Showing papers by "Lidia Morawska published in 2005"

Quantification of Particle Number Emission Factors for Motor Vehicles from On-Road Measurements

Abstract: The database on particle number emission factors has been very limited to date despite the increasing interest in the effects of human exposure to particles in the submicrometer range. There are also major questions on the comparability of emission factors derived through dynamometer versus on-road studies. Thus, the aims of this study were (1) to quantify vehicle number emission factors in the submicrometer (and also supermicrometer) range for stop-start and free-flowing traffic at about 100 km h-1 driving conditions through extensive road measurements and (2) to compare the emission factors from the road measurements with those obtained previously from dynamometer studies conducted in Brisbane. For submicrometer particles the average emission factors for Tora Street were estimated at (1.89 ( 3.40) 1013 particles km-1 (mean ( standard error; n ) 386) for petrol and (7.17 ( 2.80) 1014 particles km-1 (diesel; n ) 196) and for supermicrometer particles at 2.59 109 particles km-1 and 1.53 1012 particles km-1, respectively. The average number emission factors for submicrometer particles estimated for Ipswich Road (stop-start traffic mode) were (2.18 ( 0.57) 1013 particles km-1 (petrol) and (2.04 ( 0.24) 1014 particles km-1 (diesel). One implication of the conclusion that emission factors of heavy duty diesel vehicles are over 1 order of magnitude higher than emission factors of petrol-fueled passenger cars is that future control and management strategies should in particular target heavy duty vehicles, as even a moderate decrease in emissions of these vehicles would have a significant impact on lowering atmospheric concentrations of particles. The finding that particle number emissions per vehiclekm are significantly larger for higher speed vehicle operation has an important implication on urban traffic planning and optimization of vehicle speed to lower their impact on airborne pollution. Additionally, statistical analysis showed that neither the measuring method (dynamometer or onroad), nor data origin (Brisbane or elsewhere in the world), is associated with a statistically significant difference between the average values of emission factors for diesel, petrol, and vehicle fleet mix. However, statistical analyses of the effect of fuel showed that the mean values of emission factors for petrol and diesel are different at a 5% significance level.

Hygroscopic behavior of partially volatilized coastal marine aerosols using the volatilization and humidification tandem differential mobility analyzer technique

Abstract: [1] Coastal marine nucleation, Aitken, and accumulation mode aerosol particles with back trajectories indicative of marine origin were examined using a volatilization and humidification tandem differential mobility analyzer (VHTDMA) to reveal the volatilization temperatures of the various component species. The diameter hygroscopic growth factors of the residue particles were continually examined throughout the volatilization process. In each of the three modes the dominant particle type appeared to be composed of the same four physicochemically distinct species though in different ratios. These species exhibited volatility and hygroscopic behavior consistent with combinations of a volatile organic species, sulfuric acid, ammonium sulfate or bisulfate, iodine oxide, and an insoluble nonvolatile residue. The Aitken and accumulation mode aerosols contain large fractions of the insoluble, volatile, organic-like material, and the volatilization of this species results in a distinct increase in the water volume uptake of the particles. Of the four distinct species, only the sulfuric acid-like species constituted an increasing volume fraction with decreasing particle size. This finding indicates that nucleation mode particles constitute an acidic seed and as such would undergo acid-catalyzed secondary organic aerosol growth at a faster rate. The lack of a nonvolatile hygroscopic residue consistent with sea salt in these particles implies that the aerosolization of seawater is not the dominant production mechanism for these submicrometer coastal marine aerosols.

Influence of the diesel fuel sulphur content on the nanoparticle emissions from a fleet of city buses

Abstract: Particle emissions from twelve buses, aged 1 to 19 years, operating alternatively on low sulphur (LS; 500 ppm) and ultra-low sulphur (ULS; 50 ppm) diesel fuel were monitored at four steady-state operating modes on a chassis dynamometer. The mean particle number emission rate using ULS diesel was lower than the rate using LS diesel in each of the four modes. The fractional reduction was highest in the newest buses and decreased with mileage up to about 500,000 km, at which stage a bus was about 8 years old. No further decrease was apparent as the mileage increased thereafter. However, the mean total suspended particle (TSP) mass emission rate did not show a systematic difference between the two fuel types. When the fuel was changed from LS to ULS diesel, the reduction in particle number was mainly in the nanoparticle size range, with occurrences of the nuclei mode being significantly restricted. Overall, 58% of the particles were smaller than 50 nm with LS fuel as opposed to just 45% with ULS fuel, suggesting that sulphur in diesel fuel was playing a major role in the formation of nanoparticles. The greatest influence of the fuel sulphur level was observed at the highest engine load, where 74% of the particles were smaller than 50 nm with LS diesel compared to 43% with ULS diesel.

Air pollution levels measured at traffic hot spots : Brisbane urban corridor study

Abstract: Air pollution levels were monitored continuously over a period of 4 weeks at four sampling sites along a busy urban corridor in Brisbane. The selected sites were representative of industrial and residential types of urban environment affected by vehicular traffic emissions. The concentration levels of submicrometer particle number, PM2.5, PM10, CO, and NOx were measured 5-10 meters from the road. Meteorological parameters and traffic flow rates were also monitored. The data were analysed in terms of the relationship between monitored pollutants and existing ambient air quality standards. The results indicate that the concentration levels of all pollutants exceeded the ambient air background levels, in certain cases by up to an order of magnitude. While the 24-hr average concentration levels did not exceed the standard, estimates for the annual averages were close to, or even higher than the annual standard levels.

Assessing health risk associated with airborne polycyclic aromatic hydrocarbons by chemometrics and toxic equivalency factors

Abstract: Some polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in air and have been implicated as carcinogenic materials. Therefore, literature is replete with studies that are focused on their occurrence and profiles in indoor and outdoor air samples. However, because the relative potency of individual PAHs vary widely, health risks associated with the presence of PAHs in a particular environment cannot be extrapolated directly from the concentrations of individual PAHs in that environment. In addition, database on the potency of PAH mixtures is currently limited. In this paper, we have utilized multi-criteria decision making methods (MCDMs) to simultaneously correlate PAH-related health risk in some microenvironments to the concentration levels, ethoxyresorufin-O-deethylase (EROD) activity induction equivalency factors and toxic equivalency factors (TEFs) of PAHs found in those microenvironments. The results showed that the relative risk associated with PAHs in different air samples depends on the index used. Nevertheless, this approach offers a promising tool that could help identify microenvironments of concern and assist the prioritisation of control strategies.

Indoor Exposure to Submicrometer Particles and PM2.5 in Residential Houses in Brisbane, Australia

Abstract: As part of a large study investigating indoor air in residential houses in Brisbane, Australia, the purpose of this work was to quantify indoor exposure to submicrometer particles and PM2.5 for the inhabitants of 14 houses. Particle concentrations were measured simultaneously for more than 48 hours in the kitchens of all the houses by using a condensation particle counter (CPC) and a photometer (DustTrak). The occupants of the houses were asked to fill in a diary, noting the time and duration of any activity occurring throughout the house during measurement, as well as their presence or absence from home. From the time series concentration data and the information about indoor activities, exposure to the inhabitants of the houses was calculated for the entire time they spent at home as well as during indoor activities resulting in particle generation. The results show that the highest median concentration level occurred during cooking periods for both particle number concentration (47.5´103 particles cm-3) and PM2.5 concentration (13.4 mg m-3). The highest residential exposure period was the sleeping period for both particle number exposure (31%) and PM2.5 exposure (45.6%). The percentage of the average residential particle exposure level in total 24h particle exposure level was approximating 70% for both particle number and PM2.5 exposure.

Airborne Particulate Matter at a Bus Station: Concentration Levels and Governing Parameters

Abstract: Traffic emissions are an important contributor to ambient air pollution, especially in large cities featuring extensive and high density traffic networks. Bus fleets represent a significant part of inner city traffic causing an increase in exposure to general public, passengers and drivers along bus routes and at bus stations. Limited information is available on quantification of the levels, and governing parameters affecting the air pollution exposure at bus stations. The presented study investigated the bus emissions-dominated ambient air in a large, inner city bus station, with a specific focus on submicrometer particles. The study’s objectives were (i) quantification of the concentration levels; (ii) characterisation of the spatio-temporal variation; (iii) identification of the parameters governing the emissions levels at the bus station and (iv) assessment of the relationship between particle concentrations measured at the street level (background) and within the bus station. The results show that up to 90% of the emissions at the station are ultrafine particles (smaller than 100 nm), with the concentration levels up to 10 times the value of urban ambient air background (annual) and up to 4 times the local ambient air background. The governing parameters affecting particle concentration at the station were bus flow rate and meteorological conditions (wind velocity). Particle concentration followed a diurnal trend, with an increase in the morning and evening, associated with traffic rush hours. Passengers’ exposure could be significant compared to the average outdoor and indoor exposure levels.

Characterisation of indoor air organic pollutants in Brisbane

Abstract: The occurrence and levels of airborne polycyclic aromatic hydrocarbons and volatile organic compounds in selected non-industrial environments in Brisbane have been investigated as part of an integrated indoor air quality assessment program. The most abundant and most frequently encountered compounds include, nonanal, decanal, texanol, phenol, 2-ethyl-1-hexanol, ethanal, naphthalene, 2,6-tert-butyl-4-methyl-phenol (BHT), salicylaldehyde, toluene, hexanal, benzaldehyde, styrene, ethyl benzene, o-, m- and pxylenes, benzene, n-butanol, 1,2-propandiol, and n-butylacetate. Many of the 64 compounds usually included in the European Collaborative Action method of TVOC analysis were below detection limits in the samples analysed. In order to extract maximum amount of information from the data collected, multivariate data projection methods have been employed. The implications of the information extracted on source identification and exposure control are discussed.

Multi-criteria ranking of indoor air quality in non- industrial environments

Abstract: Relative to other western nations, there is a paucity of information on indoor air organic pollutants in Australia. While some data are available on the indoor levels of volatile organic compounds in Australian dwellings, corresponding information on polycyclic aromatic hydrocarbons levels is scarce. Therefore, this paper reports the results of the characterisation and quantification of airborne polycyclic aromatic hydrocarbons and volatile organic compounds in non-industrial environments in an Australian city. The most abundant and most frequently encountered compounds include, nonanal, decanal, texanol, acetone, formaldehyde, acetaldehyde, toluene, hexanal, ethyl benzene, the xylenes and C3-benzene. The distribution of these and other compounds found in the buildings have been rationalised in terms of indoor activities and the building characteristics (distance from a major roads, floor materials, use of air extractors etc). In addition, multi-criteria decision making procedures have been employed to rank the buildings on the basis of forty indoor air quality-influencing variables. This approach offers a useful tool that could facilitate the identification of environments requiring attention, and assist the formulation and prioritisation of control strategies.