Evaluation Of Grey Water Footprint In The Yangtze River Economic Belt Based On Triangular Fuzzy Number

Based on the uncertainty of the traditional grey water footprint model,this study introduces the triangle fuzzy number theory into the analysis of water quality water shortage,aiming at the uncertainty of the allowable limit of environmental pollutants in the grey water footprint evaluation model,and establishes the grey water footprint model and pollution risk assessment model based on triangle fuzzy number,and applies them to the grey water footprint evaluation of the Yangtze River economic belt.The innovation of the research is that it improves the disadvantage of the uniqueness of water allowable limit in the traditional grey water footprint model,and comprehensively consider the areas with strict water quality protection objectives such as ecological reserves.In the previous grey water footprint evaluation,the total pollution load can be controlled within the allowable limit,but in the areas with strict local water quality protection objectives,the pollutants may also exceed the dilution capacity of the water body,and the improved grey water footprint model can characterize the impact of pollutants on the water environment in these areas through the over standard risk rate.Compared with the traditional grey water footprint model,the improved grey water footprint model is more rigorous and can more accurately identify the water quality risk in the study area.In this paper,the temporal and spatial evolution characteristics of major pollutants in 11 provinces and cities of the Yangtze River Economic Belt are studied based on the data of pollutant discharge loads from 2014 to 2017.Then,the defects and reasons of traditional grey water footprint model in water quality evaluation are discussed,and an improved grey water footprint model is proposed based on triangular fuzzy number theory.The grey water footprint of major pollutants in 11 provinces and cities in the Yangtze River Economic Belt is evaluated by using the improved grey water footprint model,and the temporal and spatial evolution of grey water footprint and its causes are analyzed.Finally,the total grey water footprint of11 provinces and the probability of exceeding the standard are calculated,and the causes are studied based on the total water resources of each province.This study mainly draws the following conclusions:From 2014 to 2017,among the 11 provinces and cities in the Yangtze River Economic Belt,the provinces and cities with the greatest risk of chemical oxygen demand,ammonia nitrogen,total nitrogen and total phosphorus exceeding the standard are Shanghai,Anhui Province,Zhejiang Province and Shanghai Municipality.Overall,the risk of chemical oxygen demand exceeding the standard shows a fluctuating upward trend,the risk of ammonia nitrogen and total nitrogen exceeding the standard shows a downward trend,and the risk of total phosphorus exceeding the standard shows a downward trend.Shanghai has the largest total grey water footprint.The fuzzy numbers of total grey water footprint from 2014 to 2017 are(22.3 billion m3,44.6 billion m3,89.20 billion m3),(21.25 billion m3,42.50 billion m3,85.0.0 billion m3),(32.55 billion m3,61.50 billion m3,130.20 billion m3)and(38.08 billion m3,77.06 billion m3,155.20 billion m3).Yunnan province has the smallest total grey water footprint,and the fuzzy numbers of total grey water footprint are(38.35 billion m3,76.7.0 billion m3,308.08 billion m3),(37.75 billion m3,75.05 billion m3,304.05 billion m3),(31.30 billion m3,62.60 billion m3,192.02 billion m3)and(29.65 billion m3,59.20 billion m3,188.08 billion m3).On the whole,from 2014 to 2017,the total grey water footprint risk in the Yangtze River Economic Belt shows a declining trend.In 2017,the provinces and cities with the largest risk value of exceeding the total gray water footprint in the Yangtze River Economic Belt are Shanghai,Jiangsu and Zhejiang Provinces,with risks of exceeding the standard of 1.00,1.00 and 0.92 respectively,and the risk value of exceeding the standard in Yunnan Province is0.00,ranking last among 11 provinces and cities.The risk of exceeding the standard in the Yangtze River Economic Belt decreases significantly from 2014 to 2016,and increases slightly from 2016 to 2017,so it shows a trend of fluctuation and decline on the whole.