Study On The Hazard Evaluation Method Of Toxic Haze On Natural Surface Ecological Environment

Since 2013,toxic haze with high concentrations of nitrogen oxides,sulfur dioxide,and PM2.5 as the core pollutants has frequently occurred,causing degradation of forest ecosystems,degradation of grassland ecosystems,damage to lake ecosystems,and damage to farmland ecosystems.The emergence of such phenomena has caused great harm to the natural ecological environment on the surface.The natural ecological environment on the surface is the basis on which people depend for their survival.The occurrence of various pollution incidents has made them worse.The occurrence of poisonous haze has undoubtedly exacerbated its destruction,if it does not cause toxic haze to be a hazard to the surface natural ecological environment.The problem is emphasized,and the lack of assessment of hazards will eventually lead to the collapse of the natural ecological environment,affecting people’s lives and economic development.This paper is based on the premise of meeting three different requirements,and aims to evaluate the harmfulness of toxic haze to the surface natural ecological environment.The first method,in order to evaluate the cumulative damage caused by poisonous haze within a year to the natural ecological environment on the surface,and to highlight the dynamic relationship between the number of toxic haze and the number of toxic haze,the actual value of the hazard is obtained: First,through the analysis of the process of the natural ecological environmental hazards caused by each toxic haze,the hazard evaluation index characterized by the loss amount was selected.Secondly,the function Petri net is defined,and the function of the Petri net’s transition trigger rule and the state value of the library state is clarified.Then,a cumulative hazard assessment model based on functional Petri nets for regional annual toxic haze on the surface’s natural ecological environment was established,the algorithm of the model was given,and the conceptand calculation method of “Hazard degree” were proposed.Finally,the model was verified by examples.In the second method,taking into account the difference in each toxic haze event,in order to evaluate the harmfulness of a once-disturbed toxic haze on the surface ecological environment,the quantitative value of the hazard is obtained: First of all,through the analysis of the characteristics of toxic haze events and the hazard events they caused,the possible harmful events were selected as hazard evaluation indicators.Secondly,fuzzy Petri nets are defined and four fuzzy production rules are clarified.Then,a fuzzy Petri net-based model for evaluating the harmfulness of different toxic haze to the surface natural ecological environment was established,and the matrix reasoning algorithm and hazard classification criteria of the model were given.Finally,the model was verified by examples.The third method is to compare and evaluate the hazards caused by toxic haze in different areas caused by the natural ecological environment on the surface,so that the types of influencing factors are consistent,and the factors that affect the hazardous results of toxic haze are two-sided: First,using the natural disaster risk theory to find out all the factors that affect the harm of toxic haze on the surface of the natural ecological environment,established a harmful evaluation index system.Secondly,two-branch fuzzy Petri nets are defined,and the production rules and variable weight rules of two-branch fuzzy Petri nets are given.Then,a comparative evaluation model for the harmfulness of haze in different areas based on the two-branch fuzzy Petri nets to the surface natural ecological environment was established,and the matrix reasoning algorithm of the model was given.Finally,the model was verified by examples.