Hypoxic Water in Harbor Areas and its Countermeasure

Abstract

Distributions of dissolved oxygen and phosphorus concentrations were measured in a harbor area along the north coast of Osaka Bay. An anoxic water mass existed within a shallow depression in Koshienhama canal, where surfacing of anoxic water frequently occurs. Bottom anoxic water appeared beneath the surface chlorophyll maximum layer in a channel where sewage flows into. Total phosphorus concentration is higher in the upper layer than that in the lower layer, in contrast to total nitrogen concentrations. This suggests desorption of phosphorus from the bottom sediment. To pretend generation of hypoxic water, a countermeasure which uses buoyancy of river water was considered.