A Gis-based Approach to Spatio-temporal Analysis of Urban Air Quality in Chengdu Plain

Environmental pollution of urban areas is one of key factors that state authorities and local agencies have to consider in the decisionmaking process. Understanding temporal and spatial distribution of air quality at the landscape scale is essential in assessing the potential ecological conditions for ecological restoration and in making decisions for regional management. To find a compromise among many criteria, spatial analysis extended by geostatistical methods and dynamic models has to be carried out. In this case, spatial analysis includes processing of a wide range of air, water and soil pollution data and possibly noise assessment and waste management data. Other spatial inputs consist of data from remote sensing and GPS field measurements. Integration and spatial data management are carried out within the framework of a geographic information system (GIS). From a modeling point of view, GIS is used mainly for the preprocessing and postprocessing of data to be displayed in digital map layers and visualized in 3D scenes. Moreover, for preprocessing and postprocessing, deterministic and geostatistical methods (ordinary kriging, IDW, i.e., inverse distance weight) are used for spatial interpolation; geoprocessing and raster algebra are used in multi-criteria evaluation and risk assessment methods. GIS is also used as a platform for spatio-temporal analyses or for building relationships between the GIS database and stand-alone modeling tools. Finally, air quality data are generally very complex to model due to the underlying correlation among several pollutants. The significant differences among the results obtained from the techniques, indicated that proper air quality management requires sensitive air quality evaluation. It was demonstrated that geostatiscal tools integrated with time series techniques are quite appropriate techniques for air quality management. Processed data, spatial analysis and models are integrated within the framework of the GIS project, providing an approach that state and local authorities can use to address environmental protection issues. In spite of a wide range of problems associated with technical, data and financial constraints, the final results of this GIS project could contribute to improving environmental management in Chengdu Plain. The methods used can also be applied for the environmental analysis of other urban areas. DEM data processed using 3D spatial interpolation can be a valuable tool for assessing pollutant distribution in space. It can be used as screening methods to more closely target key areas and to develop more detailed measuring and modeling strategies. Integration of all data within a GIS framework therefore represents a useful approach for performing more complex environmental analyses that can support the decision-making processes of urban planning. * Corresponding author.