Settlement process of radioactive dust to the ground inferred from the atmospheric electric field measurement
Radioactive materials from the accident at Fukushima Dai-ichi nuclear power plant (FNPP) in March 2011 spread over a large area, increasing the atmospheric electric conductivity by their ionizing effect, and reducing the vertical (downward) component of the DC electric field near the ground, or...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2012-01-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/30/49/2012/angeo-30-49-2012.pdf |
| Summary: | Radioactive materials from the accident at Fukushima Dai-ichi nuclear power
plant (FNPP) in March 2011 spread over a large area, increasing the
atmospheric electric conductivity by their ionizing effect, and reducing the
vertical (downward) component of the DC electric field near the ground, or
potential gradient (PG). PG data at Kakioka, 150 km away from the FNPP,
showed independent changes compared to the radiation dose rate, and a
comparison of these data revealed the local dynamics of the radioactive dust.
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(1) The initial drop of the PG to almost zero during 14–15 March is
most likely due to radioactive dust suspended in the air near the ground
during cloudy weather. (2) An episode of PG increase to more than 50 V m<sup>−1</sup> on
16 March is most likely due to the re-suspension of the radioactive dust from
the surface and subsequent removal from Kakioka by the strong wind from the
non-contaminated area. (3) Low but finite values of the PG during 16–20 March
most likely reflect a reduced amount of radioactive material near the ground
after the above wind transported away the majority of the suspended
radioactive dust. (4) Very low values of the PG after substantial rain on
20–22 March most likely reflect settlement of the radioactive material by
rain-induced fallout. (5) Temporal recovery of daily variations from the end
of March to the middle of April with low nighttime fair-weather baseline PG
most likely reflects re-suspension of the radioactive dust into the air from
the ground and trees, and subsequent transport to the other region or fallout
to the ground until late April. (6) Weakening of the daily variation and
gradual recovery of the nighttime fair-weather baseline after mid-April
suggests a complete settlement of the radioactive material to the ground with
partial migration to the subsurface. |
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| ISSN: | 0992-7689 1432-0576 |