| Dalian city is one of the water shortage areas and the water resources development and utilization has been more and more difficult. In recent years, as reinvigorating northeast old industrial base, implementing coastal economic zone strategy and constructing northeast Asia international city, together with the human destruction of the nature, all of which increase the water supply- demand contradiction. There still some pollution sources influence the environmental quality, for example, domestic sewage, industrial wastewater, waste residue, agricultural pollution, ship pollution. Some rivers, reservoir and sea area are still in different levels of pollution and potential pollution accidents still exist.Although water pollution accidents are uncertainty, they can be forecasted and predicted according to the risk sources before outbreak. Accurate forecast and precaution can greatly decrease the possibility of occurrence and reduce the loss, and which is the first and important link of emergency management system.Taking the volatile phenol as example, this paper models the diffusion rule of certain river in Dalian city, which is helpful to make emergency plan. It includes four main aspects as follows:(1) Taking Songhua river's nitrobenzene accident as reference, the emergency monitoring, emergency treatments, ecological restoration are investigated. It deeply analyzes the deficiency of the emergency management shown in this accident.(2) The predication of pollutant emission belongs to the grey system theory. The modified model of residual and the metabolic model are used to forecast the volatile phenol emission of Dalian city, and the results can meet the secondary qualified standard. The static shows that if there are no control measures the emission will reach to 60.3 ton in 2015, which are 2.4 times of 2007. So many pollutants discharge directly will bring great pollution of river and sea area, and bring great economical losses.(3) According to the water resources situation of Dalian, one-dimensional water quality model is used to predicate the volatile phenol diffusion rule in certain river of Dalian. This paper imitates the pollution cluster formatted by instantaneous model, instantaneous integral model and continuous model. The real-time simulation of tracking on polluted water mass is realized by MATLAB. The risk evaluation system is established based on the simplication and mathematical deduction of the basic equation of pollutant transport and transformation, and it could identify, characterize and describe the environmental hazard, and estimate harmful region and duration in water environment. The results of both the simulation and the risk evaluation model are sensible and accurate, which can offer the scientific basis for environmental risk management and emergent counter plan making of accidents happened in water environment.(4) Rivers are the main fresh-water source in Dalian city, so it is important to strengthen management of river drainage area. Constructing of river management system, basin water right system, ecological compensation system are helpful to enhance the river basin comprehensive management. Useful protection measures and emergency plan can provide guarantee for the water pollution accidents to cope with the accidents actively and reduce the harm to minimum.
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