The Research Of Urban Ecosystem Health Assessment In Wuxi City Based On Emergy Analysis

In recent years,with the acceleration of urbanization process in our country,the problem of"urban disease" is spreading and the health condition of urban ecological system is being threatened.When the health condition of the human-centred urban ecological system is at risk,the survival and development of human oneself will also be seriously affected.The healthy urban ecosystem is the ultimate aim of environment control and management.Therefore,to evaluate the health condition of urban ecological system,to find out the key problems affecting the health condition of urban ecological system and to propose the measures of environment control and management for a given problem are very necessary.Wuxi city is one of the birthplaces of rural industry and commerce in our country.All kinds of problems emerged with the process of rapid urbanization,such as the ecology environment depravation,a sharp loss of biodiversity,excess intensity of land development and great pressure of population,etc.The enactment of?Opinions on further promoting the construction of "two oriented society" to firstly build a national ecological civilization demonstration city?of the twelve session of the five plenary session of the Wuxi municipal Party committee make it clear to build a national ecological civilization demonstration city until 2020 with excellent environment,controlled ecological risk,good ecological order and a high level of crowd's satisfaction.In conclusion,this paper taking the Wuxi city as the object of study to evaluate the health condition of urban ecological system through the emergy evaluating indicator system under the Application of Emergy Analysis Theory combined with Methods of set pair analysis.The main contents are as follows:In theory of urban ecosystem health as the guide,this paper expounds basic concepts,the practical meanings and the fundamental steps that related to emergy analysis as well as the relationships beteween emergy analysis and urban ecosystem health.Based on several different evaluation approaches of urban ecosystem health,emergy analysis theory is used in the assessment of urban ecosystem health.Meanwhile,methods of set pair analysis is used for uantitative evaluation.In theory of multi-ecosystem,according to four factor levels on vigor,resilience,organization,maintenance of ecosystem services,11 emergy indexes such as "emergy density","emergy currency","net emergy yield ratio","non-renewable resource ration","emergy self-sufficiency ratios","exchange fraction of emergy","environmental loading","population-carrying capacity","production of wastes","per capita of emergy","electric power ratio of emergy" are selected to establish an indices system of Wuxi urban ecosystem health.Through the values of different ecological flows,the emergy of ecological flows of the urban ecosystem of Wuxi city from 2001 to 2015 and their index values of the emergy are calculated.Then on the basis of set pair analysis model,the health condition of Wuxi urban ecological system from 2001 to 2015 are evaluated by the weight of entropy methold using MATLAB.The developing trend of the health condition of Wuxi urban ecological system is analyzed by the evaluated results in order to determine the major issues that affecting the health of the system and the targeted control and management measures are proposed based on actual problem.The research result indicates that the overall trend of relative nearness degree of the composite index of Wuxi urban ecosystem health and the optimal evaluate segregation show a downward trend at first,and then tend to smooth which yield fluctuates in the range of 0.57-0.42.The trend suggest that the health condition of Wuxi urban ecological system present a descent trend in the time period for evaluating.Meanwhile,during 2001?2015,relative nearness degree between the vitality index of Wuxi and the composite index is increased by 0.0606,relative nearness degree between organizational structure index of Wuxi and the composite index is decreased by 0.3703 which is less than half that in 2001,relative nearness degree between the index of maintenance of ecosystem service of Wuxi and the composite index is increased by 0.0606.Problems that affecting healthy development of urban ecosystem in Wuxi are found out by detailed analysis of the evaluated results which are the energy utilization structure,the ecology spatial pattern,the ecological environment quality and the commodity structure of economic and trade.