Tareq Hussein | University of Jordan (original) (raw)
Papers by Tareq Hussein
The Annals of Applied Statistics, 2014
Aerosol and Air Quality Research, 2011
International Journal of Environmental Research and Public Health, 2014
This study considers fundamental methods in occupational risk assessment of exposure to airborne ... more This study considers fundamental methods in occupational risk assessment of exposure to airborne engineered nanomaterials. We discuss characterization of particle emissions, exposure assessment, hazard assessment with in vitro studies, and risk range characterization using calculated inhaled doses and dose-response translated to humans from in vitro studies. Here, the methods were utilized to assess workers' risk range of inhalation exposure to nanodiamonds (NDs) during handling and sieving of ND powder. NDs were agglomerated to over 500 nm particles, and mean exposure levels of different work tasks varied from 0.24 to 4.96 µg· m −3 (0.08 to 0.74 cm −3 ). In vitro-experiments suggested that ND exposure may cause a risk for activation of inflammatory cascade. However, risk range characterization based on in vitro dose-response was not performed OPEN ACCESS because accurate assessment of delivered (settled) dose on the cells was not possible. Comparison of ND exposure with common pollutants revealed that ND exposure was below 5 μg· m −3 , which is one of the proposed exposure limits for diesel particulate matter, and the workers' calculated dose of NDs during the measurement day was 74 ng which corresponded to 0.02% of the modeled daily (24 h) dose of submicrometer urban air particles.
Aerosol and Air Quality Research, 2014
Ecology, 2014
In species that disperse by airborne propagules an inverse relationship is often assumed between ... more In species that disperse by airborne propagules an inverse relationship is often assumed between propagule size and dispersal distance. However, for microscopic spores the evidence for the relationship remains ambiguous. Lagrangian stochastic dispersion models that have been successful in predicting seed dispersal appear to predict similar dispersal for all spore sizes up to ;40 lm diameter. However, these models have assumed that spore size affects only the downwards drift of particles due to gravitation and have largely omitted the highly size-sensitive deposition process to surfaces such as forest canopy. On the other hand, they have assumed that spores are certain to deposit when the air parcel carrying them touches the ground. Here, we supplement a Lagrangian stochastic dispersion model with a mechanistic deposition model parameterized by empirical deposition data for 1-10 lm spores. The inclusion of realistic deposition improved the ability of the model to predict empirical data on the dispersal of a wood-decay fungus (aerodynamic spore size 3.8 lm). Our model predicts that the dispersal of 1-10 lm spores is in fact highly sensitive to spore size, with 97-98% of 1 lm spores but only 12-58% of 10-lm spores dispersing beyond 2 km in the simulated range of wind and canopy conditions. Further, excluding the assumption of certain deposition at the ground greatly increased the expected dispersal distances throughout the studied spore size range. Our results suggest that by evolutionary adjustment of spore size, release height and timing of release, fungi and other organisms with microscopic spores can change the expected distribution of dispersal locations markedly. The complex interplay of wind and canopy conditions in determining deposition resulted in some counterintuitive predictions, such as that spores disperse furthest under intermediate wind, providing intriguing hypotheses to be tested empirically in future studies.
Environmental Pollution, 2010
The type and amount of indoor air pollutants affects the comfort and quality of indoor environmen... more The type and amount of indoor air pollutants affects the comfort and quality of indoor environments. Therefore, indoor air quality is an important issue with different social, economic, and health aspects because people in developing countries spend most of their time indoors being exposed to different kinds of indoor pollutants. The indoor air quality can be assessed empirically by measuring the pollutant concentrations or can be predicted by means of mathematical models. An indoor aerosol model describes the dynamic behavior of indoor air pollutants. The basic concept of indoor air models is the mass-balance-conservation where several factors that govern the indoor particle concentrations can be described. These factors may include direct emissions from indoor sources, outdoor aerosol particles penetrating indoors as a result of the ventilation and filtration processes, deposition onto indoor surfaces, and removal from indoor air by means of ventilation. Here we present principles of indoor aerosol models and we also give examples of different kind of models.
Advances in Meteorology, 2012
Atmospheric Environment, 2014
ABSTRACT Air pollution is one of the major environmental problems that influence people's... more ABSTRACT Air pollution is one of the major environmental problems that influence people's health. Exposure to harmful particulate matter (PM) occurs both outdoors and indoors, but while people spend most of their time indoors, the indoor exposures tend to dominate. Moreover, higher PM concentrations due to indoor sources and tightness of indoor environments may substantially add to the outdoor originating exposures. Empirical and real-time assessment of human exposure is often impossible; therefore, indoor aerosol modeling (IAM) can be used as a superior method in exposure and health effects studies. This paper presents a simple approach in combining available aerosol-based modeling techniques to evaluate the real-time exposure and respiratory tract deposited dose based on particle size. Our simple approach consists of outdoor aerosol data base, IAM simulations, time-activity pattern data-base, physical-chemical properties of inhaled aerosols, and semi-empirical deposition fraction of aerosols in the respiratory tract. These modeling techniques allow the characterization of regional deposited dose in any metric: particle mass, particle number, and surface area. The first part of this presentation reviews recent advances in simple mass-balance based modeling methods that are needed in analyzing the health relevance of indoor exposures. The second part illustrates the use of IAM in the calculations of exposure and deposited dose. Contrary to previous methods, the approach presented is a real-time approach and it goes beyond the exposure assessment to provide the required information for the health risk assessment, which is the respiratory tract deposited dose. This simplified approach is foreseen to support epidemiological studies focusing on exposures originating from both indoor and outdoor sources.
A mobile laboratory was designed and built in Helsinki Polytechnic, in close co-operation with th... more A mobile laboratory was designed and built in Helsinki Polytechnic, in close co-operation with the University of Helsinki, to measure traffic pollutants with high temporal and spatial resolution under real world conditions. The laboratory provides measurements of gaseous ...
Building and Environment, 2005
The aim of this study was to examine microbial, chemical and physical (particle) emissions from o... more The aim of this study was to examine microbial, chemical and physical (particle) emissions from organic and inorganic thermal insulations with a multifunctional apparatus developed for this purpose. In addition, basic quality parameters of the insulation materials, including microbial content, ignition residue and density, were determined. The particular focus of the study was on bast fibrous insulations made of bast fibres of flax, linseed and hemp. The amounts of microbes in the dry insulations varied greatly, up to 107cfu/g. Several taxa of fungi were detected from the bast fibrous insulations, some of which may produce toxins in suitable conditions. The lowest microbial contents were found in the commercial products. However, emissions of moulds from all insulations made from bast fibres were significant at 90% RH, whereas at lower RHs they were negligible. Only a minor amount of emissions was detected from the reference materials at any RH. Emissions of bacteria were negligible for all materials and conditions. The emission levels of VOCs were negligible for all materials except recycled wood. However, several components of the VOC emissions were identified. No significant emissions of particles were detected from thermal insulations made of bast fibres of flax and hemp. In the case of insulations, particularly those made of organic fibres, it is essential to follow good manufacturing practices and to keep the insulations in a dry place throughout the manufacturing and building process in order to minimize hygienic risks in insulations.
Water, Air, & Soil Pollution: Focus, 2008
The type and amount of indoor air pollutants affects the comfort and quality of indoor environmen... more The type and amount of indoor air pollutants affects the comfort and quality of indoor environments. Therefore, indoor air quality is an important issue with different social, economic, and health aspects because people in developing countries spend most of their time indoors being exposed to different kinds of indoor pollutants. The indoor air quality can be assessed empirically by measuring the pollutant concentrations or can be predicted by means of mathematical models. An indoor aerosol model describes the dynamic behavior of indoor air pollutants. The basic concept of indoor air models is the mass-balance-conservation where several factors that govern the indoor particle concentrations can be described. These factors may include direct emissions from indoor sources, outdoor aerosol particles penetrating indoors as a result of the ventilation and filtration processes, deposition onto indoor surfaces, and removal from indoor air by means of ventilation. Here we present principles of indoor aerosol models and we also give examples of different kind of models.
Atmospheric Chemistry and Physics, 2004
During the calendar years 1998-2002, 147 clear 8 nm diameter particle formation events have been ... more During the calendar years 1998-2002, 147 clear 8 nm diameter particle formation events have been identified at the SMEAR I station in Värriö, northern Finland. The events have been classified in detail according to the particle formation rate, growth rate, event starting time, different trace gas concentrations and pre-existing particle concentrations as well as various meteorological conditions. The frequency of particle formation and growth events was highest during the spring months between March and May, suggesting that increasing biological activity might produce the precursor gases for particle formation. The apparent 8 nm particle formation rates were around 0.1 /cm 3 s, and they were uncorrelated with growth rates that varied between 0.5 and 10 nm/h. The air masses with clearly elevated sulphur dioxide concentrations (above 1.6 ppb) came, as expected, from the direction of the Nikel and Monschegorsk smelters. Only 15 formation events can be explained by the pollution plume from these sources.
Tellus B, 2008
A B S T R A C T Long-term measurements of fine particle number-size distributions were carried ou... more A B S T R A C T Long-term measurements of fine particle number-size distributions were carried out over 9.5 yr (May 1997-December 2006, in the urban background atmosphere of Helsinki. The total number of days was 3528 with about 91.9% valid data. A new particle formation event (NPF) is defined if a distinct nucleation mode of aerosol particles is observed below 25 nm for several hours, and it shows a growth pattern. We observed 185 NPF events, 111 d were clear non-events and most of the days (around 83.5%) were undefined. The observed events were regional because they were observed at Hyytiälä (250 km north of Helsinki). The events occurred most frequently during spring and autumn. The observed formation rate was maximum during the spring and summer (monthly median 2.87 cm −3 s −1 ) and the modal growth rate was maximum during late summer and Autumn (monthly median 6.55 nm h −1 ). The events were observed around noon, and the growth pattern often continued on the following day. The observation of weak NPF events was hindered due to pre-existing particles from both local sources. It is clear that regional NPF events have a clear influence on the dynamic behaviour of aerosol particles in the urban atmosphere.
Tellus B, 2008
A B S T R A C T An analysis of particle formation (PF) events over a subarctic mire in northern S... more A B S T R A C T An analysis of particle formation (PF) events over a subarctic mire in northern Sweden was performed, based on numbersize distributions of atmospheric aerosol particles (10-500 nm in diameter) and ions (0.4-40 nm in Tammet diameter). We present classification statistics for PF events from measurements covering the period July 2005-September 2006, with a break over the winter period. The PF event frequency peaked during the summer months, in contrast to other Scandinavian sites where the frequency is highest during spring and autumn. Our analysis includes calculated growth rates and estimates of concentrations and production rates of condensing vapour, deduced from the growth rates and condensational sink calculations, using AIS and SMPS data. Particle formation events with high growth rates (up to 50 nm h −1 ) occurred repeatedly. In these cases, the newly formed nucleation mode particles were often only present for periods of a few hours. On several occasions, repeated particle formation events were observed within 1 d, with differences in onset time of a few hours. These high growth rates were only observed when the condensation sink was higher than 0.001 s −1 .
Tellus B, 2008
A B S T R A C T An analysis of particle formation (PF) events over a subarctic mire in northern S... more A B S T R A C T An analysis of particle formation (PF) events over a subarctic mire in northern Sweden was performed, based on numbersize distributions of atmospheric aerosol particles (10-500 nm in diameter) and ions (0.4-40 nm in Tammet diameter). We present classification statistics for PF events from measurements covering the period July 2005-September 2006, with a break over the winter period. The PF event frequency peaked during the summer months, in contrast to other Scandinavian sites where the frequency is highest during spring and autumn. Our analysis includes calculated growth rates and estimates of concentrations and production rates of condensing vapour, deduced from the growth rates and condensational sink calculations, using AIS and SMPS data. Particle formation events with high growth rates (up to 50 nm h −1 ) occurred repeatedly. In these cases, the newly formed nucleation mode particles were often only present for periods of a few hours. On several occasions, repeated particle formation events were observed within 1 d, with differences in onset time of a few hours. These high growth rates were only observed when the condensation sink was higher than 0.001 s −1 .
Tellus B, 2008
A B S T R A C T Long-term measurements of fine particle number-size distributions were carried ou... more A B S T R A C T Long-term measurements of fine particle number-size distributions were carried out over 9.5 yr (May 1997-December 2006, in the urban background atmosphere of Helsinki. The total number of days was 3528 with about 91.9% valid data. A new particle formation event (NPF) is defined if a distinct nucleation mode of aerosol particles is observed below 25 nm for several hours, and it shows a growth pattern. We observed 185 NPF events, 111 d were clear non-events and most of the days (around 83.5%) were undefined. The observed events were regional because they were observed at Hyytiälä (250 km north of Helsinki). The events occurred most frequently during spring and autumn. The observed formation rate was maximum during the spring and summer (monthly median 2.87 cm −3 s −1 ) and the modal growth rate was maximum during late summer and Autumn (monthly median 6.55 nm h −1 ). The events were observed around noon, and the growth pattern often continued on the following day. The observation of weak NPF events was hindered due to pre-existing particles from both local sources. It is clear that regional NPF events have a clear influence on the dynamic behaviour of aerosol particles in the urban atmosphere.
Science of The Total Environment, 2012
The daily time-spent in different environments is an important factor in calculation of personal ... more The daily time-spent in different environments is an important factor in calculation of personal exposure to air pollutants. Despite this importance, the amount of research done on this topic is rather limited, especially in North Europe where the climate is rather cold. In this study, we gathered detailed information via a standard questionnaire to report the residence time and place of 167 subjects (between 2 and 93 years old) lived in Helsinki during three time periods in winter and spring 2009. Subjects spent 81%-92% of their time indoors and up to ~15% of their time outdoors. The daily time-spent in different environments was affected by several factors: ambient temperature, type of day (workday or weekend/holiday), gender, and age. Therefore, the differences occur individually and can be explained by these factors. For example, subjects spent more time at home on weekends than workdays because obviously the majority of our subjects did not have work on weekends. The time-spent at kindergarten/school/work increased with age until retirement. Females spent more time at home than males. After all, the activity pattern found in this study is rather similar to those previously reported in Germany and North America.
The Annals of Applied Statistics, 2014
Aerosol and Air Quality Research, 2011
International Journal of Environmental Research and Public Health, 2014
This study considers fundamental methods in occupational risk assessment of exposure to airborne ... more This study considers fundamental methods in occupational risk assessment of exposure to airborne engineered nanomaterials. We discuss characterization of particle emissions, exposure assessment, hazard assessment with in vitro studies, and risk range characterization using calculated inhaled doses and dose-response translated to humans from in vitro studies. Here, the methods were utilized to assess workers' risk range of inhalation exposure to nanodiamonds (NDs) during handling and sieving of ND powder. NDs were agglomerated to over 500 nm particles, and mean exposure levels of different work tasks varied from 0.24 to 4.96 µg· m −3 (0.08 to 0.74 cm −3 ). In vitro-experiments suggested that ND exposure may cause a risk for activation of inflammatory cascade. However, risk range characterization based on in vitro dose-response was not performed OPEN ACCESS because accurate assessment of delivered (settled) dose on the cells was not possible. Comparison of ND exposure with common pollutants revealed that ND exposure was below 5 μg· m −3 , which is one of the proposed exposure limits for diesel particulate matter, and the workers' calculated dose of NDs during the measurement day was 74 ng which corresponded to 0.02% of the modeled daily (24 h) dose of submicrometer urban air particles.
Aerosol and Air Quality Research, 2014
Ecology, 2014
In species that disperse by airborne propagules an inverse relationship is often assumed between ... more In species that disperse by airborne propagules an inverse relationship is often assumed between propagule size and dispersal distance. However, for microscopic spores the evidence for the relationship remains ambiguous. Lagrangian stochastic dispersion models that have been successful in predicting seed dispersal appear to predict similar dispersal for all spore sizes up to ;40 lm diameter. However, these models have assumed that spore size affects only the downwards drift of particles due to gravitation and have largely omitted the highly size-sensitive deposition process to surfaces such as forest canopy. On the other hand, they have assumed that spores are certain to deposit when the air parcel carrying them touches the ground. Here, we supplement a Lagrangian stochastic dispersion model with a mechanistic deposition model parameterized by empirical deposition data for 1-10 lm spores. The inclusion of realistic deposition improved the ability of the model to predict empirical data on the dispersal of a wood-decay fungus (aerodynamic spore size 3.8 lm). Our model predicts that the dispersal of 1-10 lm spores is in fact highly sensitive to spore size, with 97-98% of 1 lm spores but only 12-58% of 10-lm spores dispersing beyond 2 km in the simulated range of wind and canopy conditions. Further, excluding the assumption of certain deposition at the ground greatly increased the expected dispersal distances throughout the studied spore size range. Our results suggest that by evolutionary adjustment of spore size, release height and timing of release, fungi and other organisms with microscopic spores can change the expected distribution of dispersal locations markedly. The complex interplay of wind and canopy conditions in determining deposition resulted in some counterintuitive predictions, such as that spores disperse furthest under intermediate wind, providing intriguing hypotheses to be tested empirically in future studies.
Environmental Pollution, 2010
The type and amount of indoor air pollutants affects the comfort and quality of indoor environmen... more The type and amount of indoor air pollutants affects the comfort and quality of indoor environments. Therefore, indoor air quality is an important issue with different social, economic, and health aspects because people in developing countries spend most of their time indoors being exposed to different kinds of indoor pollutants. The indoor air quality can be assessed empirically by measuring the pollutant concentrations or can be predicted by means of mathematical models. An indoor aerosol model describes the dynamic behavior of indoor air pollutants. The basic concept of indoor air models is the mass-balance-conservation where several factors that govern the indoor particle concentrations can be described. These factors may include direct emissions from indoor sources, outdoor aerosol particles penetrating indoors as a result of the ventilation and filtration processes, deposition onto indoor surfaces, and removal from indoor air by means of ventilation. Here we present principles of indoor aerosol models and we also give examples of different kind of models.
Advances in Meteorology, 2012
Atmospheric Environment, 2014
ABSTRACT Air pollution is one of the major environmental problems that influence people's... more ABSTRACT Air pollution is one of the major environmental problems that influence people's health. Exposure to harmful particulate matter (PM) occurs both outdoors and indoors, but while people spend most of their time indoors, the indoor exposures tend to dominate. Moreover, higher PM concentrations due to indoor sources and tightness of indoor environments may substantially add to the outdoor originating exposures. Empirical and real-time assessment of human exposure is often impossible; therefore, indoor aerosol modeling (IAM) can be used as a superior method in exposure and health effects studies. This paper presents a simple approach in combining available aerosol-based modeling techniques to evaluate the real-time exposure and respiratory tract deposited dose based on particle size. Our simple approach consists of outdoor aerosol data base, IAM simulations, time-activity pattern data-base, physical-chemical properties of inhaled aerosols, and semi-empirical deposition fraction of aerosols in the respiratory tract. These modeling techniques allow the characterization of regional deposited dose in any metric: particle mass, particle number, and surface area. The first part of this presentation reviews recent advances in simple mass-balance based modeling methods that are needed in analyzing the health relevance of indoor exposures. The second part illustrates the use of IAM in the calculations of exposure and deposited dose. Contrary to previous methods, the approach presented is a real-time approach and it goes beyond the exposure assessment to provide the required information for the health risk assessment, which is the respiratory tract deposited dose. This simplified approach is foreseen to support epidemiological studies focusing on exposures originating from both indoor and outdoor sources.
A mobile laboratory was designed and built in Helsinki Polytechnic, in close co-operation with th... more A mobile laboratory was designed and built in Helsinki Polytechnic, in close co-operation with the University of Helsinki, to measure traffic pollutants with high temporal and spatial resolution under real world conditions. The laboratory provides measurements of gaseous ...
Building and Environment, 2005
The aim of this study was to examine microbial, chemical and physical (particle) emissions from o... more The aim of this study was to examine microbial, chemical and physical (particle) emissions from organic and inorganic thermal insulations with a multifunctional apparatus developed for this purpose. In addition, basic quality parameters of the insulation materials, including microbial content, ignition residue and density, were determined. The particular focus of the study was on bast fibrous insulations made of bast fibres of flax, linseed and hemp. The amounts of microbes in the dry insulations varied greatly, up to 107cfu/g. Several taxa of fungi were detected from the bast fibrous insulations, some of which may produce toxins in suitable conditions. The lowest microbial contents were found in the commercial products. However, emissions of moulds from all insulations made from bast fibres were significant at 90% RH, whereas at lower RHs they were negligible. Only a minor amount of emissions was detected from the reference materials at any RH. Emissions of bacteria were negligible for all materials and conditions. The emission levels of VOCs were negligible for all materials except recycled wood. However, several components of the VOC emissions were identified. No significant emissions of particles were detected from thermal insulations made of bast fibres of flax and hemp. In the case of insulations, particularly those made of organic fibres, it is essential to follow good manufacturing practices and to keep the insulations in a dry place throughout the manufacturing and building process in order to minimize hygienic risks in insulations.
Water, Air, & Soil Pollution: Focus, 2008
The type and amount of indoor air pollutants affects the comfort and quality of indoor environmen... more The type and amount of indoor air pollutants affects the comfort and quality of indoor environments. Therefore, indoor air quality is an important issue with different social, economic, and health aspects because people in developing countries spend most of their time indoors being exposed to different kinds of indoor pollutants. The indoor air quality can be assessed empirically by measuring the pollutant concentrations or can be predicted by means of mathematical models. An indoor aerosol model describes the dynamic behavior of indoor air pollutants. The basic concept of indoor air models is the mass-balance-conservation where several factors that govern the indoor particle concentrations can be described. These factors may include direct emissions from indoor sources, outdoor aerosol particles penetrating indoors as a result of the ventilation and filtration processes, deposition onto indoor surfaces, and removal from indoor air by means of ventilation. Here we present principles of indoor aerosol models and we also give examples of different kind of models.
Atmospheric Chemistry and Physics, 2004
During the calendar years 1998-2002, 147 clear 8 nm diameter particle formation events have been ... more During the calendar years 1998-2002, 147 clear 8 nm diameter particle formation events have been identified at the SMEAR I station in Värriö, northern Finland. The events have been classified in detail according to the particle formation rate, growth rate, event starting time, different trace gas concentrations and pre-existing particle concentrations as well as various meteorological conditions. The frequency of particle formation and growth events was highest during the spring months between March and May, suggesting that increasing biological activity might produce the precursor gases for particle formation. The apparent 8 nm particle formation rates were around 0.1 /cm 3 s, and they were uncorrelated with growth rates that varied between 0.5 and 10 nm/h. The air masses with clearly elevated sulphur dioxide concentrations (above 1.6 ppb) came, as expected, from the direction of the Nikel and Monschegorsk smelters. Only 15 formation events can be explained by the pollution plume from these sources.
Tellus B, 2008
A B S T R A C T Long-term measurements of fine particle number-size distributions were carried ou... more A B S T R A C T Long-term measurements of fine particle number-size distributions were carried out over 9.5 yr (May 1997-December 2006, in the urban background atmosphere of Helsinki. The total number of days was 3528 with about 91.9% valid data. A new particle formation event (NPF) is defined if a distinct nucleation mode of aerosol particles is observed below 25 nm for several hours, and it shows a growth pattern. We observed 185 NPF events, 111 d were clear non-events and most of the days (around 83.5%) were undefined. The observed events were regional because they were observed at Hyytiälä (250 km north of Helsinki). The events occurred most frequently during spring and autumn. The observed formation rate was maximum during the spring and summer (monthly median 2.87 cm −3 s −1 ) and the modal growth rate was maximum during late summer and Autumn (monthly median 6.55 nm h −1 ). The events were observed around noon, and the growth pattern often continued on the following day. The observation of weak NPF events was hindered due to pre-existing particles from both local sources. It is clear that regional NPF events have a clear influence on the dynamic behaviour of aerosol particles in the urban atmosphere.
Tellus B, 2008
A B S T R A C T An analysis of particle formation (PF) events over a subarctic mire in northern S... more A B S T R A C T An analysis of particle formation (PF) events over a subarctic mire in northern Sweden was performed, based on numbersize distributions of atmospheric aerosol particles (10-500 nm in diameter) and ions (0.4-40 nm in Tammet diameter). We present classification statistics for PF events from measurements covering the period July 2005-September 2006, with a break over the winter period. The PF event frequency peaked during the summer months, in contrast to other Scandinavian sites where the frequency is highest during spring and autumn. Our analysis includes calculated growth rates and estimates of concentrations and production rates of condensing vapour, deduced from the growth rates and condensational sink calculations, using AIS and SMPS data. Particle formation events with high growth rates (up to 50 nm h −1 ) occurred repeatedly. In these cases, the newly formed nucleation mode particles were often only present for periods of a few hours. On several occasions, repeated particle formation events were observed within 1 d, with differences in onset time of a few hours. These high growth rates were only observed when the condensation sink was higher than 0.001 s −1 .
Tellus B, 2008
A B S T R A C T An analysis of particle formation (PF) events over a subarctic mire in northern S... more A B S T R A C T An analysis of particle formation (PF) events over a subarctic mire in northern Sweden was performed, based on numbersize distributions of atmospheric aerosol particles (10-500 nm in diameter) and ions (0.4-40 nm in Tammet diameter). We present classification statistics for PF events from measurements covering the period July 2005-September 2006, with a break over the winter period. The PF event frequency peaked during the summer months, in contrast to other Scandinavian sites where the frequency is highest during spring and autumn. Our analysis includes calculated growth rates and estimates of concentrations and production rates of condensing vapour, deduced from the growth rates and condensational sink calculations, using AIS and SMPS data. Particle formation events with high growth rates (up to 50 nm h −1 ) occurred repeatedly. In these cases, the newly formed nucleation mode particles were often only present for periods of a few hours. On several occasions, repeated particle formation events were observed within 1 d, with differences in onset time of a few hours. These high growth rates were only observed when the condensation sink was higher than 0.001 s −1 .
Tellus B, 2008
A B S T R A C T Long-term measurements of fine particle number-size distributions were carried ou... more A B S T R A C T Long-term measurements of fine particle number-size distributions were carried out over 9.5 yr (May 1997-December 2006, in the urban background atmosphere of Helsinki. The total number of days was 3528 with about 91.9% valid data. A new particle formation event (NPF) is defined if a distinct nucleation mode of aerosol particles is observed below 25 nm for several hours, and it shows a growth pattern. We observed 185 NPF events, 111 d were clear non-events and most of the days (around 83.5%) were undefined. The observed events were regional because they were observed at Hyytiälä (250 km north of Helsinki). The events occurred most frequently during spring and autumn. The observed formation rate was maximum during the spring and summer (monthly median 2.87 cm −3 s −1 ) and the modal growth rate was maximum during late summer and Autumn (monthly median 6.55 nm h −1 ). The events were observed around noon, and the growth pattern often continued on the following day. The observation of weak NPF events was hindered due to pre-existing particles from both local sources. It is clear that regional NPF events have a clear influence on the dynamic behaviour of aerosol particles in the urban atmosphere.
Science of The Total Environment, 2012
The daily time-spent in different environments is an important factor in calculation of personal ... more The daily time-spent in different environments is an important factor in calculation of personal exposure to air pollutants. Despite this importance, the amount of research done on this topic is rather limited, especially in North Europe where the climate is rather cold. In this study, we gathered detailed information via a standard questionnaire to report the residence time and place of 167 subjects (between 2 and 93 years old) lived in Helsinki during three time periods in winter and spring 2009. Subjects spent 81%-92% of their time indoors and up to ~15% of their time outdoors. The daily time-spent in different environments was affected by several factors: ambient temperature, type of day (workday or weekend/holiday), gender, and age. Therefore, the differences occur individually and can be explained by these factors. For example, subjects spent more time at home on weekends than workdays because obviously the majority of our subjects did not have work on weekends. The time-spent at kindergarten/school/work increased with age until retirement. Females spent more time at home than males. After all, the activity pattern found in this study is rather similar to those previously reported in Germany and North America.