Atmospheric Transport of Polycyclic Aromatic Hydrocarbons into Three Alpine Valleys: Influence of Local-Scale Wind Patterns and Chemical Partitioning.

Current understanding of atmospheric transport of polycyclic aromatic hydrocarbons (PAHs) is limited in alpine areas due to complex meteorology and topography. To better understand atmospheric transport in these areas, we measured 16 PAHs in lichens, biomonitors of atmospheric PAHs, along three transects extending from a highway into otherwise remote alpine valleys. While the valleys neighbored one another and were morphologically similar, they differed in their orientation relative to regional winds. In the valley characterized by regional winds oriented up-valley, PAH concentrations in lichens remained consistent across the transect. In the other two valleys, where regional winds were oriented down or across the valley, 3-6 ring PAHs declined rapidly with increasing distance from the highway, and PAH concentrations in the lichens declined more rapidly for higher molecular weight PAHs than lower molecular weight PAHs. We hypothesize that this trend was driven by differences in gas-particle partitioning and vegetative scavenging between PAH congeners. These results illustrate the importance of both physical transport and chemical partitioning in alpine areas where small differences in topography can lead to significant differences in chemical transport.