露天煤矿区生态风险评价方法

Method of ecological risk assessment for opencast mine area

以露天煤矿区这一脆弱生态系统为对象进行了生态风险评价方法的探讨 ,阐述了生态风险评价的基本概念。针对露天矿区生态环境特点 ,通过描述露天矿区的主要生态环境问题 ,分析了矿区风险源、风险受体以及评价终点 ,最后建立了典型露天煤矿区生态风险的评价指标体系 。

Opencast mines distribute mainly in vulnerable environment areas in china,where the climate is drought and semiarid.The main ecological problems caused by opencast mine include destruction of intrinsic terrain and natural landscapes,solid wastes,wastewater,waste air,water and soil loss together with heavy metals pollution etc.Ecological risk assessment commonly involves exposure assessment,hazard assessment ,receptor assessment and risk characterization.The method and process of ecological risk assessment in mine area can be summarized as follows:(1) Confirming risk assessment range.Those areas where pollution have occurred or be likely to occur should be paid high attention to.(2) Risk source assessment.Risk source assessment includes risk source identification and risk source description.Risk source identification means identifying risk factor,the risk sources in opencast mine area include the destruction of intrinsic terrain and physiognomy because of digging and occupying together with poisonous and harmful substance.Risk source description is confirming probability,intensity and location of risk pressure.(3) Receptor assessment.Receptor is the segment that has been or be easily impaired in ecosystem.In opencast mine area,vegetation and soil system should be considered,especially those sensitive propagation.The possible endpoints include native propagation annihilating,vegetation degrading and typical site disappearing etc.(4) Exposure assessment and hazard assessment investigate the contact between receptor and pressure as well as receptor's impairment degree.According to landscape ecology,the opencast mine area can be divided into different fragments such as coal gangue hill,dump site,residential area etc.This paper will use ecological index,ecological frangibility degree index and ecological loss degree index to compute the ecological risk value in mine area.(1)The ecological index can reflect fragment's ecological integrality,importance and natural degree,it includes three indexes:Species original index,species diversity index and nature index.Species original index is the percentage that native species in fragment account for that in mine area;Species diversity index is the percentage that species in fragment accounts for species in mine area;Nature index is negative relation with disturbance intensity,disturbance intensity can be expressed by corridor (road and ditch etc) length per acreage in fragment,then the reciprocal is nature index.Species originality index,species diversity index and nature index synthesize the ecological index.(2)Ecological frangibility degree means the capability that population or ecosystem or landscape resists outside disturbance.Ecological frangibility degree index considers such factors as vegetation factor (bareness degree,biodiversity) and soil factor (invertebrate diversity,soil fertility,heavy metal).(3)Ecological loss degree is the product of ecological index and ecological frangibility degree index.5.Synthesis risk assessment is the last stage of ecological risk assessment in opencast mine area.Fragment's risk degree can be calculated by risk speed and the intensity grade of different risk source,the final risk value in each fragment is the product of risk degree and ecological loss degree,the risk assessment map of mine area comes into being through classifying ecological risk value.According to the risk outcome the risk,managers can put forward proper projects and make rational risk decision for minimizing ecological risk and for harmonizing the development of environment-economy in coal mine area.