Receptor-Scale Isoprene Contribution and Daylight Ozone Control in Bologna Urban Green Infrastructure

Abstract

While urban greening can enhance thermal comfort, public space quality and ecological continuity, the impact of daylight ozone formation hinges on the composition of tree species, local transport system and chemical reactions involving nitrogen oxide. For this analysis, Bologna’s tree population-specific canopy renewal target has been calculated with ten broadleaf species as P_i = f_iE_i, pollutant-response coefficient and receptor attenuation threshold using their isoprene emission potentials, statistics, ozone and nitrogen oxide response rates and daylight ozone increment for Irnerio, Montagnola, University Gardens and Berti Pichat receptors. Isoprene production is highly concentrated in Bologna’s assemblage with Platanus × acerifolia, contributing 57.90% of normalized isoprene potential, and Sophora japonica making up for additional 21.08%. The two species contribute together 78.98% of normalized isoprene emission potential with first five species providing 99.25%. Ozone has a stronger response rate compared to that of nitrogen oxides (K_O3=0.783 versus K_NOx=0.257). As such, daylight ozone increment may be adopted as the managed endpoint in canopy management. University Gardens receptor is controlled by the daylight ozone increment of 6.7% while those of Irnerio, Montagnola and Berti Pichat are 2.3%, 1.9% and 0.8%, respectively. Within the constraint of 2% daylight ozone increment, University Gardens needs to have the reduction of 70.1% isoprene production potential while Irnerio only 13.0%. Replacing completely Platanus × acerifolia and Sophora japonica results in the University Gardens’ residual daylight ozone increment of about 1.41%.