北太平洋・ベーリング海・北極海における鉄の挙動とその起源

• Published in: BUNSEKI KAGAKU
• Main Authors: 久万, 健志, 高田, 兵衛, 北山, 紗織, 小俣, 紋
• Format: Article in Journal/Newspaper
• Language: Japanese
• Published: 日本分析化学会
• Subjects: Fe(III) solubility; Humic substances; North Pacific Ocean; Bering Sea; Western Arctic Ocean; 452; Arctic; Arctic Ocean; Pacific; Arctic Basin
• Online Access: http://hdl.handle.net/2115/54678; https://doi.org/10.2116/bunsekikagaku.62.1057

海洋における3価鉄の溶解容量は著しく低いため，鉄は栄養塩と同様，海洋の基礎生産を制限する重要な元素である．海洋中深層における溶存鉄濃度は3価鉄の溶解容量によってコントロールされ，その溶解容量は3価鉄と溶存有機鉄錯体を形成する海洋性溶存フミン物質に関係していると考えられる．本論文では，北太平洋及びベーリング海海盆域における特徴的な溶存鉄及び全可溶性鉄濃度の鉛直分布を，3価鉄の溶解容量の鉛直分布をもとに解釈した．また，広大な大陸棚を有する東部ベーリング海及び西部北極海にかけて，鉄・栄養塩・溶存フミン物質を鉛直的に測定した．その結果，亜表層の低温高塩分である高密度陸棚水（DSW）中において，それらの化学成分が高濃度検出され，大陸棚堆積物からDSWへのそれらの化学成分の供給，その後の外洋への輸送が示唆された．大気，河川及び鉛直混合・湧昇と同様，大陸棚堆積物は，海洋表層への供給源として海洋の基礎生産を支える重要な役割を果たしている． Iron is an important biogeochemical trace element in the ocean. However, the stable oxidation state of iron in oxic seawater is Fe(III) with an extremely low solubility in seawater. Recent studies of the Fe(III) hydroxide solubility in seawater suggest that Fe(III) solubility is controlled by organic complexation, which plays an important role in regulating dissolved Fe concentrations in seawater. In this study, we attempted to confirm that the vertical distributions of dissolved Fe in deep water are controlled primarily by the Fe(III) solubility, which is regulated by Fe(III) complexation with natural organic ligands, comparing the characteristic vertical distributions of iron, nutrients, apparent oxygen utilization, and humic-type fluorescence intensity in deep water of the North Pacific Ocean, Bering Sea and western Arctic Ocean. Dissolved Fe distributions in deep water column are mainly controlled by the production of dissolved Fe from particulate organic matter during carbon remineralization, the particle scavenging removal of dissolved Fe, and Fe(III) complexation with natural humic substances. Iron is generally supplied to surface water by upwelling, vertical water mixing, atmospheric and riverine inputs. In the western Arctic Ocean, the subsurface maxima of iron, nutrients, and humic substances were found in the halocline layer of slope and basin regions. The new finding results from the supply of chemical components from the continental-shelf sediments and lateral transport from the shelves to the Arctic basin.