Ecological Risk Change Research Of Brownfield Region Based On GIS

Because of the high demand for energy resources,the rapid development of industrial and mining enterprises,resulting in a series of environmental problems in their development process.In recent years,China's industrial structure adjustment,the original pollution,low utilization rate of industrial and mining enterprises facing removal,adjustment and other issues,resulting in a large number of "Brownfield" in the process.The brownfield is being polluted by industrial or commercial,from the point of view of ecology,society and so on,low efficiency and need to reuse or improve the current state of utilization,but does not emphasize the intuitive completely abandoned,idle state,its existence will bring the potential harm to the ecological environment and residents of surrounding region.China's economic development pattern and industrial structure constantly changing,brownfield region management governance will be more urgent and important.In the process of brownfield region restoration,the research work of the change of ecological risk is very important.Ecological risk assessment of brownfield will provide important reference for management work of brownfield region,realize the purpose of land protection and sustainable use of land resources.This paper summarizes the theory of brownfield and the research of ecological risk,definite the connotation of ecological risk assessment of brownfield region.Through the research of ecological risk assessment framework for domestic and foreign,this paper propose a framework for the ecological risk assessment of brownfield region,the work of the change of ecological risk is divided into hazard analysis of the risk sources and ecological vulnerability analyze of risk receptor in two periods.In this paper,the ecological risk of brownfield is mainly the ecological risk of heavy metals,so before the assessment of its ecological risk needs to evaluate the heavy metal pollution,and using GIS tools provides strong support for ecological risk characterization.The main research and results of this paper are as follows:(1)This paper uses Nemero index method to evaluate the pollution of heavy metals of brownfield.The traditional Nemero index method is too much emphasis on the environmental impact of biggest pollution index,in this paper,the correlation ratio of evaluation factors and heavy metal toxicity index are used to modify the traditional Nemero index method,and the improved method is applied to an example,using GIS tools to analyze the spatial distribution of pollution in the study area.The content of heavy metal Cu and Cd in the soil was higher before remediation,and the content of heavy metal Cu and Cd in the soil decreased after remediation.Evaluation results show that the pollution of most area of the study area was heavily polluted before remediation,small part area is lighter.After remediation,the pollution level of study area was reduce,there was small part of the region for heavy pollution,most area was below moderate pollution,the area that original less pollution was reduced to below the warning line.(2)The potential ecological risk index method was used to evaluate the ecological risk of heavy metals.From the view of land use landscape,analyze the vulnerability of risk receptor by using the ecological vulnerability index,and express the spatial distribution of those by use of GIS.Then comprehensive analyze the ecological risk and ecological vulnerability,using ArcGIS extract and analyze different ecological risk level in different land use landscape.The result show that the risk of Cd was higher than Cu before and after remediation.Before remediation the ecological risk level of heavy metal Cu was below the moderate risk,and most of the area was low risk,the risk of Cu was greatly reduced after the restoration,and the ecological risk level of Cu in the study area was low risk.The ecological risk of Cd was high before remediation,most area was above strong risk level,the risk of Cd was reduced after remediation,most area was below the strong risk level.The comprehensive ecological r:isk is large before restoration,Sumen area,Jiuniugang,Shuiquan area and Chuanshanlong are above strong risk level,and these blocks below the strong risk level after restoration.This show that the repair effect was better,however,some area that still have a strong risk should be further monitoring and repair management,in addition,heavy metal Cd has greater contribution to the comprehensive ecological risk than Cu.In this paper,from the perspective of ecological vulnerability to analysis risk receptor,mainly from the perspective of land use landscape ecological vulnerability,the result show that the ecological vulnerability of cultivated land in the study area was the largest.For these area has greater ecological vulnerability and larger ecological risk should increase attention.The ability of these region to resist risk was weak,it should be further remediation,for the greater ecological vulnerability but lower ecological risk areas should be strengthen the monitoring,to prevent the occurrence of strong risk again.