WEKO3
アイテム
農業用調整池ならびに水田湛水中の水質環境の形成に関する研究
https://doi.org/10.24514/00002183
https://doi.org/10.24514/000021834123a57f-eea9-4fff-b3e9-e9de670d4881
| 名前 / ファイル | ライセンス | アクション |
|---|---|---|
nkk_report_No47p1-51p.pdf (7.3 MB)
|
|
| Item type | 紀要論文01 / Departmental Bulletin Original Article(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2019-03-22 | |||||
| タイトル | ||||||
| タイトル | 農業用調整池ならびに水田湛水中の水質環境の形成に関する研究 | |||||
| タイトル | ||||||
| タイトル | Studies on hydraulic and biochemical phonomena of an irrigation reservoir and ponded water in a paddy field | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| キーワード | ||||||
| 主題Scheme | Other | |||||
| 主題 | ミクロキスティス | |||||
| キーワード | ||||||
| 主題Scheme | Other | |||||
| 主題 | 水理学的滞留時間 | |||||
| キーワード | ||||||
| 主題Scheme | Other | |||||
| 主題 | 環境水理モデル | |||||
| キーワード | ||||||
| 主題Scheme | Other | |||||
| 主題 | 非点源排出負荷 | |||||
| キーワード | ||||||
| 言語 | en | |||||
| 主題Scheme | Other | |||||
| 主題 | water bloom | |||||
| キーワード | ||||||
| 言語 | en | |||||
| 主題Scheme | Other | |||||
| 主題 | Microcystis | |||||
| キーワード | ||||||
| 言語 | en | |||||
| 主題Scheme | Other | |||||
| 主題 | hydraulic turnover rate | |||||
| キーワード | ||||||
| 言語 | en | |||||
| 主題Scheme | Other | |||||
| 主題 | numerical simulation | |||||
| キーワード | ||||||
| 言語 | en | |||||
| 主題Scheme | Other | |||||
| 主題 | diffused pollutions | |||||
| 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 | |||||
| ID登録 | ||||||
| ID登録 | 10.24514/00002183 | |||||
| ID登録タイプ | JaLC | |||||
| 著者 |
吉永, 育生
× 吉永, 育生 |
|||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Water environment conservation in rural area is an important issue. In Japan seventy-eight percent of irrigation reservoirs are in a eutrophicated state, where the bloom of phytoplankton may occur. Massive growth of phytoplankton produces unsightly bad-smelling scum, preventing the use of water for agricultural and recreational purposes. Especially, excessive growth of cyanobacterium Microcystis on freshwater systems is a serious problem nowadays. Some Microcystis species produce toxins that cause fatal poisoning of livestock and humans. To predict and prevent nuisance Microcystis blooms in freshwater systems, it is necessary to understand the conditions that lead to Microcystis dominance. One of the specific characteristics of regulating reservoirs for irrigation is artificial exchange of water (hydraulic turnover rate) due to paddy irrigation demand. Artificial exchange of water will affect hydrodynamic conditions, which will change environmental conditions for phytoplankton growth. To our knowledge, few studies have examined both the physical and the biochemical phenomena in irrigation reservoirs, especially focusing on the relationship between the hydraulic turnover rate and Microcystis dominance. The objective of this study was to understand the both the physical and the biochemical phenomena in irrigation reservoir using the data of field measurement and numerical simulation. In addition, this study also aimed to understand nitrogen discharging phenomena from paddy field, which may have impacts on water environment of closed water bodies in all downstream watersheds. First of all, seasonal changes of vertical profile of chlorophyll a, COD_Mn and nutrient concentrations of an irrigation reservoir were examined from the results of 2 years field measurement. The reservoir had the maximum depth of 9 m, surface area of 1.2 x 10^5 m^2, maximum storage volume of 5.6 x 10^5 m^3. Hydraulic retention time was about 3 days from April to August, and was 7 days from September to March. In July, Volvox sp. became dominant when the turnover rate and nutrient supply rate was high. On the other hand, Microcystis sp. became dominant when the turnover rate and nutrient supply rate was low in September. These results was coincide with in part the occurrence of blooms of cyanobacteria in nutrient-rich and slow-flowing waters. Based on these results, a numerical model was developed to simulate changes in biomass of phytoplankton along with flow, water temperature and nutrient concentrations. The concentration of chlorophyll a was used as an index of phytoplankton biomass, and considered nitrogen and phosphorus as nutrients that affect growth of phytoplankton. The model is composed of the three-dimensional hydrodynamic model coupled with the water-quality sub-model. The three-dimensional hydrodynamic sub-model is multi-leveled, accounting for water density variations due to changes in water temperature. The water-quality sub-model calculates concentrations of nitrogen, phosphorus and chlorophyll a. Meteorological forcing parameters for the model are introduced as hour-averaged values. The calculated temperature agreed with the observed one. The calculated chlorophyll a agreed partly with the observed ones. This study demonstrates that the three-dimensional hydrodynamic model coupled with the water-quality sub-model can deal with complex changes in phytoplankton biomass in lakes and reservoirs. Furthermore, the effect of the hydraulic turnover rate on dominance of the cyanobacterium Microcystis was examined. A Microcystis bloom occurred in late summer when the daily hydraulic turnover rate decreased to 15％. From the result of principal component analysis, it could be interpreted that Microcystis bloomed during low hydraulic turnover rates and for a short duration of time, and that dissolved nutrients in the surface of the reservoir were not a critical factor for Microcystis dominance. The hydraulic turnover rate provided an index of nutrient supply rate, because the nutrient load was input mostly in the inflowing water and because the water body was well mixed. Field measurement results indicate that the low hydraulic turnover rate led to the Microcystis bloom. Finally, dissolved nitrogen concentrations in a paddy field were discussed, which have significant effects on all downstream watershed environments. Based on an experimental field study, a model was developed to simulate dissolved nitrogen in water ponded in a paddy field. As input data, the model uses meteorological data, water balance in the field, nitrogen concentration in inlet water, and the nitrogen contribution of applied fertilizer. Five model parameters need calibration. A practical application of the model is the simulation of NH_4-N and NO_2+3-N concentrations in water ponded in a paddy field. The model improves our understanding of the interactions between forms of dissolved nitrogen in ponded water and can explain the complex changes in dissolved nitrogen concentrations in water ponded on a paddy field. | |||||
| 書誌情報 |
農村工学研究所報告 en : Bulletin of the NARO, Rural Engineering 巻 47, p. 1-51, 発行日 2008-03-01 |
|||||
| 出版者 | ||||||
| 出版者 | 独立行政法人 農業・食品産業技術総合研究機構 農村工学研究所 | |||||
| ISSN | ||||||
| 収録物識別子タイプ | ISSN | |||||
| 収録物識別子 | 1882-3262 | |||||
| DOI | ||||||
| 関連タイプ | isIdenticalTo | |||||
| 識別子タイプ | DOI | |||||
| 関連識別子 | 10.24514/00002183 | |||||
| 著者版フラグ | ||||||
| 出版タイプ | VoR | |||||
| 出版タイプResource | http://purl.org/coar/version/c_970fb48d4fbd8a85 | |||||
