Variations in carbon dioxide fluxes within a city landscape: Identifying a vehicular influence

To date, studies examining carbon dioxide (CO 2 ) fluxes in urban areas have been limited compared to those in rural environments. The objectives of our study were to examine the relationship between traffic volume and CO 2 fluxes. We demonstrated that CO 2 fluxes were strongly linked with surrounding land use, specifically impervious surfaces and traffic volume. A site near downtown Syracuse in New York State (USA) had relatively constant positive fluxes (source: +39 μmol CO 2 m −2 s −1 ) throughout the year as a result of strong vehicular traffic influence from two nearby interstate highways. There was a strong positive relationship between traffic and CO 2 fluxes (r 2 = 0.93, p < 0.0001) with marked differences between the weekend days versus the workweek days. In contrast, a residential site in Syracuse was dominated by vegetative influences during the leaf-on period due to CO 2 uptake by photosynthesis, reaching a maximum negative mean diurnal flux of −11 μmol CO 2 m −2 s −1 around midday (sink). The spatial variations of CO 2 fluxes identify the critical role played by local traffic volumes in affecting the CO 2 dynamics of urban environments. Understanding the dynamic fluxes of CO 2 in urban environments has important implications for local, regional and global evaluations of CO 2 budgets and inventories, and carbon cycle and climate modeling.