Urban form and air quality in U.S. metropolitan and megapolitan areas.

摘要

The spatial form, or morphology, of urban areas may significantly affect the anthropogenic production of air pollutants. This dissertation explores the relationships between air quality and urban form at the metropolitan and megapolitan (multi-metropolitan) scale. Urban form was quantified for 86 metropolitan and 19 megapolitan areas using both pre-existing sprawl indices and multiple spatial metrics derived from remotely sensed landcover data. Air quality was assessed by measuring several key air pollutants, including the ambient concentration of ozone (O3), the non-point source emissions of the two O 3 precursors nitrogen oxides (NOx) and volatile organic compounds (VOCs), the ambient concentration and non-point source emissions of fine particulate matter (PM2.5) and coarse particulate matter (PM10), and the mobile emissions of carbon dioxide (CO2). The ambient concentrations of air pollutants were averaged over the 5-year period 1998 to 2002. While controlling for industrial emissions, climate, population and geographic area, multiple linear regression was used to evaluate the degree of association between measures of urban form and air quality. The results suggest that urban form has a measurable impact on both the non-point source emission and ambient concentration of air pollution. Urban areas that exhibited more "sprawl-like" urban forms (i.e. lower residential density, less street network connectivity, less contiguous urban development) generally had higher non-point source emissions and/or ambient concentrations of air pollution. Pre-existing sprawl indices were most significantly associated with ambient concentrations, while two spatial-metrics based measures of urban structure, urban "continuity" and urban "shape complexity," were most significantly associated with non-point source emissions. The relationships between measures of urban form calculated using spatial metrics and air pollution were most significant at the metropolitan scale. The extent of the urban area (i.e. high versus low urban threshold), however, did not significantly affect the associations between urban form, as assessed using spatial metrics, and air pollution. Understanding the relationships between urban form and air quality is an important step in identifying effective urban land use configurations and developing healthier cities.