(Shandong Eighth Institute of Geology and Mineral Exploration, Rizhao 276826)
About the author: Li Xinyong (1962-), male, senior engineer, engaged in geology and mineral resources management.
Based on the comprehensive analysis of eco-geological environment quality indexes, the fuzzy comprehensive evaluation method is determined and applied to the eco-geological environment quality evaluation in Kuishan District of Rizhao City. The results show that this method can provide more information than traditional methods, thus improving the scientific evaluation results.
Keywords: fuzzy mathematics; Comprehensive evaluation; environment quality
Introduction to 0
Eco-geological environment quality assessment is a huge systematic project, involving a wide range and many influencing factors, including the complex combination of quality and quantity, time and space. First of all, there are a lot of fuzzy phenomena in the field of environmental systems, such as the concentration of pollutants; Secondly, the traditional environmental quality assessment methods mostly adopt the comprehensive index method. After selecting the evaluation factors, the monitoring values of each evaluation factor are compared with a certain standard value of the environmental quality standard to calculate the single factor index, and then the comprehensive pollution index of environmental quality is calculated according to a certain method, and the environmental quality is manually graded according to the values of each pollution index, and finally the environmental quality is determined. This method is subjective; Thirdly, all environmental problems are the result of the comprehensive action of more than one environmental factor, and each environmental factor is composed of multiple environmental factors, so it is often impossible to make a qualitative evaluation based on the given environmental quality value of one environmental factor; Finally, through various single and comprehensive operations, a conclusion is given to the environment, but because the change of environmental quality is dynamic and continuous, the evaluation conclusion of environmental quality is also vague.
Fuzzy mathematics extends the application range of mathematics from accurate phenomena to fuzzy phenomena, and it is a science to study and deal with fuzzy phenomena. Fuzzy comprehensive evaluation is to determine the classification of environmental quality according to the theory and method of fuzzy set; It uses membership degree to describe the intermediate transition state of differences, which provides a basis for the evaluation of regional eco-geological environment quality, thus improving the scientificity of the evaluation results. This paper discusses the evaluation of eco-geological environment quality by using fuzzy mathematics method, and takes Kuishan District of Rizhao City as an example, and makes a fuzzy comprehensive evaluation by using the measured data of six indicators, such as groundwater, soil, engineering geology, hydraulic slope, Quaternary thickness and vegetation coverage.
Fuzzy comprehensive evaluation principle of 1
Let the evaluation index set (that is, the factor of environmental quality) in an evaluation unit be U = {U 1, U2, …, um}, and the evaluation standard set of environmental quality be V = {V 1, V2, …, Vn}, V 1, V2, …, Vn is Ui.
Shandong environmental geology collection
According to the definition of fuzzy mathematical relation, in this fuzzy relation matrix, rij represents the possibility that the I-th participating factor is rated as Class J environmental quality, that is, the degree of I's membership to J. Therefore, the I-th row in the fuzzy relation matrix R is RI = (Ri 1, ri2, …, rin), I = 1, 2, …, m, which is practical. The j-th column RJ = (R 1J, r2j, …, rmj) and J = 1, 2, …, n in the fuzzy relation matrix represent the membership degree of each evaluation factor to the j-th environmental quality standard.
If the fuzzy subset on the environmental factor u is
Shandong environmental geology collection
In the formula, AI (I = 1, 2, ..., m) represents the measure of the role of single-factor ui in all factors, which can be regarded as the weight of the ith evaluation factor in environmental quality assessment.
The fuzzy subset of evaluation criteria is
Shandong environmental geology collection
Where bj (j = 1, 2, …, n) represents the membership degree of vj to the fuzzy subset of comprehensive evaluation, that is, the membership degree of J-level environmental quality standard to the comprehensive quality classification.
When fuzzy vector a and fuzzy relation matrix r are known, the fuzzy subset of comprehensive evaluation can be expressed as: b = a r.
2 application examples
Taking Kuishan District of Rizhao City as an example, the application of fuzzy comprehensive evaluation method is illustrated. Table 1 gives the monitoring values of environmental indicators in this area, including soil, groundwater, engineering geology, Quaternary thickness, hydraulic slope and vegetation coverage. Therefore, a set of evaluation factors of eco-environmental quality can be established: u = {soil, groundwater, engineering geology, Quaternary thickness, hydraulic gradient and vegetation coverage}.
Table 1 comprehensive evaluation table of eco-geological environment quality in Kuishan area
2. 1 Establish evaluation set
In this paper, six important eco-environmental factors in Kuishan area are selected: soil environmental quality index P, groundwater environmental quality index F, engineering environmental quality index SE, Quaternary thickness (m), hydraulic slope (‰) and vegetation coverage (%). Combined with the actual situation in this area, the environmental quality of the above factors is divided into four grades. Table 2 lists the corresponding values of different grades of each factor.
Table 2 Evaluation Standard Table of Eco-geological Environment Quality
2.2 the establishment of membership functions
This time, the linear membership function is adopted, and the formula is as follows:
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Among them, u Ⅰ (x), u Ⅱ (x), u Ⅲ (x) and u Ⅳ (x) are the membership degrees of grade I evaluation factors to grade I-IV quality standards; A 1, a2, a3 and a4 are the four standard values of evaluation factors; X is the actual value of I evaluation factor.
First, get the membership degree from the above formula. According to the measured value x, scoring standard and membership function of each index, the membership degree (boundary value for the index with boundary and interval median value for the index with interval value) is obtained, and the membership degree matrix Rij of each evaluation point is written.
2.3 Calculation of Weight
Because the values of evaluation factors and indicators are different, the impact on the quality of eco-geological environment is also different, so the weight of each indicator at each evaluation point is calculated according to the following formula, and 1×n p vectors are determined.
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Where Wik is the index weight vector of k evaluation point I; The larger the value, the better the quality of eco-geological environment, and the reciprocal is taken in the calculation.
After calculation, the weight matrix of each evaluation index in this region is as follows:
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2.4 Fuzzy comprehensive evaluation
According to the above calculation results, the normalized weighted model formula is adopted:
Bjk=Aik Rij
Where: Bjk is the comprehensive matrix of all levels to which each evaluation point belongs; Aik is the exponential factor weight matrix of each evaluation point; Rij is the membership matrix of each evaluation point; Is a fuzzy comprehensive operator.
Calculate the rank matrix of each evaluation point as follows:
Shandong environmental geology collection
Through the comprehensive evaluation of the eco-geological environment quality in Kuishan area, the eco-geological environment quality in this area is divided into good area (ⅰ), good area (ⅱ) and poor area (ⅲ). Good area (I) is mainly distributed in the Daqu River-Dingjialou line and the western region, and is located in the water source of the middle reaches of Futuan River. The groundwater quality is good, the Quaternary is thick, and human activities are mainly agricultural, but the water body is poor. Poverty-stricken areas (Ⅲ) are mainly distributed in Futuan estuary and southern coastal zone. The groundwater quality in this area is poor, the seawater intrusion is serious, the coastal landscape is destroyed, and the area of coastal shelter forest is also decreasing.
3 Conclusion
Compared with the traditional evaluation method of geological environment quality, the fuzzy comprehensive evaluation method is reasonable and scientific, and can correctly reflect the quality of ecological geological environment. However, if the membership function is improperly established and the weight function is improperly set, it will also lead to the deviation of the evaluation results. Therefore, the fuzzy comprehensive evaluation method should be used cautiously.
refer to
Deng Julong. 1985. Basic methods of grey system, Wuhan: Huazhong University of Science and Technology Press.
Ministry of Geology and Mineral Resources.1993.gb/t14848-1993 Groundwater Quality Standard.
Xia Jun. Quality evaluation of regional environment and ecological environment. 1999. Wuhan: Wuhan University of Hydraulic and Electric Power Press.