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Material extrusion (ME) desktop 3D printing is known to strongly emit nanoparticles (NP), and the need for risk management has been recognized widely. Four different engineering control measures were studied in real-life office conditions by means of online NP measurements and indoor aerosol modeling. The studied engineering control measures were general ventilation, local exhaust ventilation (LEV), retrofitted enclosure, and retrofitted enclosure with LEV. Efficiency between different control measures was compared based on particle number and surface area (SA) concentrations from which SA concentration was found to be more reliable. The study found out that for regular or long-time use of ME desktop 3D printers, the general ventilation is not sufficient control measure for NP emissions. Also, the LEV with canopy hood attached above the 3D printer did not control the emission remarkably and successful position of the hood in relation to the nozzle was found challenging. Retrofitted enclosure attached to the LEV reduced the NP emissions 96% based on SA concentration. Retrofitted enclosure is nearly as efficient as enclosure attached to the LEV (reduction of 89% based on SA concentration) but may be considered more practical solution than enclosure with LEV.

In air quality research, often only particle mass concentrations as indicators of aerosol particles are considered. However, the mass concentrations do not provide sufficient information to convey the full story of fractionated size distribution, which are able to deposit differently on respiratory system and cause various harm. Aerosol size distribution measurements rely on a variety of techniques to classify the aerosol size and measure the size distribution. From the raw data the ambient size distribution is determined utilising a suite of inversion algorithms. However, the inversion problem is quite often ill-posed and challenging to invert. Due to the instrumental insufficiency and inversion limitations, models for fractionated particle size distribution are of great significance to fill the missing gaps or negative values. The study at hand involves a merged particle size distribution, from a scanning mobility particle sizer (NanoSMPS) and an optical particle sizer (OPS) covering the aerosol size distributions from 0.01 to 0.42 μm (electrical mobility equivalent size) and 0.3 μm to 10 μm (optical equivalent size) and meteorological parameters collected at an urban background region in Amman, Jordan in the period of 1st Aug 2016–31st July 2017. We develop and evaluate feed-forward neural network (FFNN) models to estimate number concentrations at particular size bin with (1) meteorological parameters, (2) number concentration at other size bins, and (3) both of the above as input variables. Two layers with 10–15 neurons are found to be the optimal option. Lower model performance is observed at the lower edge (0.01 2 = 0.22–0.58) shows poorer results than data with longer time resolution (R2 = 0.66–0.77). The model by the number concentration at the other size bins can serve as an alternative way to replace negative number in size distribution raw dataset thanks to its high accuracy and reliability (R2 = 0.97–1). This negative numbers filling method can maintain a symmetric distribution of errors.

Transmission of respiratory viruses is a complex process involving emission, deposition in the airways, and infection. Inhalation is often the most relevant transmission mode in indoor environments. For severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the risk of inhalation transmission is not yet fully understood. Here, we used an indoor aerosol model combined with a regional inhaled deposited dose model to examine the indoor transport of aerosols from an infected person with novel coronavirus disease (COVID-19) to a susceptible person and assess the potential inhaled dose rate of particles. Two scenarios with different ventilation rates were compared, as well as adult female versus male recipients. Assuming a source strength of 10 viruses/s, in a tightly closed room with poor ventilation (0.5 h−1), the respiratory tract deposited dose rate was 140–350 and 100–260 inhaled viruses/hour for males and females, respectively. With ventilation at 3 h−1 the dose rate was only 30–90 viruses/hour. Correcting for the half-life of SARS-CoV-2 in air, these numbers are reduced by a factor of 1.2–2.2 for poorly ventilated rooms and 1.1–1.4 for well-ventilated rooms. Combined with future determinations of virus emission rates, the size distribution of aerosols containing the virus, and the infectious dose, these results could play an important role in understanding the full picture of potential inhalation transmission in indoor environments.

More representative data on source-specific particle number emission rates and associated exposure in European households are needed. In this study, indoor and outdoor particle number size distributions (10–800 nm) were measured in 40 German households under real-use conditions in over 500 days. Particle number emission rates were derived for around 800 reported indoor source events. The highest emission rate was caused by burning candles (5.3 × 1013 h−1). Data were analyzed by the single-parameter approach (SPA) and the indoor aerosol dynamics model approach (IAM). Due to the consideration of particle deposition, coagulation, and time-dependent ventilation rates, the emission rates of the IAM approach were about twice as high as those of the SPA. Correction factors are proposed to convert the emission rates obtained from the SPA approach into more realistic values. Overall, indoor sources contributed ~ 56% of the daily-integrated particle number exposure in households under study. Burning candles and opening the window leads to seasonal differences in the contributions of indoor sources to residential exposure (70% and 40% in the cold and warm season, respectively). Application of the IAM approach allowed to attribute the contributions of outdoor particles to the penetration through building shell and entry through open windows (26% and 15%, respectively). © 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Indoor combustion processes associated with cooking, heating, and smoking are a major source of aerosols in Jordanian dwellings. To evaluate human exposure to combustion-generated aerosols in Jordanian indoor environments, regional inhaled deposited dose rates of indoor aerosols (10 nm to 25 &micro, m) were determined for different scenarios for adult occupants. The inhaled deposited dose rate provides an estimate of the number or mass of inhaled aerosol that deposits in each region of the respiratory system per unit time. In general, sub-micron particle number (PN1) dose rates ranged from 109 to 1012 particles/h, fine particle mass (PM2.5) dose rates ranged from 3 to 216 &micro, g/h, and coarse particle mass (PM10) dose rates ranged from 30 to 1600 &micro, g/h. Dose rates were found to be dependent on the type and intensity of indoor combustion processes documented in the home. Dose rates were highest during cooking activities using a natural gas stove, heating via natural gas and kerosene, and smoking (shisha/tobacco). The relative fraction of the total dose rate received in the head airways, tracheobronchial, and alveolar regions varied among the documented indoor combustion (and non-combustion) activities. The significant fraction of sub-100 nm particles produced during the indoor combustion processes resulted in high particle number dose rates for the alveolar region. Suggested approaches for reducing indoor aerosol dose rates in Jordanian dwellings include a reduction in the prevalence of indoor combustion sources, use of extraction hoods to remove combustion products, and improved ventilation/filtration in residential buildings.

Sub-micron aerosols are a vital air pollutant to be measured because they pose health effects. These particles are quantified as particle number concentration (PN). However, PN measurements are not always available in air quality measurement stations, leading to data scarcity. In order to compensate this, PN modeling needs to be developed. This paper presents a PN modeling framework using sensitivity analysis tested on a one year aerosol measurement campaign conducted in Amman, Jordan. The method prepares a set of different combinations of all measured meteorological parameters to be descriptors of PN concentration. In this case, we resort to artificial neural networks in the forms of a feed-forward neural network (FFNN) and a time-delay neural network (TDNN) as modeling tools, and then, we attempt to find the best descriptors using all these combinations as model inputs. The best modeling tools are FFNN for daily averaged data (with R 2 = 0.77 ) and TDNN for hourly averaged data (with R 2 = 0.66 ) where the best combinations of meteorological parameters are found to be temperature, relative humidity, pressure, and wind speed. As the models follow the patterns of diurnal cycles well, the results are considered to be satisfactory. When PN measurements are not directly available or there are massive missing PN concentration data, PN models can be used to estimate PN concentration using available measured meteorological parameters.

Few studies investigated residential particle concentration levels with a full picture of aerosol particles from 10 mu m to 10 mu m size range with size-resolved information, and none was performed in central Europe in the long-term in multiple homes. To capture representative diurnal and seasonal patterns of exposure to particles, and investigate the driving factors to their variations, measurements were performed in 40 homes for around two weeks each in Leipzig and Berlin, Germany. These over 500 days' measurements combined PM10 and PM2. 5 mass concentrations, particle number concentration and size distribution (PNC and PNSD, 10-800 nm), CO2 concentration, and residential activities diary into a unique dataset. Natural ventilation was dominated, the mean ventilation rate calculated from CO2 measurements was 0.2 h(-1) and 3.7 h(-1) with closed and opened windows, respectively. The main findings of this study showed that, the residents in German homes were exposed to a significantly higher mass concentration of coarse particles than outdoors, thus indoor exposure to coarse particles cannot be described by outdoors. The median indoor PNC diurnal cycles were generally lower than outdoors (median I/O ratio 0.69). However, indoor exposure to particles was different in the cold and warm season. In the warm season, due to longer opening window periods, indoor sources' contribution was weakened, which also resulted in the indoor PNC and PNSD being very similar to the outdoors. In the cold season, indoor sources caused strong peaks of indoor PNC that exceeded outdoors, along with the relatively low penetration factor - 0.5 for all size ranges, and indoor particle losses, which was particularly effective in reducing the ultrafine PNC, resulting in a different particle exposure load than outdoors. This study provides a detailed understanding of residential particle exposure in multiple homes, facilitating future studies to assess health effects in residential environments.

In this study, we measured the concentrations of accumulation and coarse particles inside an educational workshop (March 31–April 6, 2015), calculated particle emission and losses rates, and estimated inhaled deposited dose. We used an Optical Particle Sizer (TSI OPS 3330) that measures the particle number size distribution (diameter 0.3–10 μm) and we converted that into particle mass size distribution (assuming spherical particles and unit density). We focused on two particle size fractions: 0.3–1 μm (referred as PN0.3−1 and PM0.3−1) and 1–10 μm (referred as PN1−10 and PM1−10). The occupants' activities included coffee brewing, lecturing, tobacco smoking, welding, scrubbing, and sorting/drilling iron. The highest concentrations were observed during welding with PN0.3−1 (PM0.3−1) was ∼1866 cm−3 (55 μg/m3) and PN1−10 (PM1−10) was ∼7 cm−3 (103 μg/m3). The lowest concentrations were observed during coffee brewing and metal turning with PN0.3−1 (PM0.3−1) was ∼22 cm−3 (0.7 μg/m3) and PN1−10 (PM1−10) was ∼0.5 cm−3 (4 μg/m3). The emissions rate of coarse particles was 85–1010 particles/hour × cm3 whereas that for submicron particle in the diameter range 0.3–1 μm was 5.7 × 104–9.3 × 104 particles/hour × cm3 depending on the activity and the ventilation rate. The coarse particles losses rate was 0.35–2.1 h−1 and the ventilation rate was 0.24–2.1 h−1. The alveolar received the majority and particles below 1 μm with a fraction of about 53% of the total inhaled deposited dose whereas the head/throat region received about 18%. This study is important for better understanding the health effects at educational workshops.

Here, we studied the particle release rate during Electrostatic spray deposition of anatase-(TiO2)-based photoactive coating onto tiles and wallpaper using a commercially available electrostatic spray device. Spraying was performed in a 20.3m3 test chamber while measuring concentrations of 5.6nm to 31μm-size particles and volatile organic compounds (VOC), as well as particle deposition onto room surfaces and on the spray gun user hand. The particle emission and deposition rates were quantified using aerosol mass balance modelling. The geometric mean particle number emission rate was 1.9×1010s-1 and the mean mass emission rate was 381μgs-1. The respirable mass emission-rate was 65% lower than observed for the entire measured size-range. The mass emission rates were linearly scalable (±ca. 20%) to the process duration. The particle deposition rates were up to 15h-1 for 2, TiO2 mixed with Cl and/or Ag, TiO2particles coated with carbon, and Ag particles with size ranging from 60 nm to ca. 5 μm. As expected, no significant VOC emissions were observed as a result of spraying. Finally, we provide recommendations for exposure model parameterization.

To derive the comprehensive aerosol in situ characteristics at a rural background area in Saudi Arabia, an aerosol measurements station was established to Hada Al Sham, 60 km east from the Red Sea and the city of Jeddah. The present sturdy describes the observational data from February 2013 to February 2015 of scattering and absorption coefficients, Angstrom exponents and single scattering albedo over the measurement period. The average scattering and absorption coefficients at wavelength 525 nm were 109 ± 71 Mm − 1 (mean ± SD, at STP conditions) and 15 ± 17 Mm − 1 (at STP conditions), respectively. As expected, the scattering coefficient was dominated by large desert dust particles with low Angstrom scattering exponent, 0.49 ± 0.62. Especially from February to June the Angstrom scattering exponent was clearly lower (0.23) and scattering coefficients higher (124 Mm − 1 ) than total averages because of the dust outbreak season. Aerosol optical properties had clear diurnal cycle. The lowest scattering and absorption coefficients and aerosol optical depths were observed around noon. The observed diurnal variation is caused by wind direction and speed, during night time very calm easterly winds are dominating whereas during daytime the stronger westerly winds are dominating (sea breeze). Positive Matrix Factorization mathematical tool was applied to the scattering and absorption coefficients and PM 2.5 and coarse mode (PM 10 –PM 2.5 ) mass concentrations to identify source characteristics. Three different factors with clearly different properties were found; anthropogenic, BC source and desert dust. Mass absorption efficiencies for BC source and desert dust factors were, 6.0 m 2 g − 1 and 0.4 m 2 g − 1 , respectively, and mass scattering efficiencies for anthropogenic (sulphate) and desert dust, 2.5 m 2 g − 1 and 0.8 m 2 g − 1 , respectively.

The indoor-to-outdoor relationship of aerosol particles is affected by several mechanisms including penetration, ventilation rate, dry deposition rate and sources. Understanding the effect of these factors is essential for a deeper knowledge of the indoor-to-outdoor relationship. In real-life conditions, it is difficult to analyze these factors in a naturally ventilated environment. In this study, a naturally ventilated and an occupied apartment was used to investigate the indoor-to-outdoor relationship of aerosol particles by applying two different techniques; single-parameter analysis and indoor aerosol model simulation. The indoor aerosol model simulation approach can describe the effect of these factors based on high time-resolution calculations and it is a powerful and robust approach. Single parameter analysis is very simple to apply but it is valid under certain conditions. In the absence of indoor activities (i.e. nighttime) and based on the particle number concentrations, the I/O ratio was P ) was 0.3–1, the ventilation rate ( λ ) was 0.1–2 h − 1 , and the deposition rate ( λ d ) was ~ 0.15 h − 1 . The coarse particles concentration was strongly affected by indoor activities. During extreme mechanical activities (e.g. vacuum cleaning), the concentration increased by a factor of 9 (source strength ~ 160 particles/h). During children play, the coarse fraction concentration increased by a factor of 3 (source strength ~ 10 particles/h). Spraying an insect pesticide increased the coarse fraction concentration by a factor of 9 (source strength ~ 420 particles/h). Water-pipe tobacco smoking produced huge amounts of both micron and submicron particulate matter; it caused the coarse fraction concentration to significantly increase by a factor of 18 (source strength ~ 140 particles/h). The use of natural gas heater affected the submicron fraction only and did not affect the micron fraction.

There is a paucity of comprehensive air quality data from urban areas in the Middle East. In this study, portable instrumentation was used to measure size-fractioned aerosol number, mass, and black carbon concentrations in Amman and Zarqa, Jordan. Submicron particle number concentrations at stationary urban background sites in Amman and Zarqa exhibited a characteristic diurnal pattern, with the highest concentrations during traffic rush hours (2&ndash, 5 &times, 104 cm&minus, 3 in Amman and 2&ndash, 7 &times, 3 in Zarqa). Super-micron particle number concentrations varied considerably in Amman (1&ndash, 10 cm&minus, 3). Mobile measurements identified spatial variations and local hotspots in aerosol levels within both cities. Walking paths around the University of Jordan campus showed increasing concentrations with proximity to main roads with mean values of 8 &times, 3, 87 &micro, g/m3, 62 &micro, g/m3, and 7.7 &micro, g/m3 for submicron, PM10, PM2.5, and black carbon (BC), respectively. Walking paths in the Amman city center showed moderately high concentrations (mean 105 cm&minus, 3, 120 &micro, g/m3, 85 &micro, g/m3, and 8.1 &micro, g/m3 for submicron aerosols, PM10, PM2.5, and black carbon, respectively). Similar levels were found along walking paths in the Zarqa city center. On-road measurements showed high submicron concentrations (&gt, 105 cm&minus, 3). The lowest submicron concentration (&lt, 3) was observed near a remote site outside of the cities.

This is the first time to clearly derive the comprehensive physical properties of aerosols at a rural background area in Saudi Arabia. Aerosol measurements station was established at a rural background area in the Western Saudi Arabia to study the aerosol properties. This study gives overview of the aerosol physical properties (PM10, PM2.5, black carbon and total number concentration) over the measurement period from November 2012 to February 2015. The average PM10 and PM2.5 concentrations were 95 ± 78 μg m-3 (mean ± STD, at ambient conditions) and 33 ± 68 μg m-3 (at ambient conditions), respectively. As expected PM10 concentration was dominated by coarse mode particles (PM10-PM2.5), most probably desert dust. Especially from February to June the coarse mode concentrations were high because of dust storm season. Aerosol mass concentrations had clear diurnal cycle. Lower values were observed around noon. This behavior is caused by wind direction and speed, during night time very calm easterly winds are dominating whereas during daytime the stronger westerly winds are dominating (sea breeze). During the day time the boundary layer is evolving, causing enhanced mixing and dilution leading to lower concentration. PM10 and PM2.5 concentrations were comparable to values measured at close by city of Jeddah. Black carbon concentration was about 2% and 6% of PM10 and PM2.5 mass, respectively. Total number concentration was dominated by frequent new particle formation and particle growth events. The typical diurnal cycle in particle total number concentration was clearly different from PM10 and PM2.5.

The present work is a part of a scientific study conducted among several Arab countries in west Asia, under an International Atomic Energy Agency (IAEA) regional technical cooperation project for Arasia region. The project aims at producing for the first time a database of particulate matter (PM) elemental concentrations in the region that will help in future air quality studies in order to identify commonalities and differences in the presence and contribution of fingerprint pollution sources among the Arasia Member States. The first regional campaign was launched simultaneously in Lebanon, Iraq, Jordan, Syria and United Arab Emirates, using a harmonized sampling and analysis protocol of PM 10 and PM 2.5 samples. Different samples, collected between October 2014 and February 2015, from the participating countries, were analyzed by PIXE technique and gravimetric measurements were also carried out. The first results of the study will be discussed in a regional perspective. Our study shows that concentrations of fine aerosol fractions are often exceeding the WHO standard values as well as showing some disparities in the obtained values between the different sampling sites. However, some trend similarities of variations with time could also be observed, suggesting a common influence by trans-boundary or external sources of air pollution.

In this study, we analyzed the concentrations of accumulation and coarse modes measured during November 2013–July 2017 at an urban background site in Amman, Jordan. The concentrations showed distinct seasonal variations with high concentrations with a monthly average higher than 100 cm−3 and 1.5 cm−3, respectively, for accumulation and coarse modes during the winter and low concentrations with a monthly average less than 40 cm−3 and 1–1.5 cm−3, respectively, for accumulation and coarse modes during the summer. Sand and dust storms (SDS) affected the coarse mode during the early spring whereas local dust re-suspension affected them during the autumn. The gravimetric analysis confirmed the seasonal variation of the calculated particulate mass concentration but suggested that the assumption of spherical particles and unit density is not always proper. The ATR-FTIR analysis of selected filters revealed that aerosols in the background atmosphere of Amman are a mixture of locally emitted (fossil fuel combustion) and local/regional dust. Based on the 24-h average of the calculated PM10, the pollution standard index (PSI) revealed that about 81% of the days were either good or moderate air quality conditions. About 71% of the days were below the 24-h PM10 limit value according to the Jordanian air quality standards (120 μg m−3).

Air ion concentrations influence new particle formation and consequently the global aerosol as potential cloud condensation nuclei. We aimed to evaluate air ion concentrations and characteristics of new particle formation events (NPF) in the megacity of Paris, France, within the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric Pollution and climate effects, and Integrated tools for assessment and mitigation) project. We measured air ion number size distributions (0.8-42 nm) with an air ion spectrometer and fine particle number concentrations (> 6 nm) with a twin differential mobility particle sizer in an urban site of Paris between 26 June 2009 and 4 October 2010. Air ions were size classified as small (0.8-2 nm), intermediate (2-7 nm), and large (7-20 nm). The median concentrations of small and large ions were 670 and 680 cm-3, respectively, (sum of positive and negative polarities), whereas the median concentration of intermediate ions was only 20 cm-3, as these ions were mostly present during new particle formation bursts, i.e. when gas-to-particle conversion produced fresh aerosol particles from gas phase precursors. During peaks in traffic-related particle number, the concentrations of small and intermediate ions decreased, whereas the concentrations of large ions increased. Seasonal variations affected the ion population differently, with respect to their size and polarity. NPF was observed in 13 % of the days, being most frequent in spring and late summer (April, May, July, and August). The results also suggest that NPF was favoured on the weekends in comparison to workdays, likely due to the lower levels of condensation sinks in the mornings of weekends (CS weekdays 09:00: 18 × 10-3 s-1; CS weekend 09:00: 8 × 10-3 s-1). The median growth rates (GR) of ions during the NPF events varied between 3 and 7 nm h-1, increasing with the ion size and being higher on workdays than on weekends for intermediate and large ions. The median GR of small ions on the other hand were rather similar on workdays and weekends. In general, NPF bursts changed the diurnal cycle of particle number as well as intermediate and large ions by causing an extra peak between 09:00 and 14:00. On average, during the NPF bursts the concentrations of intermediate ions were 8.5-10 times higher than on NPF non-event days, depending on the polarity, and the concentrations of large ions and particles were 1.5-1.8 and 1.2 times higher, respectively. Because the median concentrations of intermediate ions were considerably higher on NPF event days in comparison to NPF non-event days, the results indicate that intermediate ion concentrations could be used as an indication for NPF in Paris. The results suggest that NPF was a source of ions and aerosol particles in Paris and therefore contributed to both air quality degradation and climatic effects, especially in the spring and summer.

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.

In this study we present the particle number size distribution (diameter 0.3–10 µm with 1-minute time resolution) inside four offices (naturally ventilated) inside two university buildings. Each office had a typical environment in terms of occupancy and furniture. We focused on the differences between workdays and weekends in terms of particle number (PN) and particle mass (PM, assuming spherical particles with unit density) concentrations. Moreover, we illustrated the effect of workers’ activity (occupancy, smoking, etc.). We also applied a simple indoor aerosol model to estimate the fate (gravitational settling and exfiltration) and source strength of aerosol particles within the measured particle size range. During workdays, the highest measured 24-hour average PM10–1 in the occupied office was 41.5 µg m–3 (PN10–1 = 2.2 cm–3) compared to 9.0 µg m–3 (PN10–1 = 1.2 cm–3) in the unoccupied offices. The ventilation rate of the offices that were opposite to each other was about 0.15 h–1 whereas it was 0.28–0.38 h–1 for the other offices, which were a bit distant from each other. The gravitational settling analysis suggested that a suitable particle density (ρp) could be ~1.7 g cm–3 with a shape factor χ ~1.57, which is similar to mineral dust particles. The gravitational settling rate of particles around 2 µm in diameter was about 0.3 h–1. The source strength of indoor dust particles was higher in the occupied and carpeted offices (re-suspension emission rate as high as 235 µg m–3 h–1) in comparison to unoccupied and uncarpeted offices (75 µg m–3 h–1). This study provided us with an insight about the effect of occupancy and carpet use on the dynamic behavior (fate and re-suspension) of dust particles inside university office buildings located in semi-arid regions.

Air pollution research and reports have been limited in the Middle East, especially in Jordan with respect to aerosol particle number concentrations. In this study, we utilized a simple "mobile setup" to measure, for the first time, the spatial variation of aerosol concentrations in Eastern Mediterranean. The mobile setup consisted of portable aerosol instruments to measure particle number concentrations (cut off sizes 0.01, 0.02, 0.3, 0.5, 1, 2.5, 5, and 10 mu m), particle mass concentrations (PM1, PM2.5, and PM10), and black carbon concentration all situated on the back seat of a sedan car. The car was driven with open windows to ensure sufficient cabin air ventilation for reliable outdoor aerosol sampling. Although the measurement campaign was two days long, but it provided preliminary information about aerosols concentrations over a large spatial scale that covered more than three quarters of Jordan. We should keep in mind that the presented concentrations reflect on road conditions. The submicron particle concentrations were the highest in the urban locations (e.g., Amman and Zarqa) and inside cities with heavy duty vehicles activities (e.g., Azraq). The highest micron particle concentrations were observed in the southern part of the country and in places close to the desert area (e.g., Wadi Rum and Wadi Araba). The average submicron concentration was 4.9 x 10(3)-120 x 10(3) cm-3 (5.7-86.7 mu g m(-3)) whereas the average micron particle concentration was 1-11 cm(-3) (8-150 mu g m(-3), assume rho(p) = 1 g cm(-3)). The main road passing through Jafr in the eastern part of Jordan exhibited submicron concentration as low as 800 cm(-3). The PM10 concentration consisted of about 40-75% as PM1. The black carbon (BC) concentration variation was in good agreement with the PM1 as well as the submicron particle number concentration.

Summarization: Indoor/outdoor aerosol size distribution was measured in four European cities (Oslo–Norway, Prague–Czech Republic, Milan–Italy and Athens–Greece) during 2002 in order to examine the differences in the characteristics of the indoor/outdoor modal structure and to evaluate the effect of indoor sources to the aerosol size distributions. All the measurement sites were naturally ventilated and were occupied during the campaigns by permanent residents or for certain time periods by the technical staff responsible for the instrumentation. Outdoor particle number (PN) concentrations presented the higher values in Milan and Athens (median values 1.4 × 104 # cm–3 and 2.9 × 104 # cm–3 respectively) as a result of elevated outdoor emissions and led to correspondingly higher indoor values compared to Oslo and Prague. In absence of indoor activities, the indoor concentrations followed the fluctuations of the outdoor concentrations in all the measurement sites. Indoor activities (cooking, smoking, etc.) resulted in elevated indoor PN concentrations (maximum values ranging between 1.7 × 105 # cm–3 and 3.2 × 105 # cm–3) and to I/O ratios higher than one. The I/O ratios were size dependant and for periods without indoor activities, they presented the lowest values for particles < 50 nm (0.51 ± 0.15) and the ratios increased with fine particle size (0.79 ± 0.12 for particles between 100–200 nm). The analysis of the modal structure showed that the indoor aerosol size distribution characteristics differ from the outdoors under the effect of indoor sources. The percentage of unimodal size distributions increased during indoor emissions, compared to periods without indoor sources, along with the number concentration of Aitken mode particles, indicating emissions in specific size ranges according to the type of the indoor source. Presented on: Aerosol and air quality research

Air pollution has been recognised as one of the major risk factors for the global burden of disease. In modern society the majority of the exposure occurs indoors where people spend most of their time. Indoor air quality may be improved with portable air cleaners utilizing various cleaning techniques, such as filtration, electrostatic precipitation, and ionization. The objective of this study was to quantify air cleaner particle removal by particle size resolved clean air delivery rates (CADR). This was obtained by utilizing particle concentration measurements and indoor aerosol modeling. Our test protocol was applied to five air cleaners designed for household and office use. For particles with diameters above 100 nm and at the chosen settings, the CADR was around 40 m3/h for an ion generator, around 70 m3/h for an electrostatic precipitator, and ranging from 100 to almost 300 m3/h for the three filter-based air cleaners. Similar performances were obtained for ultrafine particles, except for the ion gene...

We investigated the temporal variation of PM and aerosol particle number concentration (TC, D_p 0.25-32 µm) during year 2012 in Jeddah city. We focused on the daily patterns, wind sector analysis, and the effect of ambient conditions. The daily median values of the PM_(10) rarely exceeded 200 µg/m^3. The PM_(2.5) and PM_1 concentrations showed similar temporal variation with fraction of 39.5% and 19.3% of the PM_(10), respectively. The daily median values of the TC were generally below 500 cm^(-3) but showed three distinguished peaks (as high as 950 cm^(-3)) occurred during late September-early November, which was during the time of the Hajj season. These peaks were also observable in the PM_(2.5) and PM_1. The PM_(10) daily pattern on workdays and Thursdays were similar with a pronounced peak as high as 90 µg/m^3 during the morning time. The PM_(2.5) and PM_1 daily patterns were also similar to those of the PM_(10), especially on Thursdays and workdays, but with lower concentrations. The TC daily pattern was almost the same on all days showing high concentrations (between 150 and 200 cm^(-3)) during the first half of the day. The daily patterns of the TC were similar to those of the PM_1, especially on Workdays and Fridays. The emissions from the industrial city (located in the south of Jeddah) are the main source of PM in Jeddah. During the sea breeze that occurred in the afternoon accompanied low concentrations of PM and TC concentrations. The PM concentrations showed the famous U-shape with respect to the wind speed, whereas the TC was around 150 cm^(-3) when the wind speed was over 3 m/s. In general, the TC had a different behaviour with respect to the other ambient conditions than that of the PM concentrations, especially PM_(10).

Characterization of urban particle number size distribution (PNSD) has been rarely reported/performed in the Middle East. Therefore, we aimed at characterizing the PNSD (0.01&ndash, 10 &micro, m) in Amman as an example for an urban Middle Eastern environment. The daily mean submicron particle number concentration (PNSub) was 6.5 &times, 103&ndash, 7.7 &times, 104 cm&minus, 3 and the monthly mean coarse mode particle number concentration (PNCoarse) was 0.9&ndash, 3.8 cm&minus, 3 and both had distinguished seasonal variation. The PNSub also had a clear diurnal and weekly cycle with higher concentrations on workdays (Sunday&ndash, Thursday, over 3.3 &times, 3) than on weekends (below 2.7 &times, 3). The PNSub constitute of 93% ultrafine fraction (diameter &lt, 100 nm). The mean particle number size distributions was characterized with four well-separated submicron modes (Dpg,I, Ni): nucleation (22 nm, 9.4 &times, 103 cm&minus, 3), Aitken (62 nm, 3.9 &times, 3), accumulation (225 nm, 158 cm&minus, 3), and coarse (2.23 &micro, m, 1.2 cm&minus, 3) in addition to a mode with small geometric mean diameter (GMD) that represented the early stage of new particle formation (NPF) events. The wind speed and temperature had major impacts on the concentrations. The PNCoarse had a U-shape with respect to wind speed and PNSub decreased with wind speed. The effect of temperature and relative humidity was complex and require further investigations.

We developed a simple model to calculate the regional deposited dose of submicron aerosol particles in the respiratory system. This model incorporates measured outdoor and modeled indoor particle number size distributions, detailed activity patterns of three age groups (teens, adults, and the elderly), semi-empirical estimation of the regional deposition fraction, hygroscopic properties of urban aerosols, and reported breathing minute volumes. We calculated the total and regional deposited dose based on three concentration metrics: particle number (PN), mass (PM), and surface area (PSA). The 24-h total deposited dose of fine particles in adult males was around 40 μg (57×109 particles, 8×102 mm(2)) and 41 μg (40×109 particles, 8×102 mm(2)) on workdays and weekends, respectively. The total and regional 24-h deposited dose based on any of the metrics was at most 1.5 times higher in males than in females. The deposited dose values in the other age groups were slightly different than in adults. Regardless of the particle size fraction or the deposited dose metric, the pulmonary/alveolar region received the largest fraction of the deposited dose. These values represent the lowest estimate of the deposited dose and they are expected to be higher in real-life conditions after considering indoor sources of aerosol particles and spatial variability of outdoor aerosols. This model can be extended to youngsters (

Three years of aerosol particle number concentrations (PNCs), size distributions and vertical particle fluxes measured at the semi-urban SMEAR III station in Helsinki, Finland, were studied. The purpose is to study the local emission sources and their effect on particle concentrations and size distributions. By means of cluster analysis, six representative size distributions were identified. Their occurrence together with particle concentrations and fluxes were found to vary significantly with wind direction. Lower particle concentrations and fluxes were measured downwind from vegetated and residential areas compared to directions where the measurement site is downwind from roads passing near the measurement site. For these directions, contributions of the local sources on the measured particle concentrations and size distributions were evident. In particular, size distributions with a mode in the size range 2040 nm were found to be more affected by local traffic emissions, whereas the mode shifted towards larger sizes when contribution from distant sources was more evident. Using flux footprint functions, mixed vehicle fleet emission factors (EFs) were derived from the particle flux measurements. EFs of 6.03(±0.19)∙10 14 # Veh -1 km -1 and 3.65(±0.12) ∙10 14 # Veh -1 km -1 were estimated for cold (October to March) and warm (April to September) periods, respectively. Emission factors increased with decreasing air temperature ( T ) following a linear relationship EF = -0.20∙10 14 # Veh -1 km -1 °C -1 T + 6.98∙10 14 # Veh -1 km -1 (RMSE = 3.7∙10 14 # Veh -1 km -1 ). Keywords: particle number size distribution, eddy covariance, particle fluxes, vehicle emission factor (Published: 28 June 2013 Citation: Tellus B 2013, 65, 19786, http://dx.doi.org/10.3402/tellusb.v65i0.19786

Since decades, indoor aerosol models have been introduced to understand the behaviour of indoor aerosols. However, studies about model validation in multi-zone form are very rare because of the lack of high quality and well-controlled measurements. We utilized state-of-the-art measurement and modelling approaches to validate the Multi-Compartment and Size-resolved Indoor Aerosol Model (MC-SIAM) inside a two-zone apartment with natural ventilation. According to the MC-SIAM simulations, the ventilation rates ranged from 0.06 to 0.31 h–1 during closed windows and it was as high as 2.1 h–1 when a window was open; compared to the tracer gases analysis results, the ventilation rate was as high as 0.26 h–1 (closed windows) and 1.7 h–1 (open window). The internal airflow predicted with the MC-SIAM ranged from 9.3 to 11 m–3 h (tracer gas analysis 7.6–15 m–3 h) when the door between the internal rooms was opened. The methods utilized in this study have proven that indoor aerosol models such as the MC-SIAM are valid to describe the behaviour of indoor aerosol particles inside multi-zone dwellings with the assumption of well-mixed indoor air inside each zone. The next step in indoor aerosol models development should include re-suspension and new particle formation processes.

The number size distributions of aerosol particles were measured using a scanning mobility particle sizer (SMPS) at a mid-latitude forest in Japan during 20–30 August 2010. Four days during the observation period experienced new particle formation (NPF) under the conditions of low condensation and coagulation sinks. The formation rate of new particles was calculated to be in the range between 0.2 and 1.0 cm −3 s −1 for the NPF events. The growth rates of the newly formed mode of aerosol particles ranged between 5.0 and 15.7 nm h −1 . The backward air mass trajectories revealed that the NPF occurred in clean maritime air masses originated from the North Pacific, which is characterized with the low mass concentrations of aerosol components. The results from the classification analysis of backward air mass trajectories indicate that the maritime air mass conditions are frequent at this forest site and are primarily in summer season. Large increases in the number concentrations of accumulation mode particles (above 90 nm) were followed by the increased precipitation rates in the afternoon hours on the NPF event days. Therefore, the newly-formed particles would be involved in the convective cloud formation and precipitation over the studied region.

People are exposed to polycyclic aromatic hydrocarbons (PAHs) outdoors and indoors. Although there is a fair amount of literature review concerning exposure to settled dust, and in particular, to PAHs indoors, no attempts have been made to report contamination in household settled floor dust in Jordan. In this study we aimed at identifying the source origin of the PAHs as indoors or outdoors inside eight selected dwellings in Amman, Jordan. We also aimed at investigating the spatial variation of the analyzed PAHs concentrations within Amman. The floor dust samples were collected from the entrance and living room areas. The total PAHs concentrations at the living room area ranged from 65422 ng/g to about 641 ng/g. At the entrance area, the highest total PAHs concentration was about 9266 ng/g and the lowest was about 241 ng/g. The differences among dwellings for the total and individual PAHs concentrations confirms that each dwelling has its own environmental conditions and we cannot make a general conclusion with respect to the source origin as indoors or outdoors. The spatial variation of the PAHs concentrations showed that the north-eastern part of Amman had lower PAHs concentrations than that observed in the south-western part. This agrees well with a previous study about the spatial variation of fine aerosol particle number concentrations measured within the city during the same period by Hussein et al. who reported that fine particle number concentrations in the north eastern part of the city is lower than that in the south western part.

Dry deposition is a primary mechanism by which suspended particles are transported from gas onto surfaces. Prediction of this transport rate is needed in a vast range of applications, including environmental, industrial, and engineering, and in studying the impacts of aerosols. Besides air flow characteristics and properties of aerosol particles, the dry deposition velocity depends greatly on surface properties. However, existing models describe rough surfaces with only one parameter, the surface roughness height, and are therefore of limited accuracy. Here, we introduce a new, and yet simple, physical approach to account for the influence of surface roughness on the dry deposition velocity. The approach relies on a hybrid parameter that combines the surface roughness height and the peak-to-peak distance between roughness elements. Our new approach is able to predict the deposition velocity accurately, being superior to many of the earlier models, which overpredict deposition velocities by a factor as hig...

Number concentrations of atmospheric aerosol particles were measured by a flow-switching type differential mobility particle sizer in an electrical mobility diameter range of 6–1000 nm in 30 channels near central Budapest with a time resolution of 10 min continuously from 3 November 2008 to 2 November 2009. Daily median number concentrations of particles varied from 3.8 × 103 to 29 ×103 cm−3 with a yearly median of 11.8 × 103 cm−3. Contribution of ultrafine particles to the total particle number ranged from 58 to 92% with a mean ratio and standard deviation of (79 ± 6)%. Typical diurnal variation of the particle number concentration was related to the major emission patterns in cities, new particle formation, sinks of particles and meteorology. Shapes of the monthly mean number size distributions were similar to each other. Overall mean for the number median mobility diameter of the Aitken and accumulation modes were 26 and 93 nm, respectively, which are substantially smaller than for rural or background environments. The Aitken and accumulation modes contributed similarly to the total particle number concentrations at the actual measurement location. New particle formation and growth unambiguously occurred on 83 days, which represent 27% of all relevant days. Hence, new particle formation and growth are not rare phenomena in Budapest. Their frequency showed an apparent seasonal variation with a minimum of 7.3% in winter and a maximum of 44% in spring. New particle formation events were linked to increased gas-phase H2SO4 concentrations. In the studied area, new particle formation is mainly affected by condensation sink and solar radiation. The formation process seems to be not sensitive to SO2, which was present in a yearly median concentration of 6.7 μg m−3. This suggests that the precursor gas was always available in excess. Formation rate of particles with a diameter of 6 nm varied between 1.65 and 12.5 cm−3 s−1 with a mean and standard deviation of (4.2 ± 2.5) cm−3 s−1. Seasonal dependency for the formation rate could not be identified. Growth curves of nucleated particles were usually superimposed on the characteristic diurnal pattern of road traffic direct emissions. The growth rate of the nucleation mode with a median diameter of 6 nm varied from 2.0 to 13.3 nm h−1 with a mean and standard deviation of (7.7 ± 2.4) nm h−1. There was an indicative tendency for larger growth rates in summer and for smaller values in winter. New particle formation events increased the total number concentration by a mean factor and standard deviation of 2.3 ± 1.1 relative to the concentration that occurred immediately before the event. Several indirect evidences suggest that the new particle formation events occurred at least over the whole city, and were of regional type. The results and conclusions presented are the first information of this kind for the region over one-year long time period.

In this paper, we examine approaches to estimate a Bayesian mixture model at both single and multiple time points for a sample of actual and simulated aerosol particle size distribution (PSD) data. For estimation of a mixture model at a single time point, we use Reversible Jump Markov Chain Monte Carlo (RJMCMC) to estimate mixture model parameters including the number of components which is assumed to be unknown. We compare the results of this approach to a commonly used estimation method in the aerosol physics literature. As PSD data is often measured over time, often at small time intervals, we also examine the use of an informative prior for estimation of the mixture parameters which takes into account the correlated nature of the parameters. The Bayesian mixture model offers a promising approach, providing advantages both in estimation and inference.

We measured the submicron particle number concentrations in the urban/suburban atmosphere of Amman-Jordan during the spring of 2009. The main objective was to distinguish the differences in the submicron particle number concentrations with/without dust episodes. In the absence of dust episodes the concentrations showed distinguished daily patterns, which were similar at both the urban and the urban atmosphere with lower concentrations (at least 1:2) at the suburban site. The daily pattern during the first five working days (Saturday-Wednesday) was different than that that on either Thursday or Friday. During the morning rush hours the number concentrations were as high as 120×10^3 and 75×10^3 1/cm^3 at the urban and suburban sites during those workdays, respectively. These concentrations were about 21 and 14 times what was observed during the background conditions (5.5×10^3 1/cm^3 between midnight and early morning) at both sites. This suggests that traffic emissions are one of the main sources in the urban/suburban atmosphere of Amman. The number concentration of submicron aerosol particles, which originated from the nearby highway, at the urban site decreased exponentially with the wind speed. During a dust episode the total number concentration of submicron particles was about 1/5 of what is typically observed during workdays without dust episodes. The lower concentrations were attributed here for two reasons: increased wind speed and coagulation of locally emitted urban particles with the regional dust particles. These observations in the absence of dust episodes agree well with other studies for highly populated cities. The limitation of this study is the lack of information about the particle number size distribution that can reveal the modal structure of aerosol particles in Amman.

Calibration, or in other words ”validation”, of complex indoor aerosol models that simulate the dynamic behavior of particle number size distributions are often assumed to solely depend on the characteristics of the model and its setup. The user influence is rarely mentioned in that regard. This paper shows, with a simple exercise, the user influence on the calibration of an indoor aerosol model. It is also shown that a reasonable model simulation was achieved with a different understanding of the system modeled and several input parameter values. We utilized a single compartment and size-resolved indoor aerosol model approach to be calibrated against a model room. This kind of simple indoor aerosol models is very common in the literature and widely used in the analysis of indoor-to-outdoor relationship of aerosol particles. The input parameters for such indoor aerosol models are: outdoor particle number size distributions, indoor domain geometries, ventilation rate, penetration factor, and friction velocity (or deposition rate onto indoor surfaces). For simplicity, we considered the penetration factor and friction velocity are the only unknown input parameters to be chosen freely by the user so that the model is calibrated. We made it clear by this study that a user can influence the input parameter values significantly. Even though this suggests different sets of input parameter values can be valid for a model calibration, the model simulation differences between different calibration results remained within 1%. This implies that it is more challenging to calibrate a complex indoor aerosol model that requires many input parameters.

Very few real-world measurements of road dust suspension have been performed to date. This study compares two different techniques (referred to as Sniffer and Emma) to measure road dust emissions. The main differences between the systems are the construction of the inlet, different instruments for recording particulate matter (PM) levels, and different loads on the wheel axes (the weight of Sniffer was much higher than that of Emma). Both systems showed substantial small-scale variations of emission levels along the road, likely depending on-road surface conditions. The variations observed correlated quite well, and the discrepancies are likely a result of variations in dust load on the road surface perpendicular to the driving direction that cause variations in the measurements depending on slightly different paths driven by the two vehicles. Both systems showed a substantial influence on the emission levels depending on the type of tire used. The summer tire showed much lower suspension than the winter tires (one nonstudded and one studded). However, the relative importance of the nonstudded versus studded tire was rather different. For the ratio of studded/nonstudded, Emma shows higher values on all road sections compared with Sniffer. Both techniques showed increased emission levels with increasing vehicle speed. When the speed increased from 50 to 80 km hr(-1), the relative concentrations increased by 30-170% depending on the tire type and dust load. However, for road sections that were very dirty, Sniffer showed a much higher relative increase in the emission level with the nonstudded tire. Sniffer's absolute concentrations were mostly higher than Emma's. Possible reasons for the differences are discussed in the paper. Both systems can be used for studying relative road dust emissions and for designing air quality management strategies.

In this study, we present how an indoor aerosol model can be used to characterize particle emitter and predict influence of the source on indoor air quality. Particle size-resolved emission rates were quantified and the source’s influence on indoor air quality was estimated by using office model simulations. We measured particle emissions from three modern laser printers in a flow-through chamber. Measured parameters were used as input parameters for an indoor aerosol model, which we then used to quantify the particle emission rates. The same indoor aerosol model was used to simulate the effect of the particle emission source inside an office model. The office model consists of a mechanically ventilated empty room and the particle source. The aerosol from the ventilation air was a filtered urban background aerosol. The effect of the ventilation rate was studied using three different ventilation ratios 1, 2 and 3 h−1. According to the model, peak emission rates of the printers exceeded 7.0 × 108 s−1 (2.5 × 1012 h−1), and emitted mainly ultrafine particles (diameter less than 100 nm). The office model simulation results indicate that a print job increases ultrafine particle concentration to a maximum of 2.6 × 105 cm−3. Printer-emitted particles increased 6-h averaged particle concentration over eleven times compared to the background particle concentration.

We investigated the deposition rate of aerosol particles (diameter between 0.03 and 5 μm) on rough surfaces of wallpapers, wall-plasters, and two types of carpets inside a test chamber. Compared to a smooth aluminum surface, the deposition rate of aerosol particles on the tested surfaces was up to 20 times depending on the surface roughness, mixing intensity, and particle size. A rough surface with a dimensionless surface roughness height k+ 1 μm) when k+

We investigated the time span and spatial scale of regional new particle formation (NPF) events in Finland and Southern Sweden using measured particle number size distributions at five background stations. We define the time span of a NPF event as the time period from the first moment when the newly formed mode of aerosol particles is observable below 25 nm until the newly formed mode is not any more distinguishable from other background modes of aerosol particles after growing to bigger sizes. We identify the spatial scale of regional NPF events based on two independent approaches. The first approach is based on the observation within a network of stationary measurement stations and the second approach is based on the time span and the history of air masses back-trajectories. According to the second approach, about 60% and 28% of the events can be traced to distances longer than 220 km upwind from where the events were observed in Southern Finland (Hyytiälä) and Northern Finland (Värriö), respectively. The analysis also showed that the observed regional NPF events started over the continents but not over the Atlantic Ocean. The first approach showed that although large spatial scale NPF events are frequently observed at several locations simultaneously, they are rarely identical (similar characteristics and temporal variations) due to differences in the initial meteorological and geographical conditions between the stations. The growth of the newly formed particles during large spatial scale events can be followed for more than 30 h where the newly formed aerosol particles end up in the Aitken mode (diameter 25–100 nm) and accumulation mode size ranges (diameter 0.1–1 μm). This study showed clear evidence that regional NPF events can pose a significant source for accumulation mode particles over the Scandinavian continent provided that these findings can be generalized to many of the air masses traveling over the European continent.

Because aerosol particle deposition is an important factor in indoor air quality, many empirical and theoretical studies have attempted to understand the process. In this study, we estimated the deposition rate of aerosol particles on smooth aluminum surfaces inside a test chamber. We investigated the influence of turbulent intensity due to ventilation and fan operation. We also investigated two important processes in particle deposition: turbophoresis, which is significant for micron particles, and coagulation, which is relevant to ultrafine particles (UFP diameter

In this study, we developed two methods to distinguish the long-range transport (LRT) episodes from local pollution (LP) episodes. The first method is based on particle number concentrations ratio between accumulation mode (diameter > 90nm) and Aitken mode (diameter 25-90 nm). The second method is based on a proxy variable (interpolated ion sum) for long-range transported PM 2.5 The ion-sum is available from the measurements of sulphate, nitrate and ammonium at the nearest EMEP stations. We also utilised synoptic meteorological weather charts, locally measured meteorological data, and air mass back-trajectories to support the evaluation of these methods. We selected nine time periods (i.e. episodes) with daily average PM 10 >50 μg m -3 in the Helsinki Metropolitan Area during year 2002. We characterized the episodes in terms of PM 10 and PM 2.5 concentrations and the fraction of fine particles in PM 10 at an urban traffic and regional background air quality monitoring sites. Three of these episodes were clearly of local origin. They were characterized by a low average fraction of PM 2.5 (

A large fraction of urban PM 10 concentrations is due to non-exhaust traffic emissions. In this paper, a mobile measurement system has been used to quantify the relative importance of road particle emission and suspension of accumulated dust versus direct pavement wear, tire type (studded, friction, and summer), pavement type, and vehicle speed. Measurements were performed during May–September on selected roads with different pavements and traffic conditions in the Stockholm region. The highest particle mass concentrations were always observed behind the studded tire and the lowest were behind the summer tire; studded-to-summer ratios were 4.4–17.3 and studded-to-friction ratios were 2.0–6.4. This indicates that studded tires lead to higher emissions than friction and summer tires regardless to the asphalt type. By comparing with measurements in a road simulator, it could be estimated that the pavement wear due to the friction tires was 0.018–0.068 of the suspension of accumulated road dust. Likewise for studded tires road-wear was estimated to be 1.2–4.8 the suspension of accumulated dust. This indicates that wear due to friction tires is very small compared to the suspension of accumulated dust and that suspension due to studded tires may sometimes be as large as the wear of the road. But this will vary depending on, e.g. the amount of dust accumulated on the roads. An important dependence on vehicle speed was also observed. During May, the particle mass concentrations behind the studded tire at vehicle speed 100 km h −1 were about 10 times higher than that at 20 km h −1 . The speed dependence was not so pronounced in September, which could be due to less accumulated dust on the roads. The particle number size distribution of the emissions due to road wear by studded tire was characterized by a clear increase in number concentrations of the coarse fraction of aerosol particles, with a geometric mean diameter between 3 and 5 μm. The size distribution of the emissions due to the summer tire was very similar with smaller concentrations. An important limitation with the measurements presented is that they were made by using a van, which is bigger than regular cars and has bigger tires. Thus, road wear and dust suspension due to cars are expected to be different.

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.

A field measurement campaign was conducted near a major road "Itäväylä" in an urban area in Helsinki in 17–20 February 2003. Aerosol measurements were conducted using a mobile laboratory "Sniffer" at various distances from the road, and at an urban background location. Measurements included particle size distribution in the size range of 7 nm–10 μm (aerodynamic diameter) by the Electrical Low Pressure Impactor (ELPI) and in the size range of 3–50 nm (mobility diameter) by Scanning Mobility Particle Sizer (SMPS), total number concentration of particles larger than 3 nm detected by an ultrafine condensation particle counter (UCPC), temperature, relative humidity, wind speed and direction, driving route of the mobile laboratory, and traffic density on the studied road. In this study, we have compared measured concentration data with the predictions of the road network dispersion model CAR-FMI used in combination with an aerosol process model MONO32. For model comparison purposes, one of the cases was additionally computed using the aerosol process model UHMA, combined with the CAR-FMI model. The vehicular exhaust emissions, and atmospheric dispersion and transformation of fine and ultrafine particles was evaluated within the distance scale of 200 m (corresponding to a time scale of a couple of minutes). We computed the temporal evolution of the number concentrations, size distributions and chemical compositions of various particle size classes. The atmospheric dilution rate of particles is obtained from the roadside dispersion model CAR-FMI. Considering the evolution of total number concentration, dilution was shown to be the most important process. The influence of coagulation and condensation on the number concentrations of particle size modes was found to be negligible on this distance scale. Condensation was found to affect the evolution of particle diameter in the two smallest particle modes. The assumed value of the concentration of condensable organic vapour of 1012 molecules cm−3 was shown to be in a disagreement with the measured particle size evolution, while the modelling runs with the concentration of condensable organic vapour of 109–1010 molecules cm−3 resulted in particle sizes that were closest to the measured values.

This study presents an evaluation and modeling exercise of the size fractionated aerosol particle number concentrations measured nearby a major road in Helsinki during 23 August–19 September 2003 and 14 January–11 February 2004. The available information also included electronic traffic counts, on-site meteorological measurements, and urban background particle number size distribution measurement. The ultrafine particle (UFP, diameter

The properties of atmospheric aerosol particles in Marseille and Athens were investigated. The studies were performed in Marseille, France, during July 2002 and in Athens, Greece, during June 2003. The aerosol size distribution and the formation and growth rates of newly formed particles were characterized using Differential Mobility Particle Sizers. Hygroscopic properties were observed using a Hygroscopic Tandem Differential Mobility Analyzer setup. During both campaigns, the observations were performed at suburban, almost rural sites, and the sites can be considered to show general regional background behavior depending on the wind direction. At both sites there were clear pattern for both aerosol number concentration and hygroscopic properties. Nucleation mode number concentration increased during the morning hours indicating new particle formation, which was observed during more than 30% of the days. The observed formation rate was typically more than 1 cm−3 s−1, and the growth rate was between 1.2–9.9 nm h−1. Based on hygroscopicity measurements in Athens, the nucleation mode size increase was due to condensation of both water insoluble and water soluble material. However, during a period of less anthropogenic influence, the growth was to a larger extent due to water insoluble components. When urban pollution was more pronounced, growth due to condensation of water soluble material dominated.

The influence of traffic on urban air quality is highest at low wind speeds and the presence of a temperature inversion. By relying on detailed aerosol measurements conducted simultaneously at two distances close to a major road, we studied one such episode encountered in Helsinki, Finland, during the wintertime. The observed episode was characterized by exceptionally weak dilution of traffic emissions, with particle number concentration decreasing by no more than 10–30% between 9 and 65 m distances from the road. During the nighttime with relatively minor traffic flow, dilution and particle growth by vapor condensation were found to be the dominant processes in this road-to-ambient evolution stage. The latter process shifted a significant fraction of nucleation mode particles to sizes >30 nm diameter, modifying thereby the shape of the particle number size distribution. During the rush hours in the morning, particle number concentrations were elevated by approximately an order of magnitude compared with nighttime, such that also the self-coagulation of nucleation mode particles became important. Our study demonstrates that under suitable meteorological conditions (low wind speeds coupled with temperature inversions), traffic emissions are able to affect submicron particle number concentrations over large areas around major roads and may be a dominant source of ultrafine particles in the urban atmosphere. Under conditions characterized by exceptionally slow mixing, simultaneous processing of ultrafine (nucleation and Aitken mode) particles by dilution, self- and inter-modal coagulation, as well as by condensation and evaporation seriously questions the applicability of particle number emission factors, derived from the measurements at few tens of meters from the roadside.

This study evaluates the influence of aerosol processes on the particle number (PN) concentrations in three major European cities on the temporal scale of 1 h, i.e., on the neighborhood and city scales. We have used selected measured data of particle size distributions from previous campaigns in the cities of Helsinki, Oslo and Rotterdam. The aerosol transformation processes were evaluated using the aerosol dynamics model MAFOR, combined with a simplified treatment of roadside and urban atmospheric dispersion. We have compared the model predictions of particle number size distributions with the measured data, and conducted sensitivity analyses regarding the influence of various model input variables. We also present a simplified parameterization for aerosol processes, which is based on the more complex aerosol process computations; this simple model can easily be implemented to both Gaussian and Eulerian urban dispersion models. Aerosol processes considered in this study were (i) the coagulation of particles, (ii) the condensation and evaporation of two organic vapors, and (iii) dry deposition. The chemical transformation of gas-phase compounds was not taken into account. By choosing concentrations and particle size distributions at roadside as starting point of the computations, nucleation of gas-phase vapors from the exhaust has been regarded as post tail-pipe emission, avoiding the need to include nucleation in the process analysis. Dry deposition and coagulation of particles were identified to be the most important aerosol dynamic processes that control the evolution and removal of particles. The error of the contribution from dry deposition to PN losses due to the uncertainty of measured deposition velocities ranges from −76 to +64 %. The removal of nanoparticles by coagulation enhanced considerably when considering the fractal nature of soot aggregates and the combined effect of van der Waals and viscous interactions. The effect of condensation and evaporation of organic vapors emitted by vehicles on particle numbers and on particle size distributions was examined. Under inefficient dispersion conditions, the model predicts that condensational growth contributes to the evolution of PN from roadside to the neighborhood scale. The simplified parameterization of aerosol processes predicts the change in particle number concentrations between roadside and urban background within 10 % of that predicted by the fully size-resolved MAFOR model.

Summarization: Characterization and emission rates of indoor aerosols have been of great interest. However, few studies have presented quantitative determinations of aerosol particle emissions during indoor activities. In the current study we presented and investigated the physical characteristics and size-fractionated emission rates of indoor aerosol particles during different activities in a house (naturally ventilated) located in Prague, Czech Republic. We utilized a multi-compartment and size-resolved indoor aerosol model (MC-SIAM) to investigate the indoor-to-outdoor relationship of aerosol particles and also to estimate their emission rates. When the windows and the main door were closed for several hours and there were minor indoor activities that did not produce significant amounts of aerosol particles, the particle number concentration showed similar levels at different indoor locations. As expected, the natural ventilation did not provide a controlled indoor-to-outdoor relationship of aerosol particles. As previous studies have emphasized, cooking and tobacco smoking activities are major sources indoors; the total particle number concentration was, respectively, as high as 1.8×105 and 3.6×104 cm−3 with emission rates around 380 and 36 cm−3 s−1. During intensive cooking activities the outdoor aerosol particle concentrations were also affected even though windows were closed. It seems that a simple model is not able to describe the fate of indoor aerosols within a multi-compartment construction; instead, a numerical and dynamic model with a multi-compartment approach is needed. Based on the indoor aerosol model simulations, the deposition rate was comparable to previous studies with friction velocity between 10–30 cm s−1 and surface area to volume ratio around 2.9–3.1 m−1. The penetration factor was equivalent to G3 filter standards and the ventilation rate varied between 0.6–1.2 h−1. Based on the emission rate analysis, aerosol particles produced during tobacco smoking and incense stick burning remain airborne for a longer time than cooking particles. It seems that aerosol particles emitted during tobacco smoking and incense stick burning undergo different processes; therefore, there is a need for a combined physical–chemical indoor aerosol model to better describe the evolution of indoor aerosol particles due to different activities. Παρουσιάστηκε στο: Atmospheric Environment

We utilized a long-term data set of aerosol particle number size distributions (8–400 nm) in the urban background air of Helsinki during 1998–2000. We analyzed the number concentrations of both ultra-fine particles (UFP diameter

Traffic particles, total number concentration and size distribution in the range 3 nm–10 μm, as well as concentrations of carbon monoxide and nitrogen oxides were measured by a mobile laboratory at a major highway and in its vicinity, 0–140 m from the road side, in Helsinki, during the summer and winter campaigns in 2003 and 2004. The data have been analysed according to the sampling point and temperature, and classified to three wind sectors; wind blowing perpendicular to the road from northwest (S1) or to the opposite direction (S3), and wind blowing along the road (S2). The average concentrations in winter were 2–3 times higher than the concentrations in summer. In winter, 90–95%, and in summer, 86–90% of particles were smaller than 50 nm. The equations for the concentration curves in sectors S1 and S2 were derived, starting point being at the roadside. When moving 65 m from the roadside, the average concentration reduced to 39% in winter and to 35% in summer in wind sector S1 whilst in sector S2, it already decreased to 19% in summer. The size distributions showed 2–3 modes peaking at 14–23 nm (nucleation mode), 40–50 nm (Aitken mode) and 120–125 nm (accumulation mode). In wind sector S1, in winter, the nucleation mode shifted to larger sizes when moving away from the road.

This study presents an indoor aerosol model based on size-resolved and multi-compartment approach. The current indoor aerosol model is also developed with a semi-empirical technique to estimate the emission rates due to indoor sources of aerosol particles. We present in this study a methodology to predict and estimate the best-fit input parameters for the current indoor aerosol model. The performance of the current indoor aerosol model in its single-compartment form was evaluated against previously measured indoor-outdoor aerosol data sets from an office room with mechanical ventilation and a family house with natural ventilation. The indoor aerosol model simulations show that the current methodology used to predict the best-fit input parameters to the indoor aerosol model is efficient. As expected, the penetration factor, aerosol particle deposition, and ventilation rate are the most important parameters in the indoor-outdoor relationship of aerosol particles transport. The emission rate analysis showed ...