was found to be bimodal with a smaller mode (Dva ∼ 200 nm) dominating under hot air starved combustion and a larger sized mode dominating under slow burning pyrolysis (Dva ∼ 600 nm). Simultaneous reduction of PAHs, OA and total particulate matter from residential biomass combustion may prove to be a challenge for environmental legislation efforts as these classes of emissions are elevated at different combustion conditions.

Research paper thumbnail of Direct Deposition of Gas Phase Generated Aerosol Gold Nanoparticles into Biological Fluids - Corona Formation and Particle Size Shifts

PLoS ONE, 2013

An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the ri... more An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the risks associated with nanoparticle inhalation has led to the emergence of Air-Liquid interface toxicology. As a step in this process, this study explores the evolution of particle characteristics as they move from the airborne state into physiological solution. Airborne gold nanoparticles (AuNP) are generated using an evaporation-condensation technique. Spherical and agglomerate AuNPs are deposited into physiological solutions of increasing biological complexity. The AuNP size is characterized in air as mobility diameter and in liquid as hydrodynamic diameter. AuNP:Protein aggregation in physiological solutions is determined using dynamic light scattering, particle tracking analysis, and UV absorption spectroscopy. AuNPs deposited into homocysteine buffer form large gold-aggregates. Spherical AuNPs deposited in solutions of albumin were trapped at the Air-Liquid interface but was readily suspended in the solutions with a size close to that of the airborne particles, indicating that AuNP:Protein complex formation is promoted. Deposition into serum and lung fluid resulted in larger complexes, reflecting the formation of a more complex protein corona. UV absorption spectroscopy indicated no further aggregation of the AuNPs after deposition in solution. The corona of the deposited AuNPs shows differences compared to AuNPs generated in suspension. Deposition of AuNPs from the aerosol phase into biological fluids offers a method to study the protein corona formed, upon inhalation and deposition in the lungs in a more realistic way compared to particle liquid suspensions. This is important since the protein corona together with key particle properties (e.g. size, shape and surface reactivity) to a large extent may determine the nanoparticle effects and possible translocation to other organs.

Research paper thumbnail of Air contaminants in a submarine equipped with air independent propulsion

Journal of Environmental Monitoring, 2006

The Swedish Navy has operated submarines equipped with air independent propulsion for two decades... more The Swedish Navy has operated submarines equipped with air independent propulsion for two decades. This type of submarine can stay submerged for periods far longer than other non-nuclear submarines are capable of. The air quality during longer periods of submersion has so far not been thoroughly investigated. This study presents results for a number of air quality parameters obtained during more than one week of continuous submerged operation. The measured parameters are pressure, temperature, relative humidity, oxygen, carbon dioxide, hydrogen, formaldehyde and other volatile organic compounds, ozone, nitrogen dioxide, particulate matter and microbiological contaminants. The measurements of airborne particles demonstrate that air pollutants typically occur at a low baseline level due to high air exchange rates and efficient air-cleaning devices. However, short-lived peaks with comparatively high concentrations occur, several of the sources for these have been identified. The concentrations of the pollutants measured in this study do not indicate a build-up of hazardous compounds during eight days of submersion. It is reasonable to assume that a substantial build-up of the investigated contaminants is not likely if the submersion period is prolonged several times, which is the case for modern submarines equipped with air independent propulsion.

Research paper thumbnail of Laboratory evaluation of a gasifier particle sampling system using model compounds of different particle morphology

Biomass Conversion and Biorefinery, 2011

Research paper thumbnail of Saturation Vapor Pressures and Transition Enthalpies of Low-Volatility Organic Molecules of Atmospheric Relevance: From Dicarboxylic Acids to Complex Mixtures

Research paper thumbnail of On-line particle density measurements of combustion aerosols with the DMA-APM system and comparison with aggregation theory

Research paper thumbnail of Development of a High Temperature Aerosol Particle Sampling Probe for Field Measurements in Thermochemical Conversion of Biomass

Research paper thumbnail of Formation of highly hygroscopic soot aerosols upon internal mixing with sulfuric acid vapor

Journal of Geophysical Research, 2009

The hygroscopic properties of submicron soot particles during internal mixing with gaseous sulfur... more The hygroscopic properties of submicron soot particles during internal mixing with gaseous sulfuric acid have been investigated using a combined tandem differential mobility analyzer (TDMA) and differential mobility analyzer–aerosol particle mass analyzer (DMA-APM) technique. Fresh particles exhibit no change in mobility size and mass at subsaturated conditions, whereas particles exposed to gaseous sulfuric acid (109–1010 molecule cm−3, 12 s contact

Research paper thumbnail of Experimentally Determined Human Respiratory Tract Deposition of Airborne Particles at a Busy Street

Environmental Science & Technology, 2009

Traffic is one of the major sources of harmful airborne particles worldwide. To relate exposure t... more Traffic is one of the major sources of harmful airborne particles worldwide. To relate exposure to adverse health effects it is important to determine the deposition probability of the inhaled particles in the human respiratory tract. The sizedependent deposition of 12-580 nm particles was measured with a novel setup in 9 healthy subjects breathing by mouth on the windward side of a busy street in Copenhagen, Denmark. The aerosol was characterized both at the curbside and, to obtain the background concentration, at rooftop level. Particle hygroscopicity, a key parameter affecting respiratory tract deposition, was also measured at the same time of exposure. The total deposition fraction of the curbside particles in the range 12-580 nm was 0.60 by number, 0.29 by surface area, and 0.23 by mass. The deposition fractions of the "traffic exhaust" contribution, calculated as the hydrophobic fraction of the curbside particles, was 0.68, 0.35, and 0.28 by number, surface area, and mass, respectively. The deposited amount of traffic exhaust particles was 16 times higher by number and 3 times higher by surface area compared to the deposition of residential biofuel combustion particles investigated previously (equal inhaled mass concentrations). This was because the traffic exhaust particles had both a higher deposition probability and a higher number and surface area concentration per unit mass. To validate the results, the respiratory tract deposition was estimated by using the well-established ICRP model. Predictions were in agreement with experimental results when the effects of particle hygroscopicity were considered in the model.

Research paper thumbnail of Methodology for Studies on Respiratory and Cardiovascular Effects of Humans at Occupational Exposure to Airborne Nanoparticles

In production environments, airborne particles have been a threat to workers' health for several ... more In production environments, airborne particles have been a threat to workers' health for several hundred years. In 1713 the Italian physician Ramazzini published De Morbis Artificum with descriptions of health hazards in a number of different occupations. He observed, for example, that many workers who were exposed to airborne mineral particles (e.g. stone-cutters and quarrymen) got the disease we today know as silicosis.

Research paper thumbnail of A Potential Soot Mass Determination Method from Resistivity Measurement of Thermophoretically Deposited Soot

Aerosol Science and Technology, 2011

Research paper thumbnail of Methodology for Sampling and Characterizing Internally Mixed Soot-Tar Particles Suspended in the Product Gas from Biomass Gasification Processes

Energy & Fuels, 2011

When biomass is used to produce fuels and green products by thermochemical conversion, the abilit... more When biomass is used to produce fuels and green products by thermochemical conversion, the ability to handle or remove the fine particle phase in the product gas is crucial. The product gas from biomass gasification contains relatively volatile organic compounds ("tar") condensed on nonvolatile cores of, for example, aggregated soot particles and char. The problems are, for example, that particles will poison catalysts used for upgrading of the gas and loss of thermal energy occurs when carbonaceous particles are being formed. The aim of the work is to design and use novel methodologies to characterize the particles in the product gas stream. A methodology has been developed to sample and characterize fine particles by a sampling probe connected to either a denuder or a packed bed device. The system was designed to avoid condensation of organic compounds when diluting the sample and decreasing the temperature. A flame soot generator connected to a condensationÀevaporation unit was used to produce internally mixed model particles, i.e., particles consisting of a core of soot with an outer layer of condensed volatile compounds. A scanning mobility particle sizer (SMPS) and a differential mobility analyzer followed by an aerosol particle mass analyzer (APM) were used to characterize the particles. Because of the agglomerated structure of soot, the SMPS system was not adequate to fully characterize the mass of volatiles condensed onto the soot core, and therefore the DMA-heater-APM technique was used to determine the mass fraction of the condensed phase on the soot particles. The two different configurations were studied, and the sampling system was shown to work at a high load of organic mass. In both cases, the organic removal efficiency was >99.5%. Minor condensation of organics on the sampled soot was found for the denuder but not the packed bed. On the other hand, the particle losses were substantially higher for the packed bed compared to the denuder. The results showed that the tested sampling methodology can be used to get sufficient characterization of particles in the product gas and to evaluate the performance of biomass product gas cleaning systems at high temperature.

Research paper thumbnail of Direct Deposition of Gas Phase Generated Aerosol Gold Nanoparticles into Biological Fluids - Corona Formation and Particle Size Shifts

PLoS ONE, 2013

An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the ri... more An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the risks associated with nanoparticle inhalation has led to the emergence of Air-Liquid interface toxicology. As a step in this process, this study explores the evolution of particle characteristics as they move from the airborne state into physiological solution. Airborne gold nanoparticles (AuNP) are generated using an evaporation-condensation technique. Spherical and agglomerate AuNPs are deposited into physiological solutions of increasing biological complexity. The AuNP size is characterized in air as mobility diameter and in liquid as hydrodynamic diameter. AuNP:Protein aggregation in physiological solutions is determined using dynamic light scattering, particle tracking analysis, and UV absorption spectroscopy. AuNPs deposited into homocysteine buffer form large gold-aggregates. Spherical AuNPs deposited in solutions of albumin were trapped at the Air-Liquid interface but was readily suspended in the solutions with a size close to that of the airborne particles, indicating that AuNP:Protein complex formation is promoted. Deposition into serum and lung fluid resulted in larger complexes, reflecting the formation of a more complex protein corona. UV absorption spectroscopy indicated no further aggregation of the AuNPs after deposition in solution. The corona of the deposited AuNPs shows differences compared to AuNPs generated in suspension. Deposition of AuNPs from the aerosol phase into biological fluids offers a method to study the protein corona formed, upon inhalation and deposition in the lungs in a more realistic way compared to particle liquid suspensions. This is important since the protein corona together with key particle properties (e.g. size, shape and surface reactivity) to a large extent may determine the nanoparticle effects and possible translocation to other organs.

Research paper thumbnail of Detection of Soot Using a Resistivity Sensor Device Employing Thermophoretic Particle Deposition

Research paper thumbnail of Nano-objects emitted during maintenance of common particle generators: direct chemical characterization with aerosol mass spectrometry and implications for risk assessments

Journal of Nanoparticle Research, 2013

Nanotechnology gives us materials with enhanced or completely new properties. At the same time in... more Nanotechnology gives us materials with enhanced or completely new properties. At the same time inhalation of manufactured nano-objects has been related to an array of adverse biological effects. We characterized particle emissions, which occurred during maintenance of common metal nanoparticle generators and contrasted the properties of the emitted particles with those originally produced by the generators. A new approach using online aerosol mass spectrometry, for time and size resolved measurements of the particle chemical composition, was applied in combination with more conventional techniques for particle sampling and analysis, including electron microscopy. Emissions during maintenance work, in terms of mass and surface area concentration in the size range of 0.02-10 µm, were dominated by large agglomerates (1-5 µm). With aerosol mass spectrometry we show that the particle composition depends on both generator type and maintenance task being performed and that the instrument can be used for highly time resolved selective studies of metal nanoparticle emissions. The emitted agglomerates have a relatively high probability to be deposited in the lower respiratory tract, since the mean particle diameter coincided with a peak in the lung deposition curve. Each of these agglomerates consisted of a very high number (10 3 -10 5 /agglomerate) of nanometer sized primary particles originating from the particle synthesis process. This made them possess large surface areas, one of the key properties in nanotoxicology. Similar agglomerates may be emitted in a wide range of processes when nanoparticles are manufactured or handled. The fate of such agglomerates, once deposited in the respiratory tract, is unknown and should therefore be considered in future particle toxicological studies. Our results highlight the importance of including micrometer sized particles in exposure and emission assessments.

Research paper thumbnail of Size-Resolved Respiratory-Tract Deposition of Fine and Ultrafine Hydrophobic and Hygroscopic Aerosol Particles During Rest and Exercise

Inhalation Toxicology, 2007

Particle size distributions and hygroscopic growth were studied in a town in Sweden with extensiv... more Particle size distributions and hygroscopic growth were studied in a town in Sweden with extensive emissions from wood combustion. The average deposited fraction of particle number, surface area and volume dose in the human respiratory tract was estimated using the data set, as well as the typical deposition pattern of the two dominant particle source types: wood combustion and traffic exhaust. As far as we know, this is the first report on the deposited fraction and hygroscopicity of ambient particles from domestic wood combustion in the literature. The use of PM 2.5 as a substitute for the deposited dose was also tested. Source/receptor modeling and the hygroscopicity measurements showed that wood combustion and traffic exhaust are dominant sources, and that these particles have a low water uptake. Number fractions of 38 and 69% of the wood combustion and traffic particles, respectively, were deposited in the respiratory tract, and 53% of the particles were deposited as an average for the whole period. The deposited fraction of the surface area and volume dose was also calculated for wood combustion particles, with the result being 22% for both parameters. The results also revealed that the PM 2.5 average over more than 10 hours correlated well (r 2 > 0.80) with the deposited surface area and volume dose. This means that PM 2.5 can be used as proxy for the deposited dose when examining health effect relationships during short-term exposure studies if the averaging time is sufficient, while a PM 2.5 proxy is not recommended for shorter averaging times.

Research paper thumbnail of Tandem Measurements of Aerosol Properties—A Review of Mobility Techniques with Extensions

Aerosol Science and Technology, 2008

When multiple instruments are used in tandem it is possible to obtain more complete information o... more When multiple instruments are used in tandem it is possible to obtain more complete information on particle transport and physicochemical properties than can be obtained with a single instrument. This article discusses tandem measurements in which submicrometer particles classified according to electrical mobility are then characterized with one or more additional methods. Measurement combinations that are summarized here include mobility

Research paper thumbnail of Hygroscopic Behavior of Aerosol Particles Emitted from Biomass Fired Grate Boilers

Aerosol Science and Technology, 2005

This study focuses on the hygroscopic properties of submicrometer aerosol particles emitted from ... more This study focuses on the hygroscopic properties of submicrometer aerosol particles emitted from two small-scale district heating combustion plants (1 and 1.5 MW) burning two types of biomass fuels (moist forest residue and pellets). The hygroscopic particle diameter growth factor (Gf ) was measured when taken from a dehydrated to a humidified state for particle diameters between 30-350 nm (dry size) using a Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA). Particles of a certain dry size all showed similar diameter growth and the Gf at RH = 90% for 110/100 nm particles was 1.68 in the 1 MW boiler, and 1.5 in the 1.5 MW boiler. These growth factors are considerably higher in comparison to other combustion aerosol particles such as diesel exhaust, and are the result of the efficient combustion and the high concentration of alkali species in the fuel. The observed water uptake could be explained using the Zdanovski-Stokes-Robinson (ZSR) mixing rule and a chemical composition of potassium salts only, taken from ion chromatography analysis of filter and impactor samples (KCl, K 2 SO 4 , and K 2 CO 3 ). Agglomerated particles collapsed and became more spherical when initially exposed to a moderately high relative humidity. When diluted with hot particle-free air, the fractallike structures remained intact until humidified in the H-TDMA. A method to estimate the fractal dimension of the agglomerated combustion aerosol and to convert the measured mobility diameter hygroscopic growth to the more useful property volume diameter growth is presented. The fractal dimension was estimated to be ∼2.5.

Research paper thumbnail of Fine-particle emissions from solid biofuel combustion studied with single-particle mass spectrometry: Identification of markers for organics, soot, and ash components

Research paper thumbnail of Measurement Techniques for Respiratory Tract Deposition of Airborne Nanoparticles: A Critical Review

Journal of Aerosol Medicine and Pulmonary Drug Delivery, 2013

Determination of the respiratory tract deposition of airborne particles is critical for risk asse... more Determination of the respiratory tract deposition of airborne particles is critical for risk assessment of air pollution, inhaled drug delivery, and understanding of respiratory disease. With the advent of nanotechnology, there has been an increasing interest in the measurement of pulmonary deposition of nanoparticles because of their unique properties in inhalation toxicology and medicine. Over the last century, around 50 studies have presented experimental data on lung deposition of nanoparticles (typical diameter £ 100 nm, but here £ 300 nm). These data show a considerable variability, partly due to differences in the applied methodologies. In this study, we review the experimental techniques for measuring respiratory tract deposition of nano-sized particles, analyze critical experimental design aspects causing measurement uncertainties, and suggest methodologies for future studies. It is shown that, although particle detection techniques have developed with time, the overall methodology in respiratory tract deposition experiments has not seen similar progress. Available experience from previous research has often not been incorporated, and some methodological design aspects that were overlooked in 30-70% of all studies may have biased the experimental data. This has contributed to a significant uncertainty on the absolute value of the lung deposition fraction of nanoparticles. We estimate the impact of the design aspects on obtained data, discuss solutions to minimize errors, and highlight gaps in the available experimental set of data.

Research paper thumbnail of Particulate PAH Emissions from Residential Biomass Combustion: Time-Resolved Analysis with Aerosol Mass Spectrometry

Environmental Science & Technology, 2014

Time-resolved emissions of particulate polycyclic aromatic hydrocarbons (PAHs) and total organic ... more Time-resolved emissions of particulate polycyclic aromatic hydrocarbons (PAHs) and total organic particulate matter (OA) from a wood log stove and an adjusted pellet stove were investigated with high-resolution time-of-flight aerosol mass spectrometry (AMS). The highest OA emissions were found during the addition of log wood on glowing embers, that is, slow burning pyrolysis conditions. These emissions contained about 1% PAHs (of OA). The highest PAH emissions were found during fast burning under hot air starved combustion conditions, in both stoves. In the latter case, PAHs contributed up to 40% of OA, likely due to thermal degradation of other condensable species. The distribution of PAHs was also shifted toward larger molecules in these emissions. AMS signals attributed to PAHs were found at molecular weights up to 600 Da. The vacuum aerodynamic size distribution was found to be bimodal with a smaller mode (Dva ∼ 200 nm) dominating under hot air starved combustion and a larger sized mode dominating under slow burning pyrolysis (Dva ∼ 600 nm). Simultaneous reduction of PAHs, OA and total particulate matter from residential biomass combustion may prove to be a challenge for environmental legislation efforts as these classes of emissions are elevated at different combustion conditions.