Effects of Sediment Dredging on the Diffusion Fluxes of Nutrients between Sediment and Water in Dalian Bay

The diffusion fluxes of dissolved inorganic nitrogen (DIN) and phosphate (DP) between sediment and water were estimated using Fick’s first law in the area near the sediment dredging location and in the dredged area of Dalian Bay during different seasons. The environmental properties of the studied areas were also investigated. The temperature, pH, dissolved oxygen, and salinity of the bottom water of the two studied areas did not exhibit remarkable differences. The DIN and DP diffusive flux near the sediment dredging area were larger, and the content of organic matters in the sediment was higher compared with the dredged area. In conclusion, sediment dredging induced the accumulation of organic matters in the surface sediment of nearby areas and accelerated the release of DIN and DP from the sediment. Sediment dredging is thus concluded to be among the primary factors contributing to the water eutrophication in Dalian Bay.