AIR-SURFACE EXCHANGE OF POLYCYCLIC AROMATIC HYDROCARBONS IN URBAN AREAS

Nowadays, urban sprawl is a growing concern of the scientific community. One of the negative impacts bound to this phenomenon is the increased pollutant concentrations in the atmosphere and in runoff waters. Among these pollutants, polycyclic aromatic hydrocarbons (PAHs), recognized as carcinogen, show high concentrations in urban air. Urban sources of PAHs are numerous and include motor traffic, domestic heating and industrial emissions. As urban areas are characterized as having a high proportion of impervious surfaces coated with atmospherically derived organic films, the exchanges between the atmosphere and these surfaces can be a key process in the fate of PAHs in urban environments. In an effort to better understand this process, in situ measurements of surface-air partitioning for PAHs were conducted on various surfaces (roadways, parking lots, roofs, etc.) in two cities: Austin (USA) and Toronto (Canada). Air samples were collected very close to the surface using a disc-shaped sampler and at 1.5 m height, in order to investigate surface-to-air transfer. The results from this study will improve our ability to model this process and ensure a better understanding of the geochemical processes and transport fluxes of PAHs in urban watersheds that is essential for managing public safety in the urban environment.