Spatial variation in low-level ^sup 134^Cs in the coastal sediments off central Honshu in the Sea of Japan: implications for delivery, migration, and redistribution patterns

In 2014 and 2015, we examined the spatial distribution of cesium-134 (half-life: 2.06 years) from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in marine sediments within coastal–basin areas (water depths of 40–520 m) off central Honshu Island (the main island of Japan) in the Sea of Japan. The...

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Bibliographic Details
Published in:Journal of oceanography 2017-10, Vol.73 (5), p.571
Main Authors: Inoue, Mutsuo, Uemura, H, Kofuji, H, Fujimoto, K, Takata, H, Shirotani, Y, Kudo, N, Nagao, S
Format: Article
Language:English
Subjects:
Area
Bottom currents
Caesium
Cesium
Coastal waters
Coastal zone
Contaminated sediments
Electric power plants
Estuaries
Estuarine dynamics
Marine plants
Marine sediments
Migration
Migrations
Nuclear accidents
Nuclear electric power generation
Nuclear energy
Nuclear power plants
Ocean floor
Rivers
Sea currents
Sediment
Sediments
Slope
Spatial distribution
Spatial variations
Suspended particulate matter
Suspended solids
Water depth
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Summary:In 2014 and 2015, we examined the spatial distribution of cesium-134 (half-life: 2.06 years) from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in marine sediments within coastal–basin areas (water depths of 40–520 m) off central Honshu Island (the main island of Japan) in the Sea of Japan. The 134Cs concentrations in both the surface sediment (0–1 cm depth) and whole-core inventory exhibited wide variations, and were highest at the site closest to the Agano River Estuary area (6.7 Bq/kg-dry and 886 Bq/m2, respectively). This indicates that 134Cs in coastal areas was delivered by riverine suspended solids (SS). Given the spatial variation in 134Cs concentrations, we believe that 134Cs partially migrated northeastward within ~50 km along Honshu Island (at water depths shallower than ~140 m), and southwestward, including the Sado Basin area. This is predominantly attributable to the transport of SS by bottom currents and unsteady downward delivery onto the steep slopes of the basin. The total amount of 134Cs in the study area in 2014 was estimated at approximately 0.6 TBq (decay-corrected to March 11, 2011, date of FDNPP accident).
ISSN:0916-8370
1573-868X
DOI:10.1007/s10872-017-0437-x