A Study On The Nutrients Exchange Flux Between Bottom Sediment And Water Layer For Bohai Bay

In recent years, the economy has developed rapidly around the coastal zone of Bohai Bay. As a result, more and more wastewater has been discharged into Bohai Bay, and the eutrophication problem has become more serious. Sediment serves as the source and sink of nutrients, and plays an important role in the budget and dynamics of nutrients recycling in the marine water. Therefore, a study on the exchange fluxes of nutrients between bottom sediment and water layer in this typical sea area is necessary, it has great significance for the eutrophication control and environmental protection.The nutrients exchange flux between bottom sediment and water layer at 6 stations in Bohai Bay was studied in this paper form May to Oct in 2006, and the lab incubation method was adopted to simulate and measure the nutrients exchange flux under different conditions in order to study the effect of related factors. It turned out that the sediment served as the source of nutrients in Bohai Bay in most part of the time.The exchange flux of SiO32- was higher and had a stronger variation with season, the exchange flux of NO3- was higher in aerobic situation than in anoxic situation, reduced when pH or temperature of the water went higher, and had an increasing trend under the function of bioturbation while NH4+, SiO32- and PO43- just went the other way round.A 2D ecohydrodynamic model of Bohai area has been set up. This model has two sub-models: one is hydrodynamic model and the other is advection-diffusion model, where the nutrients exchange flux between bottom sediment and water layer is considered as the source of the advection-diffusion model, which relates only to the concentrations in the marine water.In this paper, numerical simulation of the nutrients exchange flux between bottom sediment and water layer at Bohai Bay was conducted using the 2D ecohydrodynamic model. By comparing the simulated data with the measured data, the contribution of the nutrients exchange flux to the marine water was gained, which showed great importance of sediment nutrients in controlling the nutrient distributions and concentrations in the whole marine water. Therefore, it is an important factor to consider in the prevention of coastal eutrophication and the model construction.