北京城市扩展的环境效应模拟与评价

基于L-THIA GIS模型,以北京为案例研究区,应用水文土壤类型、土地利用类型以及长期日降水量数据,有效模拟了长时间段内以城市扩展为主要特征的土地利用变化对水文过程以及城市非点源污染的宏观影响态势,挖掘出区域内潜在的长期污染问题及其空间分布。结果表明,虽然1996—2004年间连续干旱导致年径流量整体减少,但城八区年径流量却呈增加趋势,各分区年径流量变化幅度与耕地向建成区转化的比例具有一致性,说明保护并合理利用耕地对减少城市径流有重要意义;城市建设用地的单位面积产流量远远大于农业用地和生态用地,林地向城市建设用地转变所产生的水文效应敏感性最强,其次依次为:水域、草地、农村居民点和农业用地,林地、水域、草地等生态用地需要特别加强保护;通过L-THIA模型和GIS平台,实现了区域非点源污染的分布式模拟,结果显示城市扩展对城市非点源污染的影响大于降水变化的影响,根据模拟结果和下垫面(土地利用)对城市非点源污染的影响,初步将北京划分为4类城市非点源污染产生的敏感性区域,为土地利用管理和环境规划提供指引。

Environmental Impact Modeling of Urban Sprawl in Beijing, P. R. China

City expansion is a major driving force altering local and regional hydrology and increasing non-point source(NPS) pollution.To explore these environmental consequences of urbanization,long-term runoff and NPS pollution were assessed in Beijing,P.R.China.The assessment was based on land-use types,soil hydrology,and long term precipitation data.The environmental impact model L-THIA was used.The outcomes indicate that the area likely would be subjected to impacts from urbanization on runoff and some types of NPS pollution.Urban sprawl will increase runoff volume considerably and significantly increase losses of COD and certain heavy metals such as Pb,Zn in runoff.The results of this study have significant implications for urban planning and decision making efforts to protect and remediate water and habitat quality in the Beijing area.The techniques described herein can be used in other areas.