Environmental Capacity Calculation Of Petroleum Hydrocarbons In Laizhou Bay

As is known to all, China has a vast maritime territory area and abundant marineresources. With the rapid growth of the coastal population as well as fast developmentof the industrial and agricultural economics, an increasing number of variouspollutants mainly including petroleum, and nitrogen and phosphorus nutrients, aredischarged from land-based pollution sources, which seriously destroying the balanceof inshore marine ecosystem.Petroleum hydrocarbons (PHs) are one of the major marine pollutants and thereforehave always captured lots of the attention of the world. With the development of theoil industry, the PHs discharge from terrestrial input, as well as during the oilexploration and shipping transportation, are increasing fast, leading to thedeterioration of the marine environment.In this paper, an ecosystem dynamical model of environmental capacity of PHs wasestablished in Laizhou Bay including seven modules as follows: petroleumhydrocarbons, microorganism, atmospheric volatilization, nutrients, phytoplankton,suspended particles and hydrodynamic module. From the result of numericalsimulation of Laizhou Bay of PHs concentration distribution in the early21st century,we can find that the value of PHs distribution is high in southwest waters of LaizhouBay and the concentration of PHs in the bay is higher in summer and autumn than thatin winter and spring.As the specific seasonal variability of the PHs exists in the bay, the correspondingPHs response factor field changes over time. To obtain the ascertained PHs responsefactor field, the monthly averaged PHs concentration data and the monthly maximum PHs concentration data are adopted respectively.Meanwhile, with the analysis above,we employed the discharge optimization method to calculate the environmentalcapacity(EC) of marine pollutants in Laizhou Bay.With respect to applying the monthly averaged PHs concentration data and themonthly maximum PHs concentration data to the discharge optimization method, theprecondition of this method should be checked before calculation.Firstly, to ensure theeffectiveness of the discharge optimization method, the response factor field of pointsources of PHs was proved to be linear superposition. Secondly, PHs response factorfield based on the monthly averaged concentration field was proved to be linear, whilePHs response factor field based on the monthly maximum concentration field wasnonlinear.So the results show that the discharge optimization method based on thelinear programming (short as the linear programming method) could be used with themonthly averaged concentration field, while the discharge optimization method basedon the nonlinear programming (short as the nonlinear programming method) would beused with the monthly maximum concentration field.At last, according to the data of the monthly average concentration and monthlymaximum concentration in Laizhou Bay, the linear programming method and thenonlinear programming method were chosen respectively to calculate EC of PHs. Theresult shows that nonlinear programming method will underestimate the PHsself-purification capacity to some extent. However, from the environmental protectionpoint of view, nonlinear programming method based on monthly maximum data wasmore reasonable to calculate the EC of the nonconservative substance, like PHs.Instandard of seawater grades of I/II, EC of PHs in Laizhou Bay is4576.1t/a, while theSEC (Surplus EC) is-3523.6t/a, which means the PHs discharge should be restricted.