鹿児島大学 · 農水産獣医学域水産学系 · 助教

研究キーワードenvironmental water analysis・continuous-flow analysis・nitrogen compounds・harmful raphidophytes・Heterosigma akashiwo・algicidal bacteria

研究分野水圏生産科学・生態学、環境学

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• Morikubo S., Takahashi N., Takuma Y., Enomoto D., Nishimura T., Kumazawa Y., Kanno R., Okunishi S., Maeda H. . Analytical accuracy and environmental impact of nitrogen compound determination v2025 · 記述言語： 日本語 出版者・発行元： Desalination and Water Treatment The determination of nitrogen compounds in the environment is essential for sustainable nitrogen management. However, conventional analyses of environmental water, which often contains numerous foreign substances, typically rely on cadmium —a hazardous material. In this study, we propose an absorption spectrophotometric method using a copper–zinc reduction coil and evaluate its applicability to environmental water analysis as well as its potential for reducing environmental impact. The proposed method achieved a high recovery rate (>89 %) in environmental water recovery tests and exhibited a strong correlation with the copper–zinc reduction continuous flow analysis method in measurement results. Although seawater samples were affected by contaminants, measurements of seawater certified reference materials showed accuracies within 120 %, indicating that the method is applicable when dilution is used to mitigate contaminant effects. Furthermore, the proposed method demonstrated a markedly lower environmental impact than the conventional copper–cadmium reduction absorption spectrophotometric method. These findings indicate that the copper–zinc reduction coil absorption spectrophotometric method combines low environmental impact with performance comparable to conventional analytical techniques, making it suitable for environmental water analysis. DOI： 10.1016/j.dwt.2025.101514 Scopus
• Morikubo S., Takahashi N., Nishimura T., Takuma Y., Enomoto D., Kumazawa Y., Kanno R., Okunishi S., Maeda H. . Application of a cadmium-free continuous flow analysis system to industrial waste2025 · 記述言語： 日本語 出版者・発行元： Talanta Open Building on our previous work with natural waters, this study evaluates a cadmium-free copper–zinc reduction continuous flow analysis (CFA) system for the determination of nitrogen species—nitrate-nitrogen, ammonia-nitrogen, and total nitrogen—in industrial wastewater. A key novelty is the systematic investigation of interference from common coexisting substances in industrial effluents, such as heavy metals and organic compounds, which often compromise colorimetric detection in complex matrices. We conducted controlled spike-recovery experiments and validated results with reference materials to assess analytical robustness. The cadmium-free CFA system demonstrated analytical accuracy of ≥95 % when tested with reference materials and maintained recovery rates above 90 % in actual industrial wastewater samples across all nitrogen species, even under high-interference conditions, matching the performance of conventional cadmium-based methods. Additionally, a life cycle assessment (LCA) revealed substantial reductions in environmental and human health impacts by replacing cadmium with zinc and phenol with salicylic acid, with significant improvements in toxicity and resource-related categories. These findings demonstrate that the proposed CFA method provides both analytical reliability and environmental sustainability, confirming its suitability as a robust and eco-friendly alternative for accurate nitrogen monitoring in complex industrial matrices. DOI： 10.1016/j.talo.2025.100585 Scopus
• Shinohara K., Ito Y., Okunishi S., Maeda H. . Elucidating the seasonal dominance replacement mechanism of harmful raphidophytes Chattonella marina and Heterosigma akashiwo using the Lotka–Volt2024 · 担当区分： 責任著者 記述言語： 日本語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： Ecological Modelling Phytoplankton growth can cause red tide, lowering water quality and damaging fisheries. The simple Lotka–Volterra model (LV model), estimating the population changes in different species, is often used to analyze the growth and competition of causative species. However, the LV model has not been sufficiently applied to examining the actual occurrence and development of red tides in the field. Therefore, the mechanism of seasonal dominant species replacement and applicability of the LV model were studied to analyze the competition between the harmful raphidophytes Chattonella marina and Heterosigma akashiwo. Sensitivity analysis was performed, and optimization method of competition coefficient (α) was discussed by comparison with measured data from culture experiments. We found that it is crucial to evaluate in advance the initial cell density conditions under which the population size changes concerning α (the order of root mean squared logarithmic error ≥ 10−2). Using this as a reference, we pointed that the initial cell density difference between the two species in co-culture experiments should be as large as possible. In addition, simulation analysis using the model revealed that growth rate (r) and carrying capacity (K) determine H. akashiwo dominance in spring, and the increase in α due to rising temperatures causes C. marina dominance in summer. Comparing α of C. marina with α of C. antiqua cited from a previous study found that the formation of red tides of C. marina less than that of C. antiqua can be explained by α that is 0.42 times smaller than α of C. antiqua. Moreover, the increase in α with increasing temperature is related to the physiological and ecological characteristics of C. marina, which is more likely to dominate the space suitable for growth with temperature rise. We consider that investigations of α, in particular, contributes to modeling various competition and more improving accuracy in analyses. These results provide valuable scientific findings on the occurrence and development of red tide flagellates and their analytical method. DOI： 10.1016/j.ecolmodel.2024.110660 Scopus
• 神野 良誠, 高橋 のどか, 熊澤 頼博, 奥西 将之, 前田 広人 . デュアルフローによる自動酸分解装置の改良と実試料への応用 . 環境技術53 ( 4 ) 206 - 214 2024年7月 詳細を見る 担当区分： 責任著者 記述言語：2024 · 担当区分： 責任著者 記述言語： 日本語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： 環境技術学会 <p> 連続流れ分析（Continuous Flow Analysis）による自動酸分解装置について，コスト削減と測定の安定化を図るためにトリガー試薬およびフローの改良を行った．トリガー試薬として，Rh 試薬と比べて入手しやすいPd 試薬を検討したところ，問題なくトリガー試薬として使用できることがわかった．次に，加熱分解後に行うデバブルの位置を，加熱槽出口から1m の位置から10 ㎝へと変更した．この結果，放冷によって析出した固体による気泡の乱れが見られなくなった．さらに，分光光度検出器から誘導結合プラズマ質量分析装置（ICP-MS）の導入部を分岐するデュアルフローを開発した．このデュアルフローにより，吸光度シグナルの安定性向上およびネブライザーの詰まり軽減を実現できた．改良後の装置を用いた実試料の金属一斉分析では，標準溶液測定および添加回収試験において良好な結果が得られた．今回得られた知見は，自動前処理装置開発に関して重要な知見となり得る． </p> DOI： 10.5956/jriet.53.4_206 CiNii Research

• 自然環境中のバイオフィルムの構造と機能-光という新たな視点-
• イネに棲息する微生物-フロラ解析と環境に配慮した応用展開-
• 時空間的探索による一酸化炭素資化菌の包括的研究とその応用基盤の構築

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