Estimates of Urban Excess in PM_(2.5) Speciated Aerosol Concentrations Using the CSN and IMPROVE Networks

摘要

The spatial patterns and magnitudes of urban excess differed considerably depending on species. Urban excess estimates were lowest for AS and greatest for LAC, reflecting differences in the sources of the aerosols (e.g., primary versus secondary) as well as their distance from sources. However, the spatial extent of the impacts of LAC was the lowest of all species. In contrast, the spatial patterns in urban excess associated with AS and OC were more regional in extent, especially in the eastern United States, although impacts from local sources were also apparent. While this analysis was simplistic in approach and subject to uncertainty, it provides estimates of the relative magnitude of local versus regional contributions to aerosol concentrations and subsequently improves our understanding of the impacts of urban sources and transport into remote regions and their influence on regional background concentrations.