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mately 60 km) apart from L. volemus as well as in the saprophytic fungus Grifola frondosa (maximum = 2,800 Bq/kg FW, approximately 20–30 km).
Chapter 15

Mushrooms: Radioactive Contamination of Widespread Mushrooms in Japan Toshihiro Yamada

Abstract High concentrations of radionuclide contamination of wild mushrooms occurred near the Fukushima Daiichi nuclear power plant and along the path of radioactive plumes. This is a serious problem for the forest ecosystem and commercial wild mushroom production. Radioactivity in wild mushrooms collected from low-level contamination forest areas throughout Japan was measured approximately 6 months after the accident. In general, the radioactivity in mushrooms did not exceed those in the neighboring forest litter. However, further accumulation of 137Cs is expected in mushrooms; therefore, continuous monitoring is necessary even in low-contamination areas. We also found that residual 137 Cs radioactivity due to nuclear weapons tests, mainly in 1950s, besides fallout from the Fukushima nuclear accident still remained in soil and was accumulated by mushrooms. Keywords Chernobyl nuclear accident • Nuclear weapons tests • Radioactive fallout • Radiocesium • The University of Tokyo Forests • Transfer factor • Wild mushrooms

Abbreviations Cs DW FW

Cesium Dry weight Fresh weight

T. Yamada (*) The University of Tokyo Chiba Forest, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 770 Amatsu, Kamogawa, Chiba 299-5503, Japan e-mail: [email protected] T.M. Nakanishi and K. Tanoi (eds.), Agricultural Implications of the Fukushima Nuclear Accident, DOI 10.1007/978-4-431-54328-2_15, © The Author(s) 2013

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I K NPP NWT TF

Iodine Potassium Nuclear power plant Nuclear weapons test Transfer factor

15.1

Introduction

Fungi are one of the major and important components of forest ecosystems. Radioactive contamination of mushrooms should be considered not only from the viewpoint of food but also from the viewpoint of its effects on plants and animals, including crops, domestic animals, and wood products, through its circulation in the forest ecosystem. From 1950s to 1960s, a high uptake of 137Cs, derived from atmospheric nuclear weapons tests (NWT), by mushrooms was also noticed in Japan (Muramatsu and Yoshida 1997; Sugiyama et al. 1994; Yoshida and Muramatsu 1996). Radionuclides released by the accident at the Fukushima Daiichi nuclear power plant (F1-NPP) deposited over a wide area of East Japan. Radiocesium concentrations exceeding the safety threshold were detected in mushrooms hundreds of kilometers from F1-NPP. The Japanese interim limit for imported foods was 370 Bq/kg fresh weight (FW) of radiocesium after the Chernobyl nuclear accident in 1986 (Sugiyama et al. 1994). The interim limit after the Fukushima nuclear accident was set to 500 Bq/kg FW. However, a stricter limit of 100 Bq/kg FW was introduced in April 2012. Therefore, reducing the radiocesium contamination of food has become more important. Mushrooms have been reported to accumulate radiocesium (Byrne 1988; Kammerer et al. 1994; Mascanzoni 1987; Muramatsu et al. 1991; Sugiyama et al. 1990, 1994). For example, the transfer factors (TF) for radiocesium in mushrooms were reported to be 2.6–21 in several culture tests (Muramatsu et al. 1991; Ban-nai et al. 1994). However, the radiocesium activity ratio in mushrooms relative to the soil in a field study were rather low and the ratio was often