Study on carbonized temperature estimation of charcoal remained in burnt area in Namie Town, Fukushima

福島県浪江町の延焼地における炭の炭化温度推定に関する研究

野村 直希*; 新井 宏受*; 倉元 隆之*; 新里 忠史  ; 林 誠二*

Nomura, Naoki*; Arai, Hirotsugu*; Kuramoto, Takayuki*; Niizato, Tadafumi; Hayashi, Seiji*

東京電力福島第一原子力発電所事故の帰還困難区域に位置する福島県浪江町の山地森林において、2017年に林野火災が発生した。本研究では、土壌及びリター層中の栄養素や放射性セシウムの溶出挙動に係る林野火災の燃焼温度を推定するため、林野火災で生成された残存炭化物に着目した。林野火災により、スギ林及びアカマツ-コナラ優勢の落葉広葉樹林が延焼したため、それら林分に対照サイトを設定し、残存炭化物を対照サイトに隣接する延焼地にて採取した。採取した未燃焼リター, 人工燃焼させたリター及び残存炭化物について、TG-DTA熱分析及び赤外線吸収スペクトル解析を実施した。

In 2017, a wildfire occurred in mountainous forest of Namie Town, Fukushima Prefecture, where is designated as a difficult-to-return zone due to high radiation dose after TEPCO's Fukushima Daiichi Nuclear Power Plant accident. With the wildfire, changes of dynamics of radionuclide, especially Cs-137 was concerned. In this study, we focused residual charcoal to estimate burning temperature of surface soil and litter because it affects the dissolution behavior of nutrients and radiocesium in soil and litter on the forest floor of the burnt area. As a result of the wildfire, Japanese cedar forest and mixed forest with predominance of Japanese red pine and Japanese oak were burned, so we set up three control sites at each forest and collected the residual charcoals from burnt sites nearby unburnt locations. To clarify the carbonized temperature of residual charcoal, thermal analysis by TG-DTA and infrared adsorption spectrum analysis by micro-FTIR were conducted for litters, artificially burnt litters, and residual charcoals.