Neville D. Bofinger

Comprehensive characterization of aerosols in a subtropical urban atmosphere: particle size distribution and correlation with gaseous pollutants

This paper presents results of two years of monitoring and research on urban particulates with a focus on submicrometer particles, conducted as a part of an ongoing program on comprehensive characterization of fine airborne particulates and their effect on environmental and human exposures. A large number of data has been collected by the Air Monitoring and Research Station operating in the centre of the subtropical city of Brisbane. The Station is equipped in instrumentation for measurements of particle size distributions in submicrometer and supermicrometer ranges in addition to the standard instrumentation for monitoring of the criteria pollutants (PM10, ozone, sulphur dioxide, nitrogen oxides and carbon monoxide). The focus of this paper is on presenting results related to characterization of particle size distribution and concentration trends in the study period, correlation between particle characteristics measured by different instruments, correlation between particle and gaseous data and preliminary conclusions on source characteristics and source contribution for the investigated area. The average submicrometer particulate concentration in the study period was 7.4x103 particles cm-3, and the average number median diameter was 40 nm. The best correlated data are those for submicrometer particles and carbon monoxide and nitrogen oxides, suggesting the same source type. The lack of correlation between submicrometer and supermicrometer particle concentration data implies different sources for particles in these two ranges. Particle spectral analysis and correlation with gaseous data, indicate that motor vehicle emissions constitute the main source of ultra fine particles in the study area.

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.

Impact of Microenvironmental Nitrogen Dioxide Concentrations on Personal Exposures in Australia

ABSTRACT Indoor and outdoor NO2 concentrations were measured and compared with simultaneously measured personal exposures of 57 office workers in Brisbane, Australia. House characteristics and activity patterns were used to determine the impacts of these factors on personal exposure. Indoor NO2 levels and the presence of a gas range in the home were significantly associated with personal exposure. The time-weighted average of personal exposure was estimated using NO2 measurements in indoor home, indoor workplace, and outdoor home levels. The estimated personal exposures were closely correlated, but they significantly underestimated the measured personal exposures. Multiple regression analysis using other nonmeasured microenvironments indicated the importance of transportation in personal exposure models. The contribution of transportation to the error of prediction of personal exposure was confirmed in the regression analysis using the multinational study database.

Possible Origin for Porphin Derivatives in Prebiotic Chemistry - A Computational Study

A set of chemical reactions is postulated to account for the formation of the macrocyclic porphin structure, basic to the pyrrole derivatives chlorophyll, protoporphyrin, heme and bilirubin, important in photosynthesis, respiration and digestion. A set of equations is given for the prebiotic synthesis of porphin derivatives from the simple molecules; cyanoacetylene, diacetylene, carbon monoxide and ammonia that have been detected in space. A number of isomers of hydrogenated porphin arise which may lose hydrogen to give ultimately porphin and its dehydrogenated derivative. The reactions, while not unique, provide a pathway which has been shown to be feasible from the overall enthalpy changes in the ZKE approximation at the HF and MP2/6-31G* level

Review of empirical methods for the calculation of the diurnal NO2 photolysis rate coefficient

The rate coefficient for the photolysis of nitrogen dioxide (JNO2) is used in ambient photochemical air quality models as this photodissociation leads to the formation of tropospheric ozone. This review examines the effectiveness and efficiency of four methods for the calculation of JNO2. The nature of JNO2 is reviewed briefly with regard to temperature, pressure, zenith angle, altitude, albedo, clouds, atmospheric turbidity and atmospheric molecular absorption. Comparison of the four methods against a radiation transfer model, for three clear-sky days at different latitudes in Australia, shows that any of the methods may be used to approximate a clear-sky diurnal profile of JNO2, as the maximum variation between all models at noon was found to be 15%. However, more care needs to be taken when calculating other photolysis rate coefficients, such as JO3, as these are more susceptible to other variables such as the ozone column concentration. A simple procedure for calculating cloudy-day JNO2 is also illustrated.

Investigation of a modified Sinclair-la Mer aerosol generator in the submicrometer range

A systematic study of the aerosol output was conducted from a modified commercially available Sinclair-La Mer-type monodisperse generator (TSI 3475) in the submicrometer region. The generator produces three different types of aerosols: sodium chloride, DEHS droplets condensed on NaCl nuclei and homogeneously nucleated DEHS droplets. The first two were found io be unimodal while the last one had a bimodal distribution. The aerosol droplet size distribution of the condensed aerosols was measured as a function of nuclei concentration, saturator temperature and saturator flow. It was concluded that when nuclei concentration decreases below similar to 10(6) cm(-3) homogeneous condensation is no longer suppressed and coexistence of two kinds of aerosol droplets of different size can be observed. The size distribution of all generated aerosols was measured by a scanning mobility particle sizer (SMPS)

The Reactions of Methanimine and Cyanogen with Carbon Monoxide in Prebiotic Molecular Evolution on Earth

A primeval atmosphere is proposedcontaining simple molecules such as formaldehyde, ammonia, carbon monoxide, cyanogen andhydrogen cyanide, which have been detected in space. Chemical reactions aredescribed for the formation ofaziridine-2-one and di-azirine-3-one derivatives aspotential precursors for the original synthesesis of amino-acids, proteins, pyrimidines,purines, nicotinamide and flavin. The reactions have been shown to be kinetically feasiblefrom the overall enthalpy changes in the ZKE approximation at the MP2/6-31G* level.

Investigation of the Source of Blank Problems in the Measurement ofLead in Sub-micrometre Airborne Particulates by Inductively Coupled PlasmaMass Spectrometry

The development of a method for the determination of trace amounts of lead in airborne fine particulates using ICP-MS for sample analysis is described. A systematic approach to the reduction of blank readings and to the identification of sources of contamination was applied, using the techniques of factorial experimental design and multi-way analysis of variance (ANOVA). The former provides an economical method for indicating significant sources of contamination to the blank readings. The latter is a statistical method for the study of the effects of these sources and their interactions. It was found that a significant contribution of the high blank readings is attributable to the ‘memory effect’ exhibited by the laboratory PTFE-ware. As a result of this study, the detection limit of the method, in terms of the mass of lead on the filter, was reduced from 20 to 1 ng.

the π-electronic structure and spectra of the p-polyphenyls

This paper reports Pariser-Parr-Pople (PPP) type calculations on the polyphenyl series. It is found that series limits exist for the ionization potential and the p-band of the electronic spectrum. Studies on members of the series with non-planar geometry indicate that the most stable conformation in the isolated molecule is that in which the neighbouring rings are oriented at about 50° to each other.