Research On The Marine Environment Capacity Of Lingshui Bay In Dalian

Recently, the construction of industrial districts and town zones has been gradually extended to coastal regions with accelerated urbanization in coastal areas. As a way of comprehensive development and utilization of the bay, the sea reclamation project can effectively relieve the problem from the scarcity of land resources, which play an important role in the construction of coastal economic zone.With new space developed, however, the sea reclamation project permanently changes the natural attributes of the bay, which could leads to severe damage of its function. The construction of the large reclamation could reduce the water area, slowdown the water exchange in the bay, and then affect the marine environment capacity. Therefore, it could result in decline of the marine environment quality at original pollution condition with pollutants normally discharged. Over time, the marine ecological environmental will be damaged, even to the degree beyond the recovery.In this paper, the marine environment capacity of Lingshui Bay was studied in order to uncover the change of environment capacity of main chemical pollution factors (N, P and COD) and provide scientific evidence for avoiding further pollution, based on the actual investigation data of water quality and tidal currents before and after the reclamation project. The main results and conclusions are as follows:Firstly, comprehensive assessment of the water quality was made by using a Grey System Theory based on the water monitoring results before and after the reclamation project. Before the reclamation project, Lingshui Bay had strong water exchange capability and good water quality. However, the water exchange capability was weaken and water quality declined after the bay was changed to a trumpet-type bay.Secondly, marine environment capacities of inorganic nitrogen, active phosphate and COD were evaluated by Box Model. The retention time of these three pollutants was lengthened to2.45,2.7and5.64times, respectively, compared with those before the reclamation project. As the water area in the bay was shrunk by56%, the storage capacity of tidal water and the marine of environment capacity of the Lingshui Bay were markedly reduced.Finally, the marine environment capacity was calculated by numerical simulation which combined two dimensional tidal wave equations and diffusion equations of pollutants with the constraint condition that water quality at the bay mouth satisfies the seawater quality standard. The results of the numerical simulation confirmed the conclusions of the Box Model. It was shown that the tidal current was a kind of non-regular, semi-diurnal current and the type of the tidal current changed from alternating current to rotary current after the reclamation project, which leaded to the decrease of the water exchange rate of the bay.In summary, the function of Lingshui Bay was weakened after the sea reclamation project. The study on marine environment capacity can provide scientific evidence for restraining the spread of environmental pollution and making the decision on marine pollution prevention and control.