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Temporal evolution of charged and neutral nanoparticle concentrations during atmospheric new particle formation events and its implications for ion-induced nucleation

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Frontiers of Environmental Science & Engineering 2016年第5期10卷 143-151页

作者： E. Rohan Jayaratne Buddhi Pushpawela Lidia Morawska International Laboratory for Air Quality and Health Queensland University of Technology Brisbane QLD 4001 Australia

Time series of nanoparticle number concentration during new particle formation （NPF） events in the urban environment of Brisbane, Australia, showed that the formation of charged particles often occurred before that of neutral particles. We monitored 241 days during the calendar year 2012 over which NPF events were observed on 108 days. We studied the times at which the charged and neutral particle concentrations in the size range 1.8-3.2 nm reached their peak values and found that they were clearly different in 50 events with the peak neutral particle concentration lagging behind the charged particle concentration during 42 of these events with a mean time lag of 245-12 rain. While the charged particles were more likely to form before the neutral particles, once lbrmed, the growth rate of the particles did not depend on their charge. While ion-induced nucleation is not the dominant mechanism of NPF in the atmosphere, our observations suggest that the presence of ions in the atmosphere plays a role that cannot be ignored.

关键词： Charged particles Cluster ions secondary particles Environmental pollution

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Composition and mixing state of water soluble inorganic ions during hazy days in a background region of North China

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Science China Earth Sciences 2015年第11期58卷 2026-2033页

作者： LU YaLing CHI JianWei YAO Lan YANG LingXiao LI WeiJun WANG ZiFa WANG WenXing Environment Research Institute Shandong University Key Laboratory of Arid Climatic Change and Reducing Disaster of Gansu Province/Key Laboratory of Arid Climatic Change and Disaster Reduction of CMA Institute of Arid Meteorology of CMA School of Environment Science and Engineering Shandong University State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of Sciences

Knowledge of haze particles in background areas of North China is limited, although they have been studied well in urban settings. Atmospheric aerosol particles were collected at a background site in the North China Plain during 16–31 January, 2011. Water soluble inorganic ions of PM2.5 and physicochemical characteristics of individual particles on hazy and clean days were measured by Ion Chromatography(IC) and Transmission Electron Microscopy(TEM), respectively. Average PM2.5 mass concentration was 50.4±29.9 μg m?3 with 62.5±26.8 μg m?3 on hazy days and 19.9±11.5 μg m?3 on clean days. SO42?, NO3?, and NH4+ with a combined mass concentration of 19.0±11.5 μg m?3 accounted for 69.8%–89.4% of the total water soluble inorganic ions. Size distributions of SO42? and NH4+ showed one unimodal peak at 0.56–1.8 μm on hazy days, whereas NO3? appeared as bimodal peaks at 0.56–1.8 and 5.6–10 μm, respectively. Individual particle analyses showed that the dominant aerosols were a mixture of sulfate, nitrate, and carbonaceous species, which together determine their mixing states. 48-h air mass back trajectories on hazy days suggested that air masses crossed the polluted continental areas(such as Jing-jin-ji region and Shandong province) and entrained ground air pollutants 11–19 hours before reaching the background area. During long-range transport particles undergo ageing and tend to be internally mixed mainly due to condensation in the background atmosphere. Our results suggest that hygroscopic and optical properties of these aerosol particles in the background area differ substantially from those in urban areas.

关键词： water soluble inorganic ions individual particles secondary particles mixing state background region haze episode

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About Radiation in ^natGd for Neutron Capture Therapy

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Journal of Health Science 2016年第1期4卷 35-44页

作者： Gayratulla A. Kulabdullaev G. A. Abdullaeva A. A. Kim T. T. Rakhmonov A. Kurmantaev Institute of Nuclear Physics Uz AS Tashkent Uzbekistan University of Akhmet Yasawi Turkestan Kazakhstan

In the present work, based on publications dedicated to ^natGd natural gadolinium isotopes, characteristics of secondary particles are analysed in details for various neutron-induced reactions. Characteristics of the secondary particles produced in these reactions that make significant contribution to absorbed dose are estimated. It is also established that the main contribution to the absorbed dose is made by secondary particles produced in interactions of neutrons and ^155Gd and ^157Gd isotopes. From comparison of gamma-radiation spectra it is defined that the amount of γ-quanta with energies 0-400 keV （i.e. effective γ-quanta） produced in the （n,γ）-reaction by ^155Gd is higher than that by ^157Gd. Compared spectra of other particles （internal conversion electrons, Auger electrons, x-ray radiation） have shown that earlier used average values of their energy must be defined more precisely. When biological objects are irradiated for approximately 30 minutes by epithermal neutrons in the ^natGd NCT （Gadolinium-based neutron-capture therapy）, one should take into account energies of secondary particles produced by ^152Gd, ^154Gd, ^156Gd, ^158Gd and ^160Gd isotopes as they have high linear energy transfer （LET）. It is demonstrated that when combined, all these secondary particles can make significant contribution to the absorbed dose at neutron-irradiation of biological objects by the ^natGd NCT technique.

关键词： Nuclear reactions natural gadolinium isotopes secondary particles conversion electrons epithermal neutrons neutron capture therapy radiation biological effect.

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