Anna Worobiec

Characterisation of aerosol particles in the São Paulo Metropolitan Area

Abstract Aerosol samples were collected in the Sao Paulo Metropolitan Area, Brazil, during two periods (winter and summer) for fine and coarse particles; they were analysed by gravimetry, scanning electron microscopy, particle induced X-ray emission (PIXE) and electron probe X-ray micro analysis (EPXMA) in order to investigate the mass concentration, morphology and physico–chemical properties of the particles. The gravimetry and PIXE results confirmed that the aerosol concentration is higher in winter than in summer, as expected from the climatological conditions (dry winter and humid summer). Hierarchical cluster analysis of the EPXMA results showed the presence of metal compounds, silicon-rich particles, sulphates, carbonates, chlorides, organics and biogenic particles.

Thermal stability of beam sensitive atmospheric aerosol particles in electron probe microanalysis at liquid nitrogen temperature

Abstract Thin-window electron probe X-ray microanalysis offers new analytical possibilities for low-Z detection (i.e. elements with low atomic number; such as C, N and O). However, the quantitative analysis of individual particles raises some practical questions concerning the technique. From the analytical point of view, beam damage is one of the most important problems due to its big impact on the analysis of individual atmospheric particles. The dependence of the beam-damage effect on the type of collection substrate was studied using standard aerosol particles. Different metallic substrates were rigorously tested in relation to the beam damage effects to different kinds of beam sensitive particles. Ammonium sulfate, ammonium nitrate, sodium nitrate as well as sulfuric acid droplets were analyzed using a liquid nitrogen cooled sample stage on different metallic substrates such as Be, Al, Si and Ag. The obtained results confirm that the use of Be as a collection surface offers some advantages in order to minimize the damage to beam sensitive particles, as suggested in earlier research.

Combined SEM/EDX and micro-Raman spectroscopy analysis of uranium minerals from a former uranium mine

Samples of the secondary uranium minerals collected in the abandoned uranium mine at Pecs (Hungary) were investigated by two micro-techniques: scanning electron microscopy (SEM/EDX) and micro-Raman spectroscopy (MRS). They were applied to locate U-rich particles and identify the chemical form and oxidation state of the uranium compounds. The most abundant mineral was a K and/or Na uranyl sulphate (zippeite group). U(VI) was also present in the form showing intensive Raman scattering at 860 cm(-1) which can be attributed to uranium trioxide. This research has shown the successful application of micro-Raman spectroscopy for the identification of uranyl mineral species on the level of individual particles.

Characterisation of Individual Aerosol Particles for Atmospheric and Cultural Heritage Studies

Microanalysis of individual particles allows straightforward and advanced characterisation of environmental samples. The most obvious technique to study large microparticle populations is still electron probe X-ray microanalysis (EPXMA). Recently, technical and methodological progress has been made to remedy some of the limitations of conventional EPXMA, as, for example, in the detection of low Z-elements. Recent examples of the use of EPXMA in various environmental fields are presented, namely concerning atmospheric deposition of micropollutants and nutrients to the sea, characterisation of aerosols in the context of their effect on Global Change (remote continental and biogenic aerosols) and aerosol deposition and soiling of paintings in museums.

Investigation of inclusions trapped inside Libyan desert glass by Raman microscopy

Several specimens of Libyan desert glass (LDG), an enigmatic natural glass from Egypt, were subjected to investigation by micro-Raman spectroscopy. The spectra of inclusions inside the LDG samples were successfully measured through the layers of glass and the mineral species were identified on this basis. The presence of cristobalite as typical for high-temperature melt products was confirmed, together with co-existing quartz. TiO2 was determined in two polymorphic species rutile and anatase. Micro-Raman spectroscopy proved also the presence of minerals unusual for high-temperature glasses such as anhydrite and aragonite.

Infrared investigation of hard human teeth tissues exposed to various doses of ionizing radiation from the 1986 Chernobyl accident

Infrared spectroscopy (IR) was applied to study changes in solid teeth tissues of persons exposed to low (0.12–0.20 Gy) and high (0.5–1.7 Gy) doses of ionizing radiation during their work in the Chernobyl zone after the accident. Changes in the inorganic and organic matrix of teeth were noted for both high and low radiation doses. The obtained results demonstrated that high doses of radiation lead to imbalance between phosphate–carbonate phases level (because of increasing of CO32− content) and accumulation of soluble phosphates in the mineral part of the teeth. These changes have an effect on dental matrix strength. Low doses of radiation do not induce appreciable negative changes in the mineral part of all tooth tissues but lead to changes in organic matrix of teeth (in collagen).

Composition of prehistoric rock-painting pigments from Egypt (Gilf Kébir area)

The composition of rock-painting pigments from Egypt (Gilf Kebia area) has been analyzed by means of molecular spectroscopy such as Fourier transform infrared and micro-Raman spectroscopy and scanning electron microscopy coupled to an energy dispersive X-ray spectrometer and X-ray fluorescence analysis. Red and yellow pigments were recognized as red and yellow ochre with additional rutile.

Application of chemometric methods for classification of atmospheric particles based on thin-window electron probe microanalysis data

Abstract Conventional single-particle electron probe microanalysis (EPMA) is widely used for evaluating the sources of atmospheric aerosol. The method is capable of simultaneously detecting the chemical composition and the morphology of each particle. Computer-controlled automatic EPMA allows the analysis of huge numbers of individual particles. Cluster as well as factor analysis are used for the classification of particles based on the obtained data set. However, the method is not able to detect low- Z elements (C, N, O), therefore, e.g. organic particles can only be identified by their typical inorganic content and high background. Using a thin-window X-ray detector, the capabilities of EPMA can be extended to determine low- Z elements. The recently developed quantification method based on Monte Carlo simulations is capable to evaluate elemental concentrations in single microscopic particles, including C, N and O. It was shown that also chemical species can be determined from the obtained concentrations. Hierarchical and non-hierarchical cluster analysis, as well as principal component analysis were applied for the classification of particles based on low- Z EPMA data. A mixture of standard particles as well as atmospheric aerosol samples were used to test the classification methods. Different input data (X-ray intensities or elemental concentrations) and scaling functions were used for the chemometric methods. Cluster and factor analysis appear to be efficient tools for classification of particles based on low- Z EPMA data. As an example, atmospheric ammonium sulphate and organic sulphur were classified in separate groups, which was not possible by conventional EPMA.

The contribution of outdoor particulate matter (PM1, PM2.5, PM10) to school indoor environment

The contributions of outdoor and indoor sources to the indoor concentrations of particulate matter (PM1, PM2.5, and PM10) were investigated in a secondary school in Wroclaw, Poland. PM measurements were performed one week per month from December 2009 to October 2010. The sizes of the aerosols generated form indoor sources were in the range of 1–2.5 µm in winter and 2.5–10 µm in summer. It was found that the indoor PM1 concentrations in the school were mostly due to infiltration, with an infiltration factor of 0.65 in winter and 0.68 in summer. These findings, complemented with single particle analyses (using electron probe X-ray microanalysis) revealed that the finest particles, mostly infiltrated from outdoor air, were dominated by organic carbon, sulphates and that organic carbon particles were associated with fly ash or soil dust. Organic carbon was also associated with larger particles of fly ash or soil dust. As part of mineral dust calcium carbonate, salt particles and aluminosilicates were identified. Thus, it is necessary to evaluate the health risks posed to school children associated with the high exposure to indoor PM containing potentially toxic materials in this and probably other schools.

Air Particulate Emissions in Developing Countries: A Case Study in South Africa

Atmospheric aerosols were collected during the winter in Bethlehem, South Africa. The particulate mass concentrations, ambient carbon mass concentrations, and chemical composition of various particulate fractions showed that the area is highly polluted. The fine particle mass concentrations peaked at 1000 µg/m3 for PM2.5. Ambient carbon mass concentrations ranged from 20 to 40 µg/m3. Single particle analysis confirmed that the fine particle fraction was dominated by organic particles. The topographical conditions, causing a low inversion, together with the high amounts of emissions from biomass burning, result in unacceptable levels of air pollution and pose a considerable health threat to the population.