Radioactivity Dynamics in forests
（2015）
ＱDoes radioactive cesium move from the ground surface to underground or into groundwater? 【Movement in the water flow in the litter layer】
ＡAn investigation in Kawauchi Village, Fukushima Prefecture has revealed that the concentration of radioactive cesium in water flow on the litter layer (litter flow) was appreciably lower than that in soil and litter. Rate of radioactive cesium outflow was less than 0.01% in two months.
Investigation in Kawauchi Village in 2014 also did not detect radioactive cesium in underground water.
- Based on results from the investigation in Kawauchi Village from autumn to early winter, it was found that amount of cesium outflow by litter flow is small.
- Investigation in Kawauchi Village has also revealed that radioactive cesium (137Cs) was not detected in underground water (80 cm depth) at the slope where litter flow was confirmed.
- JAEA will continue to investigate outflow rate of radioactive cesium from forests in Kawamata Town, Kawauchi Village, and Namie Town, Fukushima Prefecture.
Fig.1 Photograph of the measurement place (Mixed forest of konara oak and Japanese ceder)
(Observation dade: from October to December, 2014)
| Area of slope | about 50 m2 |
| Flow rate | 55 L/h |
| Concentration of 137Cs | about 0.050 Bq/L （134Cs was not detected） |
| Amount of 137Cs deposition in slope | Litter：about 108 kBq/m2 Soil：about 527 kBq/m2 |
| Amount of cesium outflow (2 months from autumn to early winter) |
about 81 Bq/m2 → about 0.01 ％ |
Fig.2 Pumping underground water from observation hole using a hand pump
- Underground water in a broadleaf forest in Kawauchi Village was taken as samples. After filtrating the samples with 0.45 μm filter, the concentration od radioactive cesium was measured.
- As a result, concentration of radioactive cesium (137Cs) was lower than the normal detecyion limit of the detector (1 Bq/L). Even when the detection limit was lowered to 0.04 Bq/L, radioactive cesium was not cbserved.
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