I visited my relatives, whose house was also contaminated by radioisotopes. In Oct 2011, I piled soil on his lawn for decreasing radiation. As previously measured, radiation levels were low after soil piled (from 0.7μSV/h to 0.3μSV/h, please see another post, here). It is useful for lowering radiation from lawn.
次に以前コンクリートを塗った箇所も測定しましたが、低下したままでした(これも過去の記事を参考にしてください)。この方法も有効のようです。
Next, I measured the point where I concreted before (see previous post), and found that radiation levels were kept lowering. This method seems to be effective, too.
Previously, I washed concrete stairs with detergent for RI decontamination. This photo was taken at Oct 2011.
This photo was taken at Aug 2012. He washed twice by this detergent. This method is also effective for lowering radiation, but difficult to decrease to 0.3μSV/h.