Akira Mizohata

Factors, especially sunspot number, causing variations in surface air concentrations and depositions of 7Be in Osaka, Japan

We found that increasing sunspot number caused a significant negative effect on monthly and yearly average air concentration and yearly deposition of 7Be. For more than 15 years monthly average surface air concentration and monthly deposition of 7Be was measured in Osaka, Japan. The maximum monthly average surface air concentration of 7Be was 1.6 times higher than the minimum concentration through the fifteen year measurement span. Increase of several percent in the monthly averaged surface air concentration and monthly deposition of 7Be were observed in the monthly mean for February-March-April 1987 period following the 23 February supernova explosion in the Large Magellanic Cloud. The seasonal variation pattern which includes the lowest surface air concentration of 7Be in summer is due to the transport of air masses from low latitudes carrying low 7Be concentrations into the middle latitude region.

Comprehensive assessment of PM2.5 physicochemical properties during the Southeast Asia dry season (southwest monsoon)

A comprehensive assessment of fine particulate matter (PM2.5) compositions during the Southeast Asia dry season is presented. Samples of PM2.5 were collected between 24 June and 14 September 2014 using a high-volume sampler. Water-soluble ions, trace species, rare earth elements, and a range of elemental carbon (EC) and organic carbon were analyzed. The characterization and source apportionment of PM2.5 were investigated. The results showed that the 24 h PM2.5 concentration ranged from 6.64 to 68.2 µg m−3. Meteorological driving factors strongly governed the diurnal concentration of aerosol, while the traffic in the morning and evening rush hours coincided with higher levels of CO and NO2. The correlation analysis for non sea-salt K+-EC showed that EC is potentially associated with biomass burning events, while the formation of secondary organic carbon had a moderate association with motor vehicle emissions. Positive matrix factorization (PMF) version 5.0 identified the sources of PM2.5: (i) biomass burning coupled with sea salt [I] (7%), (ii) aged sea salt and mixed industrial emissions (5%), (iii) road dust and fuel oil combustion (7%), (iv) coal-fired combustion (25%), (v) mineral dust (8%), (vi) secondary inorganic aerosol (SIA) coupled with F− (15%), and (vii) motor vehicle emissions coupled with sea salt [II] (24%). Motor vehicle emissions, SIA, and coal-fired power plant are the predominant sources contributing to PM2.5. The response of the potential source contribution function and Hybrid Single-Particle Lagrangian Integrated Trajectory backward trajectory model suggest that the outline of source regions were consistent to the sources by PMF 5.0.

Fabrication of Reference Filter for Measurements of EC (Elemental Carbon) and OC (Organic Carbon) in Aerosol Particles

Reference filters with uniformly deposited, known masses of elemental carbon (EC) and organic carbon (OC) were produced by a spray-drying method and a carbon aerosol sampling system. Submicrometer carbon particles were produced by nebulizing a carbon black hydrosol and a potassium hydrogen phthalate (KHP; C 6 H 4 (COOK)(COOH)) solution. Total carbon (TC) concentrations measured at three different locations on the filter showed that the carbon particles were uniformly distributed on the filter. Reference filters were analyzed using thermal optical analysis methods (TOA) IMPROVE and NIOSH 5040-NIIH, and the measured concentrations of TC, EC, and OC were compared to the gravimetrically measured concentrations. TC measurements by both TOA methods used were in excellent agreement with gravimetrically measured TC. It was found that the IMPROVE method produced approximately 3.5 times as much pyrolytically generated elemental carbon (PEC) as did the NIOSH 5040-NIIH method. However, no PEC was detectable on reference filters when both EC and OC were present. This led to discrepancies in EC and OC measurement between the TOA and gravimetric methods. Better agreement was found when PEC generation of pure OC reference filters was taken into account and measurements on filters with both EC and OC deposited were corrected for PEC generation. These data imply that, when both EC and OC are present on the filter, TOA methods are often inaccurate in correctly measuring the amount of PEC generated, with the magnitude of measurement error dependent upon the type of EC and OC present in the sample. In addition, reference filters with OC deposited on top of EC and EC deposited on top of OC were generated and analyzed. From these reference filters, it was found that PEC measurements are also affected by the way in which the EC and OC deposit on the filter. Overall, the method devised here to create reference EC/OC filters is a simple technique in which EC, OC, and mixed EC-OC particles of a controlled size and chemical composition can be deposited uniformly onto filters and such reference filters will be invaluable in evaluation of TOA methods of EC/OC measurement.

Evaluation of Induced Radioactivity in 10MeV-Electron Irradiated Spices (II). .BETA.-Ray Counting.

香辛料の元素組成からリストアップされた10MeV電子線照射により生じる恐れのある (γ, n) 反応由来のβ線放出核種を検出するため照射試料のβ線計測を行った。100kGy照射した2πガスフローカウンタ, 液体シンチレーションカウンタによる計測では誘導放射能は検出されなかった。 (γ, n) 反応の標的核種を含む化合物を照射した場合の誘導放射能の値から, 天然の試料の誘導放射能は無視できるレベルであると考えられた。

Preliminary Examination of Induced Radioactivity in Pepper by 10MeV Electron Irradiation. Mesurement of .BETA.-Ray with Liquid Scintillation Counter.

β-ray measurement was performed on 10 MeV electron-irradiated black pepper and white pepper with liquid scintillation counter in order to reconfirm the wholesomeness of irradiated foods and present unambiguous data to general consumers concerning about the induced radioactivity in the irradiated foods.In irradiated black pepper no radioactivity other than from natural source, un-irradiated one, was detected. But in irradiated white pepper, it was suggested that induced radioactivity might be detected if the detection method was more improved.