| The rapid economic development of coastal areas in China has produced tremendous environmental pressure.Black water entering the sea,illegal reclamation and other issues are significant.Marine engineering construction lacks scientific argumentation,which not only has low comprehensive benefits,but also causes serious damage to the coastal waters.In recent years,with the development of water quality elimination,the quality of marine environment has gradually improved.How to make scientific use of marine resources,construct a community of shared future for the sea and build a maritime power has become an important research topic today,and the objective and practical evaluation of seawater quality is an important basis for various studies.The widely used single-factor index method has a large deviation from the real water quality for the seawater with various evaluation indexes,complex connections and fuzzy classification.In contrast,the fuzzy comprehensive evaluation method is more suitable for seawater quality evaluation.The traditional fuzzy evaluation method considers the interaction and effect of each evaluation factor,but the calculation is complex and the result is unstable.Therefore,this paper proposes an optimized fuzzy comprehensive evaluation method,and applies this method to the evaluation of seawater quality in Yoco Port,so as to study its accuracy and feasibility from of time change,level change and position change.The main research contents and conclusions are as follows :1.On the basis of traditional fuzzy comprehensive evaluation,the weights of AHP and entropy weight method are integrated to make the evaluation results more objective and accurate;The multiplicative additive model fuzzy operator not only reflects the role of the maximum pollution index,but also considers other indicators,so that the evaluation results are more comprehensive.With the help of MATLAB R2019 b software,the model calculation is simplified,and the evaluation process is more convenient and operable.The software is used to visualize the evaluation results,and the data are linked through the three-dimensional diagram,so that the evaluation results are more intuitive and vivid.2.The optimized fuzzy comprehensive evaluation method is applied to conduct a comprehensive evaluation of the water quality of Yoco Port.The evaluation results show that the overall water quality of the region is in good condition and meets the requirements of each functional area.(1)From the perspective of time change,the main influencing factors of evaluation are active phosphate and petroleum.The seawater quality grade was good in autumn 2016 and spring 2017,and the rest frequency evaluation results were excellent.However,the seawater quality showed a gradual downward trend from 2018 to 2019,and follow-up monitoring results should be paid attention to.(2)From the perspective of hierarchical change,the main influencing factors of evaluation are dissolved oxygen and active phosphate.The evaluation results of surface and bottom water quality in the offshore area of Yoco Port are almost the same,showing good consistency in general.(3)From the perspective of position change,the main influencing factors of evaluation are dissolved oxygen,inorganic nitrogen and active phosphate.Except that the GS13 site is located in the second class of seawater standards,the rest of the evaluation area meets the first class of standards.Combined with MATLAB visualization technology,it is found that the water quality around the west sun sand code head area and the east side of Jinniu code head area is relatively poor,which is in good agreement with the concentration distribution of pollutants and is greatly affected by human activities.3.Through the comparative analysis of the optimized fuzzy comprehensive evaluation method,single factor index evaluation method and the traditional fuzzy comprehensive evaluation method,it is found that the single factor method is difficult to establish a link in time change,and there is a problem that the hierarchical evaluation error is large due to the fuzzy standard division.It is difficult to find the regularity of location change only by data,and usually makes the evaluation sea area in a poor level,which may cause excessive protection of water resources;The traditional fuzzy comprehensive evaluation method has the problems of complex calculation,weight assignment,fuzzy operator and evaluation method selection affecting the final results,and the evaluation results and trends are not intuitive.The optimized fuzzy comprehensive evaluation method improves the shortcomings of the two methods,and the evaluation results are consistent with the actual situation,which is more feasible in the actual work of seawater evaluation. |
