Distributions and Behavior of Chemical Substances in Dokai Bay-an Enclosed Sea

Abstract

Three detailed surveys on chemical substances in water columns of Dokai Bay in Kitakyushu, Japan, were carried out to know actual states of their distributions and behavior in the bay. Sixteen chemicals, such as chlorobenzenes, chlorophenols and anilines, were widely detected in surface water and nine polycyclic aromatic hydrocarbons (PAHs) were detected in bottom water around center of the bay. Horizontal and vertical distributions of chlorobenzens, chlorophenols and anilines were consistent with the residual current of seawater. By comparing the decrease of their concentrations to salinity, it was elucidated that chlorobenzenes and chlorophenols were declined by volatilization and photolysis respectively, and anilines were declined by biodegradation and photolysis. On the other hand, it was strongly suggested that PAHs which adsorbed to suspended particles were swiftly settled to bottom sediment near their source with the influence of residual current.