Study On The Method Of Searching The Accidental Pollution Source Around The Drainage Area Based On The Theory Of Optimal Search

Such a series of serious water environmental pollution incidents that happened in Tuojiang River in Sichuan Province and Beijiang River in Guangdong Province have cautioned us that it is urgent for us to reply for the environmental emergency scientifically. When pollution incident happened in a drainage area, what is most important is to find out the pollution sources quickly and accurately, and check out the illegal emitting accidents. It is a dynamic changing process for the pollution source to outlet pollutant, thus, the main access to get the message of the pollution source is to inspect every outlet and the water quality of the drainage area. However, as it is constrained by technology and economy, the monitoring method stays in the routine stage, which mainly counts on human and can not implement an extensive and all-day-long inspect. As a result, it is hard to confirm the pollution source quickly and accurately just rely on the current monitoring methods, which will dally over the right time to deal with the pollution and make the drainage area worse polluted.The theory of optimal search is developed during World War II ,which is focused on optimizing the distribution of search effort when the total search efforts are limited and the target distributing is dubious. It can maximize the probability of searching the targets and minimize the effort. Therefore, the search quality can be mostly improved by optimizing the search efforts using the theory of optimal search.Based on systematically analyzing the actuality of environmental lash-up monitoring in our country, this paper introduces the theory of optimal search, and analyzes the factors that affect the optimal search of the accidental pollution sources, according to target distributing and search effort distribution. At last the optimal search method and its model system for the drainage area accidental pollution sources are concluded.Firstly, according to the characteristics of the position of pollution source, the criterion of every pollution outlet and the characteristics of the drainage area pollution, the search area is classified and the corresponding original distributing function is concluded. Through a comprehensive analysis of the current subjective probability, combined with the characteristics of the search job, a NGT method is adopted to confirm the subjective probability. Aimed at the information resource the NGT method requires, through analyzing the factors that affect the point source sewage from emitting legally, and combined with the detailed information of the drainage point pollution sources and the corresponding problems that arose when filling in the investigation table of the current pollution source, a system guide line for the management which is comprehensive and accords with the fact is confirmed, and a system that can be used to search and manage the drainage area pollution sources is carried out through software.Secondly, according to the distribution of the drainage area accidental pollution sources, the four kinds of static state detecting functions and the four kinds of dynamic detecting functions corresponding to the continuous and discontinuous drainage states of the pollution sources respectively. Aimed at the situation that the target is not found before the stated time, a track search analysis is implemented, through which it can be decided which sub-area the accidental pollution source is possibly in, although the target is not found within the stated time.Thirdly, a certain section of the upper Changjiang River is taken as the researching object, based on abundant analysis on the basic situation and the pollution source state of all the drainage areas, the Changjiang River (YiBin part), Yuexi River, Changning River with different pollution types are taken as the typical drainage areas, and the corresponding optimal search model is established, which can instruct the efforts distribution when pollution accidents take place in the area. The example study on the search method for different types of accidental pollution sources indicates that it is more probable for the drainage area accidental pollution source search method to find the accidental pollution source than the traditional ordinal search model does, and than the method which distributes search time according to the targets distributing probability does. It is 54.6% higher in average capability for the drainage area accidental pollution source search method to search the accidental pollution source than the traditional ordinal search model does. And it is 13.2% higher than the method which distributes search time according to the targets distributing probability does.