A novel technique for removing radiocesium from bamboo, and effects of bamboo chip composts on soil properties and crop growth

Bamboo forests in the Fukushima area were contaminated with radiocesium following the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. There is a need to develop technologies for remediation of contaminated bamboo forests. However, remediation technologies such as incineration of contaminated plants, which not only harms the environment but also destroy the local resources. This research introduces a novel technique, which reduces radiocesium by boiling the thinned bamboo, with the aim of commercializing the product as bamboo chip compost. We compared the ¹³⁴Cs and ¹³⁷Cs contents of boiled and unboiled bamboo chips, and also evaluated the effect of treating the bamboo boiled water extracts with bentonite. In addition, we compared the radiocesium changes and nutrient statuses of bamboo chip composts derived under aerobic and anaerobic conditions. Furthermore, we evaluated changes in soil properties and the growth of komatsuna (Brassica rapa var. perviridis) following application of final composts at 0, 2.5, 5, and 10 kg m⁻². We found that boiling bamboo with 3% NaHCO₃ for 30 min decreased the Cs content by approximately 52%, and that the 1% bentonite treatment reduced Cs contamination in water extract by 75%. The compost amendments containing boiled bamboo mixed with sub-materials under anaerobic conditions resulted in significantly lower soil Cs concentrations, than other compost amendments. The addition of aerobic composts consisting of boiled bamboo mixed with sub-materials resulted in significantly higher soil N, P levels and Komatsuna growth, with the plants containing radiocesium concentrations of <0.1 Bq kg⁻¹.