報告書番号

V08061

タイトル（和文）

植物による環境修復(8)-中国におけるカドミウム実汚染土壌の浄化-

タイトル（英文）

A feasibility study of phytoremediation for cadmium contamination in China

概要 （図表や脚注は「報告書全文」に掲載しております）

実汚染地におけるファイトレメディエーション技術の有効性、適用性（汚染レベルや気象条件など）の検証を行うと共に、栽培法の最適化を図るため、2007年と2008年の夏期に、中国（遼寧省）における実カドミウム汚染地に約2アールの試験圃場を設置して、シソ、タバコ、レタス、ヒマワリを栽植密度、根圏の大きさ、施肥条件を変えて栽培を行った。その結果、候補植物のうちタバコは現地の条件に適応せず十分な収穫量が得られなかったが、その他の植物種は比較的良好に生育した。また、植物を用いて土壌から効率よくカドミウムを除去するには、カドミウムの吸収能力に長けた植物を用いることと共に、その植物による群落が最大の光利用効率となるように栽植密度を高めること、根圏を調節することが重要であると考えられた。本研究の栽培条件下では、1kg-DWの土壌から1作あたり最大0.9mg/kgのカドミウムを除去できた。これらの結果から、カドミウム濃度が高く、栽培条件の厳しい実汚染地においてもある程度の浄化効果が確認できたことから、気温、降水量、カドミウム濃度などが本研究より穏やかな条件下であれば、栽培条件に適応した植物種の利用などにより実用に供することが可能と思われた。

概要 （英文）

A practical field test for phytoremediation was performed at a cadmium contaminated site in Liao-Ning province, China, during summer seasons of 2007 and 2008. The total Cd, Zn and Cu concentrations in the soil were about 16, 988, and 84 mg/kg, respectively. The field was positioned in a center of huge corn cropping field, and divided into 36 small blocks in size of 9 sq. meters. Four different types of crops (tobacco, perilla, lettuce, and sunflower) were selected as suitable crops for Cd phytoremediation based on our previous studies. Two of these were simultaneously cultivated in each half of the 36 blocks in the same season. Of note, the lettuce cultivation was immediately followed by sunflower cultivation in the same half of the 36 blocks in 2008. Basically, the effects of three different treatments (i.e. planting density, fertilization, and rhizosphere limitation) on cadmium uptake efficiency were compared for each crop. To observe the effect of these treatments, each crop was planted with at least three different densities, with fertilizer or not, and with physical rhizosphere limitation or not. Thus, at most six treatments in total with three replications each were prepared for the comparison, meaning that 18 blocks were occupied by one crop cultivation during a season. Results demonstrated that; 1. Increase in planting density is basically effective to increase biomass grown in an area; however, it is important to know the saturation point of radiation use efficiency in the plant community and/or the plant species specific photosynthetic capacity to maximize the biomass production in the area, 2. Plants have own cadmium uptake potential and the potential is constant under the same soil conditions even if the conditions of planting density, fertilization, and rhizosphere limitation are changed. These suggested that both of selecting hyperaccumulators and maximizing the planting density to saturation point of the radiation use efficiency in the plant community to maximize the phytoremediation efficiency in an area. In addition, we estimated the cost of a phytoremediation from the present labor time and the soil cleaning efficiency and an average costs for other steps of the settlement (e.g. transportation, incineration, and reclamation) from web.

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