Researchers in Japan have detected relatively high levels of radioactive substances in sediment in rivers running through Fukushima Prefecture, Japanese media reported. The prefectural government in January surveyed radioactive materials in soil and other sediment accumulated on the bottoms and banks of 72 rivers. They found up to 54,500 becquerels per kilogram of radioactive substances in the Maeda River in Futaba Town, where the Fukushima Daiichi NPP is situated, and 39,600 becquerels in the Hiru River in Fukushima City. They also detected more than 10,000 becquerels at five other locations in four municipalities.
The prefectural government plans to consider restricting access to rivers with high concentrations of radioactive materials. It also plans to ask the central government to remove contaminated soil and other sediment. Environment Ministry officials say the guidelines do not require decontamination outside living areas. But they add they will consider what to do with highly radioactive sediment after assessing the situation.