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Affiliation |
Engineering educational research section Civil and Environmental Engineering Program |
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Title |
Associate Professor |
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Related SDGs |
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NUKAZAWA Kei
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Degree 【 display / non-display 】
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Doctor (Engineering) ( 2013.3 Tohoku University )
Research Areas 【 display / non-display 】
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Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention) / Hydroengineering
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Environmental Science/Agriculture Science / Environmental dynamic analysis
Papers 【 display / non-display 】
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EVALUATION OF ENVIRONMENTAL DNA VARIATION FOR TURBID WATER CONSIDERING DNA STATES Reviewed
MIKAMI Yuki, XU Chen, NUKAZAWA Kei
Japanese Journal of JSCE 80 ( 25 ) n/a 2024.11
Authorship：Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers
Although the accuracy of environmental DNA (eDNA) detection is influenced by biological and environmental conditions, eDNA dynamics in turbid water is not well understood, precluding establishment of eDNA surveys in turbid water area. In this study, we evaluated the effect of different turbidity conditions on aqueous eDNA fate with different states. Water samples under five turbidity conditions (0, 20, 50, 100, and 200 ppm) were designed by mixing riverbed sediment and either distilled water or aquarium water rearing common carps (<i>Cyprinus carpio</i>). We filtered the turbid water samples using two types of glass fiber filters with different pore sizes and quantified carp eDNA using digital PCR. Consequently, as turbidity increased, the concentration of eDNA also increased; however, under high turbidity conditions, the eDNA concentration tended to decrease. These findings suggest that eDNA recovery is higher at moderate levels of turbidity owing to the adsorption of eDNA and the influence of PCR inhibitors.
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Nishimura E., Xie H., Tamai S., Nishiyama M., Nukazawa K., Hoshiko Y., Ogura Y., Suzuki Y.
Frontiers in Environmental Science 12 2024.9
Publishing type：Research paper (scientific journal) Publisher：Frontiers in Environmental Science
Studies on the conditions and pollution routes of antibiotic-resistant bacteria (ARB) in rivers can help provide countermeasures against the spread of ARB. This study focused on the pristine uppermost stream of a river, where Escherichia coli (E. coli) and enterococci were detected, although the stream flows through a pristine forest catchment. Antibiotic resistance of E. coli and enterococci isolated from the river water, riverbed sediment, and feces of waterside animals, such as birds and Mustelidae, were investigated throughout the year in the pristine uppermost sites. Antibiotic resistance was present in 1.4% (7/494) of the E. coli strains and 3.0% (24/812) of the enterococcal strains, and was low throughout the year. Although antibiotic resistance of bacteria isolated from feces was not detected in this watershed, the prevalence of multidrug-resistant E. coli was 0.4% (1/246) and 0.6% (1/172) in river water and riverbed sediment samples, respectively were observed. The presence of extended-spectrum β-lactamase (ESBL)-producing E. coli was confirmed in river water samples, and genomic analysis revealed that the samples possessed the CTX-M-15 group. Multidrug-resistant strains and ESBL-producing strains were classified as phylogroups B1 and A, respectively, which are E. coli phenotypes isolated from wild animals. Pulsed-field gel electrophoresis revealed analysis targeting enterococci that strains isolated from river water and bird feces were in the same cluster with 100% similarity. Therefore, bird feces are a source of enterococci in the uppermost stream of the river. Because multidrug-resistant bacteria and ESBL-producing bacteria were present in the pristine uppermost stream of the pristine river, urgent elucidation of the spreading routes of ARB is important.
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ASSESSMENT OF BENTHIC MACROINVERTEBRATE COMMUNITIES IN SMALL RIVER WATERSHEDS UNDER DEPOPULATION Reviewed
NUKAZAWA Kei, NAGANO Daizo
Japanese Journal of JSCE 80 ( 27 ) n/a 2024.9
Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers
Recently, the insufficient management of small to medium-sized rivers due to population decline has been a major challenge in Japan, thereby, an adaptation to future degradation of social infrastructure is required. However, the impact of the depopulation and related environmental changes (e.g., land-use changes) on riverine ecosystem is not well understood. This study aims to evaluate the benthic macroinvertebrate communities in small river chatchments under depopulation in the Kiyotake River catchment in Miyazaki Prefecture. Based on nonmetric multidimensional scaling, the community was most characterized by water quality changes associate with population changes in the study catchment. Generalized linear models revealed that the decline in watershed population led decrease in density of a macroinverteberate habit type “gliders”. This result suggests that decline in nutrient load impedes growth of riverbed algae, which is important food resource of dominant biological groups in the gliders.
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PROPOSAL OF A METHOD TO FORM SURFACE FLOW DIRECTION DATASET BASED ON ACTUAL RIVER INFOMATION Reviewed
MINEDA Haruki, NUKAZAWA Kei
Japanese Journal of JSCE 80 ( 16 ) n/a 2024.1
Authorship：Last author, Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers
Elevation and surface flow direction data are useful for the analysis of hydrologic processes in a catchment. Surface flow direction is generally determined by steepest downward slope based on depression-filled elevation data. However, since the steepest downward slope is affected by the elevation correction and errors in the input elevation data, resulted surface flow direction does not reflect the actual river geometry. Here, a method to form catchment dataset was developed based on actual river information to minimize elevation correction and improve reproducibility of river geometry. As a result, the reproducibility of river geometry was significantly improved and the elevation correction was reduced at multiple spatial resolutions from 30 m to 1000 m. In addition, the complex river geometry such as meandering and tributary confluence was reproduced while it was difficult to do in conventional approaches. This method contributes to catchment-scale flood control, wide-area river environment management, and disaster prevention measures using the digital twin.
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Mineda H., Nukazawa K., Suzuki Y.
Journal of Water and Climate Change 14 ( 12 ) 4821 - 4836 2023.12
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Water and Climate Change
Hydrological alterations by dams and climate change can reduce aquatic biodiversity by disrupting the life cycles of organisms. Here, we aimed to evaluate and compare the hydrological alterations caused by dams and climate change throughout the Omaru River catchment, Japan, using a distributed hydrological model (DHM). First, to assess the impacts of dam and climate change independently, we performed runoff analyses using either dam discharge or future climatic data (two future periods, 2031–2050 and 2081–2100 x three representative con-centration pathways). Subsequently, we derived indicators of hydrologic alterations (IHA) to quantify changes in flow alterations by comparing them to IHA under natural conditions (i.e., without dam or climate change data). We found that dams altered IHAs more than climate change. However, on a catchment-scale standpoint, climate change induced wider ranges of flow alterations, such as a further decrease in low flow metrics along the tributaries and uppermost main stem, suggesting a catchment-level shrinkage in important corridors of aquatic organisms. We also observed that the altered flow by water withdrawals was ameliorated by the confluence of tributaries and downstream hydropower outflows. Our approach using a DHM captured the various patterns of flow alterations by dams and climate change.
DOI： 10.2166/wcc.2023.538
Books 【 display / non-display 】
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宮崎県一ツ瀬川における濁水長期化 ～その原因と産官学民が連携した対策～
杉尾哲, 糠澤桂, 鈴木祥広（ Role： Edit）
パブフル 2022.2
Book type：Scholarly book
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風間 聡, 小森 大輔, 峠 嘉哉, 糠澤 桂, 横尾 善之, 渡辺 一也（ Role： Contributor）
理工図書 2020.9 （ ISBN:9784844608844 ）
MISC 【 display / non-display 】
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ダム堆砂対策による河川生態系の応答に関する事例紹介 Invited
糠澤桂，鈴木祥広
電力土木 2020.1
Language：Japanese Publishing type：Article, review, commentary, editorial, etc. (scientific journal)
Presentations 【 display / non-display 】
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大淀川水系岩瀬ダム再生事業に伴う底生動物群集への影響評価
上岡莉子，糠澤桂
令和6年度 西部支部研究発表会
Event date： 2025.3.8
Language：Japanese Presentation type：Oral presentation (general)
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宮崎県清武川水系における環境DNAを活用した生物量推定手法の有用性評価
野崎康平，三上優貴，Xu Chen，糠澤桂
令和6年度 西部支部研究発表会
Event date： 2025.3.8
Language：Japanese Presentation type：Oral presentation (general)
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DNA存在形態と抽出方法を考慮した濁水における環境DNAの変動の評価
三上優貴，Xu Chen，糠澤桂
令和6年度 西部支部研究発表会
Event date： 2025.3.8
Language：Japanese Presentation type：Oral presentation (general)
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機械学習を用いた底生動物分布モデルの転用精度向上に向けた検討
水口嶺，糠澤桂
令和6年度 西部支部研究発表会
Event date： 2025.3.8
Language：Japanese Presentation type：Oral presentation (general)
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降雨時に流出する環境DNAの分析に基づく水・陸生種の検出条件の検討
Xu Chen, 糠澤桂
2024年度日本水環境学会九州沖縄支部研究発表会
Event date： 2025.3.4
Language：Japanese Presentation type：Oral presentation (general)
Awards 【 display / non-display 】
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ELR2022つくば 優秀ポスター発表賞
2022.9 日本緑化工学会、日本景観生態学会、応用生態工学会
田中凌央，糠澤桂，鈴木祥広
Award type：Award from Japanese society, conference, symposium, etc. Country：Japan
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第55回環境工学研究フォーラム 優秀ポスター発表賞
2018.12 土木学会
西村恵美，糠澤桂，鈴木祥広
Award type：Award from Japanese society, conference, symposium, etc. Country：Japan
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応用生態工学会第22回研究発表会 優秀ポスター研究発表賞
2018.9 応用生態工学会
糠澤桂
Award type：Award from Japanese society, conference, symposium, etc. Country：Japan
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平成28年度建設工学研究奨励賞
2017.6 一般財団法人建設工学研究振興会 宮崎における分布型汚濁流出モデルの開発とその利用による河川環境・生物多様性評価
糠澤桂
Award type：International academic award (Japan or overseas) Country：Japan
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第21回地球環境シンポジウム 優秀講演賞
2014.9 土木学会地球環境委員会
糠澤桂, 風間聡, 渡辺幸三
Award type：Award from Japanese society, conference, symposium, etc. Country：Japan
Grant-in-Aid for Scientific Research 【 display / non-display 】
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流域環境管理と防疫調査を繋ぐ河川-河畔生物一斉調査手法の開発
Grant number：25K00041 2025.04 - 2029.03
独立行政法人日本学術振興会 科学研究費補助金 基盤研究(B)
Authorship：Principal investigator
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タイ国の大気降下物によるアシッドショックが水環境に与えるリスクの定量評価
Grant number：24KK0086 2024.04 - 2028.03
独立行政法人日本学術振興会 科学研究費基金 国際共同研究加速基金（海外連携研究）
Authorship：Coinvestigator(s)
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AdMitにおける河川植生伐採のマルアダプテーション回避の定量評価
Grant number：24H00329 2024.04 - 2028.03
独立行政法人日本学術振興会 科学研究費補助金 基盤研究(A)
Authorship：Coinvestigator(s)
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人口減少下での中小河川の水文・環境変化と新しい管理手法の研究
Grant number：20H00256 2020.04 - 2024.03
独立行政法人日本学術振興会 科学研究費補助金 基盤研究(A)
Authorship：Coinvestigator(s)
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蚊共生細菌ボルバキアによるデング熱の生態学的制御：安心・安価な新技術の提案
Grant number：19KK0107 2019.10 - 2022.03
独立行政法人日本学術振興会 科学研究費補助金 国際共同研究加速基金（国際共同研究強化(Ｂ))
Authorship：Coinvestigator(s)
Available Technology 【 display / non-display 】
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河川への人為負荷が生態系に与える影響の評価
水文シミュレーションによる気候変動下の流域環境評価
環境DNAの動態評価Home Page： 糠澤桂のウェブページ
Related fields where technical consultation is available：・数値解析による水文流出過程の計算
・生息環境の定量的評価方法
・河川環境調査 ・気候変動解析Message：・今後の研究計画①：耳川流域におけるダム通砂に伴う河川生態系のレスポンス評価
・今後の研究計画②：宮崎県の河川における治水・環境評価モデルの構築
・今後の研究計画③：環境DNAの動態評価研究