title: Radiocesium immobilization to leaf litter by fungi during first-year decomposition in a deciduous forest in Fukushima.
abstract: Vast forest areas in eastern Japan have been contaminated with radio-isotopes by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Radiocesium (radioCs) is known to remain bioavailable in forest ecosystems for a long time, and it is necessary to terminate the cycling process to decontaminate the forest ecosystem. We observed radiocesium concentrations of leaf litter during decomposition on a forest floor where radiocesium ((137)Cs) contamination was ∼155 kBq/m(2). Litter bag experiments were conducted with newly fallen mixed deciduous leaf litter in a deciduous forest (alt. 610 m) about 50 km from the FDNPP. Litter bags were retrieved in April, June, August, October, and December 2012. Fresh litter (137)Cs concentration was ∼3000 Bq/kg in December 2011. During the decomposition process on the forest floor, litter (137)Cs concentration increased rapidly and exceeded 25,000 Bq/kg after 6 months, whereas potassium (K) concentration in the litter was rather stable, indicating that radiocesium and K showed contrasting dynamics during the early decomposition phase. Nitrogen, phosphorus, and (137)Cs contents were positively correlated to fungal biomass, evaluated by phospholipid fatty acids in the litter during decomposition. The increase of radiocesium concentration mainly occurred during from April to October, when fungal growth peaked. Therefore, this suggests fungal translocation of nutrients from outside the litter substrate (immobilization) is the mechanism to increase radiocesium in the decomposing litter. The amount of (137)Cs contained in the 1-year-old decomposed leaf litter was estimated to be 4% per area of the soil-contaminated (137)Cs.
authors.affiliation: Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Yokohama 240-8501, Japan.
authors.forename: Yao
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Yokohama 240-8501, Japan. Electronic address: kanekono@ynu.ac.jp.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Kaneko
authors.affiliation: Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Yokohama 240-8501, Japan.
authors.forename: Taizo
authors.initials: T
authors.lastname: Nakamori
authors.affiliation: Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Yokohama 240-8501, Japan.
authors.forename: Toshiko
authors.initials: T
authors.lastname: Miura
authors.affiliation: Facility for RI Research and Education, Instrumental Analysis Center, Yokohama National University, 79-5 Tokiwadai, Yokohama 240-8501, Japan.
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Graduate School for Management of Technology, Niigata University, 2-8050 Igarashi, Niigata 950-2181, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Nonaka
authors.affiliation: Graduate School of Bioagricultural Science, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan.
authors.forename: Chisato
authors.initials: C
authors.lastname: Takenaka
mesh_terms: D018407:Bacterial Physiological Phenomena; D018533:Biomass; D002588:Cesium Radioisotopes / Q000378:metabolism*; D005227:Fatty Acids / Q000032:analysis; D065928:Forests; D062406:Fukushima Nuclear Accident; D005658:Fungi / Q000378:metabolism*; D007564:Japan; D010743:Phospholipids / Q000032:analysis; D018515:Plant Leaves / Q000378:metabolism; D011834:Radiation Monitoring; D012990:Soil Pollutants, Radioactive / Q000378:metabolism*
chemical_list: D002588:Cesium Radioisotopes; D005227:Fatty Acids; D010743:Phospholipids; D012990:Soil Pollutants, Radioactive
keywords: 137-Cs; Fukushima nuclear power plant accident; Fungi; Litter bag; Microbial biomass; Soil nutrients