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沿岸・河口域のリン循環過程におよぼす土壌物質の影響
https://fra.repo.nii.ac.jp/records/2003208
https://fra.repo.nii.ac.jp/records/2003208933fa51d-1a55-4ac0-bc1c-8ee409bfe8c8
| Item type | 紀要論文 / Departmental Bulletin Paper(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2024-04-25 | |||||
| タイトル | ||||||
| タイトル | 沿岸・河口域のリン循環過程におよぼす土壌物質の影響 | |||||
| 言語 | ja | |||||
| タイトル | ||||||
| タイトル | Effects of Soil Loading on the Phosphorus Cycle in Estuarine and Coastal Marine Environments | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| キーワード | ||||||
| 言語 | en | |||||
| 主題Scheme | Other | |||||
| 主題 | sediments; suspended matter; estuary; soil erosion; phosphorus loadings; phosphate adsorption; phosphorus forms | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||
| 資源タイプ | departmental bulletin paper | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
田中, 勝久
× 田中, 勝久 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | It is well known that phosphorus is an important component in the eutrophication of coastal marine environments and the major source of phosphorus are from the input of rivers and from the release from coastal sea sediments. However, little is known about the nature of phosphorus in riverine suspended matter and in the sediments and their behavior in estuarine and coastal marine environments. The release of phorphorus from sediments under anaerobic conditions in eutrophic coastal waters has been investigated experimentally in order to explain the origin of the eluted phosphate. The results indicate that the origin is inorganic phosphorus rather than organic phosphorus. Terrestrial soil substances contain a large amount of inorganic phosphorus together with organic phosphorus. Therefore, the origin of inorganic phosphorus in sediments and its loading process can not be clearly understood without further information on riverine suspended matter. In this study, phosphorus in riverine suspended matter was investigated for its chemical nature and its behavior in coastal marine environments. Phosphorus both in the suspended matter and in coastal marine sediments was divided into four forms: CDB-P (citrate-dithionite-bicarbonate extractable phosphorus), NaOH-P (1N-NaOH extractable phosphorus), HCI-P (1N-HCI extractable phosphorus), and organic phosphorus (Org-P), following the fractionation scheme of Williams et al. (1976a). Adsorbed phosphate (Ads-P) which desorbs rapidly in sea water was also measured by the seawater extraction technique. The results obrained are summarized below: (1) Phosphate desorption and forms of phosphorus were investigated in the suspended matter of the Ohta river and surface sediments in its estuary. Desorbed phosphate from the suspended matter increased with increasing salinity. This suggests that the desorption of phosphate will occur more extensively when the riverine suspended matter reach the sea. In the suspended matter, CDB-P was the major constituent, in which more than 50% was Ads-P. Concentrations of CDB-P were higher in the suspended matter than the surface sediments on the river mouth and Ads-P decreased markedly during the deposition of suspended matter to the sediments. These results indicate that the origin of CDB-P in the sediments is of riverine suspended matter during high discharge periods, and that desorption of Ads-P takes place during the deposition of the suspended matter to the sediments. (2) Field observations and laboratory experiments were made to examine phosphate buffering capacity of suspended sediments in the turbid Chikugo River Estuary. Maximum adsorption and minimum desorption was found in the range of salinity 1.7-3.4. Desorption of phosphate increased and adsorption decreased with increasing pH. The equilibrium phosphate concentrations (EPC) of the suspended sediments in diluted sea water were lower than in sea water. EPC in the low salinity range coincided with the maintained phosphate concentration in the low salinity turbid region of the estuary. From these results the behavior of phosphate in the estuary can be summarized as follows. First, dissolved phosphate is removed by mutual flocculation with colloidal soil substances in area of the extremely low salinity region. Secondly, the phosphate concentration is buffered by suspended sediments in the turbid water in the low salinity region. Finally, desorption of phosphate takes place with the increase of the EPC in the high salinity and low turbidity region. (3) The process of soil runoff into Hiroshima Bay from the Ohta River and the composition of phosphorus forms in several major rivers in Japan during periods of high waster discharge were investigated. In the Ohta River, most of the soil runoff occurs by terrestrial soil erosion resulting from heavy rainfall over only several days in a year. In Hiroshima Bay, the load of CDB-P during these periods reach up to 68% of the annual estimated load of phosphorus runoff, in which Ads-P comprises more than 50% on average. In several major rivers in Japan, 25 to 56% of the phosphorus in the suspended matter during these periods is CDB-P, suggesting that the CDB-P load equals or exceeds that of Org-P. (4) A comparison of the distribution of phosphorus forms in surface sediments between Hiroshima Bay, Osaka Bay and Beppu Bay was made in order to investigate the effects of phosphorus loading by soil substances and its role in the phosphorus cycle in each bay. In the sediment of the inner Hiroshima Bay, the major source of CDB-P was suspended matter in the runoff of Ohta River. Imported CDB-P was stored in the estuarine sediments after the desorption of Ads-P with increasing salinity. The remainder of CDB-P, reductant soluble phosphate (Red-P), decreased during its dispersion into the bay. In the offshore area, the libration of phosphate from the sediments occurs mainly by the decomposition of Org-P. This phosphate is readsorbed onto the surface sediments from the pore-water under anaerobic conditions. In Osaka Bay, only the concentration of CDB-P decreased markedly in the anaerobic estuary, showing that the liberation of phosphate from the sediments is dependent on the dissolution of CDB-P originating from riverine suspended matter under the anaerobic condition. In the anoxic bottom water area of Beppu Bay, the concentration of CDB-P in the surface sediments was also low compared with the aerobic estuarine sediments. In general, the concentration of NaOH-P decreased gradually from the estuary to the offshore area with the decrease of mud content of the sediment and did not change with the dissoved oxygen concentration. The concentration of HCI-P was higher in fine sand sediments. From the results of this study, it is confirmed that the runoff of soil substances plays an important role in the phosphorus cycle in the coastal marine enviroments through the desorption of Ads-P in sea water and dissolution of Red-P under anaerobic conditions. | |||||
| 言語 | en | |||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | 河川増水時に海域に負荷される懸濁土壤物質の形態別リン組成に関しては,その重要性が指摘されているにも関わらず研究はほとんどない状況にあった。また,宮栄養化した内湾域底泥からのリンの溶出源の究明が室内実験を中心に進められた結果,貧酸素環境下では底泥中の有機態リン(Org-P)よりむしろ無機態リンが溶出源であることが示された。しかしながら,この無機態リンの起源や内湾域への負荷過程については,無機態リンを大量に含む河川負荷土壌物質の特性の理解なしには不可能であり,その解明が待たれていた。本研究では,河川増水時に海域に負荷される土壤物質の形態別リン組成とその負荷過程,ならびに,土壤物質中の無機態リンの海域における挙動の解明を目的とした。得られた成果の概要は以下のとおりである。海水で土壌物質から吸着態のリン酸を繰り返し洗い出し,溶脱するリン酸の総量(吸着態リン酸量:Ads-P)を求める方法を開発した。増水時に河口域に負荷される懸濁土壌物質からの吸着態リン酸の溶脱量は塩分の増加とともに増加する。土壤物質は吸着平衡作用により河口低塩分域の溶存リン酸濃度変化を緩衝する働きを行い,河口高塩分域では、土壤物質からの吸着態リン酸の溶脱が進行する。広島湾とその湾奥部に流入する太田川をモデルとして、土壤物質の河川からの流入過程の実態を調査した結果,太田川増水時に海域に負荷される懸濁土壤物質の発生源は,河道内に堆積した土壤物質の流出より,陸上表土の降雨浸食による河川への直接の流出の割合が高いものと推定された。また,土壌物質負荷の大部分は年問数日間の集中豪雨時に負荷され,太田川増水時の高濁度土壌物質による Citrate-Dithionite-Bicarbonate 抽出リン(CDB-P: Ads-Pおよび鉄結合型リン)の負荷量は,広島湾への排水負荷原単位計算によるリン流入負荷量の68%に達し,そのうち Ads-Pは,平均して CDB-Pの50%以上を占める。一方,全国の主要な河川において増水時河川懸濁物中の CDB-P は全リン(Total-P)の25~56%を占める主要な成分となっており,その負荷量は懸濁態有機リンに匹敵,もしくはそれを上回るものと推定された。梅雨増水期の広島湾では河川から負荷された懸濁物の CDB-Pは,海域に堆積する過程で,まず大部分の Ads-P が塩分変化にともなって溶脱し,CDB-P のうち好気的条件下で溶脱しにくい画分 (Reductant soluble phasphate:Red-P)が底泥に蓄積するが,Red-P は貧酸素水塊の形成されやすい河口域から湾内に拡散する過程で溶出し,濃度が低下する。一方,溶存酸素濃度の高い沖合では,溶存リン酸の底泥から底層水への負荷は,一次生産起源のOrg-Pの分解にともなう溶出が中心で,溶出した高濃度の問隙水中のリン酸は表層泥に吸着·蓄積する。夏季の大阪湾河口貧酸素水域で急激な濃度の減少が認められるのはCDB-Pのみであり,貧酸素河口域におけるリン酸塩の溶出源が主に河川起源のCDB-Pであることが明らかになった。別府湾深部無酸素環境下では,表層泥中のCDB-P 濃度の低下が還元環境下でのCDB-P の溶出によるものと考えられ,沈降粒子中の易分解性有機リンは沈降過程で,または沈降初期に分解され,底泥中ではその後のOrg-P の分解はほとんど進まないものと推察された。NaOH-P(AI 結合型リン)は,CDB-P と同様に河川負荷の影響を受け河口域で高く,沖合では含泥率の低下にともない次第に濃度が低下するが,CDB-P の場合とは異なり,貧酸素環境下でも顕著な濃度低下は認められなかった。従って,これらは貧酸素環境下でも CDB-Pに比較して安定な成分であるものと考えられる。また,1N-HCI で抽出されるアパタイト型リンは細粒砂質域で高濃度となる傾向が認められた。 | |||||
| 言語 | ja | |||||
| bibliographic_information |
ja : 南西海区水産研究所研究報告 en : Bulletin of Nansei National Fisheries Research Instituite 巻 28, p. 73-119, ページ数 47, 発行日 1995-03 |
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| 出版者 | ||||||
| 出版者 | 南西海区水産研究所 | |||||
| 言語 | ja | |||||
| 出版者 | ||||||
| 出版者 | Nansei National Fisheries Research Instituite | |||||
| 言語 | en | |||||
| item_10002_source_id_9 | ||||||
| 収録物識別子タイプ | PISSN | |||||
| 収録物識別子 | 0388-841X | |||||
| item_10002_source_id_11 | ||||||
| 収録物識別子タイプ | NCID | |||||
| 収録物識別子 | AN00181988 | |||||
| 情報源 | ||||||
| 識別子タイプ | Local | |||||
| 関連識別子 | nnf_k_28_73 | |||||
| 関連サイト | ||||||
| 識別子タイプ | URI | |||||
| 関連識別子 | https://agriknowledge.affrc.go.jp/RN/2010510446 | |||||
| 言語 | ja | |||||
| 関連名称 | 日本農学文献記事索引(agriknowledge) | |||||
