Milan Jamriska

Differences in airborne particle and gaseous concentrations in urban air between weekdays and weekends

Airborne particle number concentrations and size distributions as well as CO and NOx concentrations monitored at a site within the central business district of Brisbane, Australia were correlated with the traffic flow rate on a nearby freeway with the aim of investigating differences between weekday and weekend pollutant characteristics. Observations over a 5-year monitoring period showed that the mean number particle concentration on weekdays was (8.8±0.1)×103 cm−3 and on weekends (5.9±0.2)×103 cm−3—a difference of 47%. The corresponding mean particle number median diameters during weekdays and weekends were 44.2±0.3 and 50.2±0.2 nm, respectively. The differences in mean particle number concentration and size between weekdays and weekends were found to be statistically significant at confidence levels of over 99%. During a 1-year period of observation, the mean traffic flow rate on the freeway was 14.2×104 and 9.6×104 vehicles per weekday and weekend day, respectively—a difference of 48%. The mean diurnal variations of the particle number and the gaseous concentrations closely followed the traffic flow rate on both weekdays and weekends (correlation coefficient of 0.86 for particles). The overall conclusion, as to the effect of traffic on concentration levels of pollutant concentration in the vicinity of a major road (about 100 m) carrying traffic of the order of 105 vehicles per day, is that about a 50% increase in traffic flow rate results in similar increases of CO and NOx concentrations and a higher increase of about 70% in particle number concentration.

Size characteristics and ageing of the environmental tobacco smoke

Abstract The work presented here is a study of the behaviour of the particulate phase of ETS under controlled laboratory conditions and in real indoor environments with the aim of providing information for assessment of human exposure to ETS. This paper reports investigations of the size distribution of ETS and changes to the distribution with time under a range of environmental conditions. Measurements were performed using two instruments, the Scanning Mobility Particle Sizer and the Aerodynamic Particle Sizer, which enabled the determination of the precise locations of ETS peaks at frequent short time intervals. While total particle concentrations or changes in concentrations are not specific markers of ETS, peaks related to ETS in the spectral distribution of atmospheric particles, for a properly designed experiment, are. The presence and locations of these peaks are characteristic of ETS in indoor environments and are clearly distinguishable from the background particle distribution. It is demonstrated that an initial ETS size distribution in an indoor environment about 10 min after generation by a human smoker has a major peak in the submicron range between 60 and 90 nm. The location of the peak does not depend on the relative humidity, but does depend on the way the cigarette is smoked. An increase in particle size in the range of 20 to 50%, takes place in the first 30 to 60 min after ETS generation and then remains unchanged for the duration of the experiment. A decrease in particle size (shrinkage), was not observed during these experiments. Particle shrinkage has been reported in the literature. Both the SS and the MS smoke reveal bimodal size distribution. In both cases the most significant, in terms of particle numbers, is the submicron peak. Natural ventilation, which is the most common type of ventilation for residences, is often not sufficient for effectively reducing human exposure to ETS. Controlled chamber experiments are useful for investigations of general trends in ETS size distribution and concentration and the results from such experiments, in most cases, correlate well with those from real indoor measurements. There are however, aspects which show certain differences between the two types of experiments. These differences indicate that chamber experiments can not fully simulate indoor measurements, and results from such experiments should be treated with caution when applied to exposure assessment.

Rapid production of protein-loaded biodegradable microparticles using surface acoustic waves

We present a straightforward and rapid surface acoustic wave (SAW) atomization-based technique for encapsulating proteins into 10 mum order particles composed of a biodegradable polymeric excipient, using bovine serum albumin (BSA) as an exemplar. Scans obtained from confocal microscopy provide qualitative proof of encapsulation and show the fluorescent conjugated protein to be distributed in a relatively uniform manner within the polymer shell. An ELISA assay of the collected particles demonstrates that the BSA survives the atomization, particle formation, and collection process with a yield of approximately 55%. The SAW atomization universally gave particles with a textured morphology, and increasing the frequency and polymer concentration generally gave smaller particles (to 3 mum average) with reduced porosity.

Deposition of radon progeny on indoor surfaces

Surface deposition is one of the main removal mechanisms of airborne aerosol particles. Yet, understanding of this process is still not adequate. This is likely to be due to deficiencies in the understanding of aerosol interaction processes including deposition and difficulties in comparing different sets of experimental data. The aim of this work was to determine deposition velocity for a spectrum of 222Rn progeny particle sizes for well defined experimental conditions and to interpret the results in a broad perspective of available literature data. Deposition velocities determined here are in the range from 2 to 3.5 m h−1 for attached fraction in the size range from 120 to 470 nm activity median diameter (AMD), in the range from 5.5 to 9.3 m h−1 for size range from 6 to 35 nm and 32.7 m h−1 for particles of size 1.3 nm. The results are discussed and compared with literature data.

Quantitative Assessment of the Effect of Surface Deposition and Coagulation on the Dynamics of Submicrometer Particles Indoors

Exposure to airborne particles indoors depends on particle concentration, which is affected by air filtration, ventilation, and particle dynamics. The aim of this work was quantitative assessment of the effects of coagulation, surface deposition, and ventilation on the submicrometer particle concentration indoors. The assessment was obtained from measured particle loss rate and deposition velocity parameters. The experiments were conducted in an experimental chamber for three different types of aerosols: environmental tobacco smoke, petrol smoke, and ambient air aerosols. Particle number concentration and size distribution were measured in the size range between 0.017 and 0.898 w m by SMPS. The average values for the overall deposition loss rates varied from 4.3 2 10 m 5 s m 1 (0.16 h m 1 ) to 1.1 2 10 m 4 s m 1 (0.39 h m 1 ). The overall deposition velocities associated with surface deposition and coagulation ranged from 9.6 2 10 m 4 cm s m 1 to 2.4 2 10 m 3 cm s m 1 , and for surface deposition only from 2.8 2 10 m 4 cm s m 1 to 6.3 2 10 m 4 cm s m 1 . For indoor conditions with an air exchange rate above 1.3 h m 1 , (natural ventilation, no filters) only a reduction in particle number of about 20% is attributed to the surface deposition and coagulation.

Source apportionment of ultrafine and fine particle concentrations in Brisbane, Australia

PurposeTo investigate the significance of sources around measurement sites, assist the development of control strategies for the important sources and mitigate the adverse effects of air pollution due to particle size.MethodsIn this study, sampling was conducted at two sites located in urban/industrial and residential areas situated at roadsides along the Brisbane Urban Corridor. Ultrafine and fine particle measurements obtained at the two sites in June–July 2002 were analysed by positive matrix factorization.ResultsSix sources were present, including local traffic, two traffic sources, biomass burning and two currently unidentified sources. Secondary particles had a significant impact at site 1, while nitrates, peak traffic hours and main roads located close to the source also affected the results for both sites.ConclusionsThis significant traffic corridor exemplifies the type of sources present in heavily trafficked locations and future attempts to control pollution in this type of environment could focus on the sources that were identified.

Sources of ultrafine particles and chemical species along a traffic corridor: comparison of the results from two receptor models

Environmental context Identifying the sources responsible for air pollution is crucial for reducing the effect of the pollutants on human health. The sources of the pollutants were found here by applying two mathematical models to data consisting of particle size distribution and chemical composition data. The identified sources could be used as the basis for controlling or reducing emissions of air pollution into the atmosphere. Abstract Particulate matter is common in our environment and has been linked to human health problems particularly in the ultrafine size range. In this investigation, the sources of particles measured at two sites in Brisbane, Australia, were identified by analysing particle number size distribution data, chemical species concentrations and meteorological data with two source apportionment models. The source apportionment results obtained by positive matrix factorisation (PMF) and principal component analysis–absolute principal component scores (PCA–APCS) were compared with information from the gaseous chemical composition analysis. Although PCA–APCS resolved more sources, the results of the PMF analysis appear to be more reliable. Six common sources were identified by both methods and these include: traffic 1, traffic 2, local traffic, biomass burning and two unassigned factors. Thus motor vehicle related activities had the greatest effect on the data with the average contribution from nearly all sources to the measured concentrations being higher during peak traffic hours and weekdays. Further analyses incorporated the meteorological measurements into the PMF results to determine the direction of the sources relative to the measurement sites, and this indicated that traffic on the nearby road and intersection was responsible for most of the factors. The described methodology that utilised a combination of three types of data related to particulate matter to determine the sources and combination of two receptor models could assist future development of particle emission control and reduction strategies.

Scaling laws of passive tracer dispersion in the turbulent surface layer.

Experimental results for passive tracer dispersion in the turbulent surface layer under stable conditions are presented. In this case, the dispersion of tracer particles is determined by the interplay of three mechanisms: relative dispersion (celebrated Richardsons mechanism), shear dispersion (particle separation due to variation of the mean velocity field) and specific surface-layer dispersion (induced by the gradient of the energy dissipation rate in the turbulent surface layer). The latter mechanism results in the rather slow (ballistic) law for the mean squared particle separation. Based on a simplified Langevin equation for particle separation we found that the ballistic regime always dominates at large times. This conclusion is supported by our extensive atmospheric observations. Exit-time statistics are derived from the experimental data set and show a reasonable match with the simple dimensional asymptotes for different mechanisms of tracer dispersion, as well as predictions of the multifractal model and experimental data from other sources.

VEHICLE EMISSIONS IN AUSTRALIA: FROM MONITORING TO MODELLING

The South-East Queensland (SEQ) region is one of the fastest growing areas in Australia. This rapid growth and the accompanying increase in vehicle kilometres travelled has brought demand for management methods to deal with air pollution.

Determination of the Activity Size Distribution of Radon Progeny

ABSTRACT There has been significant progress in techniques for the determination of the activity size distribution of radon progeny. Despite this progress, many inconsistencies still exist with respect to the activity distribution, especially in the smaller particle size range. The aim of this work is to evaluate a measurement technique for determination of the activity size distribution of radon progeny, and to investigate the effect of different screen configurations and different deconvolution procedures. The measurements were performed in a large experimental chamber, using three different sets of Wire Screen Diffusion Batteries (WSDB) constructed for these studies. Aerosol concentration and size distribution in the chamber were monitored by a scanning mobility particle sizer. The Twomey and Reconstruct deconvolution methods were used to derive the activity particle size distribution from the diffusion battery data. Investigations of activity size distribution using three WSDB sets of different sensit...