• Title/Summary/Keyword: Atmospheric aerosols

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Deposition of Aerosols on Leaves in a Cool-temperate Larch Forest in Northern Hokkaido, Japan

  • Tatsuya, Fukazawa;Naoto, Murao;Hisashi, Sato;Masahiro, Takahashi;Masayuki, Akiyama;Takashi, Yamaguchi;Izumi, Noguchi;Hiroyuki, Takahashi;Chikara, Kozuka;Rei, Sakai;Kentaro, Takagi;Yasumi, Fujinuma;Nobuko, Saigusa;Kazuhide, Matsuda
    • Asian Journal of Atmospheric Environment
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    • v.6 no.4
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    • pp.281-287
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    • 2012
  • Aerosol concentrations at the CC-Lag site in the Teshio Experimental Forest increased from winter to spring and sometimes showed extremely high values associated with Kosa and/or forest-fire events. The range and mean of the mass concentrations of aerosol chemical species were as follows: total particulate mass, 1.2-29, 5.0; elemental carbon, 0.061-2.2, 0.43; organic carbon, 0.059-3.5, 0.79; and sulfate, 0.12-6.2, 1.8 ${\mu}g/m^3$. The total masses of the deposited particles on hybrid larch and on bamboo leaves were approximately 35 and 30 ${\mu}g/cm^2$, respectively. The amounts of soil particles on the leaves were 6 ${\mu}g/cm^2$ for the upper part of hybrid larch, 2 ${\mu}g/cm^2$ for the lower part of hybrid larch, and 1 ${\mu}g/cm^2$ for Sasa bamboo leaves. The amounts of deposited black carbon were 2.3 ${\mu}g/cm^2$ for the upper part of hybrid larch, 0.6 ${\mu}g/cm^2$ for the lower part of hybrid larch, and 0.2 ${\mu}g/cm^2$ for Sasa bamboo leaves. Half of the total deposited particular mass was attached on the hybrid larch; however, most of the total deposited mass was adhered on the Sasa bamboo leaves. Regardless of the species, there tend to be more deposited particles on the leaves in the upper part than in the lower part, with only a few meters height difference. Comparing the composition of the deposited particles to that of the atmospheric aerosols without any size cut, the fractions of water-soluble material sulfate and sea salt in the deposited aerosols were about one tenth and one hundredth lower than that in the aerosols, respectively. On the basis of the measured concentration and the deposited amount on leaves, the deposition velocity of black carbon was estimated to be approximately 0.5 cm/s.

Composition of Size-Segregated Atmospheric Aerosol Collected at an Urban Roadside Environment in Jeju Area (제주지역 도로변 대기 중 에어로졸의 입경별 조성특성)

  • Hu, Chul-Goo;Kim, Su-Mi;Lee, Ki-Ho
    • Journal of Environmental Science International
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    • v.29 no.1
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    • pp.79-93
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    • 2020
  • To determine the size distributions of water-soluble inorganic ionic species (WSIS) in roadside aerosols, sampling experiments were carried out in the urban roadside area of Jeju City on August 2018 and January 2019 by using the eight-stage cascade impactor sampler. The mass of roadside aerosols were partitioned at 57% in fine fraction, 36-37% in coarse fraction, and 6-7% in giant fraction, regardless of summer and winter. The mass concentrations of WSIS except for Na+ and SO42- in roadside aerosols were higher in winter than in summer. The size distributions of Na+, Mg2+, Ca2+ and Cl- were characterized by bimodal types with coarse particle mode peaking around 3.3-4.7 ㎛ and 5.8-9.0 ㎛. The size distributions of NO3- and K+ shifted from a single fine mode peaking around 0.7-1.1 ㎛ in winter to bimodal and/or trimodal types with peaks around coarse mode in summer. SO42- and NH4+ showed a single fine mode peaking around 0.7-1.1 ㎛. The MMAD of roadside aerosols was lower than that of Na+, Mg2+, Ca2+ and Cl-. Based on the marine enrichment factors and the ratio values of WSIS and the corresponding value for sea water, the composition of roadside aerosols in Jeju City may be practically affected by terrestrial sources rather than marine source.

Improvement and validation of aerosol models for natural deposition mechanism in reactor containment

  • Jishen Li ;Bin Zhang ;Pengcheng Gao ;Fan Miao ;Jianqiang Shan
    • Nuclear Engineering and Technology
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    • v.55 no.7
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    • pp.2628-2641
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    • 2023
  • Nuclear safety is the lifeline for the development and application of nuclear energy. In severe accidents of pressurized water reactor (PWR), aerosols, as the main carrier of fission products, are suspended in the containment vessel, posing a potential threat of radioactive contamination caused by leakage into the environment. The gas-phase aerosols suspended in the containment will settle onto the wall or sump water through the natural deposition mechanism, thereby reducing atmospheric radioactivity. Aiming at the low accuracy of the aerosol model in the ISAA code, this paper improves the natural deposition model of aerosol in the containment. The aerosol dynamic shape factor was introduced to correct the natural deposition rate of non-spherical aerosols. Moreover, the gravity, Brownian diffusion, thermophoresis and diffusiophoresis deposition models were improved. In addition, ABCOVE, AHMED and LACE experiments were selected to validate and evaluate the improved ISAA code. According to the calculation results, the improved model can more accurately simulate the peak aerosol mass and respond to the influence of the containment pressure and temperature on the natural deposition rate of aerosols. At the same time, it can significantly improve the calculation accuracy of the residual mass of aerosols in the containment. The performance of improved ISAA can meet the requirements for analyzing the natural deposition behavior of aerosol in containment of advanced PWRs in severe accident. In the future, further optimization will be made to address the problems found in the current aerosol model.