Radioactivity Dynamics in forests
ＱWhen it rains, does radioactive cesium flow out of forests with soil? 【Tendency of the change of the 137Cs concentration in soil】
ＡThe concentration of radioactive cesium in soil flowing out from mountain forests is decreasing with time.
Investigations in Namie Town, Fukushima Prefecture, have revealed that the rate of 137Cs outflow (※1) in 27 months (August 29, 2013-December 1, 2015) is about 0.1% in a year, which is a bit higher than those in other investigation plots, but less than 1% in a year.(Lower-left table)
The rate of soil and 137Cs outflow increase by heavy rain about once every ten years(Investigation period: Sep 2-Dec1, 2015), but usual rate of 137Cs outflows (Investigation period: Aug 29, 2013-Sep 2, 2015) is estimated 0.05-0.24 % per a year(Lower-left table).
Surface soil deposited in soil saving dam, Namie Town was taken as samples (5 cm), and the concentration of cesium was analyzed. It was observed that the concentration of radioactive cesium is decreasing with time (Lower-right figure).
Table 1 Amount and rate of radioactive cesium and soil outflow from the soil saving dam, Kawafusa, Ogaki, Namie Town, Fukushima Prefecture
|Rate of outflowing
|Aug 29,2013 ～Dec 3,2014||0.5 m3||150 MBq||0.24 ％
|Dec 3,2014 ～Sep 2,2015||0.1 m3||30 MBq||0.05 ％
|Sep 2,2015 ～Dec 1※||1.8 m3||540 MBq||0.86 ％
|Total of investigation period||2.4 m3||720 MBq||1.14 ％
※ Rain fall in Sep 9 and 10, 2015 is 114 mm and 171 mm per a day, 20% of total rain fall of the year was fall in 2 days.
- When it rains, does radioactive cesium flow out of forests with soil? 【137Cs flow in heavy rain】
- When it rains, does radioactive cesium flow out of forests with soil? 【Relationship between the coverage rate of forest floor and flowing rate from forests】
- Where is the radiocesium in river water coming from?
- How do rainfalls affect turbidity and radioactive cesium concentrations in river water?【Example of analysis】
- What is the source of radio-cesium in the airborne dust sampling?