Circulation and Pollutant transport Processes in Shallow Estuarine

本文旨在研究半封闭海域陆源营养盐的入流行为及其与沉积物的相互作用。在此基础上，建立了考虑海底沉积物-水相互作用的水质模型。1）浅海沉积物中营养盐的释放：通过在大坂湾进行的现场调查，研究了海底沉积物的性质。通过室内试验，揭示了氮磷释放速率、反硝化速率等特征。2）陆源入流泥沙的行为：通过对大和川入流泥沙中氮碳稳定同位素的测定，了解陆源入流泥沙的行为。结果表明，大和江入海泥沙主要沉积在河口附近。3）入海营养盐负荷与实测水质的关系：采用比值单位法估算了1921 ~ 1995年的入海营养盐负荷。根据人口、牲畜和工业生产等社会经济数据，研究了来自陆地的营养负荷对大坂湾水质的影响。4）开发水质，海底沉积物-水相互作用模型：所建立的水质模型可以处理泥沙-水的相互作用，即有机碎屑从水层沉积到海底，而营养物质则从相反方向释放。对模型主参数的有效性检验表明，氮、磷对海水营养盐沉降速度较为敏感。

The purpose of the present study is to investigate the behaviors of nutrients inflowed from land area, and the interactions between sediments and water quality in semi-enclosed sea area. Moreover, a water quality model is developed based on the field survey results, which takes sediment-water interactions at sea bottom into account.1) Release of nutrients in shallow sea sediment : The sea sediments properties at sea bottom were examined by conducting the field survey in Osaka Bay. The laboratory experiments revealed the characteristics of the release rate of nitrogen and phosphorus, the denitrification rate, and so on.2) Behaviors of inflow sediment from land area : The stable isotopes of nitrogen and carbon in the sediment were measured in the Yamato River in order to comprehend the behaviors of inflow sediment from land. As a result, it is considered that most of inflow sediments are settled and deposited around the river mouth of Yamato River.3) Relationship between estimated inflow nutrient loads and measured water quality : The inflow nutrient loads from 1921 to 1995 were estimated with the ratio unit method. The effects of nutrient loads from land on the water quality in Osaka Bay were examined based on socio-economic data such as population, livestock, and industrial product.4) Development of water quality, model with sediment-water interactions at sea bottom : The developed water quality model can deal with sediment-water interactions in terms of sedimentation of organic detritus from the pelagic zone into the benthic zone and release of nutrients in the reverse direction. The validity tests of the model for the principal parameters reveal that both nitrogen and phosphorous are sensitive to settling velocity of nutrients from sea.