Circulation and Pollutant transport Processes in Shallow Estuarine

本研究的目的是研究半封闭海域陆源营养盐的行为，以及沉积物与水质的相互作用。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：通过对大阪湾的实地考察，研究了海底沉积物的性质。室内实验揭示了氮磷释放速率、反硝化速率等特征。2)陆源泥沙的行为：通过对大和河底泥中氮、碳稳定同位素的测定，了解陆源泥沙的行为。3)估算的入水营养盐负荷量与实测水质的关系：用比值单位法估算了1921~1995年的入港营养盐负荷量。基于人口、牲畜和工业产品等社会经济数据，研究了陆地营养盐负荷对大阪湾水质的影响。4)水质发展，海底沉积物-水相互作用模型：所开发的水质模型可以处理沉积物-水相互作用，包括有机碎屑从远洋带到底栖带的沉积和营养物质的反向释放。对模型主要参数的有效性检验表明，氮和磷对海洋营养盐的沉降速度都很敏感。

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.