AMS analysis of iodine-129 in aerosols from Austria

Atmospheric concentrations of many elements have been significantly increased by human activities. The quantification of these changes and their effect on the terrestrial and aquatic ecosystems is important because of their potentially adverse effects. The human nuclear activities, especially releases from the spent nuclear fuel reprocessing plants, are presently the main source of ¹²⁹I in the environment.In this work, the concentration of ¹²⁹I and the ratios of ¹²⁹I/¹²⁷I in aerosols weekly collected in Vienna, Austria (202 m a.s.l) during the year 2001 are presented. Iodine was extracted from the aerosol filters using a strong basic solution and separated from the matrix elements by anion exchange. The chemical yield of the procedure, determined by ICP-MS, ranges from 70% to 95%. The AMS results indicated that the ¹²⁹I/¹²⁷I isotopic ratios were of the order 10⁻⁸ to 10⁻⁷. The ¹²⁹I originated from gaseous emissions from the Sellafield reprocessing plant. The measured ¹²⁹I concentrations were compared with those of ⁷Be, a cosmogenic radionuclide. Although, both radionuclides exhibit nearly the same distribution pattern (higher levels in summer and lower in winter) their different origins can clearly be deduced from short term variations.     

Nanostructured Ca-based sorbents with high CO2 uptake efficiency

Calcium-based carbon dioxide sorbents were made in the gas phase by scalable flame spray pyrolysis (FSP) and compared to the ones made by calcination (CAL) of selected calcium precursors. Such flame-made sorbents consisted of nanostructured CaO and CaCO₃ with twice as much specific surface area (40-60 m²/g) as the CAL-made sorbents. All FSP-made sorbents exhibited faster and higher CO₂ uptake capacity than all CAL-made sorbents at intermediate temperatures. CAL of calcium acetate monohydrate resulted in sorbents with the best CO₂ uptake among all CAL-made ones. At higher temperatures both FSP- and CAL-made sorbents (esp. from CaAc₂·H₂O) exhibited very high initial molar conversions (95%) but sintering contributed to grain growth that reduced the molar conversion down to 50%. In multiple carbonation/decarbonation cycles, the nanostructured FSP-made sorbents demonstrated stable, reversible and high CO₂ uptake capacity sustaining maximum molar conversion at about 50% even after 60 such cycles, indicating high potential for CO₂ uptake. The top performance of flame-made sorbents is best attributed to their nanostructure (30-50 nm grain size) that allows operation in the reaction-controlled carbonation regime rather than in the diffusion-controlled one when sorbents made with larger particles are employed.     

Hourly measurement of particulate concentrations with streaker samplers and optical methods

We have studied the possibility of continuous particulate monitoring, by an optical system, on the filters of a two-stage streaker sampler. The streaker deposits, collected for PIXE analysis, have been examined off-line by measuring the attenuation of a light beam. The optical analysis provides, in a few minutes, an estimate of hourly total mass concentrations, over a one week period, for both stages, very useful as a selection for further PIXE irradiation. We describe the set-up and the calibration procedures, where PIXE plays a fundamental role in resolving different aerosol compositions and in validating the prototype performance. The results obtained over 2 weeks of operation and the comparison with the aerosol component determined via PIXE analysis, are also discussed.     

Elemental and mineral characterisation of Coastal Antarctic Aerosols in snow using PIXE and SEM-EDAX

The chemical constituents of snow from a 3 m pit sampled at a coastal Antarctic site were characterised by means of PIXE and SEM-EDAX. Oxygen isotope dating revealed that the pit spanned an 8-year period, from 1986 to 1994. Concentrations measured by PIXE ranged from less than 1 ng g⁻¹ of H₂O for Cu, and Zn to several tens of ng g⁻¹ for Si, S and Cl. The major elements found were Si, S, Al, and Na, which contributed more than 75% of the element loading. Snow layers with elevated Cl concentration were regularly found along the pit. The mineralogy of the insoluble particles determined by SEM-EDAX analyses showed that quartz, plagioclase and clays were the prevalent minerals. The proportion of each element in the insoluble phase was comparable with that previously found in similar studies.     

快中子脉冲反应堆厅内空气中裂变产物污染的研究

本文研究了快中子脉冲反应堆大厅内空气中裂变产物的污染问题。通过对ＣＦＢＲ－Ⅱ快中子脉冲反应堆爆发额定产额脉冲（１．５３×１０１６裂变）后，厅内气溶胶的取样和γ谱分析，确定了裂变产物从黄铜壳内空气中释放到厅内空气中形成气溶胶的释放份额为５×１０－３。利用此释放份额计算了厅内空气中不同放射性核素的气溶胶浓度；还计算了该堆爆发额定产额脉冲后不同冷却时间ｔ厅内空气中无分凝混合裂变产物的导出空气浓度ＤＡＣ（ｔ）值，为该堆辐射安全分析和现场辐射防护提供了依据。     

Preparation of Silica Nanostructured Spheres by Sol Spray Drying

Silica nanostructured spheres were obtained by spray drying of silica sol prepared in situ. Their morphologies were significantly affected by the aggregation of the primary particles in the sol. They had the mode of the pore sizes which was about the same order as Laser Particle Size Analyzer (LPA) diameter. Increasing the mixing ratio of the larger particles (20 nm) to smaller ones (7 nm) decreased the Brunauer, Emmett and Teller (BET) specific surface area, as expected. Pore volume decreased with the pore size distribution broadened and the mean pore diameter was not affected by the increase, due to the decrease in aggregation of the primary particles. Either the increase in the drying temperature and use of ethanol as a cosolvent made the agglomerates hollower, the larger of which with thinner shell transformed to doughnut type agglomerates, due to the structural and hydrodynamic instabilities.     

Aerosol characterisation in Italian towns by IBA techniques

The composition of particulate matter in the atmosphere of four major Italian towns (Florence, Genoa, Milan and Naples) has been studied with the extensive application of IBA techniques. The aerosol has been collected simultaneously in the four towns during the first weeks of year 2001, by two-stage continuous streaker samplers, which provide the separation of the particulate matter in two fractions. The concentrations in air of about 20 elements, and the total particulate mass, have been extracted in the PM2.5 and PM10 fractions with hourly resolution by PIXE, PIGE and optical analyses of about 2700 samples. IBA analyses have been performed at the 3 MeV external proton beam of the INFN accelerator facility at the University of Florence.     

对高效空气过滤器检漏的研究

过滤器检漏测试是洁净室的洁净和质量的决定性因素之一，因此本文从上游发尘方式的选择，到上游气溶胶粒径分布、上游气溶胶浓度，等几个方面讨论了上游尘源特性对检漏测试的影响，然后又对受上游气溶胶浓度影响的几个参数进行了论述，并且详尽阐述了它们对检漏的重要意义，以及确定原则。并得出了确定漏点所需要的最小尘粒数的取值范围应在4～6之间的结论。     

Experimental investigation on the effect of top electrode diameter in PZT thick films

We report the effect of top electrode diameter size in aerosol deposited Pb(Zr_0.52Ti_0.48)O₃ thick films (~ 10 μm-thick) with Pt top and bottom electrode. Dielectric and ferroelectric results showed that top electrode diameter of 0.5-1 mm provides reasonable performance with 1 mm being the most suitable dimension in wide range of AC electric field and frequency. The results were discussed based on the surface microstructure and Debye relaxation. The dielectric analysis showed that the properties variation was mainly due to average grain size and defect density. Debye relaxation modeling exhibited that the result is because of materials characteristic not measurement artifact. We believe the results of this study will find immediate application in design of aerosol deposition process.     

Enhanced bioactivity and biocompatibility of nanostructured hydroxyapatite coating by hydrothermal annealing

The crystallinity of hydroxyapatite (HA) coatings prepared by aerosol deposition may be increased by heating in air or low-temperature hydrothermal processing. From the X-ray diffraction and Fourier transform infrared spectroscopy results, it was revealed that the crystallinity of the HA coatings significantly increased after the post-annealing. Transmission electron microscopy showed that the conventional furnace heating induced the substantial growth of the HA crystallites, whereas the hydrothermal treatment did not bring about any remarkable change in the HA crystallite size, which remained below 20 nm. The bioactivity of the HA coatings was estimated by the acellular simulated body fluid immersion test. After immersion for 7 days, newly-precipitated apatite crystals were only observed on the surfaces of the samples hydrothermally treated at 170 and 190 °C. In addition, the alkaline phosphatase activity of MC3T3-E1 preosteoblast cells cultured on the hydrothermally treated samples was significantly higher than those on the as-deposited coating and conventional furnace heated samples. The enhanced bioactivity and excellent biological in vitro cellular response of the hydrothermally treated samples were attributed to their nanostructured nature and high degree of crystallinity.