applied sciences Article Paper Sludge Carbon as an Adsorbent for Fukushima Radiocontaminated Paddy Soil Ai Van Tran 1,* and Makoto Yanaga 2 1 Corelex SanEi Co. Ltd., Agoyama 775-1, Shizuoka Prefecture, Fujinomiya City 418-0037, Japan 2 Center for Radioscience Education and Research, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka City 422-8529, Japan;
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[email protected]; Tel.: +81-544-23-0303 Received: 28 August 2020; Accepted: 15 September 2020; Published: 17 September 2020 Abstract: Radiocontaminated soil in a paddy field in the Iitate village in Fukushima was treated with an industrial paper sludge carbon (PSC) prior to growing rice in May 2011. The results showed that the sum of the activity concentrations of 134Cs and 137Cs in the polished rice harvested in October 2011 was 30 Bq kg 1, a level much lower than the Japanese governmental safeguard value of 100 Bq kg 1. · − · − Upon contacting with the contaminated soil, the contents of calcium, magnesium, copper, potassium, and barium in the PSC were decreased. Among the PSCs impregnated with various chlorides and sulfates of the previously mentioned minerals, potassium chloride, copper sulfate, magnesium sulfate, and potassium sulfate yielded higher decontamination degrees compared to the original PSC. The results imply that radioactive cesium in the soil exchanges cations with these minerals. Keywords: paper sludge carbon; decontamination; rice; ion exchange; 134Cs; 137Cs 1. Introduction As the radiocontaminated soil from the Chernobyl nuclear power plant accident in 1986 is concerned, Guillitte and co-workers [1] proposed countermeasures such as the removal of contaminated surface soil, spraying contaminated canopies with detergents or cleaning agents, defoliation and removal of fallen leaves, as well as plowing after clear felling and prior to planting.