yrammuS 要概片山 新太74Arata KATAYAMA平野 高司75Takashi HIRANO地下水硝酸汚染を浄化対象とする電気化学支援型自立的生物脱窒システムの創製(2014採択)Development of electrochemically-assisted self-sustained biological denitrification system targeting nitrate groundwater pollution(Project 2014)開発にともなう環境撹乱が熱帯泥炭生態系の泥炭分解に与える影響の評価(2015採択)Assessment of the effects of disturbances due to land-use change on the oxidative decomposition of tropical peat (Project 2015)59Rep. Grant. Res., Asahi Glass Foundation (2018)硝酸汚染地下水の浄化を目標とし，微生物脱窒反応を電気化学的に促進するシステムを作製した．電気活性の無い典型的な脱窒細菌Pseudomonas stutzeriの脱窒反応を，あらゆるpHで不溶の固体腐植ヒューミンの細胞外電子伝達能を介して，電気化学的に促進することに成功した．反応速度解析から，脱窒プロセスに含まれる硝酸還元，亜硝酸還元，亜酸化窒素還元のいずれの反応も電気化学的に促進していることが示唆された．更に，電気化学的生物脱窒システムの長期的活性維持のために，脱窒細菌が必要とする有機物を，二酸化炭素から酢酸を生成するホモ酢酸生成細菌Sporomusa ovataを組み合わせることによって供給し，二酸化炭素と水素でP. stutzeriの脱窒反応を60日間にわたって維持することに成功した．電気化学支援型生物脱窒の自律型システム構築へ向けたさらなる研究が期待される．Aiming to remediate nitrate-contaminated groundwater, a bioelectrochemical system was constructed, which enhance the microbial denitification. The denitrifying reaction of a typical denitrifying bacterium, Pseu-domonas stutzeri, which cannot utilize electrons directly from the electrode, was successfully enhanced elec-trochemically by using solid-phase humin as external electron mediator, which was not soluble under either acid and alkaline conditions. Analysis of the reaction rates suggested all of the reactions, nitrate reduction, nitrite reduction, nitrous oxide reduction, in the denitrification process were enhanced. Furthermore, long-term maintenance of the denitrification activity of the bioelectrochemical system was enabled by providing organic substrate using a homoacetogen Sporomusa ovata, which produce acetate from carbon dioxide. This system succeeded to maintain the denitrification activity of P. stuzeri for 60 days with only carbon dioxide and hydrogen. Further study should be warranted to develp the autonomous system of electrochemically-assisted biological denitrification.東南アジアの低平地に広がる熱帯泥炭林は，膨大な量の有機炭素を泥炭として蓄積してきた．しかし，大規模な農地開発による乾燥化（地下水位の低下）が進み，微生物による泥炭の好気的分解（二酸化炭素（CO2）の放出）が加速してきている．本研究では，土地被覆条件が異なる6つの熱帯泥炭生態系においてフィールド観測を行い，泥炭分解によって放出されるCO2フラックスを定量化してサイト間比較を行うとともに，地下水位などの環境変数との関係を解析した．また，泥炭の土壌特性（密度，炭素含有量）のデータと土壌CO2フラックスの実測値から泥炭分解に起因する地盤沈下量を推定し，地盤沈下量に対する好気的分解の寄与を定量化した．Tropical peat swamp forest is widely distributed in Southeast Asiaʼs coastal lowlands and had accumulated a huge amount of organic carbon as peat in the soil. However, the peat swamp forest has been reduced and de-graded by logging, drainage and burning mainly because of land conversion to oil palm and pulp wood plan-tations during the last two decades. Such human disturbances potentially increase carbon dioxide (CO2) emis-sions to the atmosphere through enhanced oxidative peat decomposition. It is very important to assess the current carbon status of tropical peatlands and quantify the effects of disturbance on the carbon balance to
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