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Lidia Morawska - One of the best experts on this subject based on the ideXlab platform.
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a bayesian spatiotemporal model of panel design data airborne Particle Number Concentration in brisbane australia
Environmetrics, 2019Co-Authors: Farhad Salimi, Mandana Mazaheri, Samuel Clifford, Lidia Morawska, Samantha Lowchoy, Kerrie MengersenAbstract:In environmental monitoring, the ability to obtain high‐quality data across space and time is often limited by the cost of purchasing, deploying and maintaining a large collection of equipment, and the employment of personnel to perform these tasks. An ideal design for a monitoring campaign would be dense enough in time to capture short‐range variation at each site, long enough in time to examine trends at each site and across all sites, and dense enough in space to allow modelling of the relationship between the means at each of the sites. This paper outlines a methodology for semiparametric spatiotemporal modelling of data that is dense in time but sparse in space, obtained from a split panel design, the most feasible approach to covering space and time with limited equipment. The data are hourly averaged Particle Number Concentration (PNC) and were collected as part of the International Laboratory for Air Quality and Health's Ultrafine Particles from Traffic Emissions and Children's Health (UPTECH) project. The panel design comprises two weeks of continuous measurements taken at each of a Number of government primary schools in the Brisbane Metropolitan Area, with each school visited sequentially. The school data are augmented by data from long‐term monitoring stations at three locations in Brisbane, Australia. The temporal part of the model explains daily and weekly cycles in PNC at the schools. The temporal variation is modelled hierarchically with a penalised random walk term common to all sites and a similar term accounting for the remaining temporal trend at each site. The modelling of temporal trends requires an acknowledgement that the observations are correlated rather than independent. At each school and long‐term monitoring site, peaks in PNC can be attributed to the morning and afternoon rush hour traffic and new Particle formation events. The spatial component of the model describes the school‐to‐school variation in mean PNC at each school and within each school ground. The spatial term in the model is derived from a stochastic partial differential equation and approximates a Gaussian process with a Gaussian Markov Random field. Fitting the model helps describe spatial and temporal variability at a subset of the UPTECH schools and the long‐term monitoring sites, which can be used to estimate the exposure of school children to ultrafine Particles. Parameter estimates and their uncertainty are computed in a computationally efficient approximate Bayesian inference environment, R‐INLA.
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determination of the vertical profile of Particle Number Concentration adjacent to a motorway using an unmanned aerial vehicle
Environmental Pollution, 2017Co-Authors: Tommaso Francesco Villa, E R Jayaratne, Luis Felipe Gonzalez, Lidia MorawskaAbstract:A quantitative assessment of the vertical profile of traffic pollution, specifically Particle Number Concentration (PNC), in an open space adjacent to a motorway was possible for the first time, to the knowledge of the authors, using an Unmanned Aerial Vehicle (UAV) system. Until now, traffic pollution has only been measured at ground level while the vertical distribution, is limited to studies conducted from buildings or fixed towers and balloons. This new UAV system demonstrated that the PNC sampled during the period form 10 a.m. to 4 p.m., outside the rush hours with a constant traffic flow, increased from a Concentration of 2 × 104 p/cm3 near the ground up to 10 m, and then sharply decreased attaining a steady value of 4 × 103 p/cm3 beyond a height of about 40 m. While more comprehensive investigations would be warranted under different conditions, such as topography and vehicle and fuel type, this finding is of great significance, given that it demonstrates the impact of traffic emissions on human exposure, but less so to pollution within the upper part of the boundary layer.
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Suppression of Cluster Ions during Rapidly Increasing Particle Number Concentration Events in the Environment
Aerosol and Air Quality Research, 2015Co-Authors: E. Rohan Jayaratne, Xuan Ling, Lidia MorawskaAbstract:We show that the cluster ion Concentration (CIC) in the atmosphere is significantly suppressed during events that involve rapid increases in Particle Number Concentration (PNC). Using a neutral cluster and air ion spectrometer, we investigated changes in CIC during three types of Particle enhancement processes – new Particle formation, a bushfire episode and an intense pyrotechnic display. In all three cases, the total CIC decreased with increasing PNC, with the rate of decrease being greater for negative CIC than positive. We attribute this to the greater mobility, and hence the higher attachment coefficient, of negative ions over positive ions in the air. During the pyrotechnic display, the rapid increase in PNC was sufficient to reduce the CIC of both polarities to zero. At the height of the display, the negative CIC stayed at zero for a full 10 min. Although the PNCs were not significantly different, the CIC during new Particle formation did not decrease as much as during the bushfire episode and the pyrotechnic display. We suggest that the rate of increase of PNC, together with Particle size, also play important roles in suppressing CIC in the atmosphere.
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Spatial Variation of Particle Number Concentration in School Microscale Environments and Its Impact on Exposure Assessment
Environmental science & technology, 2013Co-Authors: Farhad Salimi, Mandana Mazaheri, Samuel Clifford, Leigh R. Crilley, Rusdin Laiman, Lidia MorawskaAbstract:It has not yet been established whether the spatial variation of Particle Number Concentration (PNC) within a microscale environment can have an effect on exposure estimation results. In general, the degree of spatial variation within microscale environments remains unclear, since previous studies have only focused on spatial variation within macroscale environments. The aims of this study were to determine the spatial variation of PNC within microscale school environments, in order to assess the importance of the Number of monitoring sites on exposure estimation. Furthermore, this paper aims to identify which parameters have the largest influence on spatial variation as well as the relationship between those parameters and spatial variation. Air quality measurements were conducted for two consecutive weeks at each of the 25 schools across Brisbane, Australia. PNC was measured at three sites within the grounds of each school, along with the measurement of meteorological and several other air quality param...
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Spatial variation of Particle Number Concentration in school microscale environments and its impact on exposure assessment
2013Co-Authors: Farhad Salimi, Mandana Mazaheri, Samuel Clifford, Leigh R. Crilley, Rusdin Laiman, Lidia MorawskaAbstract:It has not yet been established whether the spatial variation of Particle Number Concentration (PNC) within a microscale environment can have an effect on exposure estimation results. In general, the degree of spatial variation within microscale environments remains unclear, since previous studies have only focused on spatial variation within macroscale environments. The aims of this study were to determine the spatial variation of PNC within microscale school environments, in order to assess the importance of the Number of monitoring sites on exposure estimation. Furthermore, this paper aims to identify which parameters have the largest influence on spatial variation, as well as the relationship between those parameters and spatial variation. Air quality measurements were conducted for two consecutive weeks at each of the 25 schools across Brisbane, Australia. PNC was measured at three sites within the grounds of each school, along with the measurement of meteorological and several other air quality parameters. Traffic density was recorded for the busiest road adjacent to the school. Spatial variation at each school was quantified using coefficient of variation (CV). The portion of CV associated with instrument uncertainty was found to be 0.3 and therefore, CV was corrected so that only non-instrument uncertainty was analysed in the data. The median corrected CV (CVc) ranged from 0 to 0.35 across the schools, with 12 schools found to exhibit spatial variation. The study determined the Number of required monitoring sites at schools with spatial variability and tested the deviation in exposure estimation arising from using only a single site. Nine schools required two measurement sites and three schools required three sites. Overall, the deviation in exposure estimation from using only one monitoring site was as much as one order of magnitude. The study also tested the association of spatial variation with wind speed/direction and traffic density, using partial correlation coefficients to identify sources of variation and non-parametric function estimation to quantify the level of variability. Traffic density and road to school wind direction were found to have a positive effect on CVc, and therefore, also on spatial variation. Wind speed was found to have a decreasing effect on spatial variation when it exceeded a threshold of 1.5 (m/s), while it had no effect below this threshold. Traffic density had a positive effect on spatial variation and its effect increased until it reached a density of 70 vehicles per five minutes, at which point its effect plateaued and did not increase further as a result of increasing traffic density.
Xinming Wang - One of the best experts on this subject based on the ideXlab platform.
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Particle Number Concentration size distribution and chemical composition during haze and photochemical smog episodes in shanghai
Journal of Environmental Sciences-china, 2014Co-Authors: Xuemei Wang, Jianmin Chen, Tiantao Cheng, Renyi Zhang, Xinming WangAbstract:The aerosol Number Concentration and size distribution as well as size-resolved Particle chemical composition were measured during haze and photochemical smog episodes in Shanghai in 2009. The Number of haze days accounted for 43%, of which 30% was severe (visibility<2km) and moderate (2km≤visibility<3km) haze, mainly distributed in winter and spring. The mean Particle Number Concentration was about 17,000/cm(3) in haze, more than 2 times that in clean days. The greatest increase of Particle Number Concentration was in 0.5-1μm and 1-10μm size fractions during haze events, about 17.78 times and 8.78 times those of clean days. The largest increase of Particle Number Concentration was within 50-100nm and 100-200nm fractions during photochemical smog episodes, about 5.89 times and 4.29 times those of clean days. The Particle volume Concentration and surface Concentration in haze, photochemical smog and clean days were 102, 49, 15μm(3)/cm(3) and 949, 649, 206μm(2)/cm(3), respectively. As haze events got more severe, the Number Concentration of Particles smaller than 50nm decreased, but the Particles of 50-200nm and 0.5-1μm increased. The diurnal variation of Particle Number Concentration showed a bimodal pattern in haze days. All soluble ions were increased during haze events, of which NH4(+), SO4(2-) and NO3(-) increased greatly, followed by Na(+), K(+), Ca(2+) and Cl(-). These ions were very different in size-resolved Particles during haze and photochemical smog episodes.
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Particle Number Concentration size distribution and chemical composition during haze and photochemical smog episodes in shanghai
Journal of Environmental Sciences-china, 2014Co-Authors: Xuemei Wang, Jianmin Chen, Tiantao Cheng, Renyi Zhang, Xinming WangAbstract:Abstract The aerosol Number Concentration and size distribution as well as size-resolved Particle chemical composition were measured during haze and photochemical smog episodes in Shanghai in 2009. The Number of haze days accounted for 43%, of which 30% was severe (visibility 3 in haze, more than 2 times that in clean days. The greatest increase of Particle Number Concentration was in 0.5–1 μm and 1–10 μm size fractions during haze events, about 17.78 times and 8.78 times those of clean days. The largest increase of Particle Number Concentration was within 50–100 nm and 100–200 nm fractions during photochemical smog episodes, about 5.89 times and 4.29 times those of clean days. The Particle volume Concentration and surface Concentration in haze, photochemical smog and clean days were 102, 49, 15 μm 3 /cm 3 and 949, 649, 206 μm 2 /cm 3 , respectively. As haze events got more severe, the Number Concentration of Particles smaller than 50 nm decreased, but the Particles of 50–200 nm and 0.5–1 μm increased. The diurnal variation of Particle Number Concentration showed a bimodal pattern in haze days. All soluble ions were increased during haze events, of which NH 4 + , SO 4 2 − and NO 3 − increased greatly, followed by Na + , K + , Ca 2 + and Cl − . These ions were very different in size-resolved Particles during haze and photochemical smog episodes.
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Particle Number Concentration, size distribution and chemical composition during haze and photochemical smog episodes in Shanghai.
Journal of environmental sciences (China), 2014Co-Authors: Xuemei Wang, Jianmin Chen, Tiantao Cheng, Renyi Zhang, Xinming WangAbstract:The aerosol Number Concentration and size distribution as well as size-resolved Particle chemical composition were measured during haze and photochemical smog episodes in Shanghai in 2009. The Number of haze days accounted for 43%, of which 30% was severe (visibility
Hossain Mohammed Syedul Hoque - One of the best experts on this subject based on the ideXlab platform.
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Characterization and source apportionment of Particle Number Concentration at a semi-urban tropical environment.
Environmental science and pollution research international, 2015Co-Authors: Firoz Khan, Mohd Talib Latif, Norhaniza Amil, Liew Juneng, Noorlin Mohamad, Mohd Shahrul Mohd Nadzir, Hossain Mohammed Syedul HoqueAbstract:Principal component analysis (PCA) and correlation have been used to study the variability of Particle mass and Particle Number Concentrations (PNC) in a tropical semi-urban environment. PNC and mass Concentration (diameter in the range of 0.25–>32.0 μm) have been measured from 1 February to 26 February 2013 using an in situ Grimm aerosol sampler. We found that the 24-h average total suspended particulates (TSP), particulate matter ≤10 μm (PM10), particulate matter ≤2.5 μm (PM2.5) and particulate matter ≤1 μm (PM1) were 14.37 ± 4.43, 14.11 ± 4.39, 12.53 ± 4.13 and 10.53 ± 3.98 μg m−3, respectively. PNC in the accumulation mode (
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characterization and source apportionment of Particle Number Concentration at a semi urban tropical environment
Environmental Science and Pollution Research, 2015Co-Authors: Firoz Khan, Mohd Talib Latif, Norhaniza Amil, Liew Juneng, Noorlin Mohamad, Mohd Shahrul Mohd Nadzir, Hossain Mohammed Syedul HoqueAbstract:Principal component analysis (PCA) and correlation have been used to study the variability of Particle mass and Particle Number Concentrations (PNC) in a tropical semi-urban environment. PNC and mass Concentration (diameter in the range of 0.25–>32.0 μm) have been measured from 1 February to 26 February 2013 using an in situ Grimm aerosol sampler. We found that the 24-h average total suspended particulates (TSP), particulate matter ≤10 μm (PM10), particulate matter ≤2.5 μm (PM2.5) and particulate matter ≤1 μm (PM1) were 14.37 ± 4.43, 14.11 ± 4.39, 12.53 ± 4.13 and 10.53 ± 3.98 μg m−3, respectively. PNC in the accumulation mode (<500 nm) was the most abundant (at about 99 %). Five principal components (PCs) resulted from the PCA analysis where PC1 (43.8 % variance) predominates with PNC in the fine and sub-microme tre range. PC2, PC3, PC4 and PC5 explain 16.5, 12.4, 6.0 and 5.6 % of the variance to address the coarse, coarser, accumulation and giant fraction of PNC, respectively. Our Particle distribution results show good agreement with the moderate resolution imaging spectroradiometer (MODIS) distribution.
Stephan Weber - One of the best experts on this subject based on the ideXlab platform.
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variability of Particle Number Concentration and Particle size dynamics in an urban street canyon under different meteorological conditions
Science of The Total Environment, 2013Co-Authors: Stephan Weber, Klaus Kordowski, Wilhelm KuttlerAbstract:During a six-month study period, aerosol Number size distributions, mean meteorological conditions and turbulent exchange were measured within an urban street canyon in Essen, Germany. The findings were compared to simultaneous measurements conducted at suburban sites within the study area. The effects of turbulent exchange and different canyon flow situations on aerosol Number Concentration variability within the street canyon were studied. In comparison to a suburban background site, the busy urban street canyon aerosol Number Concentration was significantly elevated in the size range below 70 nm throughout the daytime hours. During the morning rush hour, total Number Concentrations were a factor of 2.2 higher. On average, the total Number Concentration at the street canyon site roughly doubled the suburban background Concentrations (by a factor of 1.9). The intensity of turbulent mixing within the street canyon was sensitive to the prevailing flow regime. The highest turbulent mixing during cross-canyon flow from directions downwind of the measurement spot was accompanied by the lowest Number Concentration of all flow regimes observed within the canyon. This behaviour was consistent for the different aerosol size classes considered in this study. The effects of meteorology and traffic intensity on total aerosol Number Concentrations were parameterised using a multiple linear regression analysis and indicated that turbulent mixing within the canyon, traffic intensity and NOx Concentrations were the most significant parameters. The model is characterised by an average relative uncertainty of 29%. During situations with a total Number Concentration>7500 cm(-3), a relative uncertainty of the modelled data of ±25% emerges but displays a larger deviation for low Particle Concentrations.
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Spatio-temporal covariation of urban Particle Number Concentration and ambient noise
Atmospheric Environment, 2009Co-Authors: Stephan WeberAbstract:Abstract Mobile measurements of ambient noise and Particle Number Concentrations were carried out within an urban residential area in Essen, Germany, during summer 2008. A busy major road with a traffic intensity of about 44,000 vehicles per day was situated within the study area. The spatio-temporal distribution of noise and Particles was closely coupled to road traffic on the major road. Total Particle Number Concentrations in proximity to the main road were on average between 25,000 cm −3 and 35,000 cm −3 while sound levels reached 70–78 dB(A). These estimates were more than double-fold (factor 2.4) in comparison to the urban residential background. At a 50 m distance off the road Particle Number Concentrations were decaying to about 50% of the initial value. The measurements were characterised by close spatial correlation between total Particle Number Concentration and ambient noise with correlation coefficients of up to r = 0.74. However, during one measurement day coupling between both quantities was weak due to higher turbulent mixing within the canopy layer and a change in ambient wind directions. Enhanced dilution of Particle emission from road traffic by turbulent mixing and ‘decoupling’ from the influence of road traffic are believed to be responsible.
Jorma Keskinen - One of the best experts on this subject based on the ideXlab platform.
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comparison of three Particle Number Concentration calibration standards through calibration of a single cpc in a wide Particle size range
Aerosol Science and Technology, 2012Co-Authors: Jaakko Yliojanpera, Jyrki M. Mäkelä, Kensei Ehara, Hiromu Sakurai, Kenjiro Iida, Jorma KeskinenAbstract:We carried out a set of experiments to compare three Particle Number Concentration standards (NCSs) by calibrating the same condensation Particle counter (CPC) unit (Model 3772, TSI Inc., Shoreview, MN, USA). The standards were, in the order of operation size range, the primary NCS of the National Institute of Advanced Industrial Science and Technology (AIST, Japan), the Single Charged Aerosol Reference (SCAR) (Finland), and the Inkjet Aerosol Generator (IAG) of AIST. The results obtained with the 3 standards were found to agree at all overlapping Particle sizes within the uncertainty limits. The relative expanded uncertainties varied between 0.6% and 2.6%, depending on the size and standard, while the overall agreement between the standards was within 0.5%. The observed consistency of the results is an important step toward establishing internationally coherent Particle NCSs. As a result, the CPC 3772 was successfully calibrated in a particularly wide size range, approximately from 10 nm to 10 μm. The re...
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Validating the single charged aerosol reference (SCAR) as a traceable Particle Number Concentration standard for 10 nm to 500 nm aerosol Particles
Metrologia, 2011Co-Authors: Richard Högström, Jaakko Yli-ojanperä, Jyrki M. Mäkelä, Antti Rostedt, I. Iisakka, Martti Heinonen, Jorma KeskinenAbstract:Measurement of nanometre-sized aerosol Particles is based on Particle Number Concentration measurements. The commonly used method for providing traceability for these measurements involves charging and electrical counting of aerosol Particles. This method requires that the Particles are singly charged or that the average charge is exactly known, neither of which is easy to ensure. In the device called a single charged aerosol reference (SCAR), the fraction of multiply charged Particles is minimal due to the novel operating principle of electrical charging and subsequent growth. In this study the SCAR was validated as a primary Particle Number Concentration standard. The average charge of the output aerosol was evaluated for the whole operational Particle size range. For this, the effect of the size distribution of the primary nanoaerosol and the output Number Concentration on the fraction of doubly charged and neutral Particles was measured. It was found that the uncertainty caused by assuming singly charged Particles is only 0.16%. A full uncertainty analysis was carried out for a condensation Particle counter (CPC) calibration. According to the results, the relative expanded uncertainty of calibration was 3.0%. This represents a typical uncertainty level achieved in CPC calibrations performed with SCAR. As a result of this study, SCAR was validated as a Particle Number Concentration standard suitable for traceable calibration of Particle counting instruments in the Particle size range from 10 nm to 500 nm.
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Towards traceable Particle Number Concentration standard: Single charged aerosol reference (SCAR)
Journal of Aerosol Science, 2010Co-Authors: Jaakko Yli-ojanperä, Jyrki M. Mäkelä, Marko Marjamäki, Antti Rostedt, Jorma KeskinenAbstract:Abstract A concept of realizing a standard for aerosol Particle Number Concentration was tested, based on generating singly charged aerosol Particles in the size range from 10 up to 500 nm. To this end, a device named single-charged aerosol reference (SCAR) was designed, built, and tested. The device is based on electrical charging of nanoParticles and subsequent growth of the Particles. With an accurate measurement of volume flow and electrical current from the singly charged Particles, the Number Concentration can be accurately, and in the end, traceably determined. Laboratory tests have shown that the device can be used to generate a narrow (GSD