Abstract
Concentrations of nutrients in the sediment in the estuary of the Chikugo River, Japan were surveyed before and after the flood period in 2003. The Chikugo River discharged 1900 ton of particulate nitrogen (PN) and 600 ton of particulate phosphorous (PP) in the period of 6 months (from May 1 to Oct. 31, 2003). As for the fluvial suspended sediment (SS), 70% of the total particulate phosphorous was soluble in the anaerobic conditions in the seawater.
Nutrients and organic carbon content of fluvial SS was higher than those of the estuarine sediment.
After the flood period, Fe-P, Al-P and Ads-P concentration in the sediment of the tidal flat at the front of the rivers increased. On the other hand, at the points those were far from the river mouths, the concentration of these components in the sediment of the tidal flat did not increase. It was clarified that the discharged sediment from the river basin affected the nutrient concentration and environment of the surface sediment in the estuary. Moreover, concentrations of nitrogen and organic carbon in the sediment decreased in the tidal flat. It means that organic compounds in the surface sediment were degraded in the tidal flat.
