報告書番号

U90052

タイトル（和文）

海洋におけるＣＯ２の挙動とその固定方策に関する調査

タイトル（英文）

LITERATURE REVIEW OF CO2 BEHAVIOR AND FIXATION IN OCEAN

概要 （図表や脚注は「報告書全文」に掲載しております）

海洋でのＣＯ２の挙動と固定方策について文献調査を行った。Ｂｏｌｉｎ（１９８９）によれば，炭素存在量は，大気中７２５Ｇｔに対し，表層海水中７２５Ｇｔ，中深層水中３７７０Ｇｔと推定され，中深層水が大きなリザーバーである。海洋中の主な炭素循環経路は，海洋表層で生物により溶存無機炭酸物質から生成された有機物粒子，炭酸塩粒子が沈降する炭素の鉛直輸送と，粒子が中深層で分解，溶解して再び溶存し，この中深層水が湧昇して表層に無機炭酸物質を運ぶ海洋水の鉛直循環とである。深層水が湧昇して表層水となるまでには１０３年オーダーの時間がかかると推定されているため，深層に沈降した有機物，炭酸塩粒子は中長期的に固定されたものと考えられる。表層水中の基礎生産量を増大させ，炭素の鉛直輸送量を増加させる方策，例えば微量栄養塩である鉄を表層海水に添加するなどは，炭素の鉛直輸送量を増大させ大気中のＣＯ２量を削減する可能性のある

概要 （英文）

THE BEHAVIOR OF CO2 AND ITS FIXATION IN THE OCEAN ARE REVIEWED. INTERMEDIATE AND DEEP OCEAN WATER IS AN IMPORTANT CARBON RESERVIOR. IT IS ESTIMATED THAT 37,700 GT OF CARBON IS STORED IN INTERMEDIATE AND DEEP WATER IN COMPARISON TO 725 GT EACH IN THE ATMOSPHERE AND SURFACE WATER. THE MAIN CARBON TRANSPORT ROUTES IN THE OCEAN ARE:(1) DOWNWARD FLUX CAUSED BY SINKING OF CARBONATE PARTICLES,ORGANIC PARTICLES AND SURFACE WATER AND;(2) UPWARD FLUX CAUSED BY UPWELLING OF DISSOLVED-CARBON-RICH DEEP WATER. BECAUSE IT IS ESTIMATED TO TAKE 1000 YEARS FOR DEEP WATER TO UPWELL TO THE SURFACE,ORGANIC AND CARBONATE PARTICLES THAT SINK INTO INTERMEDIATE AND DEEP WATER COULD BE CONSIDERED TO BE IN LONG-TERM STORAGE. THE MARINE ALGAE BIOMASS AND PRIMARY PRODUCTION ARE ESTIMATED TO BE 2-5 GTC AND 10-40 GTC/YEAR,RESPECTIVELY. TWO TO FIVE PERCENT OF THE PRIMARY PRODUCTION IS THONGHT TO BE TRANSPORTED FROMTHE SURFACE TO MORE THAN 1000 M DEEP AS MARINE SNOW OR FECAL PELLETS. THE FOLLOWING THREE METHODS COULD BE POSSIBLE CANDIDATES FOR REDUCINGATMOSPHERIC CO2 USING MARINE ORGANISMS: (1) INCREASING MACROALGAE BIOMASS TO BE USED AS BIOMASS ENERGY (2) FIXING CO2 AS CACO3 AS IN CORAL REEFS (3) ADDING MICRONUTRIENTS SUCH AS IRON TO OCEAN SURFACE WATER TO INCREASE PRIMARY PRODUCTION AND THE AMOUNT OF CARBON PARTICLES SINKING TOTHE DEEP LAYERS THE FOLLOWING SUBJECTS SHOULD BE STUDIED BEFORE USING THESE METHODS. (1) COST REDUCTION FOR BIOMASS PRODUCTION TO INCREASE MACROALGAE BIOMASS (2) CO2 BALANCE DURING CALCIFICATION TO FIX CO2 AS CACO3 (3) LIMITING FACTORS ON ALGAE PRODUCTION (4) HOW TO SPREAD MICRONUTRIENTS OVER VAST SEA AREAS AND HOW TO ASSESS POSSIBLE ENVIRONMENTAL EFFECTS OF ADDING MICRONUTRIENTS

報告者

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