Development of nutrient circulation model for ecological system control in estuary

河口生态系统控制中营养盐循环模型的建立为了建立河口营养盐循环模型，本文对河口、河口的营养盐行为进行了研究。主要研究结果如下：1.探讨了流域营养盐的形成机理，并建立了名取川流域的数值模型，明确了正常水流条件与洪水条件的差异。对不同输运方式下的营养盐负荷进行了评价。2.对河流营养盐输运特征进行了实测和模拟。分析了水流与河床之间的营养盐交换，确认了河床在循环过程中的重要性。3.在阿布熊河口观测到了盐楔的行为。分析了水分和养分的混合过程。4.在Dubye-Huckel理论的基础上，考虑铁与腐殖物质之间的静电相互作用，建立了河口条件下腐殖-铁复合体的平衡模型。该模型较好地解释了河口区腐殖酸-铁络合物随张力强度增加而分解的现象。5.利用潮滩模型对河口区生态系统行为进行了模拟。结果表明，沉积物上的微藻减少了模型中有机质的积累。此外，模型还表明，双壳类优势系统中有机物的流动比对照系统中更为活跃。因此，双壳类可能有助于抑制有机物的积累。考虑了海湾口的热量平衡和水交换。计算结果与观测结果吻合较好。

Title Development of nutrient circulation model for ecological system control in estuaryIn order to develop nutrient circulation model in estuary, the behavior of nutrient is investigated in river basin, river beds, rivermouth and estuary. The main results are as follows1.The mechanism of nutrient origin in river basin was surveied and a numerical model was developed in the Natori River basin, The difference between ordinal flow condition and floods was clearly observed. The nutrient load was evaluated in various mode of transport.2.The feature of nutrient transport in river was measured and modeled. Nutrient exchange between flow and river bed was anlysed and inportance of river bed was confirmed in circulation process.3.Behavior of saline wedge was observed at the Abukuma rivermouth. The mixing processes of water and nutrient were analyzed. The spread of nutrient in the sea was also studied.4.The equilibrium model for humic-iron complex in estuarine condition was developed on the basis of Dubye-Huckel theory taking account of the electrostatic interaction between iron and humic substance. The dissociation of humic-iron complex with increasing tonic strengh in estuaries was well explained by the developed model.5.Behavior of ecosystem at the river mouth was estimated by the tidal flat model. It was found that microalgae on sediment decrease the accumulation of organic matters in the model. Furthermore, the model showed flow of organic matter in bivalve-dominant system become more active than that in control system. Therefore, bivalves might be useful to inhibit the accumulation of organic matters.6.A physical model of staratification and mixing in closed bay was developed. The heat balance and water exchange at bay mouth were taken in consideration. The results show good agreement with observation.