Preliminary results on the characterisation of organic aerosols in urban schools by Aerosol Mass Spectrometry

Vehicle emissions have been linked to detrimental health effects with children thought to be more susceptible (See e.g., Ryan et al 2005). In an urban environment a major source of organic aerosols (OA) are vehicle emissions. The ambient concentration of OA is dynamic in nature and the use of an aerosol mass spectrometer can achieve the necessary temporal resolution to capture the daily variation of OA (Jimenez et al 2009). Currently there is a limited understanding of effects of long term exposure to traffic emissions on children’s health. In the present study, we used an aerosol mass spectrometer to monitor OA and determine children’s potential exposure at school to traffic emissions.In this paper, we present the preliminary results of this investigation. The study is a part of a larger project aimed at gaining a holistic picture of the exposure of children to traffic related pollutants, known as UPTECH (www.ilaqh.qut.edu.au/Misc/ UPTECH%20Home.htm).

Airborne concentration of Volatile Organic Compounds in school environment in Brisbane

Traffic emissions are considered as a major source of pollutants, particularly ultrafine particles, in the urban environment. There is an increased concern about airborne particles not only because of their environmental effects but also due to their potential adverse health effects on humans. There have been a number of studies related to the number concentration and size distribution of these particles but studies on the chemical composition of aerosols, especially in the school environment, are very limited. Mejia et. al (2011) reviewed studies on the exposure to and impact of air pollutants on school children and found that there were only a handful of studies on this topic. Therefore, the main focus of this research is on an analysis of the chemical composition of airborne particles, as well as source apportionment and the quantification of ambient concentrations of organic pollutants in the vicinity of schools, as a part of “Ultrafine Particles from Traffic Emissions on Children’s Health” (UPTECH) project. The aim of the present study was to find out the concentrations of different Volatile Organic Compounds (VOCs) in both outdoor and indoor locations from six different schools in Brisbane.

Modeling heat and mass transfer process during convection drying of fruit

Fruit drying is a process of removing moisture to preserve fruits by preventing microbial spoilage. It increases shelf life, reduce weight and volume thus minimize packing, storage, and transportation cost and enable storage of food under ambient environment. But, it is a complex process which involves combination of heat and mass transfer and physical property change and shrinkage of the material. In this background, the aim of this paper to develop a mathematical model to simulate coupled heat and mass transfer during convective drying of fruit. This model can be used predict the temperature and moisture distribution inside the fruits during drying. Two models were developed considering shrinkage dependent and temperature dependent moisture diffusivity and the results were compared. The governing equations of heat and mass transfer are solved and a parametric study has been done with Comsol Multiphysics 4.3. The predicted results were validated with experimental data.

Auger spectroscopy of stratospheric particles : the influence of aerosols on interplanetary dust

Particle collections from the stratosphere via either the JSC Curatorial Program or the U2 Program (NASA Ames) occur between 16km and 19km altitude and are usually part of ongoing experiments to measure parameters related to the aerosol layer. Fine-grained aerosols (<0.1µm) occur in the stratosphere up to 35km altitude and are concentrated between 15km and 25km altitude[1]. All interplanetary dust particles (IDP's) from these stratospheric collections must pass through this aerosol layer before reaching the collection altitude. The major compounds in this aerosol layer are sulfur rich particulates (<0.1µm) and gases and include H2S04, OCS, S02 and CS2 [2].In order to assess possible surface reactions of interplanetary dust particles (IDP's) with ambient aerosols in the stratosphere, we have initiated a Surface Auger Microprobe (SAM) and electron microscope study of selected particles from the JSC Cosmic Dust Collection.

Infrared spectra of Mg-SiO smokes : comparison with analytical electron microscopy studies

An important component of current models for interstellar and circumstellar evolution is the infrared (IR)spectral data collected from stellar outflows around oxygen-rich stars and from the general interstellar medium [1]. IR spectra from these celestial bodies are usually interpreted as showing the general properties of sub-micron sized silicate grains [2]. Two major features at 10 and 20 microns are reasonably attributed to amorphous olivine or pyroxene (e.g. Mg2Si04 or MgSi03) on the basis of comparisons with natural standards and vapor condensed silicates [3-6]. In an attempt to define crystallisation rates for spectrally amorphous condensates, Nuth and Donn [5] annealed experimentally produced amorphous magnesium silicate smokes at 1000K. On analysing these smokes at various annealing times, Nuth and Donn [5] showed that changes in crystallinity measured by bulk X-ray diffraction occured at longer annealing times (days) than changes measured by IR spectra (a few hours). To better define the onset of crystallinity in these magnesium silicates, we have examined each annealed product using a JEOL 1OOCX analytical electron microscope (AEM). In addition, the development of chemical diversity with annealing has been monitored using energy dispersive spectroscopy of individual grains from areas <20nm in diameter. Furthermore, the crystallisation kinetics of these smokes under ambient, room temperature conditions have been examined using bulk and fourier transform infrared (FTIR)spectra.

Selective reductions using visible light photocatalysts of supported gold nanoparticles

Photocatalytic synthesis using visible light is a desirable chemical process because of its potential to utilize sunlight. Supported gold nanoparticles (Au-NPs) were found to be efficient photocatalysts and the effects of the supports were identified including CeO2, TiO2, ZrO2, Al2O3, and zeolite Y. In particular Au/CeO2 exhibited the high catalytic activity to reduce nitroaromatics to azo compounds, hydrogenate azobenzene to hydroazobenzene, reduce ketones to alcohols, and deoxygenate epoxides to alkenes at ambient temperatures, under irradiation of visible light (or simulated sunlight). The reac-tive efficiency depends on two primary factors: one is the light adsorption of catalysts and another is the driving ability of catalysts corresponding to the reactants. The light absorption by Au-NPs is due to surface plasmon resonance effect or inter-band electron transition; this is related to the reduction ability of the photocatalysts. Irradiation with shorter wavelengths can excite the conduction electrons in Au-NPs to higher energy levels and as a result, induce reduction with more negative reduction potentials. It is known when irradiated with light the Au-NPs can abstract hydrogen from isopropanol forming Au-H species on the Au-NP surface. Hence, we proposed that the active Au-H species will react with the N=O, N=N, C=O double bonds or epoxide bonds, which are weakened by the interaction with the excited electrons in the Au-NPs, and yield the final reductive products. The reacting power of the Au-H species depends on the energy of the excited electrons in Au-NPs: the higher the electronic energy, the stronger the reduction ability of the Au-H species. This finding demonstrates that we can tune the reduction ability of the photocatalysts by manipulating the irradiation wavelength.

Multiphysics modelling of convective drying of food materials

Currently, 1.3 billion tonnes of food is lost annually due to lack of proper processing and preservation method. Drying is one of the easiest and oldest methods of food processing which can contribute to reduce that huge losses, combat hunger and promote food security. Drying increase shelf life, reduce weight and volume of food thus minimize packing, storage, and transportation cost and enable storage of food under ambient environment. However, drying is a complex process which involves combination of heat and mass transfer and physical property change and shrinkage of the food material. Modelling of this process is essential to optimize the drying kinetics and improve energy efficiency of the process. Since material properties varies with moisture content, the models should not consider constant materials properties, constant diffusion .The objective of this paper is to develop a multiphysics based mathematical model to simulate coupled heat and mass transfer during convective drying of fruit considering variable material properties. This model can be used predict the temperature and moisture distribution inside the food during drying. Effect of different drying air temperature and drying air velocity on drying kinetics has been demonstrated. The governing equations of heat and mass transfer were solved with Comsol Multiphysics 4.3.

Behaviour and design of cold-formed steel beams subject to lateral-torsional buckling at elevated temperatures

Cold-formed steel beams are increasingly used as floor joists and bearers in buildings and often their behaviour and moment capacities are influenced by lateral-torsional buckling. With increasing usage of cold-formed steel beams their fire safety design has become an important issue. Fire design rules are commonly based on past research on hot-rolled steel beams. Hence a detailed parametric study was undertaken using validated finite element models to investigate the lateral-torsional buckling behaviour of simply supported cold-formed steel lipped channel beams subjected to uniform bending at uniform elevated temperatures. The moment capacity results were compared with the predictions from the available ambient temperature and fire design rules and suitable recommendations were made. European fire design rules were found to be over-conservative while the ambient temperature design rules could not be used based on single buckling curve. Hence a new design method was proposed that includes the important non-linear stress-strain characteristics observed for cold-formed steels at elevated temperatures. Comparison with numerical moment capacities demonstrated the accuracy of the new design method. This paper presents the details of the parametric study, comparisons with current design rules and the new design rules proposed in this research for lateral-torsional buckling of cold-formed steel lipped channel beams at elevated temperatures.

Flexural-torsional buckling tests of cold-formed steel compression members at elevated temperatures

Current design standards do not provide adequate guidelines for the fire design of cold-formed steel compression members subject to flexural-torsional buckling. Eurocode 3 Part 1.2 (2005) recommends the same fire design guidelines for both hot-rolled and cold-formed steel compression members subject to flexural-torsional buckling although considerable behavioural differences exist between cold-formed and hot-rolled steel members. Past research has recommended the use of ambient temperature cold-formed steel design rules for the fire design of cold-formed steel compression members provided appropriately reduced mechanical properties are used at elevated temperatures. To assess the accuracy of flexural-torsional buckling design rules in both ambient temperature cold-formed steel design and fire design standards, an experimental study of slender cold-formed steel compression members was undertaken at both ambient and elevated temperatures. This paper presents the details of this experimental study, its results, and their comparison with the predictions from the current design rules. It was found that the current ambient temperature design rules are conservative while the fire design rules are overly conservative. Suitable recommendations have been made in relation to the currently available design rules for flexural-torsional buckling including methods of improvement. Most importantly, this paper has addressed the lack of experimental results for slender cold-formed steel columns at elevated temperatures.

Bomb disposal in the tropics : a cocktail of metabolic and environmental heat

Bomb technicians perform their work while encapsulated in explosive ordnance disposal (EOD) suits. Designed primarily for safety, these suits have an unintended consequence of impairing the body’s natural mechanisms for heat dissipation. Purpose: To quantify the heat strain encountered during an EOD operational scenario in the tropical north of Australia. Methods: All active police male bomb technicians, located in a tropical region of Australia (n=4, experience 7 ± 2.1 yrs, age 34 ± 2 yrs, height 182.3 ± 5.4 cm, body mass 95 ± 4 kg, VO2max 46 ± 5.7 ml.kg-1.min-1) undertook an operational scenario wearing the Med-Eng EOD 9 suit and helmet (~32 kg). The climatic conditions ranged between 27.1–31.8°C ambient temperature, 66-88% relative humidity, and 30.7-34.3°C wet bulb globe temperature. The scenario involved searching a two story non air-conditioned building for a target; carrying and positioning equipment for taking an X-ray; carrying and positioning equipment to disrupt the target; and finally clearing the site. Core temperature and heart rate were continuously monitored, and were used to calculate a physiological strain index (PSI). Urine specific gravity (USG) assessed hydration status and heat associated symptomology were also recorded. Results: The scenario was completed in 121 ± 22 mins (23.4 ± 0.4% work, 76.5 ± 0.4% rest/recovery). Maximum core temperature (38.4 ± 0.2°C), heart rate (173 ± 5.4 bpm, 94 ± 3.3% max), PSI (7.1 ± 0.4) and USG (1.031 ± 0.002) were all elevated after the simulated operation. Heat associated symptomology highlighted that moderate-severe levels of fatigue and thirst were universally experienced, muscle weakness and heat sensations experienced by 75%, and one bomb technician reported confusion and light-headedness. Conclusion: All bomb technicians demonstrated moderate-high levels of heat strain, evidenced by elevated heart rate, core body temperature and PSI. Severe levels of dehydration and noteworthy heat-related symptoms further highlight the risks to health and safety faced by bomb technicians operating in tropical locations.