Models And Warning Index System Of River Environmental Risk Based On Uncertainty Theory

The environmental risk analysis of river is considered to be an importantfoundation work of river environmental risk management. However, the uncertaintieswidely existed in the environmental risk system of river have an influence on theaccuracy of the environmental risk analysis of river., And even, wrong riskmanagement decisions may be made.This dissertation first summarized the main contents and methods of riverenvironmental risk analysis， and then reviewed the main features and researchmethods of water environmental health risk, ecological risk of sediments and suddenpollution risk of river. The research progresses of uncertainty theory and theirapplications to environmental risk system were elaborated. Based on these, threetypes of uncertain theory used in the dissertation were pointed out includingstochastic mathematic methodology, interval mathematic methodology and fuzzymathematic methodology. The three types of uncertain theory were used in the riverenvironmental risk analysis and the construction of warning index system. And theinfluences of uncertainties on the environmental risk assessment were analyzedsystematically.The main works and novel results include the following elements.(1) Anintegrated fuzzy model was developed to describe environmental health risks fromwater sources based on interval numbers. In this model, the concentrations ofcontaminations were expressed as interval numbers, which can deal with theuncertainties due to use the uniform annual values in certain degree. The assessmentsystem was classified based on fuzzy theory, which can avoid the arbitrary decisionowing to the single assessment criterion. Comparison of the interval number modeland the deterministic model revealed that the risks under the interval number modelwere higher than that under the deterministic model. The priority pollutants could beselected according to the assessment results. This research can provide some technicalsupport for the pollution risk control of river.(2) The water environmental health riskassessment model based on fuzzy integrated concentration and dynamic clusteringanalysis was established. The conception of fuzzy integrated concentrations wasstated and calculated based on the contamination’s concentrations in the dry season,medium season and abundant season and the percentages of the three seasons in the whole year. The fuzzy integrated concentrations were used to calculate the health riskof each section. According to the dynamic clustering analysis, the risks of all thesections were classified, which could provide theories basis for the selection of thepriority control section under limited economic, manpower and physical resources.(3)An integrated model for assessing the risk of river environmental pollution based onfuzziness was founded. River pollution risk was defined as the fuzzy function ofhazard and vulnerability. The fuzzy membership function of hazard and vulnerabilitywere established. The fuzzy comprehensive evaluation was used to calculate the riskof river pollution. Compared with two previous models, this model not onlyconsidered the health hazards of river from pollutants on the human body, but alsotaking the vulnerability of river into account.(4) The comparisons of the results ofwater environmental health risk assessment under three above models revealed thatthe uncertainties existed in the process of risk assessment. And it also was certifiedthat the effect of uncertainties on the assessment results was huge. In the assessmentprocess of river water environmental health risk, the uncertainties of thecontamination’s concentrations and the assessment criterion were both very important.(5) Evaluation model for ecological risk of heavy metals pollution in river sedimentsbased on fuzzy toxicity index was established. On the basis of the Risk AssessmentCode and Potential Ecological Risk Index, the concept of fuzzy toxicity coefficientwas stated, and the Modified Potential Ecological Risk Index was established basedon the fuzzy toxicity coefficient. This model would play an important role inpromoting ecological risk analysis in future.(6) Based on stochastic theory,sequential Gaussian method was used to simulate the distribution of hexavalentchromium in the groundwater of a chromium salt factory in Changsha. Thegroundwater contaminated by hexavalent chromium was selected as a source ofpollution. Unsteady two-dimensional water quality model was used to simulate theinfluence of groundwater unexpected incidents on the river water quality and the riskof downstream water intakes.(7) The warning index system for river pollution riskwas established based on fuzzy analytic hierarchy process, which included warningindex system on daily pollution risk and sudden pollution risk. The warning indexsystem could provide technical support for the risk control of river pollution in future.Aiming to the environment risk analysis of river, the uncertainties in the waterenvironmental health risk, river environmental pollution risk, ecological risk of riversediments and sudden river pollution risk were systematically analyzed, using theuncertainty theory. Several risk assessment models were established based on fuzzy mathematic methodology and interval mathematic methodology. Furthermore,Sequential Gaussian method was used to simulate the distribution of contamination ingroundwater stochastically. On one hand, this dissertation is helpful to reveal thecharacteristics of uncertainties in river environmental risk system and to betterunderstand the uncertainties in environmental risk system, which would have sometheoretical significance. On the other hand, the contents of this dissertation includedthe water environmental health risk of Chang-Zhu-Tan section of Xiangjiang River,the water environmental pollution risk of the Xiangjiang River, the ecological risk forsediments of Xiawan harbor and the risk of Xiangjiang water pollution due to thegroundwater unexpected incidents. Therefore, this dissertation would have somereference significance for the risk management of Xiangjiang River.