Innovative Method to predict Water Quality in Coastal Areas for Ecosystem

溶解氧是影响水体生态质量的关键因子之一。外部条件，如气候条件，包括降水、温度、风向和风速以及营养物负荷，其中一些特征时间短于一天，通过几个途径影响溶解氧。由于溶解氧的特征时间较短，有些特征时间具有季节性，用年平均法或季节平均法估算溶解氧的逐时变化是无效的。为了估计溶解氧浓度，一个随机的方法，而不是一个确定性的，被认为是有用的。在本研究中，根据东京湾、新寺湖和博多湾的观测数据，对低溶解氧浓度的发生进行了随机调查。在博多湾，温跃层下的溶解氧浓度取决于下层的厚度比叶绿素a浓度，光量子通量，沉积物耗氧率等，使用它们，溶解氧的变化估计与高精度。在东京湾，当东北风吹袭时，在温跃层发展和水温高于15 ℃的情况下，出现无氧、含还原硫的水体“蓝潮”。“蓝潮”的发生与风能、水体重心的变化有明显的相关性。本文介绍了一种利用氮氧化物在河口混合层中变化的测量方法，并研制了一套大型的河口氮氧化物观测系统。

Dissolved oxygen is one of the key factors on water quality for ecosystem. External conditions such as climate conditions including precipitation, temperature, wind direction and speed and nutrient loading, some of which have shorter characteristic time less than one day, influence dissolved oxygen through several paths. The yearly or seasonal average methods are ineffective to estimate hourly change of dissolved oxygen because it has a short characteristic time with some seasonally long ones. In order to estimate dissolved oxygen concentration, a stochastic method, instead of a deterministic one, is considered useful. In this study, occurrence of low dissolved oxygen concentration was stochastically investigated based on observation date in Tokyo Bay, Lake Shinji and Hakata Bay. In Hakata Bay, dissolved oxygen concentration under the thermocline depends on the thickness of the lower layr more than chlorophyll-a concentration, light quantum flux, sediment oxygen consumption rate, etc. Using them, the dissolved oxygen changes were estimated with high accuracy. In Tokyo Bay, "blue tide", which is water body with oxygen-free and contains reduced sulfur, occurs under both of the development of thermocline and water temperature higher than 15 degree when wind of north-east blows. The occurrence of "blue tide" is clearly correlated with wind energy and the change of the center of gravity of water body. The development of a large scale observation system on nitrogen oxide in an estuary was developed by using a method to measure changes of nitrogen oxide in the mixing layr of the atmosphere above the water surface.