Marine Surface Sediment Re-suspension Of N, P Cycles And The Vertical Transport Of Particulate Matter

The concentration of NH₄-N/NO₃-N /PO₄^3- in seawater changed with many factors, such as shaking velocities, shaking time, mixture ratios and grain sizes. Moreover, different forms also influenced the change of N/P between the seawater and the sediments. To separate the downward fluxes of primary settling matter and resuspended sediments, a mathematic model was proposed by boundary layer and shear stress combined wave with current. A chemical model was also used. Ca was used to trace the resuspended particulate materials, because calcium and aluminium abound in sediments. The concentration of NH₄-N in water had a negative relation with the increasing ratios between the mass of sediment and the volume of seawater. About 6h later, the concentration in water with shaking rate of 60rpm decreased to the lowest of the three rates. The concentration in water with shaking rate of 120rpm increased to the highest. when the shaking velocity was low, the concentration of NH₄-N in the sea water had a positive relation with the concentration of suspended particulate materials. When the shaking velocity was high, the concentration of NH₄-N in the sea water had a negative relation with the concentration of suspended particulate materials. It's mainly because that when the concentration of the suspended particulate materials is lower, the release is dominated, so the concentration of NH₄-N had a positive relation with the concentration of suspended particulate materials. When the concentration of the suspended particulate is higher, the absorption is dominated, so the concentration of NH₄-N has a negative relation with the concentration of suspended particulate materials. In the course of the resuspension , the fine grain sediment in the chosen sea water had the most contribution on NH₄-N of the sea water ,then was the medium and coarse grain sediment. NH₄-N mainly came from ion-exchange form,carbonate form nitrogen, the contribution of iron-manganese form nitrogen was less. The concentration of NO₃-N in water had a negative relation with mixture ratios and shaking velocities. The coarse sediment had similar trend with the fine sediment. The medium grain sediment of the chosen sea area had more contribution on sea water than the coarse and fine sediment. NO₃-N mainly came from ion-exchange form , carbonate form nitrogen, the contribution of iron-manganese form nitrogen was less. In the lower disturbance frequency(60 rpm/min), The varieties of dissolved inorganic phosphate's concentration and dissolved organic phosphate's concentration have same trend. however, In the higher disturbance frequency(120 rpm/min,150 rpm /min),the variety of DOP 's concentration has an opposite trend with that of DIP's concentration. The concentration of DIP increase with the increase of the disturbance frequency , But the concentration of DOP reduces with the increase of the disturbance frequency. Concentration of phosphorus in water has a positive relation with the increasing ratios between the mass of sediment and the volume of sea water through the experiment. Ion-exchangeable form is the first control mechanism of the phosphorus release, and iron form is the second control mechanism. This mathematic model was based on the theory of boundary layer and shear stress (combined wave with current). Through this model, the downward fluxes of primary settling matters and resuspended sediments can be separated. So the true fluxes of primary settling matter will be determined. A chemical model was also proposed. Ca was used to trace the resuspended particulate materials, because calcium abound in sediments. PON was chosen as tracer of primary sediment.