Research On Seawater Exchange And Self-purification Capacity And Pollution Emergency Countermeasures Of Pulandian Bay

Bay is an important natural resource of socio-economic factor in coastal areas.Seawater exchange capacity and self-purification capacity are crucial for the protection of marine environment and the control of pollution discharge,which play a significant role in the quality of seawater.In this paper,a simple two-dimensional steady flow is taken as an example,based on Navier Stokes equations and eddy current fuction,the calculation method of water exchange capacity and self-purification ability is put forward.It also points out the calculation methods of seawater exchange rate according to the concentration equation are not accurate.Based on the unsteady depth average equation of the unsteady three-dimensional flow,a practical numerical calculation model of three-dimensional shallow water exchange and self-purification capacity is established by numerical methods such as particle tracing,which lays a theoretical foundation for practical application.Pulandian Bay is a drowned valley,and Boji Island is at the baymouth.The east inner bay is long and narrow,surrounded by the aquaculture dams.Songmu Island and Sanshilipu port shipping area are located in the bay mouth of inner bay.With the general situation of resource environment and development of Pulandian Bay,this paper uses the complete depth average shallow water equation to simulate the tidal current field of Pulandian Bay and validates the simulation results by using the measured data.In order to study the seawater exchange and self-purification capacity,combined with remediation of Pulandian Bay,exchange rate and self-purification rate before and after the remediation are calculated,compared and analyzed,which are based on the particle tracing method and the concentration-diffusion equation respectively.The results showed that exchange rate increased from 0.2 to 0.3 and self-purification rate increased from 0.6 to 0.65,which indicated that the capacity did not improve essentially.After further analysis,we can see that although the dams are demolished after the implementation of the comprehensive remediation plan,as Pulandian Bay is a drowned valley and the east inner bay is long and narrow,the width of bay mouth is still narrow so that the seawater cannot be exchanged out easily with convection,thus limiting the enhancement of seawater exchange and self-purification capacity.The seawater exchange rate as low as 0.3 means that once oil spill occurs in Pulandian Bay,the pollutants can easily be stranded in the inner bay for a long time,while the shoreline of both sides are industrial and urban areas,so the environmental carrying capacity is so fragile that improving the capacity to prevent the risk of pollution is necessary.A strain of Pseudomonas sp.,which can degrade petroleum hydrocarbons,was isolated from the coastal waters of Pulandian Bay.Under the condition of 22? and 120r/min,the degradation rate of 0#diesel oil reached 47.2%,which provides bacteria for bioremediation of marine oil spills in this area as a relatively Ecological,environmental protection,safe treatment for the fragile Pulandian Bay to deal with the largest oil spill environmental risk.