Osaka City Institute of Public Health and Environmental Sciences, Tennoji, Osaka 543-0026, Japan
The contents of nitrogen, phosphorus, and organic matter were 2-3 times higher in the sediments collected from a sampling point located at the river end than in the sediments collected in and outside the Port of Osaka. Further, the concentrations of these elements were 9-20 times higher in the interstitial water in the sediments collected from the river end than in the sediments collected from the port area and the estimated fluxes of ammonium and phosphate ions were 2-10 times higher in the former case than in the latter case. These potential fluxes from sediments in the river end were high even in winter when the activities of microorganisms were low. The sediment in this area is very loose and can be resuspended easily by turbulence, which causes the nutrients in the interstitial water to drift away. Therefore, dredging sediments in this area is expected to be effective in reducing the pollution loads in the stagnant water area inside the port.