Though Ministry of the Environment has been measuring cesium from upper than 5cm (1.97 inch) deep under riverbed since May 2011, researching group of Kinki university found more than half of the cesium is accumulated deeper than 5cm.
They measured 53,000 Bq/m2 of cesium at 15km from estuary of Edogawa river. In that area, 56% of cesium was measured from deeper than 5cm under riverbed (about 20cm/7.87inch) this April. In 4 other locations of downstream of the branch from Tonegawa river, 47 ~ 78 % of cesium were also measured from deeper than 5cm under riverbed.
Prof. Yamazaki from the researching team comments riverbed mud can travel by typhoons even if it’s 20cm deep. Government should immediately change their way of measurement.
Iori Mochizuki